As always, your Q&A causes me to think, read and learn. You answered correctly and it helped me learn. I think the questioner may have been enquiring about Current source vs Voltage source amps. It comes up in Nelson's First Watt discussions as he has a couple of current source amps (the F1 & F2). They work well only with a small subset of speakers, but when they do, they work very well. The guy from Atmosphere described it as: "A current source amplifier has a very high output impedance- usually multiples of the speaker impedance. A voltage source amplifier has a low output impedance, usually a small fraction of the speaker impedance."
I've wondered about this issue myself, but the video didn't really address the question. Conventionally, the way we all use electrical devices is that the power supply (e.g. the utility company) does its best to control the voltage and always maintain it to their spec. The devices that consume power are all wired in parallel; each of them is designed for a fixed voltage, and is free to choose how much current to take. However, in some weird alternate universe (but using the same laws of physics that we already have), the power supplier could be in control of the current and do its best to always maintain the current flow at a constant level, at its spec. Then, all of the power-consuming devices would be wired in series. Each of the power-consuming devices would be designed for a fixed current, and would be free to choose how much voltage to take. Each device's on/off switch would be wired as a shunt across the device. If you look at a lab power supply, it has knobs for both a voltage limit and a current limit. It is able to do either style of operation. Back to the world of audio power amplifiers, I consider a voltage amplifier to be one where the output voltage to the speaker is proportional to the line-level input voltage, and the speaker decides how many amps to consume. Speaker impedances are different at different frequencies. If you pick a frequency where the speaker impedance is low, you'll get more current and thus *more* power sent to the speaker at that frequency. An audio amplifier designed as a current amp would operate so that the output *current* sent to the speaker is proportional to the line-level input voltage. The speaker would then decide how many volts to consume. If you picked a frequency where the speaker impedance is low, you'll get lower voltage and thus *less* power sent to the speaker at that frequency. The possible advantage to this style of operation is that the magnetic field strength, I believe, is proportional to the current, not the voltage. So, if the speaker was designed to work in this manner, you'd have a more linear relationship of sound pressure to the line-level input of the amplifier. So really, the central question that I have is whether speakers are primarily designed for (a) the amplifier to control the voltage and the speaker to control the current, or (b) the amplifier to control the current and the speaker to control the voltage.
(a) You could build an amplifier that does (b), but with most speakers, you would get a huge frequency response peak at the speaker's resonant frequency (frequencies).
The question was about voltage-feedback amplifiers versus current-feedback amplifiers. We all know that audio amplifiers need both voltage and current gain, but that wasn't the question. The most fundamental reason why amplifiers are designed to control output voltage, is that's what loudspeakers are designed for. Speaker designers try to make the frequency response flat, when the speaker receives a constant voltage. Amplifiers can certainly be designed to control their output current, i.e., make it follow the input signal voltage. At very low frequencies, this can be used to reduce woofer distortion, but there are several problems with current-output amplifiers: 1. They don't like open-circuit loads. If a speaker isn't connected, the output voltage goes very high. 2. They push far more power into speakers at frequencies where the impedance goes up, and put less power into low-impedance speakers (or combinations of speakers in parallel). Since all speakers have at least one (two if a ported design) impedance peaks in the bass region, this tends to play havoc with the low-end frequency response. 3. They won't damp a speaker's tendency to ring after transients: Damping factor approaches zero. Amplifiers have been built which control to current at low frequencies, and fade over to voltage control at higher frequencies. But these need to be customized to work with particular speakers.
I think you're right about the original question! But I like to rephrase the rest of your reaction... The most fundamental reason why amplifiers should control output current, is that's how an electro-dynamic driver works. The output of a driver (SPL) is direct related to the current through the voice coil, and that relation is defined by the force factor (F = BL x I). Speaker designers try to make the frequency response flat. But if you drive a driver with voltage, all irregularities in the impedance translate to irregularities in the frequency response, and the increase in impedance at high and low frequencies makes the frequency response roll off at both ends (makes the response more rounded than flat), although the upper response on-axis is somewhat compensated by the horn effect and the break up at high frequencies. Amplifiers can certainly be designed to control their output current, i.e., make it follow the input signal voltage. This will eliminate all types of distortion which are related to impedances (which Klippel, the expert on driver and loudspeaker measurements, calls ‘current distortion’). Especially the midrange distortion and the intermodulation distortion by low frequencies, is lowered. There are several problems with voltage-output amplifiers: 1. They don't like low impedances and short-circuit. If there is a low impedance or a short circuit, the output current goes very high. 2. They push far more power into speakers at frequencies where the impedance goes down, and put less power into high-impedance speakers (or combinations of speakers in series). Since all speakers have at least one (two if a ported design) impedance dips, one in the midrange and one in the bass region (if a ported design), this tends to play havoc especially with the mid range frequency response. 3. The damping of a driver is very dependent on impedances and changes in impedances: voice coil resistance, temperature modulation, inductance and current modulation of the inductance and the impedance of the crossover filters: The actual damping is unstable and so is the response at resonance, which is problematic especially for ported designs. But there are other and better ways to control the resonance: in the driver, in or with the enclosure, electronically in the crossover or with EQ.
Saying an amp is "high current" is more or less a marketing thing. Though in practice it means an amplifier may be more stable at loads much lower than 8 or 4 ohms. And that its power supply is capable of delivering enough current that it is under stressed in typical loads. That is really all it means.
With audio, probably the most common use of a current amplifier (AKA a Transconductance amplifier) is inductive loops used to provide clean audio direct to hearing aids. In that application you have a loop of a small number of turns of wire (2 or 3 maybe), which may be over many square meters. With such coils, it's the current that produces the magnetic fields. For the same reason as Paul talks about voltage amplifiers also amplifying current, you can use a voltage amplifier to drive a loop, but because the impedance of the loop is much lower than that of a speaker, you are likely to blow fuses, or trigger the amplifier protection circuit quite a lot. For this reason, you can get transconductance amplifiers designed for induction loops, that generate current in preference to voltage, and more importantly the current is proportional to the input voltage, so you get less distortion.
Tought this would be voltage mode vs current mode amplification like for example questyle uses in their amps and daps. Like the cma800r headphone amplifier amplifiea the aignal in current domain.
Current amplification or voltage amplification to do work depends on the load or resistance. Actually impedance is more relevant in this case. Speakers are a wacky reactive load and dip and peak all over the spectrum of sound frequencies. I wish more speaker companies would publish impedance curves, 8 ohms nominal (average) is kind of useless.
That's why I love Dayton Audio, even if they're meant more for vehicles than hifi. Every one of their models has a datasheet that includes an impedance chart, not to mention full physical size diagram. Extremely useful, since they make many with same nominal impedence but the charts are very different, some flatter and some more bass-y.
While the output stage of a power amp increases the current, it has a very low output impedance (fraction of an ohm). That makes it a voltage source and not a current source. That's very important because a current source cannot properly drive an electromagnetic loudspeaker. In most cases the final stage is some form of voltage follower where the voltage gain is virtually unity but can drive many amps into a speaker load.
Not quite. Evey amplifier can be alternately viewed as a voltage source in series with an impedance (Thevenin equivilent) or as a current source in parallel with an impedance (Norton equivilent). So no, the value of the impedance does not make that distinction. The output impedance determines the power ceiling for the amplifier. If you view it as a voltage source then the output impedance acts as a voltage divider with the load. Attempting to draw too much current causes a greater portion of the voltage across the output impedance and the voltage across the load drops, preventing it from creating more current. If you view it as a current source than it acts as a current divider. If the load requires the voltage to be too high, then the parallel impedance will shunt the current, limiting how much voltage the load can drive. So in either case, the power is limited. An emitter-follower is used because it has a very low output impedance and can therefore support very high power output. Strictly speaking, Paul's use of the term power amplifier IS incorrect. What really makes the an amplifier a voltage amplifier or a current amplifier is in what respect the gain is measured. A voltage amplifier would output a voltage as some factor of the input voltage, regardless of input current. A current amplifier would output a current as some factor of the input current, regardless of voltage. You can also have a trasconductance amplifier that outputs a current as a factor of the input voltage and a transimpedance amplifier that outputs a voltage that is a factor of the input current. So, since he always references the signal as a voltage, all of his amplifiers are really voltage amplifiers. For a given input, the given output will have a given voltage. The current varies based on the impedance of the speakers. But using the term "current amplifier" as he does, albeit incorrectly, does drive home the point that the final power output must be able to source a more significant amount of current than the initial voltage gain stage which is likely a common-emitter amplifier, likely with a kilo-ohms or two of output impedance.
I interpret the question about voltage and current amplifiers, not amplification stages within a power amplifier. And I would like to see Chris answering that question!
This is a very poor and incorrect explanation. Audio amplifiers amplify voltage. It is highly misleading to say amplifiers amplify current. The output power of an amplifier is Watts = current X volts. The current an amplifier can deliver is determined by the components and design of the output stage and power supply. Draw too much current and the voltage will collapse and this defines the power rating of the amplifier. An amplifier with hefty output transistors and a substantial power supply is able to deliver a voltage at higher current than a lesser amplifier. The hefty amplifier does not “amplify” current, it is simply able to have higher current dragged out of it. This explanation is totally confusing as it does not explain Ohm’s Law, the relationship between voltage, current and resistance.
dtemp132 Paul’s attempted explanation implies that there are two different types of amplifier and you have a choice. This is wrong. Another way of looking at it.... as the volume control is turned up so the voltage to the speaker increases and it sounds louder. The speaker has a low impedance so draws a substantial current from the amplifier. Keep turning up the volume and the voltage and current rises but there will be a point where the amplifier cannot supply enough current to deliver the higher voltage. This limit depends on the design of the output stage and its power rating. The beefier the output stage the higher current it can deliver and the more Watts available.
I think you misunderstood the question. Current-drive amps are not as common. The question was why they're not common but all you did was explain the different stages of a normal voltage-drive amplifier.
@@oysteinsoreide4323 Yes. Paul uses the term current amplifier incorrectly. What he really means is a low impedance voltage amplifier that is capable of supplying high current. But he sets the voltage gain, not the current gain. So the current is ultimately determined be the speaker load. In reality, a current gain doesn't mean that there is no increase in the voltage. What it means is that the gain is measured by output current, and the voltage is determined by the load. You have current amplifiers which output a specific current as a product of the input current and you have transconductance amplifiers which output current as a product of the input voltage.
I agree. It would seem logical to use a transconductance amplifier on the output stage since the magnetic coils that are being driven are ultimately controlled by current instead of voltage. I think that is the rationality behind the original question.
This explains alot. I wonder why other than a few manufacturers more dont produce a hybrid amp with tubes in the pre-amp (section) and transistors in the power amp (section).
We use current amplifiers a lot for digital signalling. For example when we want to drive lots of digital inputs beyond the fanout of a single digital output, the current amplifiers provides the necessary power required to drive the inputs. The voltage at digital inputs is the equivalent logic signalling voltage of the original digital output. They are often called buffers.
Is Globalnet for the Powerplants ever comming back? I bought a new Powerplant in 2018 and never had the opportunity to use it. It's been down for a couple of years now.
I'm definitely no expert and still learning, but I literally laughed out-loud when you read the question because it has to be about the 23rd time you have covered this topic! ha ha
I haven't seen the others; but, this explanation is: 1. Wrong. 2. Doesn't answer the question that was asked. Both problems arise from Paul's incorrect use of the term "current amplifier." I assume he is doing that in an attempt to simply explanations; but, it is confusing and in this instance led to answering the wrong question. What Paul is referring to is simply an output voltage amplifier that has a very low impedance. A current amplifier or transconductance amplifier has an output current that is a factor of the gain and the output voltage is determined by the speaker impedance. This question asked why transconductance power amplifiers are not more common. They make logical sense. Speakers are driven by electromagnets. Magnetic fields are dependent on current, not voltage. So it makes sense to drive what is actually driving the speakers -- especially since speaker impedance varies with frequency.
Is there really circuitry that specifically increases current? I always just assumed that If your amp increases the voltage to, say 20v and you had 4 ohm speakers, the current would be 5 amps unless there were current-limiting circuits to prevent the amp from burning up. If you had a 20v signal and a 4 ohm load, but somehow ended up with more than 5 amps of current, wouldn't you be arrested for violating ohms law?
Your understanding is basically correct. The reason why we talk about current gain in amplifiers, is that the output stage is designed to be able to conduct a large amount of current, if the speaker draws it. The output stage is driven by circuitry which provides only milliamps of current, then the output devices can multiply that to many amperes as demanded by the speaker.
@@marianneoelund2940 Current is a product of voltage and impedance and is not changed, amplified, or multiplied on its own. Paul is following the saying, if you cant intrigue with intelligence then baffle with bullshit.
What if I have a 2 V 1 mOhm 2000 amps speaker ? Seriously, you're talking about speakers, but some of us sometimes need to, for example, add current to a simple TTL squarewave, not only to listen music.
Paul, first of all great job, keep it up. I appreciate how difficult it is to simplify topics to make them accessible to a wider audience. My understanding of current vs voltage amplifiers somewhat differs from yours. My understanding is that a voltage amplifier amplifies voltage therefore voltage is the primary parameter imposed to the load. As such the current load is given by I=V/Z (current = voltage/load impedance). In a current amplifier current is amplified. In this case current is the primary parameter imposed to the load. as such, the voltage at the load terminals is V=Z*I. In control theory for instruments we use current loops quite a bit because such signals are not as affected by interference as well as impacted by cable impedance (voltage drop). In a speaker I am not sure why you would use a current amplifier and in fact it would make a speaker resonance much worse (remember, voltage at the speaker terminal need to go up as we want to feed the same current in a load that is going up in impedance as a result of the cone resonance characteristics).
Paul interprets the question as it was about the different stages within a power amplifier. There you have a voltage amplification stage and a current or power stage. But I think the question was different. About voltage and current amplifiers. Some reasons for a current amplifier: - An electrodynamic driver is driven by current (as we all learned at high school, electrodynamic motors are driven by current, not by voltage, power or charge). So the output (in SPL) is direct related to current (SPL ≈ F = BL x I). - Lower distortion, all distortions related to impedances, changes and modulation of impedances ('current distortion') are eliminated. Especially the midrange distortion and the intermodulation distortion by low frequencies, is lowered. - A stable frequency response. Electric damping, for example, is influenced by impedances, changes and modulation of impedances (for example by temperature, excursion, current, cone movements and even sound). So the frequency response is not effected by those changes or by changing the speaker cable and there is also no power compression. Damping of the resonance you can do in other and much better (stable) ways (in the driver, in or with the enclosure, in the crossover or with EQ). - More high frequency output. Although with a current amplifier you have to compensate for a raised on-axis response by the horn effect and break up of the driver.
Yea, Paul keeps using the term "current amplifier" incorrectly and it is leading to a lot of confusion. I can understand that he is trying to simplify things by not discussing output impedance; but, he needs to find a simplified term that doesn't overlap with a preexisting and well defined term.
@@Paulmcgowanpsaudio Nice. Looking forward to that Jazz album. Let's hope it's not into the 40+ bucks range; the vinyl revival has done enough damage already.
@@QoraxAudio Well, unfortunately, because of our goals of producing ultra perfect vinyl, this will be released as a two-disc set on virgin vinyl at 45 rpm and only from a single master. That's expensive and it's likely to be more like $60.
@@Paulmcgowanpsaudio That's a pity, because I think most people will probably be fine with spending twice the money for a high quality record compared to an average record, but three times the price is a step too far for most.
I had to check out psaudio.com. Clicked on products, then music, then on the discs. I was impressed how good the performances were. The piano playing in particular was excellent.
If you have high voltage and low resistance you will get high current. So my guess is that there is some impedance involved on the voltage amplifier stage and in the current amplification stage has close to zero impedance.
A little confusing. Maybe better to say that typically all power amplifiers have a (voltage) gain stage that drives the output stage that typically has little to no voltage gain. It is that output stage that has to drive the low impedance speaker loads. The so called current amplifiers are just capable of driving excessively low speaker loads, like in the 2 ohm range.
That rack of modular synthesizer, i wonder if it’s behringer or moog lol. A moog of that size from the 70s would be the price of a new full ps audio system, but I haven’t seen a Behringer rack that big yet.
You may find this interesting that in 2014 Moog made 5 copies of Keith Emerson's setup ,don't know the cost but all sold. ua-cam.com/video/qz4Iko0tRiY/v-deo.html
Lee Kumiega I remember those being more than a hundred and fifty thousand dollars!! A Behringer setup like Paul’s (if it is so) might cost 3-7k. Looking more closely, it’s more than likely moog mixed with some diy.
volt × amp = watts The amplifier follows ohm's law! To make a motor run faster or a light bulb to shine brighter we need more volts. But also more amp. I do not think it is so easy to amplify the amp! Amp comes from power supply. If you have a 50volt transformer and 10 amp. If you take and regulate 50 volts to 25 volts then you have 20 amp! Most amplifiers do not output more than the transformer provides. If it gives 50 volts then you do not get more volts out to the speaker than that!
@@ford1546 It isn't the language. Your statements are factually wrong in any language. There are voltage sources and there are current sources. A voltage source outputs a defined voltage and the current varies with the load. A current source outputs a defined current and the voltage varies with the load. Either way, the output impedance of the source determines how much power output is possible. That much said, Paul's use of the term "current amplifier" is wrong. What he really means is low impedance output voltage amplifier so that it can source high current.
Isn’t voltage a measure of electrical potential? And current is the flow of the electrons coming from this potential when you complete a circuit through a given resistance, the overall result of which is power? If this is true, how does the premise of a voltage amplifier versus a current amplifier make sense? They are two parts of an equation. Don’t amplifiers amplify the voltage and handle the amount of current depending on he resistance? Do they amplify the current instead?
Any audio amplifier you're likely to encounter is designed to produce an output voltage proportional to the input voltage. When connected to a speaker load, the speaker sets the amount of current. We do talk about amplifier output stages as current-amplification stages (because they are controlled by much smaller currents than they send to the load), but it isn't the amplifier which decides how much current to put out; its job is just to control voltage. It's possible to design amplifiers which push current to the load, which is proportional to the input voltage. They're rarely useful in audio applications, though. We use them in applications like flight controls, to drive electro-hydraulic valves for example, where the response is specified as a function of current.
It's possible to design amplifiers which push current to the load, which is proportional to the input voltage. They're very useful in audio applications, to drive loudspeaker drivers, where the response is specified as a function of current (SPL ≈ a, F = m x a, F = BL x I).
@@JerryRutten My thoughts exactly. A speaker's impedance varies with frequency. That would represent a distortion of a voltage signal where the magnetic field differed by voltage at different frequencies. But for a transconductance amplifier, the current and therefore the magnetic field driving the speaker would always be a linear function of the source voltage.
@@timharig It is amazing (or even idiotic) that aren't far more current-drive amplifiers around. Especially because of the heavy modulations of the voice coil resistance, voice coil inductance and back-emf voltage, which all distort and/or compress the sound, disturb passive crossovers and power amplifiers. It seems that amplifier designers don't have a clue how drivers work, and that (a lot of) driver designers don't know you can build other type of amplifiers. And I think that Chris Brunhaver should discuss the subjects related to loudspeakers, power amplifiers and related topics, Paul is fundamental wrong on the different topics.
I was one of the first purchasers of the first release from Octave records "Out of Thin Air". I did not care for the recording method one bit. It was more a recording of the room characteristics and not that of the piano, itself. The microphone needs to be close miked. I want to hear the instruments themselves, not the recording space with a piano in the background. Very disappointed.
Well yes but amplifies very in current output for instance you could have two amplifiers 1 at 70 Watts 1 at 75W one has 13 amps of output power the other one has 19 amps about put power a high voltage output means nothing needs to be in the other way. What is the current output of a Stella amplifier?
With all due respect, I would delete this video. The reason you use a current amplifiers is SAFETY!!! @ 4:59 you misspeak and conflate power with current. You cannot “need” voltage AND power when voltage is on the same side of the equation as the current. P(power) = V(voltage) x I(amps) @ 5:52 you imply that the output from the preamp is "large" then the current amp makes it “powerful.” This is incorrect. I have a $10 bill that says none of your preamps output more than +1.228 Volts nominal (+4), or +0.447 Volts nominal (-10). Not the 30~40 volts mentioned @ 3:25 I drive my woofers @ ~70 volts when I'm hammering them. en.wikipedia.org/wiki/Line_level I don't even need to go to your website to know this. Frankly you should have caught yourself at this point and re-thought the video. Surely you know the output voltage of preamps you build? BTW The mixing console behind you is a +4 device. God only knows what the Rhodes piano (to your left) is. I have seen wild variations over the years, largely dependent on the amount of beer dumped in to the damn things. There is no denying that Rhodes sound though. Think you can not make power with high voltage? How do you think the power company supplies entire city blocks with power from a primary line the size of your little finger? Hint: High voltage low current. That primary line is either at the top of the pole, or underground. Years ago I worked as a lineman, you cannot make grounding errors, ever. You don't get a hum, you get an explosion. With voltage amplifiers, the trade off is the need for massive amounts of insulation to prevent injury and/or death. You can make a voltage amplifier generate power. For instance, in a microwave oven you need high voltage. There is no way to get the magnetron to develop the frequencies needed, without voltage. All the current in the world will not work. Consequently it's all about voltage step up. A cheap 1500 watt microwave oven will often weigh less than a 250 watt audio power amp of decent quality. To be fair I'm sure there are some class D amps that may weigh less. Lets be real, those are a crime against humanity. If you were to drive a speaker with high voltage, the connectors would have to be very far apart to prevent arcing. The flux loss for having thick varnish on the speaker coil wire would large, as there would be fewer windings in a given geometric volume This would also apply to the internal connections of the actual components caps, resistors coils, transistors, and etc. Say you're rocking hard to a RUSH (RIP Neil) song and your infant crawls behind the speaker, bumps the exposed connectors. POOF, there is a cloud of smoke shaped like your child. This is why we don't use high voltage in AUDIO power amplification, as the frequencies are low enough. With current amplifiers, the trade off is mass. Meaning larger discrete components, heavier complete products, and infants that stay alive. Unless of course you drop the amp on the infant, in which case gravity is the enemy, not the electrical potential. This not trolling, and I do greatly respect your work. I feel as though your scope was too narrow, if you have looked out to other applications of “power,” beyond audio, then I think you would have seen this. I field phone calls from “engineers” daily At some point in the conversations they will say something along the lines of “Well you understand I am an engineer.” I reply, “I'm sorry.” They will then say, “I said I'm an engineer.” I then reply, “Yes I heard you, I'm sorry.” With respect and a touch of sarcasm, Don Edit: Had a loose quotation mark in there.
this is the audio equivalent to an English teacher going on a 10 paragraph tirade about someone mis-using "there", "they're", and "their" - when it was just a typo all along.
Whilst a stand alone preamp might only output 1.228 volts ,the front end of the power amp to which the preamp is connected will indeed boost that voltage. Hence, voltage amplification. This could easily reach say 10 volts, which then needs converting to low impedance at the output stage of the amp. Hence, current amplification.
Agree, this is really misleading. This is high school physics. All audio amps are voltage amps as the voltage is what defines your audio signal level. And all audio amps have some level of power output, even it is quite tiny for a pre-amp. The term "power amp" is alright although such an amp is also a voltage amp, cause power is energy/time and a passive speaker is essentially turning electric energy from the power amp into acoustical energy (and heat). The term "current amp" is plain misleading for audio products.
I don't agree ( I am also an EE) there's no such thing as a "voltage amplifier" or "current amplifier". All amplifiers are power amplifiers. Power Pain = Pout/Pin, expressed in db it is 10log( Po/Pin) talking about one of your power amps as an amplifier with 30 dB gain is silly. If the input impedance is 47K, and the output impedance if 8 ohms, and the input is 1 V, and the output is 30V, the gain is NOT 30 dB, it is 58.2 dB (10 log (Po/Pin) ) anything else is just nonsense.
All power amplifiers are power amplifiers. But a power amplifier can control (via negative feedback, as you should know as an EE) the voltage or the current, which changes the output impedance. Zo ≪ Zload: voltage-control or voltage-drive Zo ≈ Zload: power drive (no or very low feedback) Zo ≫ Zload: current-control or current-drive And talking about power is silly, because the force in an electrodynamic driver is created by current (F = BL x I). SPL is linear related to current, power is linear related to sound power (SWL) and sound particle velocity (SVL) is (backward!) linear related to voltage (an (electrodynamic) microphone generates voltage). You hear the sound pressure (SPL), not the sound particle velocity (SVL) and not the sound power (SWL). And being an EE is not an argument, especially when you don't have also a degree in electrodynamics, acoustics and/or loudspeaker design. There are more people around here being an EE...
The marketing behind the terms typically infers the power supplies ability to keep stability at a given speaker load. And minimize vdroop at high output volumes and/or drive low impedence loads like 2 ohms. In technical terms it really should be line level verses speaker level as you mention. But.. Buzzwords sell product.
You are right! Voltage doesn't drive loudspeakers. Current (moving charge) drives electrodynamic loudspeakers, (static) charge (the integral of current) drives electrostatic loudspeakers. On the other hand, voltage is generated by microphones, and by electrodynamic loudspeakers! There seem to be people around which do like the distortion of the voltage feedback of loudspeakers and call it 'electric damping', other people don't like that and call it loudspeaker reactance and current distortion!
@@jamesplotkin4674 I've always found it helps me to understand the flow of electricity by comparing it to hydraulics. I think a good way to think about it is that the pipe is like an electrical wire, which has low, but not zero, resistance. A constriction of the flow in the pipe (a narrowing or a partially open valve) is like a resistor. Water pressure is directly analogous to voltage. Water flow (volume) is directly analogous to current. Even concepts like Ohms Law work properly using pressure, volume of flow, and constrictions.
this is a stupid answer. you need a voltage amplifier because of the impedance curve of a loudspeaker, which 99% of the time is not a straight line. with a current amplifier, the amount of amplification is antiproportional to the resistance/impedance, that’s ohm’s law. in a voltage amplifier, the resistance (almost) doesnt have any effect on the amplification.
As always, your Q&A causes me to think, read and learn.
You answered correctly and it helped me learn.
I think the questioner may have been enquiring about Current source vs Voltage source amps.
It comes up in Nelson's First Watt discussions as he has a couple of current source amps (the F1 & F2). They work well only with a small subset of speakers, but when they do, they work very well.
The guy from Atmosphere described it as:
"A current source amplifier has a very high output impedance- usually multiples of the speaker impedance.
A voltage source amplifier has a low output impedance, usually a small fraction of the speaker impedance."
You keep teasing us with that Modular Moog. We need a tour!
2:49 beginning of explanation
I've wondered about this issue myself, but the video didn't really address the question. Conventionally, the way we all use electrical devices is that the power supply (e.g. the utility company) does its best to control the voltage and always maintain it to their spec. The devices that consume power are all wired in parallel; each of them is designed for a fixed voltage, and is free to choose how much current to take. However, in some weird alternate universe (but using the same laws of physics that we already have), the power supplier could be in control of the current and do its best to always maintain the current flow at a constant level, at its spec. Then, all of the power-consuming devices would be wired in series. Each of the power-consuming devices would be designed for a fixed current, and would be free to choose how much voltage to take. Each device's on/off switch would be wired as a shunt across the device. If you look at a lab power supply, it has knobs for both a voltage limit and a current limit. It is able to do either style of operation.
Back to the world of audio power amplifiers, I consider a voltage amplifier to be one where the output voltage to the speaker is proportional to the line-level input voltage, and the speaker decides how many amps to consume. Speaker impedances are different at different frequencies. If you pick a frequency where the speaker impedance is low, you'll get more current and thus *more* power sent to the speaker at that frequency.
An audio amplifier designed as a current amp would operate so that the output *current* sent to the speaker is proportional to the line-level input voltage. The speaker would then decide how many volts to consume. If you picked a frequency where the speaker impedance is low, you'll get lower voltage and thus *less* power sent to the speaker at that frequency. The possible advantage to this style of operation is that the magnetic field strength, I believe, is proportional to the current, not the voltage. So, if the speaker was designed to work in this manner, you'd have a more linear relationship of sound pressure to the line-level input of the amplifier.
So really, the central question that I have is whether speakers are primarily designed for (a) the amplifier to control the voltage and the speaker to control the current, or (b) the amplifier to control the current and the speaker to control the voltage.
(a)
You could build an amplifier that does (b), but with most speakers, you would get a huge frequency response peak at the speaker's resonant frequency (frequencies).
Take a quick reading about this www.current-drive.info/
The question was about voltage-feedback amplifiers versus current-feedback amplifiers. We all know that audio amplifiers need both voltage and current gain, but that wasn't the question.
The most fundamental reason why amplifiers are designed to control output voltage, is that's what loudspeakers are designed for. Speaker designers try to make the frequency response flat, when the speaker receives a constant voltage.
Amplifiers can certainly be designed to control their output current, i.e., make it follow the input signal voltage. At very low frequencies, this can be used to reduce woofer distortion, but there are several problems with current-output amplifiers:
1. They don't like open-circuit loads. If a speaker isn't connected, the output voltage goes very high.
2. They push far more power into speakers at frequencies where the impedance goes up, and put less power into low-impedance speakers (or combinations of speakers in parallel). Since all speakers have at least one (two if a ported design) impedance peaks in the bass region, this tends to play havoc with the low-end frequency response.
3. They won't damp a speaker's tendency to ring after transients: Damping factor approaches zero.
Amplifiers have been built which control to current at low frequencies, and fade over to voltage control at higher frequencies. But these need to be customized to work with particular speakers.
I think you're right about the original question! But I like to rephrase the rest of your reaction...
The most fundamental reason why amplifiers should control output current, is that's how an electro-dynamic driver works. The output of a driver (SPL) is direct related to the current through the voice coil, and that relation is defined by the force factor (F = BL x I). Speaker designers try to make the frequency response flat. But if you drive a driver with voltage, all irregularities in the impedance translate to irregularities in the frequency response, and the increase in impedance at high and low frequencies makes the frequency response roll off at both ends (makes the response more rounded than flat), although the upper response on-axis is somewhat compensated by the horn effect and the break up at high frequencies.
Amplifiers can certainly be designed to control their output current, i.e., make it follow the input signal voltage. This will eliminate all types of distortion which are related to impedances (which Klippel, the expert on driver and loudspeaker measurements, calls ‘current distortion’). Especially the midrange distortion and the intermodulation distortion by low frequencies, is lowered.
There are several problems with voltage-output amplifiers:
1. They don't like low impedances and short-circuit. If there is a low impedance or a short circuit, the output current goes very high.
2. They push far more power into speakers at frequencies where the impedance goes down, and put less power into high-impedance speakers (or combinations of speakers in series). Since all speakers have at least one (two if a ported design) impedance dips, one in the midrange and one in the bass region (if a ported design), this tends to play havoc especially with the mid range frequency response.
3. The damping of a driver is very dependent on impedances and changes in impedances: voice coil resistance, temperature modulation, inductance and current modulation of the inductance and the impedance of the crossover filters: The actual damping is unstable and so is the response at resonance, which is problematic especially for ported designs. But there are other and better ways to control the resonance: in the driver, in or with the enclosure, electronically in the crossover or with EQ.
Saying an amp is "high current" is more or less a marketing thing. Though in practice it means an amplifier may be more stable at loads much lower than 8 or 4 ohms. And that its power supply is capable of delivering enough current that it is under stressed in typical loads. That is really all it means.
With audio, probably the most common use of a current amplifier (AKA a Transconductance amplifier) is inductive loops used to provide clean audio direct to hearing aids. In that application you have a loop of a small number of turns of wire (2 or 3 maybe), which may be over many square meters. With such coils, it's the current that produces the magnetic fields. For the same reason as Paul talks about voltage amplifiers also amplifying current, you can use a voltage amplifier to drive a loop, but because the impedance of the loop is much lower than that of a speaker, you are likely to blow fuses, or trigger the amplifier protection circuit quite a lot. For this reason, you can get transconductance amplifiers designed for induction loops, that generate current in preference to voltage, and more importantly the current is proportional to the input voltage, so you get less distortion.
Tought this would be voltage mode vs current mode amplification like for example questyle uses in their amps and daps. Like the cma800r headphone amplifier amplifiea the aignal in current domain.
Current amplification or voltage amplification to do work depends on the load or resistance. Actually impedance is more relevant in this case. Speakers are a wacky reactive load and dip and peak all over the spectrum of sound frequencies. I wish more speaker companies would publish impedance curves, 8 ohms nominal (average) is kind of useless.
That's why I love Dayton Audio, even if they're meant more for vehicles than hifi. Every one of their models has a datasheet that includes an impedance chart, not to mention full physical size diagram. Extremely useful, since they make many with same nominal impedence but the charts are very different, some flatter and some more bass-y.
While the output stage of a power amp increases the current, it has a very low output impedance (fraction of an ohm). That makes it a voltage source and not a current source. That's very important because a current source cannot properly drive an electromagnetic loudspeaker. In most cases the final stage is some form of voltage follower where the voltage gain is virtually unity but can drive many amps into a speaker load.
Not quite. Evey amplifier can be alternately viewed as a voltage source in series with an impedance (Thevenin equivilent) or as a current source in parallel with an impedance (Norton equivilent). So no, the value of the impedance does not make that distinction.
The output impedance determines the power ceiling for the amplifier. If you view it as a voltage source then the output impedance acts as a voltage divider with the load. Attempting to draw too much current causes a greater portion of the voltage across the output impedance and the voltage across the load drops, preventing it from creating more current.
If you view it as a current source than it acts as a current divider. If the load requires the voltage to be too high, then the parallel impedance will shunt the current, limiting how much voltage the load can drive.
So in either case, the power is limited. An emitter-follower is used because it has a very low output impedance and can therefore support very high power output.
Strictly speaking, Paul's use of the term power amplifier IS incorrect. What really makes the an amplifier a voltage amplifier or a current amplifier is in what respect the gain is measured.
A voltage amplifier would output a voltage as some factor of the input voltage, regardless of input current. A current amplifier would output a current as some factor of the input current, regardless of voltage. You can also have a trasconductance amplifier that outputs a current as a factor of the input voltage and a transimpedance amplifier that outputs a voltage that is a factor of the input current.
So, since he always references the signal as a voltage, all of his amplifiers are really voltage amplifiers. For a given input, the given output will have a given voltage. The current varies based on the impedance of the speakers. But using the term "current amplifier" as he does, albeit incorrectly, does drive home the point that the final power output must be able to source a more significant amount of current than the initial voltage gain stage which is likely a common-emitter amplifier, likely with a kilo-ohms or two of output impedance.
I interpret the question about voltage and current amplifiers, not amplification stages within a power amplifier. And I would like to see Chris answering that question!
This is a very poor and incorrect explanation. Audio amplifiers amplify voltage. It is highly misleading to say amplifiers amplify current. The output power of an amplifier is Watts = current X volts. The current an amplifier can deliver is determined by the components and design of the output stage and power supply. Draw too much current and the voltage will collapse and this defines the power rating of the amplifier. An amplifier with hefty output transistors and a substantial power supply is able to deliver a voltage at higher current than a lesser amplifier. The hefty amplifier does not “amplify” current, it is simply able to have higher current dragged out of it. This explanation is totally confusing as it does not explain Ohm’s Law, the relationship between voltage, current and resistance.
Thank you, I think your explanation is more clear
dtemp132 Paul’s attempted explanation implies that there are two different types of amplifier and you have a choice. This is wrong. Another way of looking at it.... as the volume control is turned up so the voltage to the speaker increases and it sounds louder. The speaker has a low impedance so draws a substantial current from the amplifier. Keep turning up the volume and the voltage and current rises but there will be a point where the amplifier cannot supply enough current to deliver the higher voltage. This limit depends on the design of the output stage and its power rating. The beefier the output stage the higher current it can deliver and the more Watts available.
I think you misunderstood the question. Current-drive amps are not as common.
The question was why they're not common but all you did was explain the different stages of a normal voltage-drive amplifier.
Do you know of an amp with no voltage gain before the current stage?
I agree he didn't answer the question!
@@oysteinsoreide4323 Yes.
Paul uses the term current amplifier incorrectly. What he really means is a low impedance voltage amplifier that is capable of supplying high current. But he sets the voltage gain, not the current gain. So the current is ultimately determined be the speaker load.
In reality, a current gain doesn't mean that there is no increase in the voltage. What it means is that the gain is measured by output current, and the voltage is determined by the load.
You have current amplifiers which output a specific current as a product of the input current and you have transconductance amplifiers which output current as a product of the input voltage.
I agree. It would seem logical to use a transconductance amplifier on the output stage since the magnetic coils that are being driven are ultimately controlled by current instead of voltage. I think that is the rationality behind the original question.
This explains alot. I wonder why other than a few manufacturers more dont produce a hybrid amp with tubes in the pre-amp (section) and transistors in the power amp (section).
We use current amplifiers a lot for digital signalling. For example when we want to drive lots of digital inputs beyond the fanout of a single digital output, the current amplifiers provides the necessary power required to drive the inputs. The voltage at digital inputs is the equivalent logic signalling voltage of the original digital output. They are often called buffers.
So does power amp equal current amp? Because I found a power amp but it’s rated 500watts.
The question to this answer could have been: Explain power amplification without Ohm's law.
He isn't an engineer. Don't expect him to know what ohm's law is.
Is Globalnet for the Powerplants ever comming back? I bought a new Powerplant in 2018 and never had the opportunity to use it. It's been down for a couple of years now.
I'm definitely no expert and still learning, but I literally laughed out-loud when you read the question because it has to be about the 23rd time you have covered this topic! ha ha
I haven't seen the others; but, this explanation is:
1. Wrong.
2. Doesn't answer the question that was asked.
Both problems arise from Paul's incorrect use of the term "current amplifier." I assume he is doing that in an attempt to simply explanations; but, it is confusing and in this instance led to answering the wrong question.
What Paul is referring to is simply an output voltage amplifier that has a very low impedance.
A current amplifier or transconductance amplifier has an output current that is a factor of the gain and the output voltage is determined by the speaker impedance.
This question asked why transconductance power amplifiers are not more common. They make logical sense. Speakers are driven by electromagnets. Magnetic fields are dependent on current, not voltage. So it makes sense to drive what is actually driving the speakers -- especially since speaker impedance varies with frequency.
Is there really circuitry that specifically increases current? I always just assumed that If your amp increases the voltage to, say 20v and you had 4 ohm speakers, the current would be 5 amps unless there were current-limiting circuits to prevent the amp from burning up. If you had a 20v signal and a 4 ohm load, but somehow ended up with more than 5 amps of current, wouldn't you be arrested for violating ohms law?
Yes. In a purely resistive circuit. But we are dealing with inductive loads so no violation of ohms law. The impedance is changing.
Your understanding is basically correct.
The reason why we talk about current gain in amplifiers, is that the output stage is designed to be able to conduct a large amount of current, if the speaker draws it. The output stage is driven by circuitry which provides only milliamps of current, then the output devices can multiply that to many amperes as demanded by the speaker.
@@marianneoelund2940 Current is a product of voltage and impedance and is not changed, amplified, or multiplied on its own. Paul is following the saying, if you cant intrigue with intelligence then baffle with bullshit.
I had to pause the vacuum tube video to come here and straighten this out.
What if I have a 2 V 1 mOhm 2000 amps speaker ?
Seriously, you're talking about speakers, but some of us sometimes need to, for example, add current to a simple TTL squarewave, not only to listen music.
Thank You Paul. That was the Best explanation.💯👍✌️
Paul, first of all great job, keep it up. I appreciate how difficult it is to simplify topics to make them accessible to a wider audience. My understanding of current vs voltage amplifiers somewhat differs from yours. My understanding is that a voltage amplifier amplifies voltage therefore voltage is the primary parameter imposed to the load. As such the current load is given by I=V/Z (current = voltage/load impedance). In a current amplifier current is amplified. In this case current is the primary parameter imposed to the load. as such, the voltage at the load terminals is V=Z*I. In control theory for instruments we use current loops quite a bit because such signals are not as affected by interference as well as impacted by cable impedance (voltage drop). In a speaker I am not sure why you would use a current amplifier and in fact it would make a speaker resonance much worse (remember, voltage at the speaker terminal need to go up as we want to feed the same current in a load that is going up in impedance as a result of the cone resonance characteristics).
Paul interprets the question as it was about the different stages within a power amplifier. There you have a voltage amplification stage and a current or power stage.
But I think the question was different. About voltage and current amplifiers.
Some reasons for a current amplifier:
- An electrodynamic driver is driven by current (as we all learned at high school, electrodynamic motors are driven by current, not by voltage, power or charge). So the output (in SPL) is direct related to current (SPL ≈ F = BL x I).
- Lower distortion, all distortions related to impedances, changes and modulation of impedances ('current distortion') are eliminated. Especially the midrange distortion and the intermodulation distortion by low frequencies, is lowered.
- A stable frequency response. Electric damping, for example, is influenced by impedances, changes and modulation of impedances (for example by temperature, excursion, current, cone movements and even sound). So the frequency response is not effected by those changes or by changing the speaker cable and there is also no power compression. Damping of the resonance you can do in other and much better (stable) ways (in the driver, in or with the enclosure, in the crossover or with EQ).
- More high frequency output. Although with a current amplifier you have to compensate for a raised on-axis response by the horn effect and break up of the driver.
Yea, Paul keeps using the term "current amplifier" incorrectly and it is leading to a lot of confusion. I can understand that he is trying to simplify things by not discussing output impedance; but, he needs to find a simplified term that doesn't overlap with a preexisting and well defined term.
Does Octave records also do analogue releases?
Soon, yes. We are working on vinyl releases fir each of our recordings. They will be 45 rpm virgin vinyl masters.
@@Paulmcgowanpsaudio Nice. Looking forward to that Jazz album.
Let's hope it's not into the 40+ bucks range; the vinyl revival has done enough damage already.
@@QoraxAudio Well, unfortunately, because of our goals of producing ultra perfect vinyl, this will be released as a two-disc set on virgin vinyl at 45 rpm and only from a single master. That's expensive and it's likely to be more like $60.
@@Paulmcgowanpsaudio That's a pity, because I think most people will probably be fine with spending twice the money for a high quality record compared to an average record, but three times the price is a step too far for most.
@@QoraxAudio I agree which is why we limit the run to only 500 copies.
answer starts at 2m50s
You sir deserve a bank balance amplifier
I had to check out psaudio.com.
Clicked on products, then music, then on the discs.
I was impressed how good the performances were.
The piano playing in particular was excellent.
Thanks. Yes, Don Grusin is an amazing talent. Did you have a chance to hear Temporary Circumstances? One of my favorites.
Voltage is one of the two factors of power (along with current). this explanation was very deceiving.
If you have high voltage and low resistance you will get high current. So my guess is that there is some impedance involved on the voltage amplifier stage and in the current amplification stage has close to zero impedance.
A little confusing. Maybe better to say that typically all power amplifiers have a (voltage) gain stage that drives the output stage that typically has little to no voltage gain. It is that output stage that has to drive the low impedance speaker loads. The so called current amplifiers are just capable of driving excessively low speaker loads, like in the 2 ohm range.
Where i can send you the questions ?? :) Thanks :)
Simple description Paul! Great way to describe!!
That rack of modular synthesizer, i wonder if it’s behringer or moog lol. A moog of that size from the 70s would be the price of a new full ps audio system, but I haven’t seen a Behringer rack that big yet.
You may find this interesting that in 2014 Moog made 5 copies of Keith Emerson's setup ,don't know the cost but all sold. ua-cam.com/video/qz4Iko0tRiY/v-deo.html
Lee Kumiega I remember those being more than a hundred and fifty thousand dollars!! A Behringer setup like Paul’s (if it is so) might cost 3-7k. Looking more closely, it’s more than likely moog mixed with some diy.
Three Bode frequency shifter modules make me think a very authentic looking copy of a Moog Modular.
volt × amp = watts
The amplifier follows ohm's law!
To make a motor run faster or a light bulb to shine brighter we need more volts. But also more amp.
I do not think it is so easy to amplify the amp! Amp comes from power supply.
If you have a 50volt transformer and 10 amp. If you take and regulate 50 volts to 25 volts then you have 20 amp!
Most amplifiers do not output more than the transformer provides. If it gives 50 volts then you do not get more volts out to the speaker than that!
@Lloyd Stout Ok. Not so easy to explain with words. I do not live in an English speaking country and have to use google translate.
@@ford1546 It isn't the language. Your statements are factually wrong in any language.
There are voltage sources and there are current sources. A voltage source outputs a defined voltage and the current varies with the load. A current source outputs a defined current and the voltage varies with the load.
Either way, the output impedance of the source determines how much power output is possible.
That much said, Paul's use of the term "current amplifier" is wrong. What he really means is low impedance output voltage amplifier so that it can source high current.
Isn’t voltage a measure of electrical potential? And current is the flow of the electrons coming from this potential when you complete a circuit through a given resistance, the overall result of which is power? If this is true, how does the premise of a voltage amplifier versus a current amplifier make sense? They are two parts of an equation. Don’t amplifiers amplify the voltage and handle the amount of current depending on he resistance? Do they amplify the current instead?
Any audio amplifier you're likely to encounter is designed to produce an output voltage proportional to the input voltage. When connected to a speaker load, the speaker sets the amount of current.
We do talk about amplifier output stages as current-amplification stages (because they are controlled by much smaller currents than they send to the load), but it isn't the amplifier which decides how much current to put out; its job is just to control voltage.
It's possible to design amplifiers which push current to the load, which is proportional to the input voltage. They're rarely useful in audio applications, though. We use them in applications like flight controls, to drive electro-hydraulic valves for example, where the response is specified as a function of current.
It's possible to design amplifiers which push current to the load, which is proportional to the input voltage. They're very useful in audio applications, to drive loudspeaker drivers, where the response is specified as a function of current (SPL ≈ a, F = m x a, F = BL x I).
Marianne Oelund Thank you!
@@JerryRutten My thoughts exactly. A speaker's impedance varies with frequency. That would represent a distortion of a voltage signal where the magnetic field differed by voltage at different frequencies. But for a transconductance amplifier, the current and therefore the magnetic field driving the speaker would always be a linear function of the source voltage.
@@timharig It is amazing (or even idiotic) that aren't far more current-drive amplifiers around.
Especially because of the heavy modulations of the voice coil resistance, voice coil inductance and back-emf voltage, which all distort and/or compress the sound, disturb passive crossovers and power amplifiers.
It seems that amplifier designers don't have a clue how drivers work, and that (a lot of) driver designers don't know you can build other type of amplifiers. And I think that Chris Brunhaver should discuss the subjects related to loudspeakers, power amplifiers and related topics, Paul is fundamental wrong on the different topics.
I have the Dave Grusin CD Homage to Duke, I reckon it's the best sounding CD I own. I'll have to check out Don Grusin.
I WANT that Moog and the Rhodes.
Emotiva XPA HC - 1 High current Monoblock VS. XPA - DR1 Differential Reference?, Read the specs?
Fantastic explanation Paul...👌
I was one of the first purchasers of the first release from Octave records "Out of Thin Air". I did not care for the recording method one bit. It was more a recording of the room characteristics and not that of the piano, itself. The microphone needs to be close miked. I want to hear the instruments themselves, not the recording space with a piano in the background. Very disappointed.
Currently : E=Mc2
Neil D'Souza More currently: E^2 = (mc^2)^2 + (pc)^2
Thanks Paul
Well yes but amplifies very in current output for instance you could have two amplifiers 1 at 70 Watts 1 at 75W one has 13 amps of output power the other one has 19 amps about put power a high voltage output means nothing needs to be in the other way.
What is the current output of a Stella amplifier?
Mmmm octave studios, please tell me there’s 12 steps to get up to the booth 😂
With all due respect, I would delete this video.
The reason you use a current amplifiers is SAFETY!!!
@ 4:59 you misspeak and conflate power with current. You cannot “need” voltage AND power when voltage is on the same side of the equation as the current.
P(power) = V(voltage) x I(amps)
@ 5:52 you imply that the output from the preamp is "large" then the current amp makes it “powerful.”
This is incorrect. I have a $10 bill that says none of your preamps output more than +1.228 Volts nominal (+4), or +0.447 Volts nominal (-10). Not the 30~40 volts mentioned @ 3:25 I drive my woofers @ ~70 volts when I'm hammering them.
en.wikipedia.org/wiki/Line_level
I don't even need to go to your website to know this. Frankly you should have caught yourself at this point and re-thought the video. Surely you know the output voltage of preamps you build?
BTW The mixing console behind you is a +4 device. God only knows what the Rhodes piano (to your left) is. I have seen wild variations over the years, largely dependent on the amount of beer dumped in to the damn things. There is no denying that Rhodes sound though.
Think you can not make power with high voltage? How do you think the power company supplies entire city blocks with power from a primary line the size of your little finger? Hint: High voltage low current. That primary line is either at the top of the pole, or underground. Years ago I worked as a lineman, you cannot make grounding errors, ever. You don't get a hum, you get an explosion.
With voltage amplifiers, the trade off is the need for massive amounts of insulation to prevent injury and/or death. You can make a voltage amplifier generate power. For instance, in a microwave oven you need high voltage. There is no way to get the magnetron to develop the frequencies needed, without voltage. All the current in the world will not work. Consequently it's all about voltage step up. A cheap 1500 watt microwave oven will often weigh less than a 250 watt audio power amp of decent quality. To be fair I'm sure there are some class D amps that may weigh less. Lets be real, those are a crime against humanity.
If you were to drive a speaker with high voltage, the connectors would have to be very far apart to prevent arcing. The flux loss for having thick varnish on the speaker coil wire would large, as there would be fewer windings in a given geometric volume This would also apply to the internal connections of the actual components caps, resistors coils, transistors, and etc.
Say you're rocking hard to a RUSH (RIP Neil) song and your infant crawls behind the speaker, bumps the exposed connectors. POOF, there is a cloud of smoke shaped like your child. This is why we don't use high voltage in AUDIO power amplification, as the frequencies are low enough.
With current amplifiers, the trade off is mass. Meaning larger discrete components, heavier complete products, and infants that stay alive. Unless of course you drop the amp on the infant, in which case gravity is the enemy, not the electrical potential.
This not trolling, and I do greatly respect your work. I feel as though your scope was too narrow, if you have looked out to other applications of “power,” beyond audio, then I think you would have seen this.
I field phone calls from “engineers” daily At some point in the conversations they will say something along the lines of “Well you understand I am an engineer.”
I reply, “I'm sorry.”
They will then say, “I said I'm an engineer.”
I then reply, “Yes I heard you, I'm sorry.”
With respect and a touch of sarcasm,
Don
Edit: Had a loose quotation mark in there.
ohhh you're THAT guy... im so sorry 😭😭
this is the audio equivalent to an English teacher going on a 10 paragraph tirade about someone mis-using "there", "they're", and "their" - when it was just a typo all along.
PS: he's obviously trying to speak down to the average person who isn't an electrical engineer.
Whilst a stand alone preamp might only output 1.228 volts ,the front end of the power amp to which the preamp is connected will indeed boost that voltage.
Hence, voltage amplification.
This could easily reach say 10 volts, which then needs converting to low impedance at the output stage of the amp.
Hence, current amplification.
Agree, this is really misleading. This is high school physics. All audio amps are voltage amps as the voltage is what defines your audio signal level. And all audio amps have some level of power output, even it is quite tiny for a pre-amp. The term "power amp" is alright although such an amp is also a voltage amp, cause power is energy/time and a passive speaker is essentially turning electric energy from the power amp into acoustical energy (and heat). The term "current amp" is plain misleading for audio products.
Thanks for the explanation!
fantastic
Ya I was like ummm all amps use voltage and current...
And then you watched the video?
the answer starts at 2:50
I don't agree ( I am also an EE) there's no such thing as a "voltage amplifier" or "current amplifier". All amplifiers are power amplifiers. Power Pain = Pout/Pin, expressed in db it is 10log( Po/Pin) talking about one of your power amps as an amplifier with 30 dB gain is silly. If the input impedance is 47K, and the output impedance if 8 ohms, and the input is 1 V, and the output is 30V, the gain is NOT 30 dB, it is 58.2 dB (10 log (Po/Pin) ) anything else is just nonsense.
All power amplifiers are power amplifiers. But a power amplifier can control (via negative feedback, as you should know as an EE) the voltage or the current, which changes the output impedance.
Zo ≪ Zload: voltage-control or voltage-drive
Zo ≈ Zload: power drive (no or very low feedback)
Zo ≫ Zload: current-control or current-drive
And talking about power is silly, because the force in an electrodynamic driver is created by current (F = BL x I). SPL is linear related to current, power is linear related to sound power (SWL) and sound particle velocity (SVL) is (backward!) linear related to voltage (an (electrodynamic) microphone generates voltage). You hear the sound pressure (SPL), not the sound particle velocity (SVL) and not the sound power (SWL).
And being an EE is not an argument, especially when you don't have also a degree in electrodynamics, acoustics and/or loudspeaker design. There are more people around here being an EE...
@@JerryRutten I disagree
Fred Zlotnick That’s your good right! But a missed opportunity. You should dive into some sound engineering.
voltage is cheaper to make, typically used for driving headphones. It can't drive loudspeakers.
The marketing behind the terms typically infers the power supplies ability to keep stability at a given speaker load. And minimize vdroop at high output volumes and/or drive low impedence loads like 2 ohms. In technical terms it really should be line level verses speaker level as you mention. But.. Buzzwords sell product.
You are right! Voltage doesn't drive loudspeakers. Current (moving charge) drives electrodynamic loudspeakers, (static) charge (the integral of current) drives electrostatic loudspeakers.
On the other hand, voltage is generated by microphones, and by electrodynamic loudspeakers! There seem to be people around which do like the distortion of the voltage feedback of loudspeakers and call it 'electric damping', other people don't like that and call it loudspeaker reactance and current distortion!
Toroidal is expensive and heavy
Sounded like he was explaining something to a five year old. But that's about as technical as he gets.
A good question and an abysmal answer. You could have provided more detail and still kept it for the average non technical customer. Shame.
Voltage is like the size of a water pipe.. current is the power required to make to make the water flow through that pipe
Voltage is like pressure. Current is like flow.
Brad Walker That’s better.
@@bradwalker1259 The pipe is the resistor. Voltage controls how far the water exits.
@@jamesplotkin4674 I've always found it helps me to understand the flow of electricity by comparing it to hydraulics. I think a good way to think about it is that the pipe is like an electrical wire, which has low, but not zero, resistance. A constriction of the flow in the pipe (a narrowing or a partially open valve) is like a resistor. Water pressure is directly analogous to voltage. Water flow (volume) is directly analogous to current. Even concepts like Ohms Law work properly using pressure, volume of flow, and constrictions.
@@bradwalker1259 Nice ;-)
Hmmm...
No comments.
this is a stupid answer. you need a voltage amplifier because of the impedance curve of a loudspeaker, which 99% of the time is not a straight line. with a current amplifier, the amount of amplification is antiproportional to the resistance/impedance, that’s ohm’s law. in a voltage amplifier, the resistance (almost) doesnt have any effect on the amplification.
IMHO this wasn't a very good answer and my guess is this isn't even what the person was asking about!
Crazy uncle can't stay on point. Senility isn't pretty.