Hi John! I'm an electrical engineer and former high school, college and vocational electronics teacher. I'm really big on education for this subject, and you make some of the best practical no-nonsense videos. You really are providing a great service for folks who want to learn practical electronics and amplifier theory. I remember hearing you mention that you are reluctant to ask for support from your subscribers, but I'd really like to donate to support your channel. Do you have any methods set up for this, like a PayPal? Maybe Patrion in the future? Thanks for what you do!
Hi John. As I've told you before, I used to watch you on your old channel. It would be interesting to see if some of your old builds are still around / in use, such as the folded horn main speakers or the acrylic sub, along with some of the other topics you used to bring up, the "thinking out of the box" type of stuff you used to do. But what I'd like to see from you is what you can do with a single, generic transistor, such as the lowly 2N3904 or 2N3906, or equivalent. I know you've already covered some basics, but maybe you could come up with some ways to show how to coax relatively high performance (for a low power, gen-purpose unit) and how to optimize the circuit, even if it means adding add in few more passive components. I know a single 2N3904 can be used for a really nice dynamic microphone preamp, and with the addition of another cap, can be turned into an electret microphone preamp.
Hello, that is nice video about Damping factor. All time you are speaking of 8Ohms speakers, but if I want to connect tactile transducer to the amp ant it's a 4 ohm load, like the Earthquake Quake Q10B 1000 watss in max with 4Ohms and Response frequences : 5 Hz à 70 Hz and max amplitude is 50 mm at 22 Hz. Which damping factor do i need in amp to handle tactile transducer well and effectively??? Thank you.
the best amplifiers have a high damping factor before introducing negative feedback... using negative feedback to increase the damping factor produces unpredictable distortions that are difficult to measure with traditional methods. the best amplifiers have the damping factor that does not change with the frequency. these rules apply only for audio engineering purposes ... for hifi at home they are not necessary.
I have a question that is not related to D class amplifiers and damping factor. It's about building a low sensitivity low noise electret microphone for a video camera use. The problem is that the camera in question has no preamplifier settings and everything is controlled by AGC (which is very typical solution on entry level cameras). The camera is also ingeniously paired with very loud preamplifiers, which results very loud distorted audio with almost any typical consumer level electret microphone. Simply put the microphone input is practically f*ked up by a very stupid design flaw as far as I can tell, and rectifying the issue can become either very cost defective or impractical (such as professional level microphones or dedicated audio recorders). This is very unfortunate as the camera excells on its video features. On the other hand, if the microphone signal is attenuated before it gets to the preamplifier stage, in my experience the noise floor increases to unacceptable levels very easily. Therefore I would like to try to build an electret microphone which has relatively low sensitivity (I suppose one needs to find low sensitivity capsules for this) but more importantly, very low noise floor. I've seen some of the videos on YT (mainly on EEVblog) how to achieve this, and I am wondering whether would you have any heads up where from to begin with this kind of project? And thanks for the very resourceful channel, definitely one of the best on audio tech on UA-cam!
No, the gain in the preamplification stage is too high for the power supply rails' voltage. Hence the clipping and high noise floor. Nothing much you can do besides put a resistor or two in series before the input side of the gain stage. I'd just buy a new camera though LOL
Thanks for the reply although it a bit delayed in this particular case:) What I found trough experimenting that some microphones simply have lower noise floor than others. If you buy a cheap one, you often "get what you pay for", and buying a more expensive one will likely just give you "diminishing returns", as usually with everything.
@@outolempinimi5165 it sounded to me as if the noise floor was from the electronics in the camera not the mic itself. Could be wrong though...hope it worked out eventually buddy 🙂
@@daniellyons-kl3ru Yes I have to elaborate a bit. The camera itself has a defect (or a "feature") in this particular case as the AGC sits about 10dB higher than it should. Something probably went wrong with the camera software development and it never got fixed via firmware updates. Despite that, it was possible to get decent results with a microphone with costed about half of the price of the cameras itself. However, because the microphone (with its own power source) was bigger than the camera it kind of defeated the purpose.
@@outolempinimi5165 Auto Gain Control? Meaning software controlled attenuation in the digital domain... Yeah can see why that went wrong then lol. Fun fact.. if you attenuate a signal using all 16 bits IE at 0dB ceiling by -3dB.. that signal is now an 8 bit signal. And the power is reduced by 50%. However, to the non linear human auditory system's perception... this is the equivalent of saying 'turn the TV down ever so slightly'. LOL. Gain reduction should not really be done in the digital/software domain.. or at least not without using very high bit depths IE 32 bit.
Hi John, I like just about every video you make but now that have asked . . . I’m very curious how the new Bluetooth speakers (ie JBL Charge, Bose soundlink mini, etc) can create such an incredible sound out of a very small box/tube. Apart from passive speakers they must also use DSPs. Could one create a similar sound as a DIY project? I found that some Bluetooth modules have some sort of dsp functions but those functions are not (or at least not easily) accessible. I’d love to hear your thoughts on this soon subject.
Subjective question:I have listened to all types of amplifiers (tube, solid state class A and AB, class D), my personal preference is solid state class AB by a wide margin.Do you have a "preferred type" to do most of your listening?You made an interesting comment about negative feedback being almost everywhere (which is true). I still cant figure out why some "audiophiles" are so dead set against it, they claim it is unnatural - but that ain't the case.
Love the vids, I do learn quite a bit. Could you do a video on how to wire up a potentiometer for volume and/or on/off with a BT Amp board? I know there are boards out there with potentiometers included, but would be nice to be able to use existing from an old radio if available.
Hi John - Here's a question for you, please. I'm intrigued by these amazing Class-D amplifiers, and I am thinking of using multiples of these in one speaker. What I mean is . . . one TPA3116 driving a main bass speaker, another driving a mid-range speaker, and another driving a tweeter. So three Class-D amplifiers feeding different speaker drivers in the one speaker housing; Each of the three amplifiers being fed by the output of an active crossover. Does that seem like a good idea / a good project? Do you envisage any issues or problems to be encountered with such a project? Thank you
Q: I just picked up a few lm1875,lm3886,tda7293 to play with, I'm planning on reproducing the experiments you did with testing their outputs with various input voltages. Any other favorite chips you recommend exploring? PS: big fan of your channel between you and Rod Elliot I've learned a lot about amplifiers.
How do.you connect a scope to a class D amp? These usually have a bridge output so you cannot ground one side of the output. I suppose you have an ungrounded input signal so it's all floating.
I have seen many designs incorporating tda7293/tda7294 with 2sc5200 and 2sa 1943 at its output.. can u make a video on the output power and distortion figures. It's cheap but is it any good to use?
Meowwrrr... Just wondering, since (certain) cats can hear up to 85kHz, if there is a way to generate a high frequency call, loud enough to be heard from a cat several hundred yards away (but not humans, who would not like to hear yelling in the middle of the night). My main problem would be the transducer at say 30-40 kHz.
There are a ton of these modules on the market right now. I'm thinking about building a Dayton Audio 2X50 watt amp for a desktop speaker system featuring a pair of old Dynacoustics PS10 bookshelf speakers. That will be way more than I need for the application, but I'm hoping it will give me lots of clean headroom. Have you tested any of these?
Ken, if you want to play with these class-d modules there is a nice website www.diyaudio.com/forums/class-d/ I have a couple of these different boards myself. What I really like are the mono TPA3118D2 boards that cost like 2USD on aliexpress. Remove a resistor to lower the gain and almost no hiss on the output. I actually use this cheap board on a solar panel in the garden when it is nice weather outside. Beats all the BT speakers in sound quality and doesn't cost anything. I've placed a really small heatsink on the IC but even doubt it is necessary. If the weather is crap I can even power these boards from a 5V usb power bank, they have less power but still work.
Damping factor is the ratio of the load impedance to the amplifier's output impedance so changing the load will change the ratio. Lower impedance demands more current from the amplifier and the circuit may not be able to deal with the current and the extra heat.
drabara - To you it might look like a mess but I’m sure John knows where everything is by heart. He’d have to search for things if he would organize his desk. Some brains are wired differently then others. Speaking from experience and or myself.
Thank you all for the answers,i understand what possible causes could be but its old Sony Home Theater System from 2000 :-P and before you say buy new one i will but im interested on what could i do in the meantime to mitigate. I have full schematics and service manual and it looks like amp gain is fixed and volume is controlled by the preamp since volume adjustment does not affect hiss and only mute disables amp chip and hissing goes away. Unfortunately amp chip is some sony in house designed part so no datasheet to adjust its gain. So i would like to see John explain how to make some output filter or something because its common problem and putting resistor in series with speaker destroys frequency response right?(no scope to test it:-( Possibly how to reduce speaker sensitivity?I find this interesting and he is definitely the man to ask.
I can't promise to help, i'm not at all an expert, but i'd be curious to take a look at schematics. However, i suspect there night not be a fix for the noise :( except by complete redesign of the stage in this case.
What does it use for a volume control? Multichannel units from this time were notorious for using PGAs (or source selector + tone control + PGA ICs) of modest to downright poor dynamic range. My parents used to have a mid-2000s Kenwood that was audibly (if acceptably) noisy on speakers and almost unusable on headphones, as the headphone output employed a simple resistor dropper that did not provide enough attenuation for just about any regular headphone.
My front speakers use a transformer and diode bridge for power my sub uses regulated supplies. Why is it at anything over 3/4 volume my sub seems to plateau and the front do not? specs below if interested I built my own 5.1 channel amp TDA 2030 20v rear 8 ohm and center 8 ohm and TDA 7293 front 8 ohm 27v x2 and sub 4 ohm 32v x2 OMG a Catruption! lol
What do you mean by "plateau"? Clipping? What is the efficiency of front and sub speakers, respectively, and is the architecture lightweight (drywall) or massive (brick, concrete)? And why would one use regulated supplies on a sub amp? They're not switch-mode supplies, are they? I sort of suspect either too much of an efficiency delta, or maybe some power supply issues. Hard to tell without a lot more details.
front speakers 92 db crossed over to the amp at 80Hz 6db the sub is rated 96 db (+- 3db) and crossed over at 60 Hz 6 db this helps tune it to the room (I have a very 70 Hz boomy room) changing the sub to flat makes it louder but only because of the huge hump in response it has. with the sub crossed over at 60 Hz its more in the 93 db range the sub is also in a small sealed box good for 28Hz f3 by plateau i mean it dose not sound like it is getting louder it starts to fall behind the front speakers at lower volumes the sub has great response and really out classes the front speakers leading to it being turned down to about 2/3 of sub volume but i would like to know if the it is the power supplies limiting it or what. as to why i used them, all i had at the time. I do plan to change them out as can afford to. when i was making plans i had a 500va 30x2 transformer in mind.
It sounds like the the amps powering each set has a different gain factor, meaning as the source volume goes up, the amplification does not rise linearly between them. I doubt it has anything to do with the power supply.
John, you are in my top 5 utuber's for education and entertainment. Keep up the great videos and thanks!!!!
Happy to see your 4 legged apprentice is still helping you
Hi John! I'm an electrical engineer and former high school, college and vocational electronics teacher. I'm really big on education for this subject, and you make some of the best practical no-nonsense videos. You really are providing a great service for folks who want to learn practical electronics and amplifier theory.
I remember hearing you mention that you are reluctant to ask for support from your subscribers, but I'd really like to donate to support your channel. Do you have any methods set up for this, like a PayPal? Maybe Patrion in the future? Thanks for what you do!
Hi John. As I've told you before, I used to watch you on your old channel. It would be interesting to see if some of your old builds are still around / in use, such as the folded horn main speakers or the acrylic sub, along with some of the other topics you used to bring up, the "thinking out of the box" type of stuff you used to do.
But what I'd like to see from you is what you can do with a single, generic transistor, such as the lowly 2N3904 or 2N3906, or equivalent. I know you've already covered some basics, but maybe you could come up with some ways to show how to coax relatively high performance (for a low power, gen-purpose unit) and how to optimize the circuit, even if it means adding add in few more passive components. I know a single 2N3904 can be used for a really nice dynamic microphone preamp, and with the addition of another cap, can be turned into an electret microphone preamp.
I'd like to see some comparisons in amplifier design between loudspeaker and headphone amplifiers.
Hello, that is nice video about Damping factor. All time you are speaking of 8Ohms speakers, but if I want to connect tactile transducer to the amp ant it's a 4 ohm load, like the Earthquake Quake Q10B 1000 watss in max with 4Ohms and Response frequences : 5 Hz à 70 Hz and
max amplitude is 50 mm at 22 Hz. Which damping factor do i need in amp to handle tactile transducer well and effectively??? Thank you.
the best amplifiers have a high damping factor before introducing negative feedback...
using negative feedback to increase the damping factor produces unpredictable distortions that are difficult to measure with traditional methods.
the best amplifiers have the damping factor that does not change with the frequency.
these rules apply only for audio engineering purposes ... for hifi at home they are not necessary.
I have a question that is not related to D class amplifiers and damping factor. It's about building a low sensitivity low noise electret microphone for a video camera use. The problem is that the camera in question has no preamplifier settings and everything is controlled by AGC (which is very typical solution on entry level cameras). The camera is also ingeniously paired with very loud preamplifiers, which results very loud distorted audio with almost any typical consumer level electret microphone. Simply put the microphone input is practically f*ked up by a very stupid design flaw as far as I can tell, and rectifying the issue can become either very cost defective or impractical (such as professional level microphones or dedicated audio recorders). This is very unfortunate as the camera excells on its video features.
On the other hand, if the microphone signal is attenuated before it gets to the preamplifier stage, in my experience the noise floor increases to unacceptable levels very easily. Therefore I would like to try to build an electret microphone which has relatively low sensitivity (I suppose one needs to find low sensitivity capsules for this) but more importantly, very low noise floor. I've seen some of the videos on YT (mainly on EEVblog) how to achieve this, and I am wondering whether would you have any heads up where from to begin with this kind of project?
And thanks for the very resourceful channel, definitely one of the best on audio tech on UA-cam!
No, the gain in the preamplification stage is too high for the power supply rails' voltage. Hence the clipping and high noise floor.
Nothing much you can do besides put a resistor or two in series before the input side of the gain stage.
I'd just buy a new camera though LOL
Thanks for the reply although it a bit delayed in this particular case:) What I found trough experimenting that some microphones simply have lower noise floor than others. If you buy a cheap one, you often "get what you pay for", and buying a more expensive one will likely just give you "diminishing returns", as usually with everything.
@@outolempinimi5165 it sounded to me as if the noise floor was from the electronics in the camera not the mic itself.
Could be wrong though...hope it worked out eventually buddy 🙂
@@daniellyons-kl3ru Yes I have to elaborate a bit. The camera itself has a defect (or a "feature") in this particular case as the AGC sits about 10dB higher than it should. Something probably went wrong with the camera software development and it never got fixed via firmware updates. Despite that, it was possible to get decent results with a microphone with costed about half of the price of the cameras itself. However, because the microphone (with its own power source) was bigger than the camera it kind of defeated the purpose.
@@outolempinimi5165 Auto Gain Control? Meaning software controlled attenuation in the digital domain... Yeah can see why that went wrong then lol.
Fun fact.. if you attenuate a signal using all 16 bits IE at 0dB ceiling by -3dB.. that signal is now an 8 bit signal. And the power is reduced by 50%.
However, to the non linear human auditory system's perception... this is the equivalent of saying 'turn the TV down ever so slightly'. LOL.
Gain reduction should not really be done in the digital/software domain.. or at least not without using very high bit depths IE 32 bit.
Hi John,
I like just about every video you make but now that have asked . . .
I’m very curious how the new Bluetooth speakers (ie JBL Charge, Bose soundlink mini, etc) can create such an incredible sound out of a very small box/tube. Apart from passive speakers they must also use DSPs. Could one create a similar sound as a DIY project? I found that some Bluetooth modules have some sort of dsp functions but those functions are not (or at least not easily) accessible. I’d love to hear your thoughts on this soon subject.
Subjective question:I have listened to all types of amplifiers (tube, solid state class A and AB, class D), my personal preference is solid state class AB by a wide margin.Do you have a "preferred type" to do most of your listening?You made an interesting comment about negative feedback being almost everywhere (which is true). I still cant figure out why some "audiophiles" are so dead set against it, they claim it is unnatural - but that ain't the case.
Love the vids, I do learn quite a bit. Could you do a video on how to wire up a potentiometer for volume and/or on/off with a BT Amp board? I know there are boards out there with potentiometers included, but would be nice to be able to use existing from an old radio if available.
I do have a video about potentiometers and how to wire them up.
Hi John - Here's a question for you, please.
I'm intrigued by these amazing Class-D amplifiers, and I am thinking of using multiples of these in one speaker.
What I mean is . . . one TPA3116 driving a main bass speaker, another driving a mid-range speaker, and another driving a tweeter.
So three Class-D amplifiers feeding different speaker drivers in the one speaker housing; Each of the three amplifiers being fed by the output of an active crossover.
Does that seem like a good idea / a good project?
Do you envisage any issues or problems to be encountered with such a project?
Thank you
To avoid your camera power problem ,Can you modify your camera to get directly 5 volt from a simple mobile charger or power bank?
Q: I just picked up a few lm1875,lm3886,tda7293 to play with, I'm planning on reproducing the experiments you did with testing their outputs with various input voltages. Any other favorite chips you recommend exploring?
PS: big fan of your channel between you and Rod Elliot I've learned a lot about amplifiers.
Class D amps that run directly off either DC or AC supplies - is there any particular reason why one might be able to perform better than the other?
How do.you connect a scope to a class D amp? These usually have a bridge output so you cannot ground one side of the output. I suppose you have an ungrounded input signal so it's all floating.
I have seen many designs incorporating tda7293/tda7294 with 2sc5200 and 2sa 1943 at its output.. can u make a video on the output power and distortion figures. It's cheap but is it any good to use?
Meowwrrr... Just wondering, since (certain) cats can hear up to 85kHz, if there is a way to generate a high frequency call, loud enough to be heard from a cat several hundred yards away (but not humans, who would not like to hear yelling in the middle of the night). My main problem would be the transducer at say 30-40 kHz.
There are a ton of these modules on the market right now. I'm thinking about building a Dayton Audio 2X50 watt amp for a desktop speaker system featuring a pair of old Dynacoustics PS10 bookshelf speakers. That will be way more than I need for the application, but I'm hoping it will give me lots of clean headroom. Have you tested any of these?
Ken, if you want to play with these class-d modules there is a nice website www.diyaudio.com/forums/class-d/ I have a couple of these different boards myself. What I really like are the mono TPA3118D2 boards that cost like 2USD on aliexpress. Remove a resistor to lower the gain and almost no hiss on the output. I actually use this cheap board on a solar panel in the garden when it is nice weather outside. Beats all the BT speakers in sound quality and doesn't cost anything. I've placed a really small heatsink on the IC but even doubt it is necessary. If the weather is crap I can even power these boards from a 5V usb power bank, they have less power but still work.
Can we still boost the bass in this amplifier??
How come on these board they always use electrolytics when they are not supposed to be good for audio circuits?
Could the damping factor change when you change the load from 8 to 4 ohms?
Why are some amps only rated for use with 8 ohm loads?
Damping factor is the ratio of the load impedance to the amplifier's output impedance so changing the load will change the ratio.
Lower impedance demands more current from the amplifier and the circuit may not be able to deal with the current and the extra heat.
Great video's, just one comment, how do you find your stuff? Organise your desk... Its much nicer to work and make video's from an neat desk...
drabara - it looks like a typical engineering workbench to me.
It's not mess, it's convenience!
drabara - To you it might look like a mess but I’m sure John knows where everything is by heart. He’d have to search for things if he would organize his desk. Some brains are wired differently then others. Speaking from experience and or myself.
You should have seen Jim William's bench!
I know, he was a genius creating in total disorder... also to mislead his competitors...
What is damping factor? Why is it always talked about with high end amps?
Was it just me or at 2:42 did the pencil appear behind the waveform?
Class D amplifier hissing noise and how to mitigate?
Ognjen Čolić if it's plain white noise hiss, it's because of too high gain, and it applies to all amplifier classes
Don't put your preamp on the same power supply as the amplifier.
Thank you all for the answers,i understand what possible causes could be but its old Sony Home Theater System from 2000 :-P and before you say buy new one i will but im interested on what could i do in the meantime to mitigate.
I have full schematics and service manual and it looks like amp gain is fixed and volume is controlled by the preamp since volume adjustment does not affect hiss and only mute disables amp chip and hissing goes away.
Unfortunately amp chip is some sony in house designed part so no datasheet to adjust its gain.
So i would like to see John explain how to make some output filter or something because its common problem and putting resistor in series with speaker destroys frequency response right?(no scope to test it:-(
Possibly how to reduce speaker sensitivity?I find this interesting and he is definitely the man to ask.
I can't promise to help, i'm not at all an expert, but i'd be curious to take a look at schematics. However, i suspect there night not be a fix for the noise :( except by complete redesign of the stage in this case.
What does it use for a volume control? Multichannel units from this time were notorious for using PGAs (or source selector + tone control + PGA ICs) of modest to downright poor dynamic range. My parents used to have a mid-2000s Kenwood that was audibly (if acceptably) noisy on speakers and almost unusable on headphones, as the headphone output employed a simple resistor dropper that did not provide enough attenuation for just about any regular headphone.
hi good job id like to know to calculate damping factor on my tube amp class a thanks
My front speakers use a transformer and diode bridge for power my sub uses regulated supplies. Why is it at anything over 3/4 volume my sub seems to plateau and the front do not? specs below if interested
I built my own 5.1 channel amp TDA 2030 20v rear 8 ohm and center 8 ohm and TDA 7293 front 8 ohm 27v x2 and sub 4 ohm 32v x2
OMG a Catruption! lol
What do you mean by "plateau"? Clipping? What is the efficiency of front and sub speakers, respectively, and is the architecture lightweight (drywall) or massive (brick, concrete)? And why would one use regulated supplies on a sub amp? They're not switch-mode supplies, are they?
I sort of suspect either too much of an efficiency delta, or maybe some power supply issues. Hard to tell without a lot more details.
front speakers 92 db crossed over to the amp at 80Hz 6db the sub is rated 96 db (+- 3db) and crossed over at 60 Hz 6 db this helps tune it to the room (I have a very 70 Hz boomy room) changing the sub to flat makes it louder but only because of the huge hump in response it has. with the sub crossed over at 60 Hz its more in the 93 db range the sub is also in a small sealed box good for 28Hz f3
by plateau i mean it dose not sound like it is getting louder it starts to fall behind the front speakers at lower volumes the sub has great response and really out classes the front speakers leading to it being turned down to about 2/3 of sub volume
but i would like to know if the it is the power supplies limiting it or what. as to why i used them, all i had at the time. I do plan to change them out as can afford to. when i was making plans i had a 500va 30x2 transformer in mind.
It sounds like the the amps powering each set has a different gain factor, meaning as the source volume goes up, the amplification does not rise linearly between them. I doubt it has anything to do with the power supply.
thank you!