Measuring amplifier slew rate - Class AB vs D
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- Опубліковано 31 січ 2024
- All you need to know how to measure amplifier slew rate and what is actually is.
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More testing, more experiments, more fun! - Авто та транспорт
People can talk shit on Facebook all they want. They are not helping the “Inexpensive” SQ community anywhere near as much as you.
This is the most detailed explanation of the slew rate I've heard to this date. And I was wondering if that's why class D sounded so different than AB to the Q community. THANKS FOR THIS.
Thanks mate! Very detail and very educational, thanks again for all the work and sharing to all of us that are interested
That was a great informative learning video. Nice job
I wonder if the amp being designed for 20-20k hz is affecting the squareness of the sign wave when you go beyond 20k? Maybe something in the amp is trying to limit the frequency range?
Think about frequencies above 20k as "headroom". If an amplifier performs very good above 20k, that means it will perform better below 20k.
I always thought they had some sort of filter between 22k and 25k.
I guess you could say that Alpine V12 is a hi-rez amp before hi-rez existed. Lol
(proper) class D amps are designed w/ a very steep low pass filter a little above 20kHz. (for the reasons mentioned in the video starting at 29:00)
Yes! More information!
So, although headroom (having 250W for your mids, but using 10W) might provide a lower THD, but you have a worse slew rate? Would you be better off with clean, lower power amp running at 75% vs a high power amp running at 10%?
One thing I learned while trying to learn how to play guitar is that almost all amps have a certain tone they only achieve by pushing the preamp and then using master volume to “attenuate” overall output.
That is a great question, but that will depend on the amp. In both of your scenarios, you could have identical slew rate🤷
It'd be cool to see if there's an actual difference in S.Q. between Class A/B Vs. Class D amplifiers. Maybe expensive Class A/B vs. expensive Class D? Give both designs the best chance at proving whether that 'myth' can be busted or confirmed? Maybe see how cheap how either design can be made untill performance suffers?
Interesting video very informative, I loved it but I would say It's generally advisable to avoid driving audio amplifiers with signals that approach their limits, especially with continuous full-volume square waves. If you need to test the amplifier's performance or measure its capabilities, it's better to use signals that are within the normal operating range of the amplifier. Additionally, ensure that the amplifier is adequately cooled, and monitor for any signs of distortion or stress on the system. I actualy don't no the specs of the amps so maybe you weren't but just a word of caution' great work....cheers.
Answered my question😂 I thought it would depend frequency, no wonder you tested at 20k
I replaced my old Alpine MRP- 300 class ab with a new Alpine R-A60F R-Series
At first, I didn’t really see a difference in sound quality, so it aggravated me. Knowing that I wasted all my money on a new amplifier for nothing so at that point, I made it up in my head that the class ABB sounded better at higher frequencies.
At this point I’m not really sure anymore. I don’t push the new Alpine amp to its limits so I’m never getting any distortion I think as long as you set your gains properly making sure you’re not feeding too many volts when it comes down to clarity you should be safe at that point .
The rest is just going to rely on tweaking equalizers to your specific needs
This sounds like an improvement to me. You're getting double the power as well as better efficiency.
Why did you multiply the voltage times time for the first amp and divide the voltage by time for the second amp ?
Because for the first amp, the time is in nS, for the second it's in uS .
@@RAW-CAt Real confusing the way you did that. 4.15 uS is just 4150 ns.
@@RAW-CAt I understand that conversion of the time requires multiplication to make its uS , but after you made the units match the first amp had its converted time measurement multiplied by voltage ,but on the second amp you divided voltage by uS
If it's at all possible I'm very curious how the very popular JP and mimimaxx amps from down4sound measure
Unfortunately all the American brands are unobtainable for me.
@@RAW-CAtdownforsound is just Korean amps that’s all. They are very decent but are strictly made for spl
@@julesbruchez-theartofgrapp9646There's no such thing as "just Korean".
just like class AB, class D amps can measure 'perfect' depending on their architecture/design.
it basically boils down to price range (the entry level got way better over the last decade) w/ 'top of the line' always being 'over achievers' (doing more than is really needed for a lot of extra $:} ).
ps: ABX testing should be fun...
i'm very skeptical of claims coming from 'golden ears' simply because there's Zero data to back up the claims.
there are indeed 'freak instances' where ppl can hear even ultrasounds and be bothered by it, but it's a relatively rare occurrence.
for most ppl 30 yrs old anything above 15-16kHz is silence...
Any new feedback on class a/b versus class d ? I’m a believer that class d “higher end” amps can sound just as clean, but if I’m wrong I’ll respect it
The more I look into amps, the less I differentiate between the classes.. Good amps perform good, bad amps perform bad. Regardless of the class.
@@RAW-CAt much love Cat thank you 🙏
You used a square wave? To test it?
Yes, a square wave is the only way how you can measure an amplifiers slew rate.
FUN FUN FUN
MRV-F900 is top of V12 :)
Yes it is, beast of an amp😎
Class D: The RC-filter visibly drops the slew rate. I was waiting for you to test without the filter, but no
I will figure it out, just give me some time🙃
@@RAW-CAt Probably the @thulinp is right and you used a too powerful low pass RC filter, you can verify it by measuring the impact on the sinevawe for the same frequence (20KHz in that case). RC filter you used is a single pole and has 6dB roll off per octave and may affect the 20KHz signal in your setup significantly. Take a measure without any filter.
Power amplifiers have some RC filters at input so to feed it with a pure square wave in theory should be OK .
First lol
We call it slew rate, but it is actually simply clipping. But what is clipping is the current into the dominant pole capacitor. Think of it this way and all the mystery disappears.
I'm sorry, but you are not right. Clipping is increase of harmonics content because of power supply "bottoming out", whereas slew rate is simply a measure of how an fast an amplifier can increase it's output voltage. A square wave and a clipped sine might look similar but it's not the same thing.
@@RAW-CAt try again. I am right. You need to think in the domain of current into a capacitor.
No, 'Slew Rate' is NOT 'Clipping. Slew rate and clipping are not directly connected, but there can be an indirect relationship. In amplifiers with lower slew rates, fast-changing signals may not be accurately reproduced, and this limitation can contribute to distortion. Fast-changing signals can lead to transient voltage spikes that may cause clipping if the amplifier's response is not fast enough. In summary, while slew rate and clipping are separate characteristics, a higher slew rate can contribute to better handling of fast signal transients, potentially reducing the risk of distortion due to clipping in certain scenarios. It's important to consider both parameters. This video is shows us how to do things properly at home and there is no mystery here, it's very well understood and well explained. And your in the wrong place to discuss "Dominant Pole Capacitors" as it's no fun at all.
@andymouse slew rate limiting absolutely is clipping. The clipping happens when the input stage runs out of current drive to feed the dominant pole capacitor. If you look at the current in this capacitor with an input of high enough frequency and amplitude to cause slew rate limiting you will see a sine wave with flattened peaks.the drive current has limited. The reason it doesn't look like clipping at the output is because you are now looking at voltage which is in quadrature with the capacitor current. Make the measurement.
You read my comment, any more is simply out of context for this video...Cheers.@@donepearce
At 9 minutes. U decided to use a square wave input to compare the 2 designs..YOU JUST HANDICAPPED THE BETTER AMP.in this case..the class ab.. no disrespect.. do the test again with sine wave..and compare the harmonics . Compare bandwidth at different loads. The class ab doesnt care. The class d rolls off the bandwidth with any imp above or below the target freq of the output filter
All of the testing that you are talking about is done with distortion testing. Have a look at a few of my previous videos. There I analyse Harmonics, linearity, frequency response and other things with much more sensitive equipment and on different loads. This video is only about square waves and slew rate.
@@RAW-CAt well i acted like an old drunk
Youre correct.