Hello buddy ol' pal ol' friends
I'm putting my feelers out once again now that I am temporarily located in the Los Angeles area and I am wondering if anyone in CA or the surrounding area is willing to measure one of my DIY amplifiers.
I've been trying to get it measured by a third party for years.
I've never gotten the amplifier in question to produce any visible distortion and the sims suggest obscene levels of low distortion. I would like some third party verification.
Please, thank you, and hugs for all. 🙂
I'm putting my feelers out once again now that I am temporarily located in the Los Angeles area and I am wondering if anyone in CA or the surrounding area is willing to measure one of my DIY amplifiers.
I've been trying to get it measured by a third party for years.
I've never gotten the amplifier in question to produce any visible distortion and the sims suggest obscene levels of low distortion. I would like some third party verification.
Please, thank you, and hugs for all. 🙂
amplifier
We can measure your amplifier with one of our Audio Precision's
Zed Audio Newbury Park CA 40Km N of Los Angeles.
805 499 5559
We can measure your amplifier with one of our Audio Precision's
Zed Audio Newbury Park CA 40Km N of Los Angeles.
805 499 5559
Thanks MOER, I forgot to mention that I'm only willing to do the measurements while being there in-person.
Also that my funds are extremely limited.
@Nigelwright I am not sure what it is you are attempting to say lol.
Also that my funds are extremely limited.
@Nigelwright I am not sure what it is you are attempting to say lol.
Amplifier measurement
OK my name is Steve Mantz
Nigelwright not everyone is attuned to your sense of humour
OK my name is Steve Mantz
Nigelwright not everyone is attuned to your sense of humour
"Anyone willing to measure my amplifier?" and nigelwright7557 said " Yes its 180cm by 100cm by 200cm" , I think it was kind of funny.
Have you considered investing in test equipment? in your case you don't need to invest much, a Focusrite Scarlett 2i2 3rd gen is $150 USD shipped, you also need some cables and connectors and thats it, for software theres a lot of freeware like REW, even ARTA allows you to use all of its functions without a cost, you can use it to measure the basics such as frequency response, noise, THD, THD+N, IMD and so on.
Not as good as an Audio Precision but pretty close.
Not as good as an Audio Precision but pretty close.
Hey Kitty, I'm sorry but I couldn't get past the second sentence. There's something not quite right there ...
Dude, you can totally 'measure' the amp yourself! You could call it, I dunno ... self amp measurement or make it on your own measurement or something ...
Anyhow, I think I might see the issue. It's here:
I've never gotten the amplifier in question to produce any visible distortion and the sims suggest obscene levels of low distortion.
I've been there, that's why it's familiar. It sound's like you're looking at a 'scope at the beginning of the sentence; but then by the end, you sound like you're puzzled that you can't see the low level stuff. That's the stuff that you ONLY get from a spectrum analyzer.
[yes i know it sounds ... dirty. The best my buds and I could cum up with is Rectum Spectralizer® !!11!1! Ouch]
So a 'scope is great to see basic waveform clipping and stuff [setting up a simple class A amp] but the human eye just can't detect the very small, subtle changes to the curve of the side of a sine wave.
So it would be nice if we could somehow switch the small changes into bigger, noticeable changes that the unaided human can see. Somehow change. Somehow transform.
.
.
.
Well, guess what, as it so often starts:
There was once this old white guy who ...
Yep. His name was Prof. Fourier and he was Spanish or something.
What's really cool is he didn't just figure out the math to turn one into the other but something more ... fundamental. As Einstein noticing that a Newtonian gravity field is just another way of looking at curved spacetime; Monsieur Fourier discovered that a complex curvy-wervy waveform IS a combination of many different, simple sine waves. And vise-versa.
So you just need a different instrument, a rectu ... spectrum analyzer!
And you have one! The computer you're typing on. It's just a math program [aren't they all!] that can analyze the waveform and transform it into something more visually discernible.
This all isn't quite right, but it should help demystify your dist. measurement frustration.
We had a guy here who breathed this stuff, Sigh -- we miss him! 😉 [Sy]
Cheers,
Jeff
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Im guessing you are asking about where to get the stuff?
You can buy a Scarlett here Focusrite Scarlett 2i2 3rd Gen 2-In, 2-Out USB Audio Interface
Then just download ARTA and you are ready to go ARTA Software
If you are looking for explanations on the concepts I mentioned in my previous post, just Google THD (Total Harmonic Distortion), IMD (Intermodulation Distortion) and frequency response.
Measuring THD with a Scarlett + ARTA will get you around 0.0004% THD @1KHz and 0.002% THD @ 10 KHz., your amp must be really really good to have better specs than that. Note that these are THD specs and not THD+N which will be considerably higher.
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To be a little more clear, I have a QA401 and victors oscillators along with a distortion amplifier.
I spent years designing the amp specifically to produce cosmic levels of negative feedback without going unstable.
I eventually succeeded and I spent about a year trying to get it to produce distortion trying all manner of direct and indirect methods.
The only time I managed to get distortion to pop up was when the solder was melting off the board from being overdriven so hard.
I did manage to extrapolate in one test that the real life distortion seems to be close to the sims though.
I used the system as an error correction for another system, then I overdrove the other system until the distortion was very close to 0db.
I then applied an adjustable level of feedback to the EC and only got a small portion of the way through the adjustment before the distortion went from near 0db to under the -125db noise floor.
I did a rough calculation on how far down the distortion would go based on how many turns I had left on the feedback pot.
In other words I used the other amplifier to increase the dynamic range of the measurement.
The sims say that the distortion is below -300db to 100khz and the bandwidth is between 20Mhz and 100Mhz depending on parts and implementation.
There is much more I could say but there is no point, I just want to get it verified by a third party.
I spent years designing the amp specifically to produce cosmic levels of negative feedback without going unstable.
I eventually succeeded and I spent about a year trying to get it to produce distortion trying all manner of direct and indirect methods.
The only time I managed to get distortion to pop up was when the solder was melting off the board from being overdriven so hard.
I did manage to extrapolate in one test that the real life distortion seems to be close to the sims though.
I used the system as an error correction for another system, then I overdrove the other system until the distortion was very close to 0db.
I then applied an adjustable level of feedback to the EC and only got a small portion of the way through the adjustment before the distortion went from near 0db to under the -125db noise floor.
I did a rough calculation on how far down the distortion would go based on how many turns I had left on the feedback pot.
In other words I used the other amplifier to increase the dynamic range of the measurement.
The sims say that the distortion is below -300db to 100khz and the bandwidth is between 20Mhz and 100Mhz depending on parts and implementation.
There is much more I could say but there is no point, I just want to get it verified by a third party.
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With the entire entertainment industry being under quarantine, this thread is promising some welcome relief. Off to buy popcorn.
The very low levels of distortion you say your amp has requires a whole ‘nother league of measurement tools and capability. You are on right track with Victors oscillator. You also need the 60dB high gain ultra low distortion amp to amplify your low distortion to measurable levels, then you need a notch filter to attenuate to fundamental 1kHz oscillator. To do this requires a person with the right (expensive) gear and training. Maybe only a handful of people On DIYA capable of actually doing this correctly. Even a AP system doesn’t go that low without the extra doo-dads.
It’s all very academic because if you can’t see the distortion at -130dB levels of amateur audio gear, you probably can’t hear it anyway.
For normal DIY amps with measurable distortion, REW, a sound interface like Scarlett Solo or 2i4 work just fine. Pay attention to proper grounding, shielding, and use batteries for everything. No wall plugs of any kind on test instruments or laptops.
Howto - Distortion Measurements with REW
It’s all very academic because if you can’t see the distortion at -130dB levels of amateur audio gear, you probably can’t hear it anyway.
For normal DIY amps with measurable distortion, REW, a sound interface like Scarlett Solo or 2i4 work just fine. Pay attention to proper grounding, shielding, and use batteries for everything. No wall plugs of any kind on test instruments or laptops.
Howto - Distortion Measurements with REW
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Yeah, I have a number of pieces of equipment I have designed that significantly surpass existing standards so my intention is to bring them to market.
So what I really want as far as the amp is concerned is just a piece of paper that I can show to an investor saying this is the measured spec shown by a reliable third party, even if that measured spec just shows that the AP couldn't reveal any distortion.
The amp is the only thing I've made so far that can't be shown to an investor in a meaningful capacity without third party verification.
Cordell's distortion amplifier was practically useless to me since it didn't provide enough gain.
I considered using a variation of my amp to craft a super high gain ultra low distortion version of cordell's distortion magnifier but I failed to see the point because even if I succeeded, third party verification is going to be required anyway for my purposes.
As far as audio goes it's pretty academic except for the fact that I can cheat out some efficiency with low bias class AB without losing performance and the fact that the PSRR is practically infinite so I can cheap out on the PS a bit, however the operational bandwidth might make it useful in other use cases.
So what I really want as far as the amp is concerned is just a piece of paper that I can show to an investor saying this is the measured spec shown by a reliable third party, even if that measured spec just shows that the AP couldn't reveal any distortion.
The amp is the only thing I've made so far that can't be shown to an investor in a meaningful capacity without third party verification.
Cordell's distortion amplifier was practically useless to me since it didn't provide enough gain.
I considered using a variation of my amp to craft a super high gain ultra low distortion version of cordell's distortion magnifier but I failed to see the point because even if I succeeded, third party verification is going to be required anyway for my purposes.
As far as audio goes it's pretty academic except for the fact that I can cheat out some efficiency with low bias class AB without losing performance and the fact that the PSRR is practically infinite so I can cheap out on the PS a bit, however the operational bandwidth might make it useful in other use cases.
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So I just got it measured and it was high distortion with incorrect and varying gain which means it is currently broken in some way and I'm 3000 miles away from my lab to troubleshoot it. Figures. /sigh