If i really understand this mathematics , you push to distort a very low distortion circuit, drive with its distortioned signal another distortionless circuit and you think that if you ran a global feedback from the output of the second amp to the input of the first amp , you have the sum of both distortion figures, am i right?
I'm not sure what you mean, there was no square wave, just a sine wave. I simply adjusted the gain of the amp until the distortion peaks hit the 0db point so I had a 0db reference to compare the EC to.
I used DBV. As I said above my reference for 0db was to make sure that the peaks of the measured harmonics were hitting 0db so I could track that point downward from 0db when the EC was applied. I used a variety of voltage levels to refer to measurement to. It was not constant. Before I got the distortion magnifier I just turned the gain dial up on the oscillator until I saw distortion.
The only time I saw distortion without the distortion magnifier was if I was literally melting the solder on the board. My main problem in general has simply been the fact that I haven't been able to see any distortion at all for long time when using this circuit without using low performance subcircuits.
Typically speaking though my initial voltage preference is between 5-10v p-p because that is what my reference headphone use when playing loudly so I like to know what the distortion into my headphones are. Other than that I use a 4 or 8 ohm power resistor as a load.
I'm pretty sure benchmark posted better numbers and I've seen similar numbers around here and there. In any case it's fairly easy to do with lower power amps.
I'll try that. So what happens after that? What do I gain? Also is there a way to read that paper without paying $50?
I really super don't care about being famous. I just want to not make a miserable wage in crappy place.
No, if I understand you correctly. I don't really know how to explain it simpler than I have though.
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Find us measurements of any commercially available power amplifier doing -150 dB THD. The Benchmark AHB2 is rated at -119 (not even THD+N) on their spec sheet.
I think Scott, Jan and others are trying to figure out what you mean by -x dB distortion. Normally that would mean that the RMS level of all higher harmonics together is x dB softer than the fundamental, but then a signal with 0 dB distortion would have far less resemblance to a sine wave than a square wave, so your claim that your 0 dB-distorted reference still looks like a sine wave doesn't make sense. So apparently you mean something else.
Hmmmm. Well I just made the sure the highest peaks of the harmonics were touching the 0db point or at least very close so I had a reference to compare to. I followed the peaks after applying the EC. The entire distortion spectra looked identical, just downshifted after applying the EC. There was definitely not a square wave on the scope though. It's possible I was too zoomed in on the top of wave to notice, I was more concerned with not hitting the clipping point. I'll redo the tests once I set up the bench and find some time.
dB is a ratio, there is no '0dB point'. There's only '0dB referred to x'. What is the x level?
Can you make a drawing?
Jan
Can you make a drawing?
Jan
I'll try to post a screenshot of what I mean. Trying to remember how to hook up the distortion analyzer at the moment haha. Having used it for a while.
It seems that I somehow killed my 20vac wallwart in the last 9 months so I need to order another one before I can use the distortion magnifier again.
I threw together a quick example circuit using the LT1364 as a main amplifier. I had it drive 12.9v p-p into 100 ohms. For some reason I can't replicate a 0db harmonic in this set-up. Maybe my memory is fuzzy because I did these tests almost a year ago but I'm sure I got down to at least -5db without clipping. Anyway this is what I have now
The red overlay is the overdriven lt1364 and the green overlay is with the EC applied.
Another example showing a similar config with a lesser performing version of the EC to show that the harmonics are almost identical but downshifted
This is just an absolute bare minimum set-up. The problem arises when I make a serious set-up out of it and I can't see the distortion without resorting to trickery.
I threw together a quick example circuit using the LT1364 as a main amplifier. I had it drive 12.9v p-p into 100 ohms. For some reason I can't replicate a 0db harmonic in this set-up. Maybe my memory is fuzzy because I did these tests almost a year ago but I'm sure I got down to at least -5db without clipping. Anyway this is what I have now
The red overlay is the overdriven lt1364 and the green overlay is with the EC applied.
Another example showing a similar config with a lesser performing version of the EC to show that the harmonics are almost identical but downshifted
This is just an absolute bare minimum set-up. The problem arises when I make a serious set-up out of it and I can't see the distortion without resorting to trickery.
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Not possible. I'd put the noise floor on an exceptionally superb amp, measured in z real RF screen room at maybe -140 dbm. 100 W is +50dbm. If amp was perfect, that would net -190 dbr S/N. Your measurement puts you 100db past that. Might say I'm dubious.
Doc
Doc
Thaumaturge, I'd recommend reading the previous posts that will address your point.
Mod kind of clipped this from another thread into its own thread suddenly because it was off topic.
I wasn't really wanting to make a big thread out of it but since we are here now I might as well see where it leads.
I could benefit from having more experienced people helping me pick this thing apart.
Mod kind of clipped this from another thread into its own thread suddenly because it was off topic.
I wasn't really wanting to make a big thread out of it but since we are here now I might as well see where it leads.
I could benefit from having more experienced people helping me pick this thing apart.
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Okay, I'll go back and review thread. But not likely to accept readings beyond black body curve.
Doc
Doc
Here's another example with higher averaging and better EC.
It's 12.1v into 100 ohms using the Lt1364 as the main amplifier.
Before EC:
After EC:
I can keep making it better but you get my point.
It's 12.1v into 100 ohms using the Lt1364 as the main amplifier.
Before EC:
After EC:
I can keep making it better but you get my point.
...so where is the -150dB figure coming from? Your noise floor is, at best, -120dB bellow the signal.
I think you should use your "-290 db distortion" measurement system to definitively measure the awful audio corruption introduced by "normal" power cords. This will provide definite PROOF for those audiophools with $1,000 power cords!!
I have. Twice, to make sure I didn't miss anything. 🙂
It is.
The answer as to why has been answered, by somebody as knowledgeable and a respected authority on these subjects, Scott Wurcer;
And further expanded here;
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To answer your question, the Cordell distortion magnifier magnifies the harmonics allowing me to see below the normal noise floor of the device. I can see down to -150db using the distortion magnifier. Noise floor prevents me from going much below -130db under the best circumstances otherwise.
The quotes you posted were based upon their misunderstanding that I was literally trying to measure -290db in raw form. We are past this now. You definitely did not read this thread twice. I've been over this thoroughly. Please read carefully.
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You can see/measure the H peaks if they are boosted up out of the noise, ok, that sorta kinda maybe makes sense. But you still claim seeing -160db below the noise floor. How?
Dude for real please read the posts. I literally made like 6+ posts answering your question.
I don't want to repeat myself again. It's like 12 AM and I really don't have time at the moment to go into it again. Sorry if that's a bit harsh. Maybe tommorow.
I don't want to repeat myself again. It's like 12 AM and I really don't have time at the moment to go into it again. Sorry if that's a bit harsh. Maybe tommorow.
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