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Old 6th November 2012, 11:12 PM   #11
cotdt is offline cotdt  United States
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dsdjoy, this is very interesting. Thanks for sharing. I'm not sure what is going on here, maybe there is more than just THD difference going on, but I will try something similar with my own amps.
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Old 6th November 2012, 11:56 PM   #12
GregH2 is offline GregH2  Australia
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I suggest a single stage amp in the NP zen style with a switch for turning on and off feedback...
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Old 7th November 2012, 04:27 AM   #13
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The problem with simple analogue solutions, as stated earlier, is that the distortion is usually level dependent. That means not only will distortion vary widely at different points of the voltage swing but at different average levels and even the frequencies present as well.
I doubt that will give the OP any meaningful output other than a sort of showpiece to demo what some bad distortion forms can sound like.
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Last edited by Ian Finch; 7th November 2012 at 04:31 AM.
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Old 7th November 2012, 07:30 AM   #14
aarvin2 is offline aarvin2  Mauritius
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HI guys thanks a lot for you input , actually I would use this 10% THD figure to simulate the sound on a crappy little system and someone cranking his system or dj equipment up. I don't quite know which harmonics will get distorted, but do you know what type of distortion i'm talking about ??

For example the sound of a mixer when it plays in red , or the guy that plays his car system at 100% or the guy with a boom box cranked to the max.

How could I simulate it using electronics at the touch of a switch of a button, then disable this function at will.

Thanks in advance for your help guys!
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Old 7th November 2012, 08:09 AM   #15
bonalux is offline bonalux  Italy
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Use a tube amp instead
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Old 7th November 2012, 09:21 AM   #16
DF96 is offline DF96  England
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So in order to 'calibrate' the distortion of real circuits used in real situations (where distortion varies massively with signal level), you want to make an unusual circuit with distortion which does not vary with signal level - thereby ensuring that it cannot sound anything like any normal setup?

I think you may have fallen into the common trap of not remembering that distortion varies greatly with signal level.
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Old 7th November 2012, 09:33 AM   #17
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Why not just use 2 pre amps? If you use the correct pre amp circuits you can just force feed the 2nd pre amp so you will have input distortion. The 2nd pre amp can then be used to adjust volume. Similar to some guitar amp circuits. Depends on the circuits you want to use though. You may be better off with a signal processor.
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Old 7th November 2012, 09:52 AM   #18
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Yes, I think the OP is referring to clipping, principally. Of course, in power amplifiers that goes with other horrors like power supply overload and more distortion but perhaps if you simply reduce the rail voltages until you get some nice flat topping as seen on the 'scope (I assume you have access to an oscilloscope) or even a bit of rail stickiing for good measure. That should start to sound pretty awful even if you only look at 10% of the waveform voltage as distortion.

Obviously, as the point has been several times, only signals exceeding the clipping threshold will distort, which may be never, sometimes or all the time depending on your programme material and level, just like it happens in the situations given as examples.
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Old 7th November 2012, 12:55 PM   #19
aarvin2 is offline aarvin2  Mauritius
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I am sorry maybe I did not express myself well. On my computer when using my DAC , the level on my computer is set on HALF , but when I set it on FULL , the sound has a certain characteristic where all the flaws of the recording tend to poke out.

For example sibilances become very apparent, and if a track is harsh, it will really sound harsh.

Just try it if you have a PC, you surely can make a difference in the CHARACTERISTIC of the sound when it is at full level. But at Half level, the sound is very gorgeous and sweet.

I have volume matched the loudness to compare the sound, don't worry.


So could I have a signal going into an amp circuit on one side having a very low distortion, then send the same sound signal on the AMP used in the soundcard , and them combine the signals ? then have a switch on the distorted signal to use it when I need it ??
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Old 7th November 2012, 01:38 PM   #20
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Quote:
Originally Posted by cotdt View Post
People cannot recognize even 5% harmonic distortion added into their music via DSP in double blind tests. With pure piano music, low notes only, no high frequency content, it is 3%. I would say 10% is reasonable.

0.1% may be a lot of distortion for a DAC or an amp, but you sure as hell can't hear it according to psychoacoustics research. The papers are publically available for anyone interested.

Harmonic distortion is a meaningless measurement that a lot of engineers believe in, but is not supported by any scientific research.
Klippel have an online test using music either clean or with added non-linear distortion.
Through my speakers I could hear distortion down to -48dB or 0.39% reliably.

Listening Test
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