Hi guys I know this is a very strange question but for example I am assembling an amp, and I would like to have 10% of THD at the control of a switch, what could I do to get it ??
Please feel free to be very technical about the parts and methods to be used to get 10% of distortion but then when i don't want it I just switch it off and listen to my super low distortion sound again.
I would like the 10% distortion to be added to the output signal(at any volume), instead of just distorting the output signal by cranking the volume.
Thanks in advance for your help guys!!
Please feel free to be very technical about the parts and methods to be used to get 10% of distortion but then when i don't want it I just switch it off and listen to my super low distortion sound again.
I would like the 10% distortion to be added to the output signal(at any volume), instead of just distorting the output signal by cranking the volume.
Thanks in advance for your help guys!!
You need to think more about what spectral content you want. You could have it all as second harmonic, or spread over harmonics 2-10 for example.
Maybe stating why you want it will help guide you.
Either way, it's not going to be easy to achieve with a switching type action unless you use DSP.
Maybe stating why you want it will help guide you.
Either way, it's not going to be easy to achieve with a switching type action unless you use DSP.
I am not sure what you are up to...
10% Distortion is A LOT for an amp.
A difference between 0.015% THD and 0.030% THD at 1khz & 1Watt can be recognized already. Anything above 1% should be avoided.
Then 2nd harmonic distortion sounds different from 3rd harmonic,....
If you would like to have just really distorted sound,
Google for "Guitar Distortion Pedal" and put such device on the signal input of you amp.
Or distort some mp3 musik using PC Audio effect tools, burn it onto CD-rom and enjoy
10% Distortion is A LOT for an amp.
A difference between 0.015% THD and 0.030% THD at 1khz & 1Watt can be recognized already. Anything above 1% should be avoided.
Then 2nd harmonic distortion sounds different from 3rd harmonic,....
If you would like to have just really distorted sound,
Google for "Guitar Distortion Pedal" and put such device on the signal input of you amp.
Or distort some mp3 musik using PC Audio effect tools, burn it onto CD-rom and enjoy
Hi guys I know this is a very strange question but for example I am assembling an amp, and I would like to have 10% of THD at the control of a switch, what could I do to get it ??
Please feel free to be very technical about the parts and methods to be used to get 10% of distortion but then when i don't want it I just switch it off and listen to my super low distortion sound again.
I would like the 10% distortion to be added to the output signal(at any volume), instead of just distorting the output signal by cranking the volume.
Thanks in advance for your help guys!!
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.
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.
Hi,
Its a relatively easy stage to add before the volume control, though its hard
to add so quiet passages are distorted the same amount as loud passages.
10% of THD covers a multitude of sins, from just pure 2nd harmonic which
will sound OK to say an even spread of higher harmonics (still 10% THD)
which will sound utterly grim / unlistenable, with horrible intermodulation.
A CMOS inverter might work quite well, but I know little about adding
distortion to a full range music signal, a lot more for guitar and bass.
rgds, sreten.
Its a relatively easy stage to add before the volume control, though its hard
to add so quiet passages are distorted the same amount as loud passages.
10% of THD covers a multitude of sins, from just pure 2nd harmonic which
will sound OK to say an even spread of higher harmonics (still 10% THD)
which will sound utterly grim / unlistenable, with horrible intermodulation.
A CMOS inverter might work quite well, but I know little about adding
distortion to a full range music signal, a lot more for guitar and bass.
rgds, sreten.
You need a very efficient compandor process to get a constant signal level in the middle. Feed this at the level of 10mV to a BJT. That will give you 10% 2nd, which will be roughly 10% THD - you can adjust a bit up or down. The expander part of the compandor will then give you the original signal level, but now with 10% distortion.
I can't imagine why you would want to do this.
I can't imagine why you would want to do this.
I just had the opportunity to compare two completely identical amplifiers, the only difference being that one fixed at 0.025% THD, whereas the second, identical amp was fine-tuned to deliver 0.015% THD in one listenting session and to 0.025% THD in a second listening session. In both sessions the amps were compared:
0.025% THD vs. identical amp with 0.015% THD
0.025% THD vs. identical, fine-tuned amp with 0.025% THD
Measurements were done before listening session using 1khz sine-wave and 1 WAtt RMS output.
The difference in sound was very noticeable between the 0.015% and 0.025% version in direct A/B comparisons: The added 2nd and 3rd harmonics of the higher THD-version added some richness and full-ness to the sound.
Of course measurements with 1khz sine-wave can not be compared with playing complex signals (Musik). With Complex signals also intermodulation distortion comes into play.
And also I listen to music usually at higher output levels than 1 Watt ( Higher level = higher distortion from the power amp).
Here is a good article about distortion:
6moons.com - industry features: "Distortion &*Negative Feedback" by Nelson Pass
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Amp design is a push-pull stage with two transistors ( precisely a MU-follower with 2 SIC Jfets in output stage).
Amp is fed with balanced signal into input stage consisting of long tailed pair, using small amount of negative feedback.
These amp design and the 2 output jfets work mostly in perfect symmetry, resulting in cancellation of 2nd harmonics.
By doing minor tweaks of resistor connected to source-pin of one of the output transistors ( or by inserting a less well matched jfet) the symmetry is disturbed and 2nd harmonics is increasing, also 3rd to some extend.
You can argue that such small circuit changes resulted in sound changes, and that it was no the change in THD. I can't prove the opposite.
What led me to my conclusion is that I played with many variations of the circuit, always measuring (THD and 2nd to 5th harmonics), listening and comparing the modified versions to the original amp. In all attempts I was only able to have the same sound from both amps, if 2nd and 3rd harmonic levels of them were identical.
Also I can't argue that I can hear 0.015% THD. The given values are only reference values measured at low output level. In real listening situation with real speakers for this amp the values rise to approx. 0.15% to 0.30% THD at 10 Watts, and then also intermodulation distortion (I can't measure) probably plays a role.
Also I should note that I used Air Motion Transformer tweeters which extend to beyond 40khz and have extremely low distortion when reproducing music at mid and high frequencies. This way smaller differences in amp distortion are not masked so much by - usually - higher speaker distortion.
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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.
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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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!
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!
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.
I think you may have fallen into the common trap of not remembering that distortion varies greatly with signal level.
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.
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.
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.
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 ??
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 ??
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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