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How do i create second harmonic distortion?
How do i create second harmonic distortion?
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Old 5th November 2017, 12:17 AM   #1
filthyone is offline filthyone
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Question How do i create second harmonic distortion?

Hi everyone,
as the title suggests, i want to create (on purpose) second harmonic distortion, preferably on a line signal level.

What would be an easy way to accomplish this? I would also very much like to be able to control the amount of the effect (the percentage of the 2nd harmonic).

I thought of using something like a misbiased emitter follower or something similar. Can anyone think of an easier way to do it?

The reason for this weird quest, is that i would like to "study" the effects of 2nd harmonic distortion on real music, to listen and learn what it sounds like, and hopefully understand why some people kind of like it, or at least don't get bothered by it (choob lovers etc...).

Also, could this be done in audacity? (i'm a little lazy)

Thanks very much for any info.
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Old 5th November 2017, 01:22 AM   #2
PeteMcK is offline PeteMcK
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maybe worth a read:
Soft Clipping
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Old 5th November 2017, 01:51 AM   #3
filthyone is offline filthyone
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Quote:
Originally Posted by PeteMcK View Post
maybe worth a read:
Soft Clipping
I have read this article, but soft clippers produce predominantly odd harmonics. Are you suggesting a single diode soft clipper?
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Old 5th November 2017, 02:16 AM   #4
JMFahey is offline JMFahey  Argentina
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Symmetrical clippers produce mainly odd harmonics.
Unsymmetrical clippers produced mainly even harmonics.
Sharp clipping produces high order harmonics.
Soft/rounded clipping or curve nonlinearity produce lower order harmonics.

So in a nutshell, you will not produce just second harmonic and nothing else, but with careful selection of parameters you can produce relatively soft and "musical" lower order even harmonics.

That´s the generic recipe, now you will have to shake your lazyness , and read and experiment a lot
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Old 5th November 2017, 03:51 AM   #5
bwaslo is offline bwaslo  United States
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How do i create second harmonic distortion?
A JFET grounded source stage that has no source degeneration (bypass the source bias drop resistor with a big cap) and running relatively low current is pretty good at doing 2nd harmonic distortion.
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Old 5th November 2017, 05:26 AM   #6
mt490 is offline mt490
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If you are designing an experiment I would probably tend to digital synthesis methods as these provide the greatest possible flexibility and opportunity to isolate desired parameters.
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Old 5th November 2017, 05:30 AM   #7
tomchr is offline tomchr  Canada
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If you only clip one half of the sine wave, you get second order harmonic distortion.

Tom
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Old 5th November 2017, 08:14 AM   #8
AndrewT is offline AndrewT  Scotland
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A single ended stage with resistor loading, that is driven to near the supply rails will produce a very distorted sinewave. Most of that distortion is 2nd harmonic.
At low levels the distortion is very low, at medium levels the distortion is just about audible.
At high level the distortion is gross.

Is there a circuit that adds a nearly constant proportion of 2nd harmonic?
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Old 5th November 2017, 08:43 AM   #9
Elvee is offline Elvee  Belgium
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You can insert this halfwave/soft clipper in the signal line: it is almost passive, just requiring a static bias requiring no current (a battery or a big cap), produces ~90% second harmonic, and has many parameters to play with, to adjust the distortion profile:
-The values of R1 R2
-The tap ratio if you use a potentiometer
-The negative bias voltage
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Old 5th November 2017, 08:50 AM   #10
Mooly is offline Mooly  United Kingdom
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How do i create second harmonic distortion?
You can play around with this in Audacity. Try 3 or 6db for a start, save your file under another name and then compare using an ABX comparator such as Foobar.

For a real circuit I would go with a JFET as in post #5.

You can even try that for real by simulating it in LTSpice (make a stereo pair) and applying a .wav file to the sim and then capturing the output.
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