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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, 09:16 PM   #31
scottjoplin is offline scottjoplin  Wales
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Quote:
Originally Posted by Bigun View Post
But for some music, a SET amp does wonders. Go figure.
Any particular kind or recordings?
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Old 5th November 2017, 10:00 PM   #32
Bigun is offline Bigun  Canada
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How do i create second harmonic distortion?
The SET amp I made uses the non-linear 6AS7, doesn't put out much power and does nicely on Jazz, vocal in general. It can be used on anything at low volume but complex music at higher volume is less good - of course for a few years it was all I had. It was my first ever tube amp. Once I put in a DIY SS amp I realized where it's shortcomings were.

I have a JJ-2A3 tube with nice Sowter OT for a mono amp waiting to be built for half a decade already. And I have a plan to build a Shindo Claret preamp driving a Sindo Cortese amp which employs local feedback, having reverse engineered both of these designs - although I don't have the same specialized tubes it will still be a fun build based around a 6AV5 perhaps. One day. In the meantime, SS through and through.
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Last edited by Bigun; 5th November 2017 at 10:04 PM.
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Old 5th November 2017, 10:17 PM   #33
scottjoplin is offline scottjoplin  Wales
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I wonder whether with relatively simple music, ie few instruments the predominantly second harmonic distortion isn't too bad and perhaps in the case of brass instruments with their odd harmonics can actually mellow their sound a bit
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Old 5th November 2017, 10:30 PM   #34
Bigun is offline Bigun  Canada
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How do i create second harmonic distortion?
I think there are two aspects. A bit of 2nd order can mask higher orders, a decreasing set of harmonics. For a simple tube amp without feedback and simple music this seems to work well and the masking means it doesn't sound too distorted. However, put enough complex tones in there and it gets dominated by IM distortion which just ain't nice, it's all muddy. Purposely adding more 2nd harmonic to get some 'warmth' is a different thing, it's not with the aim of masking higher orders but I think you end up with the same limitation of IM products muddying things up. The problem is that most schemes for adding 2nd harmonics is volume-dependent, so louder and more complex music generates too much distortion. It tends to make bass sound flabby. A multi-amped system with clean signal on the bass and a bit of 2nd on the mids/treble might be a good compromise.
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Old 6th November 2017, 12:44 AM   #35
nironiro is offline nironiro  Croatia
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Bigun, yes that's exactly how the harmonic enhancer works, only frequencies above HPF are altered, usually around 3kHz.

Harmonic enhancers are standard in broadcasting on FM and TV.
One of the most popular is Aphex Aural Exciter, you can find it in almost every recording studio too.

In Audacity there is plugin for Harmonic Enhancer, nice to playing with and graphically see the effect.
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Old 6th November 2017, 09:32 AM   #36
sesebe is offline sesebe  Romania
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What do you think about using 1 diode bypased by a resistor in series with the feedback resistor of the final amplifier?
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Old 6th November 2017, 10:23 AM   #37
Diabolical Artificer is offline Diabolical Artificer  United Kingdom
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The easiest way to produce a 2nd harmonic is with two signal generators connected via a T connector with 600 ohm termination on the end of the two OP's.

I also saw this recently - YouTube where he's using some sort of software to create sines. Havn't dug deeper yet.

A.
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Old 6th November 2017, 09:38 PM   #38
PRR is offline PRR  United States
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2nd harmonic on an arbitrary wave is easily created with a simple BJT.

10K pots in and out would allow mixing this with the original source for any desired amount of 2nd.

Note that in ALL simple distortions, the % of distortion rises with signal level. None for very small signals, more for fairly large signals. 2nd rises nearly as level; 3rd rises faster.
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File Type: gif BJT-2ndHarm.gif (14.8 KB, 88 views)
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Old 6th November 2017, 10:01 PM   #39
bwaslo is offline bwaslo  United States
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How do i create second harmonic distortion?
Quote:
Originally Posted by Bigun View Post
I added distortion to a couple of my amps, didn't like it either so took it out. It was a big surprise for me that I actually like high feedback low distortion amps ! But for some music, a SET amp does wonders. Go figure.
I have to wonder how much of that might be due to the very low damping factor that SET amps typically have. Into most speakers, that will cause a bump at bass frequencies where impedance peaks, i.e., something like punching-in the loudness button on an older receiver. Also usually an upper mid frequency impedance bump will cause voices to be more prominent with a SET.
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Old 7th November 2017, 08:40 PM   #40
udok is offline udok  Austria
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Use Octave or Matlab:
This adds -46 dB 2nd order distortion:

x = wavread('input.wav');
y = x + 0.01*x.*x;
wavwrite(y, 48e3, 16, 'output.wav');
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