Tuned circuits in guitar amps?

M

Mr songwriter

New member
I read a comment somewhere that certain guitar amps (I'm pretty sure they were talking about valve amps) have circuits in them that are tuned to resonate at frequencies that will make the guitar sound good, presumably, if this is the case, they would be designed to work best with a standard tuned (A = 440 Hz) guitar. Does anyone know any more about this?
 
I don't know about that, but certainly many guitar amps have more harmonic distortion than would be acceptable in other audio circuits. And that sounds better for sure.
 
I doubt it. I've never heard of it either. Realizing how many different frequencies just a standard tuned guitar produces on just a single note on a single string is already enough to make your head hurt. Ofcourse it's possible to make a filter that boosts at a sertain frequency, but I can't think why that would sound "better".
 
Halion said:
I doubt it. I've never heard of it either. Realizing how many different frequencies just a standard tuned guitar produces on just a single note on a single string is already enough to make your head hurt.
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That's interesting, I've just Googled that and apparently these are the overtones that are produced by one guitar string:

root 1 1=1.0 tonic
1st 2 1=1.0 tonic
2nd 3 3/2=1.5 perfect 5th
3rd 4 1=1.0 tonic
4th 5 5/4=1.25 major 3rd
5th 6 6/4=1.5 perf 5th
6th 7 7/4=1.75 dominant 7th
7th 8 1=1.0 tonic
8th 9 9/8=1.125 major 2nd
9th 10 10/8=1.25 major 3rd
10th 11 11/8=1.375 between 4th and dim 5th
11th 12 12/8=1.5 perfect 5th
12th 13 13/8=1.625 between aug 5th and maj 6th

...so, yes, as you say, it might be pretty tricky.

Ofcourse it's possible to make a filter that boosts at a sertain frequency, but I can't think why that would sound "better".
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Well I thought they might have designed the circuits to boost notes like E, A, D or G, which might make open chords/strings sound brighter and/or stronger. I had a vague idea they did that with effects pedals too (chorus maybe?)
 
I did this with one of my old amps. I changed the frequency of the bass boost so that it would accentuate my open D string (we tuned down a full step) It worked quite well until we played something in a different key, then it wasn't very useful.
 
Farview said:
I did this with one of my old amps. I changed the frequency of the bass boost so that it would accentuate my open D string (we tuned down a full step) It worked quite well until we played something in a different key, then it wasn't very useful.
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Yes, I suppose you would end up needing a different amp for every song, which wouldn't be very practical unless you were in U2 or someone like that.
 
Most transformers will have some resonant frequency effects. These are easily damped. What you may be referring to is the Transformers's bandwidth. Above and below certain frequencies a transformer's coupling efficency will drop. The transformers in guitar amps are designed to couple frequencies that guitars produce. Part of an amp's sound has to do with the harmonics the transformer attenuates. There are other factors of course but all things being equal if you change the transformer in a tube amp ( or any amp ) the amp's characteristic sound may change for reasons stated above
 
Henry Mars said:
Most transformers will have some resonant frequency effects. These are easily damped. What you may be referring to is the Transformers's bandwidth. Above and below certain frequencies a transformer's coupling efficency will drop. The transformers in guitar amps are designed to couple frequencies that guitars produce. Part of an amp's sound has to do with the harmonics the transformer attenuates. There are other factors of course but all things being equal if you change the transformer in a tube amp ( or any amp ) the amp's characteristic sound may change for reasons stated above
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OK, I've just done a little reading around about valve amps and it seems that I know less about them than I thought I did, but from what I've read, I'm guessing you're talking about the output transformer:

The role of the audio output transformer is to match the impedance of the speaker to the valves. The valves are high voltage, low current devices, hence they have a high impedance, usually a few thousand ohms. The output transformer matches this to the 8 ohm speakers.

...and what I've read confirms what you're saying about the bandwidth and frequency response of the output transformer affecting the sound, so that may well have been what the original comment was about. Thanks.
 
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