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Try not to confuse gain and level.
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Education is what you're left with after you have forgotten what you have learned. -
I NEVER use a distortion analyzer on guitar amps. You can only QUANTIFY distortion with an analyzer, no QUALIFY it. Sure, you might want to employ FFT analysis which is more detailed, but the best piece of test equipment is you ears.Comment
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...has anyone ever evaluated the sonic-to-saleability transfer function of an amp using an FFT? I don't think so....Originally posted by jrfrond View Post
...you gonna let a software FFT program tell you what sounds good? I don't think so.....
...obviously, I agree +100%!...and the Devil said: "...yes, but it's a DRY heat!"Comment
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I think the basic premise of this post is 'Is there any way to tell "good" distortiom from "bad" and/ or identify and replicate "good" distortion using currently available equipement.
The short answer is no. But there is a lot of opinion about "good" vs. "bad" distortion. I've heard many "tones" used well and sound good that I would personally hate for my style of playing. So it becomes very subjective. As far as technology has come we still haven't managed to isolate much about those qualities that make one guitar amp better than another. There are, of course, some obvious stand outs. Still, usually these are associated with specific guitars and/or players. So guitar amps remain as much an art as a science.
I guess there aren't enough critical, amp buying musicians to merit a profitable demographic. Otherwise ther would certainly be a lot more info on the subject of "bad" vs. "good" distortion in guitar amps.
Listening and field testing are still the best diagnostic tools for guitar amps.
Not so much an answer as an explaination I guess.
Chuck"Take two placebos, works twice as well." Enzo
"Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas
"If you're not interested in opinions and the experience of others, why even start a thread?
You can't just expect consent." HelmholtzComment
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"V4 IS paralleled triodes." You have 2 tubes designated as V4 then? I'll assume that V4 right after V1B is actually V3? I hope that V2 (PI) is the tube that is actually closest to the power tubes & that signal wires are not criss crossing back & forth.
I think that you want a volume control right after V1B. I also think that R12 needs to be bigger. If you want to keep a low-ish value in R12 you might want to consider more headroom in the following stages (4.7K-10K cathode resistor), so as not to overly compound distortion generated early in the circuit.
Tube numbers are confusing the issue, so this is what I see:
input triode with little attenuation before>parallelled gain stage, again with relativeley little attanuation before>another paralleled gain stage feeding a plate fed tone stack.
Even if you had just input stage followed by a volume control>plate fed tone stack you would still have bucketfulls of gain, you'd probably only need a tiny volume control value after the input stage.
If you have 4x12A#7 tubes, with 2 1/2 for the OD channel, an input stage followed by a gain stage, followed by a cathode follower feeding the tone stack should still be ample.Comment
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Very good point sirOriginally posted by Old Tele man View Post
I think FFT analysis and spectrogram plots, combined with some sort of "standard pick attack and string decay" stimulus, could tell us a lot about the harmonic fingerprints of different amps. I wouldn't be surprised if Line 6 et al. used techniques like this.
However, this is all getting too much like my day job, and there's probably no point anyway, since this magic sonic-to-saleability transfer function doesn't exist. I'll stick to designing industrial instrumentation, where the customer at least can express what he wants in numbers. Sometimes. Sort of.
By the way, I once tried hooking up a high-gain distortion pedal to one of those distortion analyzers. It was an automatic type with a digital readout, and I got a reading of about 10000% THD."Enzo, I see that you replied parasitic oscillations. Is that a hypothesis? Or is that your amazing metal band I should check out?"Comment
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And there you go, a number to beat.
Looking at his schematic, I suspect the " V4" in the lower left was meant to be V3.Education is what you're left with after you have forgotten what you have learned.Comment
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...was that a DUMBLE Simulator Pedal by any chance (wink, wink)?Originally posted by Steve Conner View Post...and the Devil said: "...yes, but it's a DRY heat!"Comment
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Like I said, the best analysis tool is the ears, and the best test meter is the face of the guitarist playing the amp. The bigger the smile and funnier the "stank face" is on their face, the better the distortion.
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