Re: What's the difference?
- From: John King <kingsx@xxxxxxxxxx>
- Date: Tue, 14 Mar 2006 17:32:32 GMT
Gareth Magennis wrote:
"Justin Meyers" <motorbret@xxxxxxxxxxxx> wrote in message news:isidnShF5NmnFYvZnZ2dnUVZ_sOdnZ2d@xxxxxxxxxxxxxxx
What's the difference sonically, how it sounds, between pre-amp crunch and power-amp crunch? Basically, between havin pregain at 10 versus postgain at 10 and obviously using the other to keep at respectable volumes?
If you look at a preamp valve distoritng on a scope, you will see it is asymetric - i.e. the top half of the waveform is quite different from the bottom half. You also see a lot of complex variations and the waveform doubling back on itself rather strangely. That gives a harder, edgier tone with a lot of harmonics. When you drive power tubes into clipping they generally clip a lot more smoothly, you will end up with much more of a square wave, and as they are run in push-pull configuration, each half of the waveform is generally pretty much the same and you get a smoother kind of sound. Output tubes are usually pentodes or pentodes run in triode configuration, pre-amp valves are usually triodes. Each have different characteristics, especially in distortion.
Lots of good explanation there for technically 'how and why'
there is a sonic difference between the sounds of overdriven
preamp and power amp tubes; but not much in the way of
explanation of how the difference sounds. It can be difficult
to verbally articulate and quantify such a variable and subjective thing. The two stand out adjectives in the above
paragraph are "edgy" and "smooth"...
To my ears, an overdriven preamp usually sounds harsh, as compared to the more linear and mellow sound of when a power
tube reaches saturation, and the signal begins to clip.
Though I have stated a preference for power tube saturation
in the past, and still feel that way for the most part; I also
acknowledge the usefulness of preamp distortion, and sometimes
a bit of each added together is a mighty sweet sound.
Still, given the choice of a hybrid amp with tubes only on
one end, I'll take mine in the power amp thank you. Part of
the reason for that lies in my belief that not only does the
power tube's saturation sound better to me; but also the
damping (or lack thereof) of the speaker; the speaker's
breakup, and the acoustic coupling of a fairly loud amp with
the body of a guitar all contribute to the 'tone' that I find
'right' for me in many playing situations. The high gain preamp
sound has its own merits, but IMO is no real substitute for
the the things that make up the OD sound from the power end
of the amp.
Just another 2¢
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