Gain stages before or after the tonestack...

[bruno]

Hello,

this might be a really subjective subject, due to personal opinions (likes/deslikes), and due to the context of different amps and topologies.

In general, and obviously this does not apply to all amps, but to most kind I've experimented with. Using more than one gain stage before a plate fed tonestack or before a cathode follower driven tonestack, seems to yield a more throaty, blury in a nice way, sort of overdrive (marshall like if you will).

Using a regular plate fed tonestack with extra gain stage added after, usually yield a gainy overdrive that seems to have more note definition and headroom. Like the amp is always cleaner even at full distortion (fender territory but with more gain).

I know this depends highly on the context of the amp being used and the rest of the circuit. I've heard amps that used plate fed tonestacks with later gain stages sounding exactly like hot rodded marshalls. So you might take this with a grain of salt, as it does not apply to all cases, just my overall experience.

Anyone care to share if this happens with most of your builds, or any of the amps you've tried?

[jjasilli]

Dave Funk's Tube Amp workbook has a chapter on this topic:  gain stages before & after the tonesatck.  Some examples ac30 1+0; Typical Fender 1+1; Boogie 1+2; Soldano SLO-100: Clean 3+0, Dirty 5+0.  "The more gain stages the smoother and more compressed the tone." 

[harryk]

Just today I was looking one more time Trainwreck Express schematics and finally noticed that Ken Fisher mated typical Fender and Marshall  preamps to one unique Express preamp. I have build several Express incarnations with 2x6V6, 2xEL34, 2xECL86 etc. and it never came to my mind that they sound hotrodded Marshalls, but have unique sound. Express has two gain stages after plate driven tonestack. It has huge amount pretty clean gain and still sound is pretty compressed in the end when you crank it. Maybe someone can explain it.  Harry

[jojokeo]

In my experiences your thoughts seem to be close to mine in that there's a "throaty/blurry in a nice way" sound description after the first stage w/ following stages after the stack - I think of this to be a more bluesy type of distortion and characteristic and when the stack is placed later on, the sound is definately more crunchy-Marhsallesque meaning more definitive, refined and controlled.

If you think about it, it seems to make sense for it to be this way. Why? When the signal is controlled & shaped early and then goes through further stages unshaped, uncontrolled, and unfiltered, you're going to get more overall harmonics and frequencies added back like that are present in a tweed amp and you lose that earlier controlled definitional-bandwidth. This is the hallmark rich gainy sound attributed to blues.

[bluesbear]

Not sure exactly how this applies, but the tone controls seem to have more affect if placed before the gain stages. I'm not sure why, but it seems that a bunch of gain hitting the tone stack is harder to modify. Maybe if the stack is directly after the input stage, the signal is so attenuated, it can never quite recover to Marshall territory, at least not with the same type of gain.
Dave

[JayB]

Not sure exactly how this applies, but the tone controls seem to have more affect if placed before the gain stages. I'm not sure why, but it seems that a bunch of gain hitting the tone stack is harder to modify. Maybe if the stack is directly after the input stage, the signal is so attenuated, it can never quite recover to Marshall territory, at least not with the same type of gain.
Dave

The tone stack after the gain stages is still functional and works fine. It's just that you don't get to adjust the frequencies before they get distorted like you do when the tone stack is before the gain stages like fenders. Plus the tone stack after the gain stages acts like a master volume would.

I tried two tone stacks before, one before the gain and one after. It made adjustment harder to set on one depending on how the other was set. You could get some really nice tones but was a pain in the neck to accomplish. Would of worked  better if the second tone stack could boost frequencies like how the EQ in the Boogie MK series.

[jojokeo]

+1 Jay. In my Dumblewatt amp I use a typical Tweed tone control on the first stages for that reason (and also to preserve more gain when the OD is not activated) so that when the OD circuit is activated, it's easier to dial in. Then in my OD tone stack I only use a T/B control to keep things easier. But, I can still tailor the mids by using a 3-way toggle - simple and effective.

[jjasilli]

jojokeo, interesting concept!