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"Backwards" Fender Preamp Anyone?

6/27/2003 4:15 PM
Man o'Blues "Backwards" Fender Preamp Anyone?
Anyone tried putting the tone stack after the second stage in a standard BF preamp? I found this in one of Kevin O'Conner's TUT's. Looks like this:  
1st gain stage -> cap -> volume -> 2nd gain stage -> tone stack  
According the Kevin, this config allows the 2nd stage to clip from the full output of the 1st stage, thus causing preamp distortion. The EQ now shapes a distorted signal as opposed to a clean one in the classic circuit.  
I'd love to hear any feedback on this afa tone and quality of distortion goes. I would imagine this setup sounding harsh but maybe not?
6/27/2003 4:26 PM
TheElectricMoron Re: "Backwards" Fender Preamp Anyone?
5F6A anyone??  
6/27/2003 4:38 PM
Chris ( CMW amps )

With a few tweaks it's pretty fat sounding with a faster/sooner breakup . This topology is also used in the Fender Vibroking , Tonemaster and DualProf. .  
It's not the same as a 5F6A , plexi or AC30TB ( no direct coupled cf ) but it's pretty cool .  
6/27/2003 5:02 PM
TheElectricMoron The Full Monty
Just seemed like at that point the CF would be a tonal obligation {;-)  
6/27/2003 5:17 PM
Nathan Noel
Re: "Backwards" Fender Preamp Anyone?
I've got that sort of thing in a P-P 6V6 based amp right now and like it pretty well, it's got a bit more crunch that it did before. Makes for a useful pre-PI master volume than you'd get with the usual Fender pre.
6/28/2003 1:57 AM

It can get buzzy, particularly in the low end with too much signal. Fender and Marshall knock the signal down with the mixing divider. The Vox topboost uses a radical hi-pass. I've been using something in-between.
6/28/2003 5:45 PM
bob p
"It can get buzzy, particularly in the low end with too much signal. Fender and Marshall knock the signal down with the mixing divider. "
fwiw, i think of the 'late' tonestack (following the second stage) as having a harsher or for the lack of a better term, a more 'metallic' distorted sound, compared to a more 'organic' distortion when the tonestack follows the first stage and attenuates the signal before passing it to the 2nd stage.  
some of this is probably due to the fact that the first stage's output overdrives the second stage's input pretty easily when the tonestack is removed. i've been thinking that it would probably be worthwhile to put a trim pot between the first and second stages if you move the tonestack after the second stage -- this would allow you to control how hard the second stage gets hit, which could tame the level of distortion somewhat. i've been thinking that it would be great to limit the signal somewhat so that the 2nd stage gets compressed, but not harshly overdriven, as i prefer the distorted tone to come from later stages in the amp. anyone?

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