Plz some advice on te tone stack scaling down

[JebemMajke]

I ve built Sunn Spectrum preamp, Alembic F2B and and Ampeg SVT ( ROG's ginger ), FET versions ofc, and I ll be putting them in one box. An idea comes to my mind, i would like to use this amps tone stack http://www.webphix.com/schematic%20heaven/www.schematicheaven.com/fenderamps/bassman_135_schem.pdf plus that bright switch from F2B. And after scaling down that tonestack am I to do that with 120pf from bright switch ( which would go to 1200pf ) and those 0.047 uF and 1M ohm from deep switch?

[PRR]

> after scaling down that tonestack

Why?

[JebemMajke]

To try and reduce noise.  I ve read about that on this forum, that scaling down tonestack's helps with noise problem, and Alembic F2B has some noise. It's not that bad until I cascade it into some other pedal, or until I drive it with fuzz face. Sounds sweet but it's noisy as hell.

[Seljer]

http://en.wikipedia.org/wiki/Prototype_filter#Impedance_scaling

basically, to halve the impedance, double the capacitors and halve the resistors/potentiometers and the shape of the filter won't change

[JebemMajke]

Ok, i know that but my question is should i do that with "deep switch" 1M resistor and 0.047uF Cap on that fender bassman's tone stack and also i want to implement bright switch from original schematic http://music-electronics-forum.com/attachments/1963d1204940568-alembpre.gif, do i need to to do that with that 120pf cap?

[PRR]

> To try and reduce noise

Of course.... but if your FET(?) load resistors are not a lot lower than 39K (the plate-node impedance of Fender 12AX7 stages) then scaling is not useful. Scale when you have 5K load resistors or use chips with very-small output impedance.

[JebemMajke]

4.1k with Alembic's load and 20.1k with Sunn Spectrum's FET preamp. So can i still scale Sunn down or should i keep the original values? BF245 b's are in F2B and BF245 a's are in Sunn. Should i go for FETs with more gain in order to get lower than 5k load?

[JebemMajke]

4.0k with bf245c in Sunn FET version. So tone stack scaling down is and option now?