Question about tone stack

[pdf64]

I've not tried that Route 66 tone system yet but doesn't the bass control move the level of everything other than bass down? So is kinda like a regular mid control?

DrZ seem really well designed / built amps EXCEPT for the standby (on tube rectified amps), which sits between the rectifier and reservoir cap.

That schematic must be wrong regarding the bias supply, in that the bias output should be taken from the 2nd smoothing cap, rather than the (grounded) control wiper!
Pete

[Mick Bailey]

Yes - the bias takeoff should be from the second cap.

In practice this stack works well. The bass does take off some of the lower-mids but the treble manages to stay intact. The disadvantage I've found is the attenuation of the upper-mids when the treble is rolled off. This is because of the bandpass effect caused by the 0.0047uf treble and the 1M pot itself. I use a resistor from the treble wiper to the tone stack output to reduce this - think I'm running with 100k right now.

[Chuck H]

I just wanted to tack this onto the thread...

The OP is concerned about losses in the TS. There is no need to worry about this IMHE. The full TMB stack in an amp that has only one preamp tube and a LTP PI would still require substantial voltage division or loading before the PI to reduce gain. If, for example, the topography is like the standard Fender "normal" channel, but without the loading affect of the peripheral circuits (so just one 12ax7 preamp tube) a typical guitar input signal would have the amp overdriving at about two on the volume knob. You would need to load the output of the second triode with a resistor as low as 15k or 22k to get down to typical BF Fender gain levels. My point is just that since the OP intends to play clean for the most part the loading of the normal TMB stack isn't at all problematic.