TMB tone stack -- what tube and components?

[bluefoxicy]

I'm trying to figure out how I should do a TMB tone stack, which seems to be extremely gain-sucking. I just want to compensate for gain with a preamp tube (in a silicon amp circuit your op-amp should be able to push way more amplification anyway, so this only applies to tubes).

I've taken a glance at a Fender schematic or two and decided to model based on that:



Fender uses a 12AY7. For gain stage 1, use R1=1.5k, C1=25uF (no low-end roll-off), and R3=100k. Gain stage 2 grid anode-follows gain stage 1. Expose the stage 2 anode to B+ directly (no plate resistor). For R2, use 100k. Tone stack cathode-follows gain stage 2, between the cathode and R2.

I'm thinking possibly 2.2k or 1.2k instead of 1.5k on R1; I'm not sure the tone stack's inherent impact on lows and highs, though more resistance rolls off more high-end so I would think I'd want a bit colder bias (2.2k) to compensate. Then again, with R2=100k even with no plate resistor, that's pretty cold already; warming the signal in stage 1 just a tad can't hurt.

I'm also curious if there's a reason to try to use 500k or 1M pots for the treb/mid/bass knobs, or if I should just use a standard set with 250k treb/bass and maybe 25K mid.



I'm also not quite savvy enough to pick my own cap values... anyone want to give me a hand on this one? I might just pick defaults, or use a Tone Modeler stack I developed a while back...



Thoughts?

[Bruce / Mission Amps]

I'm trying to figure out how I should do a TMB tone stack, which seems to be extremely gain-sucking. I just want to compensate for gain with a preamp tube (in a silicon amp circuit your op-amp should be able to push way more amplification anyway, so this only applies to tubes).

I've taken a glance at a Fender schematic or two and decided to model based on that:



Fender uses a 12AY7. For gain stage 1, use R1=1.5k, C1=25uF (no low-end roll-off), and R3=100k. Gain stage 2 grid anode-follows gain stage 1. Expose the stage 2 anode to B+ directly (no plate resistor). For R2, use 100k. Tone stack cathode-follows gain stage 2, between the cathode and R2.

I'm thinking possibly 2.2k or 1.2k instead of 1.5k on R1; I'm not sure the tone stack's inherent impact on lows and highs, though more resistance rolls off more high-end so I would think I'd want a bit colder bias (2.2k) to compensate. Then again, with R2=100k even with no plate resistor, that's pretty cold already; warming the signal in stage 1 just a tad can't hurt.

I'm also curious if there's a reason to try to use 500k or 1M pots for the treb/mid/bass knobs, or if I should just use a standard set with 250k treb/bass and maybe 25K mid.



I'm also not quite savvy enough to pick my own cap values... anyone want to give me a hand on this one? I might just pick defaults, or use a Tone Modeler stack I developed a while back...



Thoughts?

I can't remember if you said you've built anything at all yet but all these questions you've been asking all over this website are really things you personally need to do yourself and experiment to your heart's content.
There is a VERY good reason you see these same circuits over and over and over again... so unless you build and tweak an amp you have built, you'll mentally wear yourself out with all this stuff.
As far as the tone modeler thing goes... just about every build I know has done this same thing with many variable components and it is ASTONISHING how many go back to the original values found in every Fender, VOX or Marshall amp ever built.
So I would say shit or get off the pot there buddy and build something.

[bluefoxicy]

I can't remember if you said you've built anything at all yet but all these questions you've been asking all over this website are really things you personally need to do yourself and experiment to your heart's content.
There is a VERY good reason you see these same circuits over and over and over again... so unless you build and tweak an amp you have built, you'll mentally wear yourself out with all this stuff.

I'm a little poor, and planning on a new amp that's going to cost several hundred to build.... <_<;

I built one small Class A single ended amp so far, that's it. 6V6 and 12AX7.

[isaac]

Just use a Fender normal channel BF twin preamp. It sounds great. if it drives your phase inverter too much, as it does in a 18w Marshall many times, just put in a voltage divider right before the coupling caps, depending on what you get the values will change but a common one here, is about a 1M in line, and a 220k to ground, for a preamp that drives quite a bit, because that will limit your signal to about 20% of what it was. you could do 1M and 1M and get 50% of what is was. It just depends. Anyway, regarding the twin preamp the tonestack works great, puts out good gain sounds really nice, and is nicely moddable, although dont ever put a 25k pot in for mids. It GREATLY reduces the ability of the bass pot to function, although putting in a resistor between the mid pot's bottom lug and ground and using a switch to short it out (basically taking it out of the circuit) will give you a really nice boost. About 33k is great there. but make it switchable, and there is a way to do Foot switchable but its a little bit complicated to explain without a schematic and it can be really susceptible to noise. but do it right and i to works nicely.