BMP tone control: output hog?

[Bucksears]

I noticed that the Thunderchief with the tonestack added also includes an additional transistor/resistor to ground prior to the tonestack. I'm thinking about replacing the three-band eq in the Thunderchief and JCM800 with the BMP tone + AMZ Presence Control. Does the BMP (or any other tone control) suck that much overall output that it needs a little extra 'oomph' before it?

Thanks,
Buck

[brett]

Hi
the BMP tonestack has plenty of issues with it.
It needs low output impedance from the previous stage, has high output impedance itself, and loses frequencies across the board when set "flat".
If you download Duncan's Tonestack calculator and work out a BMP tonestack with a 10k pot instead of a 100k pot, things will work much better.
cheers

[Mark Hammer]

Most of them, yes.  Except that it is probably wiser to stick the oomph after the tonestack, rather than before it.

Years ago, Steve "T-Boy" Morrison who was the brains behind AMPAGE and is the current brains/webmaster behind the Music Electronics Forum, had a great little article in POLYPHONY about a solo/tonestack-cancel mod to Fender or Marshall amps (or anything using that same tonestack configuration).  All it involved was lifting the connection between the midrange pot (or fixed resistor on amps that had only treble/bass) and ground.  I did it to my old blackface Tremolux and boy did it make a noticeable difference!  Easily a 4-5db volume increase, and with the absence of the classic fender midscoop a lot more "meat" to the tone.

A great mod, but ample evidence of the need for gain recovery after such tonestacks.

[petemoore]

  Take a look at BMP's recovery stage, right after the passive TC and it's passive losses.
 If input to the TC is sufficient and strong enough loudness and low enough impedance [try driving with buffer] that's good.
 If 'it' is straining for output when TC adjusted is 'so', you may want more.

[Bucksears]

Thanks guys.
So is the BMP tone circuit a bad choice for a single knob tone control? I'd like something a little more effective than the classic Marshall 3-band config.
I tried the SWTC on my GGG Dist+, but it didn't do much.

- Buck

[Mark Hammer]

The BMP is a great tone control for some tonal goals, and less so for others.  Same with a t/m/b stack or the SWTC.  Take a look at the SWTC Pt II article over at AMZ for some very clever ideas about how you can achieve useful tonal variation with minimal penalty in your output level.

[John Lyons]

The BMP tone control is a great one (BSIAB, BOX Of Rock etc etc)  Just tack it on and see what you come up with.
Going to Duncan's amp page and getting the tone stack calculator is highly reccomended as a learning tool so see what's going on with tone stacks, as Brett mentioned.
If you need more output volume just add the stage like the actual big muff does as petemoore said.
Adding the AMZ presence control is even better!

John