AMZ presence control

[Lucas Grijande]

Hi, i'm wondering if would be possible to put one like this inside my guitar....In the article (at the end) , Jack Orman says:

"All of the examples above are with the tone control driven by a low impedance such as an opamp or even a mini booster..."

I want to put this instead of the tone control in my guitar... I'm not sure at all but i think guitar signal is HI impedance!!! Help me please!!!

[Ge_Whiz]

Yes, I've done it. Sounds good.

I used a single bipolar transistor unity-gain buffer before and after it. The only problem is that, while such buffers theoretically give unity gain, in practice the gain is significantly less than 1, so after two stages and losses in the tone circuit itself, the output is substantially less than the 'straight through' signal. I can't be bothered to fix it now, but in future I'll use a third booster stage to recover the signal level to the original. If I'd used an op-amp as the second stage coming out of the tone circuit, this would have been easy to fix.

The other thing is that with the potentiometer values in Jack's article, I found the range of the two controls, particularly the treble/bass, to have long 'tails' where the sound didn't change much, so I experimented with various pot values and fixed resistors to improve the range. At the end of the day, however, you are a bit limited for values of 'guitar' pots, but could substitute other 16mm diameter types. Experiment beforehand - YMMV.

[Mark Hammer]

I would not recommend sticking this inside your guitar.  Or rather, this may not work out as well for you as you hope.  It *will* reduce the signal level enough that you will not be able to operate it passively.  This is not as simple as changing a cap on your tone control.  You will require a gain-stage/preamp to compensate for the signal loss, and this will require on-board power, a place to stick the battery, and a way to shut the battery off (i.e., installing a stereo phone jack instead of the mono one presently there).

None of that is the "kiss of death" - I have had an on-board preamp in one of my guitars for over 20 years - but it may be more trouble than you want for something you may only want to use sometimes rather than always.

If you DO want it, any simple FET-based preamp (such as a Stratoblaster or Don Tillman's preamps) will do the trick.