BMP Tonestack Pops

[Brushthrower]

Hey all,

I recently built a bmp tonestack to tack onto the end of a fuzz circuit based on the following vero:

http://www.aronnelson.com/gallery/main.php/v/Cab42s-layouts/bmp_tonestack.jpg.html

Unfortunately it pops like a mofo when engaged/disengaged. I wired up the circuits separately and its definitely the bmp that is causing the pop. Tried placing pulldown resistors at the front and end of the circuit which didn't help. Any advice on remedy this problem?

Cheers.

[petemoore]

  Sounds like maybe the switch is 'wierd'.

[thedefog]

How do you have the switch wired in relation to the fuzz circuit?

[Mark Hammer]

I can't see any drawings at the moment, including the linked-to file, so forgive my ranting if it doesn't apply.

If you are using a switch to remove the tonestack from the signal path, and there is a DC-blocking cap just ahead of the tonestack circuit (or after it), that cap will need to have a path to drain off at all times, or else you will continue to get pop.  perhaps the safest thig to do is not "bypass" the tonestack, but disable it instead.

There are two components that go to ground in the traditional BMP tonestack: a cap and a resistor.  The connection of the resistor can be lifted without harm, to disable the highpass side of the tonestack, since the cap is always connected to the tone-pot, and never has a "free end".  The lowpass side, has a cap to ground, however if a medium-high value resistor (e.g., 100k-470k) is inserted between the cap and ground, then it is as if the cap isn't there, even though it is still draining off to ground.

So, consider this strategy (assuming it is relevant; remember, I can't see any pictures).  Insert a 220k-470k resistor between ground and the ground side of the resistor and capacitor in the tonestack.  Connect the (former) ground end of those two components to a toggle that either ties them to ground, or lifts that connection.

This will not "bypass" the tonestack, but will limit 90% of its effect.  There will still be a slight effect of the tone control in terms of introducing a little more treble, but there will be no midscoop, and introducing treble will not be offset by loss of bass.  But best of all - no pop.

[Brushthrower]

Hi guys,

Thanks for the replies. My camera is on loan at the moment so I can't provide you with photos of the wiring, but I used the ggg wiring for two circuits when I set them up on separate switches.

http://www.generalguitargadgets.com/pdf/two_in_one_wiring.pdf?phpMyAdmin=78482479fd7e7fc3768044a841b3e85a

Here's the layout of the vero I used for the tonestack:



Here is the fuzz circuit I used:



I'll make up a sketch of how I connected the two using one switch when I have a bit more time, but its nothing out of the ordinary. I'll give your suggestion a shot too, Mark. I was wondering if placing a bypass spdt switch in the circuit to bypass the tonestack, but not the gain recovery stage might work (if that makes sense).