Tonepad ts9 level pot not going all the way down

Started by pastiche, October 21, 2013, 09:10:34 AM

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pastiche

Hi guys - building another ts9, this is the fifth one I've done on this schem, Basically, the level pot (100k at rh side of schem) when at full ccw still produces   moderate level. All my others are silent. I've tried a different pot.  Where to next?

pastiche


Here's the schem, any pointers would be gladly received. Cheers

duck_arse

is the 1k in the right spot, at the cw end of the pot, and is your Vb good/correct/right? there is not really much to go wrong in that area, except wiring.
You hold the small basket while I strain the gnat.

amptramp

Returning the CCW end of the pot to ground rather than Vb is possible with this circuit and it would mean the electrolytic cap driving it could be polarized with the negative end aimed at the 1K resistor.  With six connections to Vb, there is bound to be some crosstalk as the impedance at this point is not that low.  You could buffer Vb with an oip amp but most people don't want more complication.

The other way of thinking is, if you can't fix it, feature it.  This makes it impossible to turn the volume down entirely. making it impossible for an adjustment to leave you with no signal, a rather frightening thing on stage since you don't know where to look for the problem.

pastiche

Yes I suppose it could be a feature. It kind if effects tone at the bottom, some sort of phase cancellation maybe? Weird...