1776 Multiplex with charge/discharge trimmers

Posted by MAO on
URL: http://guitar-fx-layouts.238.s1.nabble.com/1776-Multiplex-with-charge-discharge-trimmers-tp29819.html

05/04/2016 - Verified
05/07/2016 - Try 1M2 (or 1M) for the 2M2 if detune is shallow

I added trimmers for the charge and discharge resistors. The default setting for the 1M "charging" trimmer is 1 Meg and 47k for the 100k "discharge" trimmer.  See build doc for details.

The 2k V-Adj trimmer requires precise adjusting, see build doc and video for procedure. (Note, in the video he says probe the Anode of D3, it's actually the Cathode. The build doc shows it correctly)

Build Doc

V-adj Calibration Video 

I also added optional green LEDs to improve PT2399 noise performance (thanks Jon Patton!)

The layout should fit in a 1590BB, towards the bottom with top mounted jacks and rotary switch.  Hopefully low profile stomp switches will fit under the board. If not, a 1790N will do the trick, plus the modulation add-on board would fit easily too.  

Modulation Board

NOTE: the TL072 is upside down and there are 2 10u tantalum caps. Also, I would suggest going with 2n2 for the 1n caps.