VCA Decay (r123) mystery...help troubleshoot?
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VCA Decay (r123) mystery...help troubleshoot?

by stinki on Sat Oct 27, 2012 12:38 pm

hi, maybe somebody can help me troubleshoot. I've built a xox and have added a bunch of mods, all on knobs and switches etc:

pwm, res boost/adjust, bass boost, increased low filter lowend, envelope range x2, note on forever (12v to d35 & d36), fmod vco & fmod vca, variable vca decay..

i had everything working great for a while, aside from some minor thing or another coming loose every few weeks. i wanted it to be reliable, so i undid all the mods, and re-did them more neatly and securely. i also added 2 more mods...variable accent decay, and overdrive.

somehow, somethings gone strange.

everything works great and sounds fine now, except for 2 things..

1 variable vca decay - tried both a 1m linear and log pot, with resistors of 1m down to 10k. Using slow tempo, checked and rechecked connections..No effect on the sound. But there seems to be a normal decay even with r123 completely removed. r123 has no effect at all. wha? how should i retrace my steps to figure out where something went wrong...to me this is one of the most important mods, i'm desperate to get it working again.

2 variable accent decay - the directions for this leave a little to be desired. which pin exactly is pin 4 of ic11? the middle pin on the side of the chip nearest the edge of the board? middle & 1 leg of the pot should both go to the anode of d28? i did this, but it had a different effect than it's supposed to i'm sure...perhaps related to my r123 problem??

really appreciate any tips, thanks
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Joined: Mon Mar 01, 2010 10:53 pm

Re: VCA Decay (r123) mystery...help troubleshoot?

by isak on Sat Nov 03, 2012 7:19 pm

Hi there

I did the vca decay with 1M pot and 5k resistor this way it work the best for me.
I can't help with the accent decay tho, sorry.

Isak E.

Posts: 835
Joined: Wed May 27, 2009 3:54 pm

Re: VCA Decay (r123) mystery...help troubleshoot?

by antto on Sun Nov 04, 2012 7:04 am

looking at my code it looks like C36 is making the additional bump on the VCA during an accent
iirc this (RC-Decay) envelope is added to the vca and so it works even if the main Volume envelope is down
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