Ocelot OC2 distorting after several months of use?

[Wizardofwoz66]

I built an ocelot for a buddy several months ago, and all of a sudden about a week ago he complained that it was doing weird things. I met up with him today, and it's definitely distorting when hit hard (he's playing a bass with pretty hot active pups). I tested it on a few guitars and my passive pup bass at home, it's definitely clipping something in the circuit, because the lower output guitars didn't do it - gotta be something not getting enough voltage I would think? The clipping happens regardless of pot positions unless all are at 0 since they're all essentially just passive volumes for individual octaves. I opened it up and there's nothing obviously wrong with it (all ICs are seated properly in sockets, no broken solder joints etc). Any thoughts on where to begin here? It's strange that it started out of nowhere.

 

[Wizardofwoz66]

Aha! I finally found a useful thread discussing this. They mention increasing R6 instead, this is where my electronics knowledge takes a dive - is there an advantage to changing r5 VS r6? They're both used to set the gain of the input.

Do you hear the distortion in the original nonpitched signal, or just the octaves? If it's both...
Could try changin Rf(R5) on the input buffer for less gain.
Gain is currently at 4.5 there.
A 7k would get you 3.6
5k - 2.8
Can quickly test by clipping a 20k in parallel with the 10k R5 for 6.67k.(or solder an 1/8w to the other side)

If that fixes it, could squeeze a 5k resistor in series with a 5k trimpot maybe?

 

[jwin615]

At this low of resistances and gains, I can't see it mattering but I'm sure there's a best practice re energy wasted to ground... Probably recommended to keep the math easier if I had to guess though(10k).

 

[Wizardofwoz66]

https://www.talkbass.com/threads/oc-2-clipping.1027629/

Here is said thread for all interested