Help with SF Fender Twin tremolo (ultra linear model)

[Wes]

I'm experiencing what seems to be clipping of some sort with this circuit.
It's not the ticking you get, it's got a capacitor added on to alleviate that
issue.

If intensity and depth are off everything is fine.

If you turn them up everything works fine until there is a lot of effect
or you strum really hard- especially on the lower strings. Then it's a choppy
sound/clipping sound.

I've tried a new tube and double checked the values of the components
and even tried it without the cap that was added to take care of the ticking.

If you guys have any advice as to what this may be I'd greatly appreciate it.

Could it be a bad trem-bug?

[pdf64]

Is this with the master volume turned up full?
If not, turn it up full and adjust the channel volume to get sound level - choppy clipping still there?
Peter.