Reverb "Clipping" Sound

[Vice/President]

Hello my patient friends of the forum.  After completing the rub-a-dub and having some time to really experiment with it, I've started to notice that it has a clipping noise.  I have a clean boost in my chain that when engaged really makes the clipping sound more prominent, though when it's off it's still pretty noticeable. It happens especially if I'm using a pick and a strong attack when I'm playing, though it's noticeable on softer strumming and picking as well, especially in the low end.  I've checked in the enclosure and no wires seem to be touching.  Other than the clipping noise, it is working perfectly.  The noise is comparable to tube rattle, though I'm certain it's not my amp because the sound doesn't happen if the reverb is off. I even turned the reverb on my amp all the way up to see if it would happen then and it doesn't unless the pedal is engaged.  So, I think I'm somehow clipping the circuit, and am wondering if you guys have had any similar experiences to this, and if so, what can I do to increase the circuit's resistance to clipping? Thanks!

[midwayfair]

The input op amp on the Rub A Dub has 2x gain. If you use higher output pickups or using a boost in front of the Rub a Dub, you can exceed the 2.5V peak-to-peak that the Belton Brick can handle.

You can reduce R3 to 180K or increase R2 to 360K, with either change making the input stage 2x gain. You then have to double R5 to 24K (or 27K for a very slight boost) to get the output to unity. Basically, you're flipping whether the boost happens before or after the brick.

This change does add a tiny bit of noise at the output; in general it's a little better to cut the signal after the digital module, but the brick is fairly quiet regardless.

If you're actually overdriving the op amp, then you'll have to make other changes.

Hmmm, I've been meaning to probe the pins on the brick like I did on the PT2399 to find out if the LED limiter will work ...

[Vice/President]

Thanks Jon! I'll definitely see if swapping them out helps.  Your explanations are super thorough, much appreciated!