Hi folks I'm new here. I am working on an OTS special for a friend who got it on fleaqbay a while ago. We've been in contact with Nik.

There were a number of modifications done mostly having to do with non standard parts. I've replaced all of them with standard value components of the correct type. Between that and the bass pot being the wrong value, and the mid pot having an unsoldered lead I've put it back to the proper clean tone and it sounds lovely in clean and in overdrive.

But my friend likes distortion. Lots of it. So he's been running guitars with humbuckers and switching on the overdrive and the FET at the same time from the footpedal. And that's when trouble starts, He plays with a heavy pick hand. So after about three mid register notes the amp chokes, splutters and gags like a kid playing a kazoo for a second, collects itself and we're back to just fine clean tones.

I have changed the 2K resistor on the FET board to 4K and have twiddled the 10k pot-which only modulates the input from the FET jack.

So I started swapping tubes and found a combination that was nearly good enough-a 12AU7 a 12AY7 and a 12AX7 in the phase inverter position.  Go back to a 12AX7 and it goes right back to choking and gagging with heavy pick attack, humbuckers, and overdrive and FET engaged.

But still not perfect and a lot less output volume.

So here's my speculation. I *think* the FET section is driving the preamp too hard and I need to reduce its effect to a manageable level.

Any thoughts, ideas, hunches, experience, comments, helpful hints?

Thanks.

If you plug into the FET channel V1 is out of circuit I think so changing that valve will have no effect. Don't think you can plug into both.

FET  channel is intended as an acoustic input so best ignore that. Plug into V1 set the internal OD trimmer to get the sound you like (most people set it it 9:30 to 11:00 o'clock) . Then OD distortion is governed by the Level control. Be aware that huge distortion is not really this amps forte, but I would consider using a distortion pedal on the clean channel as this channel takes pedals really well.

HTH

I think I scored a trifecta on this amp-the FET was out of whack, the PAB was out of whack, and the overdrive pot was set far too high for this player. Also, a number of parts of the incorrect value and type had been installed, perhaps in an effort to get this amp dialed in.Perhaps  the original owner got PO'ed at it because it sounded as the new owner described it "like chewing aluminum foil"-it was painful to listen to it.

Putting back the correct value and type of parts brought the clean tone into line, and the other stuff fell into line when I figured out what it did and its connection to the whole.

It sounded so good this afternoon that I've been scheming on how to get my hands on one.

Thanks to Nik Azam for all his assistance-he really helped me out.