I just bought a used Marshall DSL401 40W tube amp.

Great amp, except one problem. When reverb is on ANY setting other than zero, when switching from either Overdrive channel back to Clean there is this huge volume swell that at first sounds like feedback. It lasts a second or two and ends with a reverb spring type ring. Right away I knew it was a problem with reverb. I turned reverb to zero and switched channels several times (it only happens when going from Overdrive to Clean not the other way around). With reverb on zero there is no problem at all. But even with reverb at 1 I get this big noise. The first time it happened I thought I had the volume on Clean maxed out and was getting feedback. But the noise only lasts about 2 seconds and then the Clean channel was fine.

I am not a technical type at all. I can change tubes and bias an amp but not a whole lot more.

Does anyone here have any idea what would cause this and how to fix it? If it is simple I could do it myself (replace a resistor etc...)

Thanks in advance for any help you can offer.

Wes

I am new to the forum, but I was searching for mod solutions on this amp as I also own one. For someone peculiar on tone as me, this amp has issues, especially if you play live in a small club. This amp could handle small club situations but only on green (clean) channel because this has the only adequate bottom end sound. The orange has a decent overdrive crunch, but bass has almost no adjustment room. The Red channel does horrible things with the 16 ohm thin paper speaker that warrants no attempt at achieving a tone to perform or record with.

These things should not happen to a Marshall amplifier at all or any amplifier that is sold in the price range the DSL401 is in. I did not pay full price for this amp and nor should anyone for that matter, unless you are novice enough to not percieve or listen for these shortcomings, and the name Marshall means too much to you. There really is no use in overdriving those tall skinny tubes unless you could drive more speakers which it can't.

The lack bottom end on lead channels sounds like a fender problem, and it probably is. Perhaps the best solution is a 'blackfacing' of this Marshall or a mod that full developes the green channels tonal qualities, then using your favorite pedal for crunch and distortion.
However, this amp is just dyin' for that 6L6 boost in the orange/red positions. If anyone has help on this let me know.

RV