Hello Richard.
I've got a dt50/112 with almost the same issue : only difference is that behavior is the same on both canal A & B.
Assuming we're facing the same dysfonctionning, here is what i can tell you :
As you may know these amps use a Digital Signal Processing module between the input signal and the power amp module itself in charge of simulating 4 different topologies.
To do so a special component called a Codec is in charge of Analog to Digital conversion ; the digital flow is then procesed by the DSP, sent back to the codec and finally converted back to an analog signal before being applied to the power amp module.
So I first checked the codec output on a scope : signal is wrong at this stage ; so the issue has nothing to do with the power amp module itself (whatever so called line 6 experts may tell you).
In "our" case, the codec IC is partially fried, sending wrong numbers to the DSP
I've not totally solved the problem yet since i've discovered a flaw in the electronic design wich must be adressed first (otherwise the issue will hapen again)
If you're interrested i wil be glad to tell you more.
still working on it
Pierre-François
