[morzh]

At that point, something told me to check fuse F2.

it is OK to call me something.
The 330 Ohms backfed the 46V to the output amps but was too much to provide for the current drawn, hence the sagging.
Power as expected. (yeah, missing fuse is still power )


Now, when you are speaking of the distortion when half way up or so, have you seen it on the scope or you just heard it?
Again, you need to check the rect bridge as suggested before.
However, if you see it is OK (I would use an analog Ohmmeter for that), a semiconductor bridge does not really degrade.

Again, we need to see the scope pics of the current distortion, both at the input of the output amp and the output. and make sure the distortion you hear is not something that comes from circuits before.