Re: Slight whining buzz
If it's only on one channel and not the other, you can pretty much rule out everything after the first part of the preamp.
Check the shorting piece on the input jacks on that side. If one of them has a chunk of grundge keeping it from shorting properly, you might have some noise.
Not the trannies. Might be a noisy 68K resistor coming in off that side's input jack. If you have a few minutes, you can take a soldering iron and touch each solder joint starting at those input jacks. Because its not happening on the other side, that has me taking this angle.