Class D is just Dandy!

@islandmandan , I'm with Al on this one. The amp should be fine with no input connected, go ahead and disconnect  the input and see if you still have that noise. If so => amplifier, if not => input

Thank you Al, Ralph, for your always valuable input. I will re-insert the Class D amp into the system (I was taking time off from the noise, and very much enjoying the SET 300B in the system), and try what you have suggested. I'm wondering why, though, a single module, in stereo mode, is quiet, but a dual module/single power supply with both modules set to bridged mode is so darned noisy?

Thanks,
Dan

@islandmandan , I don't have a good answer for that right now- but when we do this test then we will know more.

Hello Al, Ralph, all,

I disconnected the inputs on my stereo dual module Class D amp last night, and the right channel was silent. Inexplicably, the left channel was still noisy. Today, I rounded up some spare I/C's that were long enough to reach between the preamp/processor and the amp, disconnected the leads from the pre-pro to the separate tube preamp, and connected the amp directly to the pre-pro. The two channel and three channel Class D Audio amps are now quiet as a tomb.

From here on out, all my HT and multi-channel listening will be through the Class D amps, and two channel listening will be through the SET 300B and Transcedent Sound Grounded Grid preamp.

So your idea of the problem being input-related was spot-on. I also found I had my surround speakers connected to the rear surrounds on the pre-pro, which may have been causing some of the problems as well.

So, everything is working much better now, though I will be limited in my use of the Class D amp. I will have to re-think my connections to see how I can better utilize the Class D stereo amp, but at least for now, mission accomplished in attaining blessedly silent noise-free listening.

For that, I can't thank you men enough. Having your input on this forum is a true blessing!

Regards,
Dan 
  

^^Good work- Glad you got it sorted!