I've been busy but have read through everything each of you contributed. I'm very grateful to everybody for taking the time to offer thoughts. Thank you.
Here's the update:
I used what time I had to reroute and reconfigure the two electrical circuits in the house per my last posting. My back is sore, my fingertips roughed up. And when I finally had everything put back together... Can you wait?! ... No change. I kinda expected that, being a pessimist at heart, but was still disappointed. Hey, at least I lowered the ground resistance to near zero in the system's circuit.
So I kept poking and think I have probably found the real culprit: the Rowland preamp.
I should have tried some of these things first, as they're simpler, but alas, we all learn by experience, yes?
Turns out that when I run my DAC straight into the amps, the hum is barely audible. (It's a Mac server, so I can control the volume through iTunes.) That also seems to eliminate that digital equipment as the cause per se.
But here's the salient clue, something I hadn't tried before: If I disconnect all source cables from the preamp, and then disconnect the preamp from the AC power, leaving the preamp and amp connected ... the hum remains. Yikes.
I opened the preamp and looked at the power board. There is a cap with one leg connected to the ground screw via a PCB trace, but the solder connection is hair-thin. I've contacted Rowland to ask if that trace is supposed to be stronger, which I'm capable of addressing myself. But if that's not it, I'm awaiting their response, which I assume will include sending the preamp to them.
The greatly reduced hum has also allowed me to identify a little RFI in one channel, but I'll take one thing at a time.
If this stimulates any thoughts, I'd be glad to read them. Otherwise, this feels more solid to me and I hope it's the beginning of the solution.
Thanks again, all.
Here's the update:
I used what time I had to reroute and reconfigure the two electrical circuits in the house per my last posting. My back is sore, my fingertips roughed up. And when I finally had everything put back together... Can you wait?! ... No change. I kinda expected that, being a pessimist at heart, but was still disappointed. Hey, at least I lowered the ground resistance to near zero in the system's circuit.
So I kept poking and think I have probably found the real culprit: the Rowland preamp.
I should have tried some of these things first, as they're simpler, but alas, we all learn by experience, yes?
Turns out that when I run my DAC straight into the amps, the hum is barely audible. (It's a Mac server, so I can control the volume through iTunes.) That also seems to eliminate that digital equipment as the cause per se.
But here's the salient clue, something I hadn't tried before: If I disconnect all source cables from the preamp, and then disconnect the preamp from the AC power, leaving the preamp and amp connected ... the hum remains. Yikes.
I opened the preamp and looked at the power board. There is a cap with one leg connected to the ground screw via a PCB trace, but the solder connection is hair-thin. I've contacted Rowland to ask if that trace is supposed to be stronger, which I'm capable of addressing myself. But if that's not it, I'm awaiting their response, which I assume will include sending the preamp to them.
The greatly reduced hum has also allowed me to identify a little RFI in one channel, but I'll take one thing at a time.
If this stimulates any thoughts, I'd be glad to read them. Otherwise, this feels more solid to me and I hope it's the beginning of the solution.
Thanks again, all.
