Component grounding

@williewonka -- Thanks, Steve, I'll try that. The amp has a three-prong connection. Defeating the ground prong with the cheater plug made the hum go away.

Something funny happened yesterday. The integrated has a function that allows you to bypass the preamp section and use the output control on the source component instead (the DAC, in this case). I tried that for the first time yesterday and the hum came back. When I reengaged the preamp section, the hum went away again. 

Thanks for the helpful input. 

I introduced a 'new' integrated into my system and a hum appeared. In fact, I had owned this same model integrated about 10 years ago and seem to recall a hum at that time too. My tech friends assert that there are no technical defects, just something peculiar about the components' interaction. The hum goes away when I plug the amp into the second receptacle of the wall outlet, or when I use a cheater plug to connect it to the Shunyata. 

Ultimately I modified a power cord, disconnecting the ground wire. That took care of the hum, but then I began to worry that the amp was now ungrounded. So I installed a wire between the phono ground post and the grounding posts on the Shunyata. Maybe it's not necessary. 

@williewonka  -- Yes I know it's not an ideal solution.

I will try your suggestion to run the wire to the RCA terminal. 

@atmasphere  -- Thanks for this. You're right, it's complicated. (You are also right that the grounding post made no difference.)

 

I'm starting to wonder if the problem has more to do with the DAC. As I wrote above, when I disengaged the preamp section of the amplifier to control the volume with the DAC output control, the hum came back, even though I was still using the modified power cord on the amp. But then again, this didn't happen with two other amps I had on hand. 

@williewonka  -- I tried the RCA terminal solution but it had no effect. 

 

@atmasphere  -- No no, I meant the preamp section of the integrated. It has a feature that let's you bypass the preamp section and use the output control on the DAC instead. When I did this, the hum came back. I don't know what that means, but you're right, the issue must reside with this particular amp because I've never had a hum otherwise. 

@williewonka  -- Exactly. When I unplugged the amp from the Shunyata (using the non-modified power cord) and plugged it into the free receptacle on the wall duplex (the Shunyata occupying the other receptacle) the hum disappeared. So that would suggest . . . what? That the isolated zones on the Shunyata are not so isolated after all? 

This got me thinking. Several months ago I opened the DAC to try a specialty fuse. To free the cover, you have to disconnect the chassis ground.

 

--As I wrote earlier, when I disengaged the preamp section on the integrated and engaged the output control on the DAC, the hum came back. Also, over the last few weeks as I've been trying different combinations in order to try to identify the culprit, I noticed that the hum kicked in when I connected the interconnects from the DAC to the integrated. It didn't happen when the components were merely plugged in and powered on. (Although this still doesn't explain why the hum didn't happen with either of the other two integrateds that I tried.) --

 

Anyway, this morning I decided to open the DAC again to check whether I reattached the ground chassis correctly. I discovered that there was no shoulder washer. Whether I lost it or it was never there, who knows. So I installed a nylon washer and powered up again. 

 

No difference. Still a hum. 

I also tried connecting the integrated and DAC to a single zone. No difference. 

 

So perhaps the integrated has a bad chassis ground? 

@williewonka -- Thanks for all your advice thus far. It's much appreciated.

 

The neutral collar is the outer metallic 'shield', correct? If so, I did run a wire from the ground post on the Shunyata to the collar of an RCA of the integrated. No effect. You mention a similar operation with the DAC? 

 

You're right that it would make the most sense to just connect the integrated to the wall. But I like what the Shunyata does for the integrated. It doesn't suck a lot of juice so I don't think I'm losing much in terms of power. The other components are just a DAC and transport, so the Shunyata is not taxed. 

OK, I can't post the link. Anyway, it doesn't say more than I just said. 

@atmasphere -- That's starting to seem to me like a likely explanation also. Plus the fact that the hum begins when the interconnects are inserted, not when everything is simply powered on. But I really didn't do anything to the DAC except switch the fuse. I'm very careful when doing any kind of operation with my equipment, and as I said earlier, there is no hum with the other two integrateds. One is a solid state, the other a tube.

 

I installed the nylon washer between the chassis and the ground wire ring. Then a ground washer screws against the ring. Is it worth trying another nylong washer between the ring and the ground washer? 

I wish I could post a photo of what I mean. If you follow this link to page 7, it talks about a ground wire running from a grounding block on the floor of the chassis to a screw on the side of the top cover. Before you can do anything internally, you have to disconnect this wire from cover; otherwise you can't get the cover out of your way. So, what I did, I put a nylon washer between this wire (which has a ring termination) and the chassis. Then a ground washer goes onto the end to screw it all down. Does that make sense?