Component grounding

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? 

@rfprice - obviously there is some pretty strange grounding issues at play here and without being there it is difficult to advise on a solution

RE:..

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.

This indicates to me that the DAC is causing the issue not the integrated

- did you try grounding the neutral side of the output from the DAC as I suggested above??? i.e.

1. try connecting a piece of wire to the ground point on the power conditioner
2. Also try the ground point on an outlet
3. then touch the other end to THE NEUTRAL COLLAR ONLY of any unused RCA socket on your amp
4. the hum should disappear.

(Although this still doesn’t explain why the hum didn’t happen with either of the other two integrateds that I tried.) --

This is because the other two integraed amps had a different grounding scheme

You say it only hums if you bypass the pre section of the integrated

- wih both DAC and itegrated plugged into the shunyata in any combination

- but IT DOES NOT HUM if the integrated is plugged into the wall outlet

- and IT DOES NOT HUM if the pre section is NOT bypassed

So I think you have one of two possible solutions/choices.

Personally, I have ONLY EVER plugged my intergated or amp directly into the wall outlet - it allows the amp to excercise if full dynamic prowess.

I no longer use a power conditioner of any type, just a power distribution box with no "isolatoin" or filtering, but I do have a device like the Shunyata Venom Line Defender to protect the gear from surges - I also have a surge supressor on my electrical panel

Sorry I could not be of more assistance

Regards - Steve

@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. 

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. 

 

That sounds like a problem with the DAC. So if the amplifier is using its internal preamp, no hum, but if you connect the DAC to one of the inputs and use the preamp section's volume control- you have a hum (or buzz), right?

If yes it suggests an issue with the DAC. Since you did something to it as suggested in the posts above, it might be that there's more to it than a missing shoulder washer.