Component grounding

I installed the nylon washer between the chassis and the ground wire ring.

That doesn't sound right! If there is a connection to the chassis (and I'm assuming it comes from the center pin of the IEC connector) it would not be insulated from the chassis by a nylon washer!

Am I misunderstanding?

 

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.

@rfprice 

Hm. That kind of suggests an isssue with the amp. Have you tried other amps when the preamp is in the system?

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.

This is caused by something called a ’ground loop’. Its generally a sign that some part of the system is inappropriately grounded. I’m not talking about the power cord and its ground connection nor the use of a grounding post (which I think you’ll find won’t help).


I’m talking about the way a component is internally grounded. How it should work is if there is a metal chassis, it should be grounded thru the power cord. But if the audio circuit inside is directly grounded to the chassis it leaves the circuit open to ground loops. To avoid this, none of the audio circuit should be tied to chassis, instead an impedance of some sort (a resistor perhaps) should go between the two, allowing the audio circuit to float at ground potential (this is the reason why RCA connectors have insulating shoulder washers to insulate them from the chassis, even though the barrel connection is 'ground'). The resistor should be high enough resistance (if a resistor is used) to prevent the ground loop.


I’ve really boiled this down; grounding can be a very complex issue!


If you own a component that has a poor internal grounding scheme (IOW its use causes a ground loop in your system) you can get around the problem by use of an isolation transformer between the AC outlet and the component. Its not the best solution (you have to get a big enough transformer) but it does work. I prefer to have the grounding of the components set up properly to begin with...