topping D30 buzzing (leaking AC)

[mercury]

Greetings, ASR

I have a topping D30. Recently I noticed it a buzz sound coming from the speakers and isolated it to the topping D30. It is not super loud at normal listening but it bothers me nonetheless. Measured the AC coming out of the line out and got a reading of ~ 3.5v. It was measured with a super cheap multi meter so probably not very accurate. Anybody experiencing similar issues?

 

[Noodles]

Sounds like a ground loop, check it on another outlet or in another house

 

[mercury]

Sounds like a ground loop, check it on another outlet or in another house

What would the ground loop be caused by? The D30 is not connected to anything. I have tried with various outlets in the house but it still buzzes. It is also, the only equipment that has this issue. I am beginning to think it is kaput.

 

[Noodles]

Oh wait, my bad. The RCA out should be 2V. Most times the RCA in on other equipment can be overdriven with too much Voltage to the point where it exhibits a certain buzzing or crackling.
It's weird that it goes up that high ... - level it to 2V and try again.

 

[mercury]

The thing is, the ~3.5v RCA output is there with no input signal.

 

[Noodles]

There is still going to be some voltage when the unit is powered and no signal is given, but 3.5 is a lot.
Unit is prolly busted, you hear the buzzing with no signal on your speakers i take it ?

 

[mercury]

Yeah, there is a buzz through the speakers with no signal. It is barely noticeable at the nine o'clock position of the volume but at 12 o'clock you know something is wrong. Initially I thought it was my amplifier which pissed me off a great deal.

My understanding is that the D30 gets 15V DC from the wall wart so there should be no AC coming from the line out with no signal. I am guessing that the cheap wall wart power supply is leaking some AC which is not filtered internally by the D30. Unfortunately, my multimeter is pretty useless and cannot measure any AC from the DC plug.

I have to borrow a bench power supply from a friend and see if it still buzzes.

 

[mercury]

Just a follow up on the topping D30 buzzing. It was caused by the floating ground design of the DAC and the connection to the specific amplifier. Connecting it to a different amp produces no buzzing.

 

[mercury]

Yet another follow up. The D30 seems very susceptible to AC noise. Some days it is very quiet and some days it is picking up a lot of noise. Here is trace I took with a scope.

 

[Nibelungen]

Yes, i have similar problem. We have not ground loop. With an groundloop, the frequency would be 100(120 for you) hertz. If no signal on unit, the stabilizer does not work . i use xlr transformer for my monitors. The sound, of course, becomes darker, but there are no problems with interference. I think that LPSU fix this problem better.