You are not logged in. Please login or register.
RME User Forum → ADI-2 & 2/4 Pro series, ADI-2 DAC series → ADI-2 DAC hum
Hello!
I have a ADI-2 DAC. The Line Out is connected to my power amplifier with XLR:s, i.e. a balanced connection. As long as the DAC is turned on everything works just fine, no problems, but if I turn of the DAC (but not the power amplifier) there is a loud hum in the speakers. This has never happened before. Until recently I had a Lynx Hilo connected in the same way without any problems. What to do?
I probably also ought to mention that my power amplifier has a ground connection.
Disconnect the SPDIF coax cable. Same problem? Disconnect the ADI power supply. Same problem?
Yes. It is the same problem if I disconnect the spdif coax. And also if i disconnect the ADI power supply. It starts humming.
So you get hum when no other cables/connections exist other than the XLR cables? Makes me wonder then if those cables are soldered incorrectly, with ground or Pin 1 removed on one side. To check that you could also additionally connect an RCA cable between power amp and DAC.
I doubt the DAC is at fault here. If the same cables worked with the Hilo, that one might have been ground-connected to your power amplifier in some way.
I tried with another pair of XLR:s. Same problem. Still Humming.
The Lynx Hilo had a ground-connected power-plugg and was connected to the same power-outlet as the power amplifier. The ADI has no grund-connected power-plugg.
I can not connect the power-amplifier and the DAC with a RCA. The amplifier has no inputs for RCA. It is for XLR:s only.
Hi again. I connected the DAC to another Power-amplifier. Problem gone. Seems the problem has to do with the power amplifier itself. Strange. This has never happened before, but the ADI-DAC has no ground-connection, i.e. no power plug with ground connection. I have never used a DAC or Preamp with no ground-connection before.
Now I suddenly have another problem.
You can easily 'ground' the DAC by connecting housing or RCA ground with the other unit. But basically the problem is somewhere else. Does that power amplifier have a ground-lift switch (usually on the back) that needs to be changed?
Hi again. Yes, it has a ground lift switch. Switching it is lowering the amount of hum, but it does not disappear. There is still a significant and unacceptable amount of hum. When I connect the DAC to my other Power amplifier the speakers are dead silent.
A question concerning ground. Are both the RCA and XLR-shield connected to the chassis? Is it balanced internally as well?
Yes, full ground to chassis connection. I don't understand the second question.
Concerning my second question. I can´t explain it better myself, so if you excuse me I will paste an explanation from Wikipedia.
"Most audio products (recording, public address, etc.) provide differential balanced inputs and outputs, typically via XLR or TRS phone connectors. However, in most cases, a differential balanced input signal is internally converted to a single-ended signal via transformer or electronic amplifier. After internal processing, the single-ended signal is converted back to a differential balanced signal and fed to an output.
A small number of audio products have been designed with an entirely differential balanced signal path from input to output; the audio signal never unbalances. This design is achieved by providing identical (mirrored) internal signal paths for both the "non-inverting" and "inverting" audio signals. In critical applications, a 100% differential balanced circuit design can offer better signal integrity by avoiding the extra amplifier stages or transformers required for front-end unbalancing and back-end rebalancing. Fully balanced internal circuitry has been promoted as yielding 3 dB better dynamic range, as explained above, though at increased cost over single-ended designs."
Best Regards
That's in the manual. It has a balanced signal path inside.
Ah. Thank You. I had not noticed it was in the manual. Sorry.
I have been trying to figure out why my power-amplifier is humming.
I connected one of the DAC.s RCA line-outs with the ground rail in the outlet, and the hum disappeared.
I have been in contact with the constructor of the power amplifier, and he says it is built according to some sort of standard concerning ground, but I honestly don´t understand what that means. I am no electrician so it is difficult for me to figure out what this is about. But as long as the power amplifier is connected to the CD-player I suppose it is also connected to the same ground as the power-amplifier as the CD-player has a grounded power-plug. If I disconnect the CD-player, the the humming starts again.
Regards
Hello again!
After trying to figure out why I get hum when I connect ADI-2 to my power-amp, I can´t see no other reason than the difference in ground-connection when comparing the ADI-2 and my power-amp. My power-amp has a grounding connected to the chassis and to the ground-rail in the power outlet in the wall. The ADI-2 has no grounding to the ground-rail at all. When connecting one of the DAC.s RCA with the ground rail, the hum disappears. This is not a perfect solution however. I find this a bit confusing, cause I would have expect the ADI to be usable with grounded gear.
Regards
The ADI should get your power amp's ground through the XLR cable. It seems your power amp has no ground connection of pin 1 of the XLRs to ground. If so that is not under our influence, and not an industry standard at all.
To me it sounds like the ground lift switch of the amp might not be working ok, It looks (sounds) like it is permanently in ground lift. Try wiggling it a few times and if that helps maybe some contact spray.
Or there is something wrong with the XLR cables, you will need a cable checker or multimeter to be 100% sure.
If you have a multimeter you could also check MC's theory and see if there is a connection between ground and pin1 of the amp itself.
Goood luck!
Vincent
RME User Forum → ADI-2 & 2/4 Pro series, ADI-2 DAC series → ADI-2 DAC hum
Powered by PunBB, supported by Informer Technologies, Inc.