DSjr Single-Ended Ground Loop Problem


#1

I have a DirectStream Junior, which is manifesting an unusual ground loop problem, for which I am unsure how to correct.

If I connect a single output (unbalanced) from the DSjr to either input of a 2-channel power amp, there is no ground hum. When I connect the second channel - I get a pronounced hum. To clarify, I can connect left output to right input, left to left, right to left, right to right - it doesn’t matter - no hum. It’s when I add the second connection, I get the hum.

Note that when using balanced connections, there is no hum.

I am experiencing this issue with three different 2-channel power amps (Bryston, Halo, Sony ES). Strangely, I’ve also tried using a pair of monoblocks (Cary 300B tube amps) - and they don’t produce the hum.

Note that for the sake of completeness, I connected the power amps and the DSjr into the same power outlet. The hum persists.

I suppose I should try engaging the DSjr attenuator, to see if that corrects the hum - as there is also white noise present - enough to be bothersome.

Any suggestions as to what might be happening here, and how to address this problem?


#2

Do you get a “hum” or a “buzz” when this happens? I am guessing a buzz because it sounds like a ground loop. Can you try an AC cheater plug on the power amp to see if that matters?


#3

Yes, it is sounding and acting like a ground loop. The odd part is that I have to connect both left and right channels to produce the 60Hz buzzy hum. If either channel is connected by itself, the 60Hz noise does not appear (or maybe it’s buried in the slight amount of white noise that is also present?).

Given that both channels have to be connected, it is acting as though the ground loop is actually between the left and right channels of the DSjr. I notice that the output jacks are isolated from the chassis, so perhaps that is a possibility?

I tried lifting the ground on the amps - but no change in behavior.

Thanks for responding.


#4

Perhaps you have a power cord or ground wire going thru the loop formed by the two interconnects? In general you don’t want wires going thru the loops formed by other wires. The output jacks have their grounds tied together on the Jr.


#5

Interesting suggestion, and of course, spot on. The interconnects were forming a receiving loop of some sort. By repositioning them, the hum could be reduced somewhat. There were no power cords involved (they are now, and have been, as separated as possible).

In the end, I switched cable manufacturers, and the problem pretty much disappeared.

On a related topic, I engaged the output attenuator, to get rid of noise (my power amps have too much gain) - and we must have had a power glitch or something, because when I brought the DAC out of standby, the attenuator had removed itself from the circuit. I didn’t notice and when I hit “play” I was greeted with a blast of sound I will not soon forget. No speaker damage done, luckily.

Is there a possibility of providing a setup choice - to choose the “default” position of that relay? Or perhaps even lock it engaged? It sure would provide a measure of safety for those of use who must use it.

Thanks (for your help and designing/building a great product).


#6

A power glitch shouldn’t change the attenuator setting. The only times I know of it spontaneously changing is sometimes during a software update (the more common glitch during software update is that one channel will change volume.) Could you keep a watch for anything that changes the attenuator, I’ll keep an eye out here too.

Could you run a little experiment for me? If you press the Mute button on the remote do you hear a relay click? If not that’s a problem with the attenuator, on power up we mute, then toggle the attenuator twice to keep the relay contacts clean and then (if appropriate) unmute.


#7

Pressing mute, I do not hear a relay click. Powering down (using power switch on back panel) I do. When reapplying power, I am also hearing a click at the end of the boot process.

Also, if I power down (using power switch on back panel) with attenuator engaged, when I reapply power, the unit comes up with attenuator disengaged. It does, however, remember its last used volume setting.


#8

Thanks. I can confirm all of your tests and they indicate at least two bugs in the user interface. I’ll make sure they are fixed in the next release.

Bug 1) Pressing mute should do a hardware mute (with the mute relay) as well as a software mute (“multiplying samples by 0”)

Bug 2) The system should always boot with the same attenuator setting that it had when powered off.

I don’t know when these two bugs crept in and I’m very surprised that more people have noticed/reported bug # 2.


#9

The DSJr i ordered arrived today, yay!, but i’m having this exact same issue with a buzz on the single ended outputs when both are connected. I’ve tried various things [different interconnects, different power cables, ground cheater power cable]. In the end I set it up with the simplest setup i could think of, the DSJr and an X-Can headphone amp are connected to the same outlet [which is a dedicated circuit, the x-can is a 2 prong wall wart, so the ground to the Jr should be the only one], and there’s no input connected to the Jr. With both singled ended outputs connected to the X-Can there’s a distinct buzz on in the headphones, changing the input, volume, or attenuation on the DSJr doesn’t change anything. I’ve tried 3 different sets of interconnects. I’ve ensured that neither power cable is near the interconnects [as much as possible], even with short interconnects i still get it. Disconnecting either input fixes it. Any suggestions?


#10

Sounds like a ground loop. Can you try a three prong to two prong AC cheater plug on the DSJ?


#11

Just tried DSJr on 2 prong cable + X-Can [2 prong wallwart] still the exact same issue, tried 2 different sets of interconnects. Nothing else connected to DSJr, just headphones plugged into the X-Can. This is the same result as with my main power amp (Musical Fidelity A5), I have an Arcam solo that’ll i’ll also test with.


#12

DSJr to the Arcam solo also exhibited the same issue. Other sources including a GCPH phono stage, Linn Genki CD player & Bluesound node streamer all perform fine connected to the same power outlet & interconnects. I’ve tried AudioQuest, VDH & Nordost interconnects with any noticable difference. I’m out of ideas at this point.


#13

Maybe Ted has an idea. Otherwise, let’s get you in touch with Jeremy on Monday and we’ll figure it out. So sorry this happened on a weekend, a weekend you’re expecting to simply enjoy your new DSJ.crying_gif


#14

Until you Superfell said that the Jr with other output devices also generated a hum I was going to suggest turning the wall wart over on the X-Can headphone amp. If there’s a hum no matter what the device downstream of the Jr is I don’t what else to suggest than a call to support.


#15

mwaustin, you mentioned changing cables fixed this for you, which cables did you switch to?


#16

i to have exact same problem DS j and ground loop noise. i have tried everything , but no change .

i have quite a loud buzz humm , but only from ps audio DSj . tried difference amp , all power lead into single outlet , power leads to thor smart power board , ever thing in post above , no change .frown

also i have ps audio restarting , and showing 60r on screen.confused

i have not updated with huron yet , i have spent all nite re trying to get rid of hum ground loop. i have had this since the ist time i got the DS j. around dec 2016.

i love the sound , using DSJ roon, pioneer , marantz integrated, redgum power amps ,wink


#17

Hmm, I just see this thread now. I had the same problem when I first connected my DSJ. Most notable through the Neumann speakers which seems to be a lot more sensitive. Through the Audionet mono amps I didn’t notice it. Anyhow when I connected through XLR the problem was gone.


#18

I received my DirectStream Jr last week and have been struggling with the same ground hum issue described in this discussion. I tried all kinds of configuration changes for days. Then in desperation went on line and found this forum. I have read this discussion carefully twice and I don’t see a specific solution proposed other than switch to XLR cables which will not work with my current preamp. The hum only occurs when the Jr is the input source into my preamp. My CD player using its internal dac or tape deck don’t cause a hum. They never did. Unpluging my computer from the system does not add or remove noise. I simply did not have this noise before with the prior NuWave3 DAC.

I am using a VTL preamp and Bryston power amp. All cables are top notch Cardas including the power cords.

I have moved the equipment around to get the DAC as far way as possible from the power amp. The interconnects are as far away from the power cords as possible. Definitely not touching or looped. I tried different power cables. I put a 3 to 2 prong plug on the power cord going into the DAC as well. This made no difference at all.

The only difference I noticed in my situation is that the one interconnect versus two does not change the hum level in the side which is attached.

So far I have reduced the hum from very noticeable to a lower level but it is still there.

So… what exactly would the next step be other than returning this unit and asking for my trade-in back?

Thanks for any help you can provide.

Dan…


#19
Daniel Rosenberg said

I received my DirectStream Jr last week and have been struggling with the same ground hum issue described in this discussion. I tried all kinds of configuration changes for days. Then in desperation went on line and found this forum. I have read this discussion carefully twice and I don’t see a specific solution proposed other than switch to XLR cables which will not work with my current preamp. The hum only occurs when the Jr is the input source into my preamp. My CD player using its internal dac or tape deck don’t cause a hum. They never did. Unpluging my computer from the system does not add or remove noise. I simply did not have this noise before with the prior NuWave3 DAC.

I am using a VTL preamp and Bryston power amp. All cables are top notch Cardas including the power cords.

I have moved the equipment around to get the DAC as far way as possible from the power amp. The interconnects are as far away from the power cords as possible. Definitely not touching or looped. I tried different power cables. I put a 3 to 2 prong plug on the power cord going into the DAC as well. This made no difference at all.

The only difference I noticed in my situation is that the one interconnect versus two does not change the hum level in the side which is attached.

So far I have reduced the hum from very noticeable to a lower level but it is still there.

So… what exactly would the next step be other than returning this unit and asking for my trade-in back?

Thanks for any help you can provide.

Dan…


Hello Dan,

Thanks for posting your issue. From what you describe it sounds like a specific interaction in your system is causing some noise. Our only recommendation other than lifting the ground would be to use XLR interconnects. As this is not an option for you we can recommend that you have a look at this tutorial regarding ground loops and hum:

http://www.psaudio.com/ps_how/how-to-find-and-fix-hum/

Regarding a return we ask that you contact us at service@psaudio.com about this. We’ll need your serial number and contact information to ascertain the warranty status of your DsJ.

Thanks,

  • Jeremy

#20

I have found two work arounds for this issue after having tried most cures for ground loops over a few months time ;

One way is by using an audio isolation transformer that galvanically isolates DSJ RCA left and right channel grounds in the recieving end (transformer inputs)

The other way is to convert the DSJ XLR outs to unbalanced using an external converter, either active or one using isolated line transformers.
Note that simply soldering /buying an adapter cable just using XLR hot or cold + ground (DSJ) -> RCA (recieving end) will hum just as the unbalanced outputs.
The hum is unfortunately present on DSJ XLR hot and cold as well, although in phase meaning that it gets balanced out in the reciever.

I don´t think many users reflect over this issue, as most of the times normally one uses XLR on equipment of this class.

For me this means that I avoid to connect my headphone amlifier to the DSJ RCA and instead connect it to fixed line out
on my Hegel 360 instead - which is connected balanced to DSJ.

I have decided to accept this limitation / flaw as the DSJ sounds so good compared to any other DAC I have listened to so far.