How to resolve a ground loop hum from my Direct Stream DAC


#1

I am getting a 120 Hz electrical hum in both of my speakers and I have traced the source back to the RCA outputs from my PS Audio Directstream DAC. The hum goes away when I unplug my DAC, when I use a “cheater plug” on my PS Audio DS DAC power cord, or when I unplug the RCA cables from either the PS Audio DAC or my Primaluna integrated amplifier. I have tried different RCA cables, and regardless the cable used the hum is still present in the speakers. I have also connected the PS audio DAC into different RCA inputs in my PL integrated amplifier, but the hum is still present. Both the Primaluna and the PS Audio DS DAC are plugged into an Audioquest Niagara 1000. When I replace the Niagara 1000 with a standard, cheap multi outlet, the hum is still present. This is why I am convinced that the electrical ground hum/buzz is coming from the RCA outputs on my PS Audio DS DAC. Besides using the cheater plug, are there any suggestions as to what I might do to fix the ground feedback/hum?


#2

Unfortunately what you are experiencing is a common when you run a fully balanced device into a single ended device. For some reason the amps from Primaluna/Mystere brands are all prone to this. I have a Mystere brand tube amp that exhibits the same behavior if I try to use a fully balanced preamp from the SE outputs. The only way around it that I have found without the use of one of the devices from Jensen Transformers is to use a cheater plug on one or the other. Even using an XLR to SE cable won’t work.


#3

What about grounding chassis to chassis with an old run of lamp wire?

Are all of your units plugged into the same wall plate? Make sure they are.

Ted/Paul/Expert: Why don;t modern Hi Fi companies put a grounding terminal on chassis anymore? All my old equipment from the 70s have this feature… Acutally, most of my equipment from then only have 2-prong plugs also… hmmm…

Peace
Bruce in Philly


#4

Thanks! I’ll continue to use the cheater plug for now; just using feels like I’m avoiding some of the benefits of the Audioquest Niagara 1000.


#5

Try changing out the ac power cord with another one. Could be compatibility issues.


#6

Yes, I have tried three different power cords. All three produce that 120 Hz buzz.


#7

I assume there is no other equipment such as cable TV box hooked up to your audio system?


#8

I suspect you have a piece of connected equipment plugged into a different house circuit than your other stuff. Common issue … (pun), I just had it happen with my piano keyboard, headphone amp, equalizer, and amp… one of the pieces I accidentally had plugged into another house circuit… HUMMMMMMM… or you have a broken Audioquest Niagra.

Seriously, just try this… Plug in only the minimum equipment to play music… completely remove the Niagra from the system. Use only one input to the DAC. Use only one out type to the PL (RCA only). Remove ALL other inputs to the PL. Plug you PL, PS AUDIO only into the same wall faceplate. Do you get hum? I will bet you don’t get hum. If you do, disconnect the USB/Ethernet connection to the DAC.

If you get hum with this minimal 2-device setup, something is broken.

I own the DirectStream DAC and a PrimaLuna Dialog Premium HP integrated and do NOT have this problem.

Again, remove EVERYTHING from the system and start ultra-basic. Then add one piece at a time. You will find the bugger.

BTW - this has NOTHING to do with cheap cables… although, you may try swapping some out.

In the last 6 months, I had three DACs plugged into my PL all at once, and a Nikko '70s era tuner (still plugged in). All plugged into a TrippLite filter/transformer thingy plugged into a single wall socket (a dedicated 20Amp circuit- dedicated breaker) Never humm.

PS: if you use a power conditioner with a transformer (they all have them as I understand) then ALL your equipment must plug into this thing or you can get a loop (so I’ve been told - I never had a problem because I follow the rules).

Peace
Bruce in Philly


#9

Thanks Bruce. Currently my system is pretty simple: PS audio, Rega P6, and the Prima Luna HP. All of these are plugged into the audio quest Niagara 1000. The only thing I have plugged into the PS audio DAC is the wired ethernet connection to my home network. Additionally, I have a power cord connected into it, and the two RCA cables going out into my PL HP. When I run just that set up, I still get a hum.


#10

Hmm… did you try disconnecting your Rega? Disconnect everything… not just power cords… remove everything. Assume nothing.

Peace
Bruce in Philly


#11

Isn’t there a phono preamp in the mix somewhere?


#12

Check and see if the DS rca connectors are loose. I know people complained in the past about it. If loose…the connections will not make proper contact and could cause hum.


#13

Yes, but I’ve removed it to isolate the system. The hum was still there.


#14

They are a bit loose. How do I address that?


#15

Paul recommended super glue. Loose rca jack on DS


#16

The loose connection is between the male portion of the Audioquest cinnamon RCA cable and the female portion of the RCA connector on the DS DAC. Not sure I want to superglue the cable onto the back of the unit.


#17

No don’t do that… I meant the female jack connection on the DS only,not your cable into the rca.


#18

Try an ethernet cable with shield grounded on only one end. This worked for me. Bluejeans makes one. -This was a tip on the PSA forum.


#19

I recommend you to buy a unit that separates the safety ground on the power side between mains and DS power inlet.
This unit is called an isolation transformer and can be made in a few ways.
The one you look for is a fully galvanically isolated type with center tapped ground on the secondary side.
Such a unit will allow you to “open” the groundloop as with a cheater plug but still maintaining safety ground on your DS.
Getting decent and transparent isolation transformers for audio use will be much more expensive, that I can promise you.
The isolation transformer should feed the Directstream only and nothing else for this arragement to work.
Units like this for home use can be bought in Sweden, and I´m sure you can find it as well where you live.
My DS draws 20W from the mains, it is an EU model (don´t know yours) and a transformer a little larger than your DS power rating should do the job just fine.


#20

Do you have a link I can check?