• Registered: 2023-03-13
  • Posts: 6

Topic: Ground issues when connecting ADI-2 Pro FSR to mixer

I have a laptop connected to the ADI-2 Pro. I have XLR outs connected directly to active monitors and the sound is perfect.  I also use phone 3/4 out for headphones and again, the sound is perfect. 

The problem is when I attempt to connect to a mixer which has RCA inputs. I've tried the TS outs from the rear using TS-RCA adapters and both phone outs from the front of the unit using TRS-RCA cables.  In all cases I get ground noise and significant audio degradation (I lose the top end). I'm guessing this is a fairly common problem? Is there a wiring solution?

**apologies of this has already been covered in the forum, I did search but couldnt find anything**

2 Reply by emeissl (edited by emeissl 2023-03-13 06:21:36)

  • From: living in Cologne
  • Registered: 2022-01-14
  • Posts: 40

Re: Ground issues when connecting ADI-2 Pro FSR to mixer

Just use the rear XLR, as you do for channel 1/2 and Phone out 3/4 only with a trs stereo rca adapter for channel 3/4. This will work.

On the Adi2Pro balanced phones out needs both DACs. So you can't use these in combination with the XLR out simultaneously.

Cheers, Ernst

ADI-2 PRO FS R BE / ADI-2 DAC FS / some old multibit treasuers ;-)
  • Registered: 2023-03-13
  • Posts: 6

Re: Ground issues when connecting ADI-2 Pro FSR to mixer

Thats great, thanks!  So just a simple TRS-stereo RCA adapter will do the trick, I'll get onto it!  So, presumably if I remove the XLR outs from the back I could use both phone outs with adapters to give me two independent stereo outs to the mixer and still overcome the ground noise issues?

4 Reply by KaiS (edited by KaiS 2023-03-13 14:40:20)

  • KaiS
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Re: Ground issues when connecting ADI-2 Pro FSR to mixer

roblee303 wrote:

...The problem is when I attempt to connect to a mixer which has RCA inputs. I've tried the TS outs from the rear using TS-RCA adapters and both phone outs from the front of the unit using TRS-RCA cables.  In all cases I get ground noise and significant audio degradation (I lose the top end). I'm guessing this is a fairly common problem? Is there a wiring solution?

Ground loop noise, and loss of high end are loosely related or completely unrelated.

The signal loss might origin from the mixer input being overloaded by inaudible high frequency noise.


I guess the ground loop noise disappears if you unplug USB (just for testing) - typically this noise is generated by the laptop.


In this case following solutions are possible:

• Using an Optical digital connection, laptop to ADI-2, instead of USB

• An audio ground isolator, e.g.:   
https://www.thomann.de/de/radial_engineering_sb_6.htm
https://thumbs.static-thomann.de/thumb/thumb80x80/pics/bdb/351955/9550348_800.jpg

• An USB isolator, e.g.:
https://www.amazon.de/Topping-Isolator- … amp;sr=8-6
https://m.media-amazon.com/images/W/IMAGERENDERING_521856-T1/images/I/51cGzwgyp5L._AC_SY300_SX300_.jpg

• Using one common mains power strip for ALL connected devices without exception, and keeping ALL power, USB and audio lines close together to minimize the loop area, can improve, but not remove the noise.
Sometimes grounding ADI-2, e.g. at a d-sub connector screw, can additionally improve the situation:
https://www.amazon.de/Warmbier-Erdungsb … amp;sr=8-5
https://m.media-amazon.com/images/W/IMAGERENDERING_521856-T1/images/I/51fkZPlKJfL._AC_SX679_.jpg

KaiS's Website

  • From: living in Cologne
  • Registered: 2022-01-14
  • Posts: 40

Re: Ground issues when connecting ADI-2 Pro FSR to mixer

It was too early for me to read clearly. Thought, you were using XLR (ch1/2) AND wanted to use balanced headphone out at the same time, yet this probably was a misunderstanding. Sorry for that.
Probably the device would have shown an error in that case.

BR

Cheers, Ernst

ADI-2 PRO FS R BE / ADI-2 DAC FS / some old multibit treasuers ;-)
  • Registered: 2023-03-13
  • Posts: 6

Re: Ground issues when connecting ADI-2 Pro FSR to mixer

Thanks for the reply.  I've tried unplugging the usb from the laptop and have all units powered from the same wall unit but this does not affect the noise.  I did try touching a wire from the RCA socket sleeve to the earth point on the chassis of the mixer and this did reduce the noise significantly but not completely. I may try hardwiring this from the cable?  or perhaps connecting to the ADI-2 using a grounding plug (as you suggested) would be a better option?  I know I still have the option of audio ground isolators as an option too, but I want to make sure there isnt a simpler (cheaper) wiring solution first!

7 Reply by KaiS (edited by KaiS 2023-03-14 22:38:11)

  • KaiS
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Re: Ground issues when connecting ADI-2 Pro FSR to mixer

roblee303 wrote:

..I did try touching a wire from the RCA socket sleeve to the earth point on the chassis of the mixer and this did reduce the noise significantly but not completely. I may try hardwiring this from the cable?  or perhaps connecting to the ADI-2 using a grounding plug (as you suggested) would be a better option?...

This is unusual, there’s something wrong with the RCA cables.

Try different ones, I’ve seen bad cables - often LOOKING expensive - quite often these days, that do not make reliable ground contact.

You can try bending the RCA’s outer contacts VERY SLIGHTLY inward, until plugging needs a little force, but often the plugs internal riveting is insufficient too.

Even the TRS-RCA adapters are under suspicion.


Best, skip the adapter and use TRS-RCA hardwired cables, the very basic with plastic-moulding are often the most reliable ones.
It’s NOT rocket-science.

An extra ground wire ADI-2 / mixer should not be necessary if the audio interconnects work correctly.

Grounding ADI-2 or addition of a ground wire ADI-2 to mixer is a last resort.
Better fix the real source of the problem.
An extra ground can introduce a ground loop for your other configurations.

KaiS's Website

  • Registered: 2023-03-13
  • Posts: 6

Re: Ground issues when connecting ADI-2 Pro FSR to mixer

...and the struggle continues!  I've just tried a y splitter cable (TRS to RCA) using the phone out but I still get the same noise through the mixer.  I should also add that this is only an issue when connecting the ADI-2 to the mixer, other equipment connected to the mixer is fine and also taking XLR outs from the ADI-2 straight to powered monitors is fine.  Grounding the Adi-2 is my next step, and if that fails I'll try an audio ground isolator (but I'm v. reluctant to do this).

9 Reply by KaiS (edited by KaiS 2023-03-19 07:44:35)

  • KaiS
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Re: Ground issues when connecting ADI-2 Pro FSR to mixer

roblee303 wrote:

...and the struggle continues!  I've just tried a y splitter cable (TRS to RCA) using the phone out but I still get the same noise through the mixer. ....

roblee303 wrote:

... touching a wire from the RCA socket sleeve to the earth point on the chassis of the mixer ...  did reduce the noise significantly but not completely. I may try hardwiring this from the cable?

Did you try this already?


Try that again, simply unplug one RCA on the mixer and make it’s outer sleeve touch the mixer ground screw, or move ADI-2 to make it’s case touch the mixer’s earth point.

If this helps, with any piece of wire, establish such a connection, even mixer’s side RCA sleeve to mixer’s ground screw might do the job.


Might be the mixer has an unusual RCA ground configuration, the existence of an extra ground screw points to that.

Usually only RIAA turntable inputs offer such a screw.
What’s the model of the mixer, and what’s the labeling on it’s RCA input?

KaiS's Website

  • Registered: 2023-03-13
  • Posts: 6

Re: Ground issues when connecting ADI-2 Pro FSR to mixer

I didnt hardwire a connection from the RCA sleeve to ground on the mixer but I did wrap a wire around the sleeve and connect to the ground - it was a good connection.  It reduced the noise a bit but there is still a lot of noise.  The mixer is an Allen and Heath DB4.  I do have a couple of older mixers lying around that I might try just in case its something peculiar about the DB4.

  • Registered: 2023-03-13
  • Posts: 6

Re: Ground issues when connecting ADI-2 Pro FSR to mixer

...just tried an old Allen and Heath Xone 62 and had the same issue.

12 Reply by KaiS (edited by KaiS 2023-03-19 10:40:23)

  • KaiS
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Re: Ground issues when connecting ADI-2 Pro FSR to mixer

Wire ADI-2 case to mixer ground?

https://www.allen-heath.com/media/Xone_DB4_Back_HR_28002.jpg
• Which Line in do you use?
• Line/Phono switch outer position?
• ADI-2 output level and mixer gain set reasonable?

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