Headphone output noisy without audio ground noise loop isolator

I’ve copied my comment from [solved] High noise level at all times - #22 by ericfontainejazz below:

The headphone output on my ModDwarf that just arrived today is very noisy. Using the power supply that came with it out of the box. It has the same noise regardless of whether I plug in any other connectors (other than power and headphones).

I also have had a similar but much quieter noise on my ModDuo, though I am using another 12V supply for that (that came with an old labtop, which is 5A and only has 2 power plugs instead of 3 plugs). Swapping the powersupplies results my ModDuo output become more noisy than it was before, and the ModDwarf being less noisy than it was before. But the ModDwarf is still much noisier with the good power supply than the ModDuo is with the bad power supply that came with the ModDwarf, so most of the problem seems to be with the internal circuitry of the ModDwarf, but some of the problem seems to be from the power supply that came with the ModDwarf. (note: I’m plugging both power supplies into the same wall outlet.) So in summary the noisiness from most noisy to least noisy is:

  1. ModDwarf with its original power supply
  2. ModDwarf with another powersupply from a labtop
  3. ModDuo with the ModDwarf’s original power supply
  4. ModDuo with another powersupply from a labtop

Now a trick as mentioned is to insert an audio ground noise loop isolator between the headphone output and your headphones…I happened to have one (I got mine for $6 from PJRC Store ). That dramatically cuts down on noise coming into the headphones.

Though at least there is no noise on the actual balanced line outputs, when routed to another mixer or interface which accepts balanced line as input.

Anyway, as I guess I am a betatester for moddwarf, I’d recommend the devs take a look at this ground noise problem…and maybe consider including a headphone ground loop isolator when shipping it if can’t be addressed in hardware.

Got my Dwarf today. The headphone jack produces very little noise, much less than the Duo I had before. I get some noise from the input, though when connecting my Yamaha Montage. The weird thing is that when connecting my Yamaha MODX - which is the cheap version of the Montage - it is not producing noise…

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Can’t it be a ground loop issue?

I used the Rolls Buzz Off device to get rid of the high pitch. This from output Dwarf to interface.
I also bought new cables and one big power block for plugs to count out other causes.
It seems to be connected to Dwarf but not sure what exactly.

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