Headphone output silent when same output connected to output 1 and 2

On my MOD Dwarf if I connect the same output to both output1 and output2, the output on the headphone goes dead silent. It is like the 2 output channels are canceling each other out in the headphone. If I connect input 1 to both output 1 and output 2, I get nothing in the headphones. If I only connect to one of the outputs I get the stereo signal.

If I take a distortion pedal for example, and connect input 1 to it’s input, and connect output 1 of the distortion plugin to output2 while the direct signal is still going to output1, I get the sound of both, but if I connect in addition to this output1 of the distortion plugin to output1 of the dwarf, I only get the “clean” signal.

My use case is that I would like to have output 1 with cab simulation, while output 2 without cab simulation (so prepared for the signal to be sent to a power amp and cabinet). Ideally I would like to be able to pick which output the headphone is using (output1, output2 or output1+output2). So far I was unable to find anything that could help me with that.

Wow :dizzy_face:, this is really strange ! It’s like the phase is inverted after your outputs !

  • Did you try with another pair of headphone ?
  • can you check if your headphone jack is plugged all the way through your the output jack of the Dwarf ?
  • Is this the same with the jacks outputs ?
  • You have the sound of both on each output or clean on the left and distortion on the right ?
  • if you turn of the distortion, you get nothing, right ?
  • This I don’t understand what you did, could you precise ?

It shouldn’t be a problem, and it should be straight forward…

yes, exactly, it’s very weird.

yes, same result

I have checked, I can’t push the jacks any further in.

I’m not sure what the question is :frowning: Output1 and output2 works fine. If I use 1 for cabsimmed, 2 for not cabsimmed output, I get the appropriate outputs.

If I have anything connected to either outputs (1 or 2) I hear both of them in left and right of the headphones.

This configuration gives me only clean tone only. If I disconnect one of the distortion outputs from output1 or output2, i get both distorted and clean outputs in both left and right headphones.

Okay, I really thinks there is a problem with the headphone output of your unit, but it could be a software problem since I think it does this :

take your software outputs 1 & 2
=> revert the phase of the 1st or 2nd output
=> merge it in mono
=> send this to both headphone outputs

Do you have the last firmware ?

I think you should send a request with these infos to the support : MOD Audio - Customer Support Form

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I have, which I think is the latest.

I will drop a mail to the support.

can you try to do the same connection with a simple meter, to make sure this is not a simple signal phase cancellation?
like so:


Sure, It’s not cancelation, I did the following:

The meter shows the same output but if I toggle the bottom switches second switch from the top, the power meter reading gets output but I get no distorted sound on the headphones.

The rackarack plugin also has an option to negate polarity, which also has no effect on this.

However if I take 2 rackaracks and turn on the negate polarity on one of them only, I get the distorted sound in the headphone again.

that seems like a plugin issue to me. that inverse polarity parameter could be broken perhaps.
honestly don’t know why a distortion would need such a thing.

I think it just underpins your theory. If I negate polarity on one of them the sum of the phase shifted and not phase shifted signal will be 2x instead of 0 I believe.

not sure what you mean, the summing of phase-inverted waves results in no signal.
waves cancel each other out when one of then is inverted in phase.

right, and this is exactly what happens when I route both distortion to output1, I get only the clean sound on output1 and on headphone outputs.

However if I change the output of one of the distortions to output 2, I get no output on the headphones when both devices are in the same phase-shift setting, but i get output when they are in different phase-shift settings. Also please bare in mind that on my unit (I’m not sure if that’s how it’s supposed to work) but headphones seem to mix both output1 and output2 to both left and right on the headphone.

This also works with ANY plugin. As soon as I put in the same signal to output1 and output2, that signal disappears from the headphone output, so the underlying issue isn’t plugin specific. The signal also disappears from the headphones if I just connect input1 to output1 and output2.

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ok I think I understood, thanks for explaining in detail.

doesnt seem like a software issue to me, but a hardware one. like a trace that gets where it should not…
please write to support@mod.audio and mention this thread so we can return your unit for a fix (or most likely a board replacement)

I have already written to the support via the contact form, sofar I haven’t received any response.

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ok then please be patient, it is just a few of us taking care of things now.


I’m back after getting a replacement unit the headphone output seems to be working as “expected” output1 goes to left, output2 goes to right.

I can’t seem to be able to find the settings where i can pick which output goes to the headphone (output1, output2, or the current setting output1 to left, output2 to right).

I don’t think you can, but if needed you can switch the virtual cables going to output 1 & 2.

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:frowning: so.my particular use case is:
output 1 - with cab sim to the front of house
output 2 - without cabsim to my power amp

headphone output to inear monitor. But in this case i guess i would need stereo → mono jack connector, to overcome this.

Am I correct in assuming that this is a physical wiring limit and not a software one?

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yes, headphones match what the output jacks are mapped into. there is always only 2 audio outputs in hardware on the dwarf

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I understand the number of output port limitation. I was wondering if the headphone left/right channels are hardwired to output left/output right or it’s just some Jack connection that is made by default.

they are connected directly on the PCB/hardware, so not possible to setup differently