Crunchy horrible sound Mod Duo X except when bypassed

Hi Guys,

Again, I am having trouble with my Mod Duo X.
It is much like the problem I had before: Mod Duo X problem no sound only when bypass

I am using loop 1 in the send/return loop of my amplifier.

  • When not connecting the Mod Duo X in that send/return loop -> perfect sound
  • When connecting the MDX loop 1 in that send/return loop, and bypassing loop 1 -> perfect sound
  • When connecting MDX in loop 1, and pulling just one purple cable from input 1 to output 1 -> horrible crunchy sound.

Changing the master volume does not help (changes the volume, but still the sound is horribly distorted).
Input gain is set to 0%.
It gets weirder:
Changing the output volume of loop 1 -> has no effect!
Changing the output volume of loop 2 -> changes the volume! (but still crunchy output). How is that possible. I really have only loop 1 connected. The loops are not configured in stereo mode.

Changing cables (several ones) did not help. Also when bypassing the loop 1 everything works fine.

Also it happened suddenly. I was recording for a while, and then all of a sudden this happened.

Can anyone help please.

I was about to record the biggest hit ever written, but meanwhile I forgot how it goes…

PS: I made a video of the situation.

Hi @jk_sigtermans,

Sorry to hear you are having this issue.

There is a possibility you are facing a Ground Loop situation. Its a tricky thing to identify so we have put some information here:

If the problem persists, please open a support ticket sending an email to and share the video you made so our staff can help you.



Thank you @Leo_Germani , the ground loop situation might very well be the case. I will follow-up a.s.a.p.

KR Kjeld

@Leo_Germani It was at least the ground loop situation, my audio amplifier was ground lifted. I customized it with a grounded cable and it took away part of the problem.
Still the combination of the Mod Duo X and amplifier, BlueGuitar Amp1, seems not to be stable.
I have send the support team of BluGuitar a message, see if they recognize the problem.
Thank you for (partly) pointing me in the right direction.

Hello @jk_sigtermans,

a friend of mine uses the BluGuitar Amp1 and I have the ModX as well as the Mod. Maybe I can ask him to find the solution. Would you mind to post a picture of your cabling setup and settings as well as the mod pedalboard you use in your setup via pedalboard sharing if it is a special one? What kind of guitar do you play?

If you use the ModX as an effect insert, what is the FX Gain switch position? Manual says as follows:
FX Send-Output and FX-Return Input levels dependent on switching
LOW: -10dBU +/-1dB or 0.7V P2P
HI: +4dBU +/-1dB or 3.46V P2P
FX Send-Output impedance: < 1.3kΩ
FX Return-Input impedance: > 18kΩ

You find the FX Loop level switch on the underside of your BluGuitar amp as shown on page 34/86 in the pdf.

Greetings and God bless, Marius

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