1

MU524 Vari-Mu Tube Compressor / Re: MU524 is noisy

« on: January 18, 2026, 09:56:23 AM »

No, I have tested some more now and the tube does not affect the problem at all.

2

MU524 Vari-Mu Tube Compressor / MU524 is noisy

« on: January 02, 2026, 11:13:52 PM »

Hi,

I have had this issue since I built the compressor, but I set it aside for a while. I’ve now taken the time to do a proper fault-finding session and would appreciate your guidance.

On startup the compressor is quiet, but after a few minutes it begins to crackle and gradually becomes more and more noisy. The crackling noise is only affected by the OUT pot. None of the switches affect it at all, and changing JMP1 has no effect either.

Here is what I have checked and observed so far:

• I have tried the unit in different lunchboxes.
• I have gone through the setup procedure again and all values seem correct, except for the following:
  
  
  • In step 6 (“Check that output voltage has risen to 3–4 VAC”), I measure 2.6 VAC with the OUT pot set fully counter-clockwise.
  • TR5 (ATN2) does not produce a clicking sound at the end position, although the trimmer itself functions correctly (step .
• I have re-soldered most of the joints at this point.
• Tapping on components has not revealed any intermittents or changes in the noise.

Please let me know if there are any specific areas or measurements you would recommend checking next.

Best regards,
Otto

3

DI503J Triple DI and Re-Amp / Schematics and trimpot

« on: January 02, 2024, 04:57:10 PM »

Hi!

I just finished the DI503J and I's my first real build since school (20 years back) and it was very a real pleasure! Definitely gonna buy more kits!

1. I followed the Setup guide, but did I miss some info about the trim-pot? What's it for?

2. I also noticed that the link for the schematics don't work. Error 404.

3. And finally an observation, I think i noticed that the sound was a little thin when I plugged an amp into the Instrument Out compared to going straight into the amp. Could this be the case? And is it something I can correct?