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Old 4th December 2011 | Show parent
Originally Posted by tenkas View Post
This is info I have found a year ago... I just copy pasted it in a text file and do not have the sources... I believe it was on the presonus forum, you can probably google it.

Guys I thought some of you FIREPOD users might run into this problem and I finally found the fix after two times sending the unit back to Presonus and coming back from them with Problem Not Found:

Ok Folks!
here is the fix. it is an easy one and as expected, a ground loop (I know - I had to battle this in my amps...)
1. Take the case off your Firepod. You need a Phillips screwdriver and a 1/2" hex socket for the rear jack nuts.
- There are 2 screws on the top, 2 on the bottom and 3 on the rear (the S/PDIF and the two MIDI mounting screws) .
- Remove the 16 rear jack sockets with the 1/2" hex socket.
- remove the two side brackets.
- Disconnect the Power connector from the PCB board.
You are cleared now to carefully slide the case out:

2. Now... can you can see that S/PDIF socket? Can you see the metallic part that is between those two RCA connectors? BINGO!!!

When the case is on, it creates a groundloop that induces the hum by touching the case and it needs to be isolated...
This is confirmed by Presonus as beeing an issue on older (2 years ago) Firepod construction that apparently was fixed at one point using an S/PDIF socket that doesn't have that metallic part, or something similar).
The metallic part does NOT have to touch the case by any means since it does not have any electrical use at that point.

--->>> continuing in the next post since I am allowed to only post 4 images per post...

continuation from previous post...

3. So, I simply used masking tape to isolate it from the case:

4. I mounted the case back (don't forget to connect the power connector back in its place in the PCB board), using all the screws BUT THE S/PDIF one and VOILA!
NO MORE HUM! Problem solved!

Wanted to post this here knowing of the fact that there are Firepod owners that have the same issue, and hopefully this way providing an easy fix - enjoying this way a hum-free excellent piece of gear!
Can someone confirm this?

I'm having a groundloop issue whenever I want to plug in a guitar and I just can't seem to get rid of it. Signal chain:
GTR (tried several) -> PreSonus FirePod -> 2x Phonic P6A Monitors or headphones (no difference)

I tried ungrounding everything and to ground everything. What do I need to unground here:
- Laptop
- Firepod

The problem is fixed when I put my pedalboard after my guitar, but I dont always want that.
To clear this up: the noise in this thread is just the regular noisefloor, right? I've actually just seen this post (the one I quoted above) regarding the groundloop. Before I want to open it up, I actually want to know if there's anything I'm doing wrong. It might just be the way I've got it hooked up.