Humming Pod

[gabster]

Hi Folks!

Great to be here (heard of it from Audiodude of a post on the bwacksforum.com).

I thought of starting this thread even if the Firepod I own is currently taken care of by the folks at Presonus (THANK YOU!)... anyway here is the case:

Please keep in mind that this exact behaviour is the same on one of my friend's Firepod also that lives a couple blocks away from me.

The problem (hum):
New Firepod, all is fine, etc., but the MAIN CR output has a 60 cycle hum in the studio monitors and it's being heard ONLY if I turn the volumes on the monitors past say half. Both channels. Also heard on the PREs out (but not so accentuated)...

The setup:
Not even connected to the PowerBook - simply the Pod has only the power adapter connected to it. No mics in, no headphones in, nothing but the cable for the audio out.

I contacted Presonus - the folks there were very helpful and I might have even discussed with Rick Naqvi :D - I don't remember) among others.

What I tried (without success):
- Balanced 1/4" cables (base/sleeve/tip).
- Checking for the hum by inserting a headphone on the MAIN CR outputs. Obviously that line level is so low that I was not able to hear anything.
- Lifted the ground on the studio monitors in hope of breaking any possible ground loops.

The room is wired to the same breaker and the outlets are grounded. Also there are no fluorescent lights.

As I said the Pod is taken care off at the moment (I think it just arrived there) but I only was curious to know if I was missing something, or stuff like this. It is interesting that the same behaviour occurs with my friend's Pod...

Thanks a lot!
GAbi.

[itsplayed]

Please keep in mind that this exact behaviour is the same on one of my friend's Firepod also that lives a couple blocks away from me.

Hi gabster, good to have you aboard,

I'm assuming that you ruled out the monitors themselves.

Is there a nearby radio or TV transmitter within a mile or so of your system?

[gabster]

Thanks itsplayed...

Yep - monitors are rulled out. And nope there is no transmitter nearby. I thought of that possibility as well...

Thanks,
Gabi.

[ricknaqvi]

Try lifting the ground on the computer.

I had a similar issue when using my Dell XPS laptop. After lifting the ground on the powersupply of the computer, it was clean as a whistle.

(I actually wound up pulling of the third prong of the powersupply. Not something I would recommend, but I was out on a gig and didn't have a groundlift so I had to improvise!:D )

[gabster]

Hi Rick...

Thanks for the reply.

But I don't even have a computer connected to the Pod. That's what puzzles me...

thanks,
Gabi.

[itsplayed]

Have you tried plugging the card into different circuits?

[TubeGeek]

Hello everyone,

I have the same problem with my firepod. A small faint hum in my monitors. I have checked my balanced trs to xlr cables and they are good.

I recently relocated and the hum has followed me so it is not bad wall grounds. I have checked all wall outlets where I am living now and they are good. I have tried connecting to different outlets etc and still nothing seems to get rid of the hum.

I have my firepod connected to my mac via firewire.

The hum was not present when I purchased it back in May 2006.

Gabi...have you solved your hum? Good to see fellow amp builders here!

[gabster]

TubeGeek!!!! is that you from the 18watt forum???? Ha! I am not the only one tube head tinkering with digital audio (don't tell the other community or else they will ex-comunicate me lol).

My latest Humming Firepod Updates:

I received it back from Presonus where after two audio tests it passed. So it returned to me with "no problems found"...

I plugged it in, (please note: same wall outlet, far from any buz/hum sources, balance cables and no computer plugged to it - simply Firepod->monitors via CR OUT), and he HUM IS STILL PRESENT :-(

In fact I discovered the the hum is still present with the MAIN volumes all the way down!!! And I discovered that it is more accentuated on one channel whereas on the other the hiss is more accentuated.

I started seriously suspecting the Power Adapter, so I called presonus and they are sending a new one to me. I am skeptical that it will solve the trouble but I will try it nevertheless.

I became however very curious to hear from other Firepod users if they do have this hum on theirs and it always passed as unheard? Not sure - As I said a friend, a couple blocks away from me has the same exact issue.

Will post the results after receiving the new Power Adapter...

Thanks you,
GAbi.

[TubeGeek]

I am 100% positive it is something to do with the firepod because I have connected my monitors to other recording platforms and they don't hum.

I hope it is the power adaptor...that would be a easy fix. I will be anxiously waiting to hear your results.

[Audiodude]

If your Firepod is humming...


Did you try teaching it the words?:rolleyes:

Sorry, couldn't resist.

[gabster]

I am 100% positive it is something to do with the firepod because I have connected my monitors to other recording platforms and they don't hum.

I hope it is the power adaptor...that would be a easy fix. I will be anxiously waiting to hear your results.

I REALLY do wish that the power adapter is the culprit... I hoped that the hum would be catched in the two tests that were conducted on it. Oh well.

thanks,
gabi.

[TubeGeek]

Have you received the new power adaptor?

[gabster]

TubeGeek...

Not yet. Apparently they sent it two days ago so I am looking at getting it sometimes early next week. I will definitely post the results...

Rick: Any suggestions what could be wrong? If it's not the power supply - I've hit a wall. I'll be actually posting some sound samples with the hum.

Thanks.
Gabi.

[TubeGeek]

I will be at that wall with you Gabster.

It does sound like a power supply hum...so it could be that a filter cap has dried out and stopped working or something to that effect. If it is not the power transformer/supply/adaptor then I'd start looking into filtering in the power supply.

BTW... I left my firepod on continuously day and night for two months before the hum appeared. It is hard for me to forget that the hum is there. It is like having hum in an amp;)

[ricknaqvi]

Gabster,

I wish I could tell you what the problem might be but unfortunately this forum is the first time that I have heard of this issue. After shipping tens of thousands of these, we are definitely in tune with common problems that people might have and unfortunately this is not a common one. However, I don't doubt that it is real for both of your guys.

Most of the time, a ground hum is solved by lifting the ground on *the computer*, not the Firepod. But if your Pod is humming with no computer, then there is obviously an issue that we didn't catch back at the factory when we got it back.

However, I will promise that we'll get to the bottom of it. If it is not the powersupply, please contact me or Wesley directly. (Same for you Tube Geek)

Thanks,

[gabster]

Rick...

Thanks a lot for your help! It is GREATLY appreciated!
I really hope this thing will be solved because I really like the Firepod. It has very transparent pres at an excellent and accessible price.

I will get back with results once the new adapter arrives. You are right, TubeGeek... There might be a dry electrolitic or something.

Anyway - thanks Rick again!

GAbi.

[jmail]

I don't know about the brick's tolerances on your box, but have you checked your house's voltage? An under-voltage may cause trouble with electronic gear. Have you tried the box in other rooms of the house, and other locations besides where you are? Have you and your friend tried to swap set-ups? Are you certain your cables to the monitors are good? Home-built, or store-bought? Are the pre-amp gains up or down?

[Casioman]

Hi everyone
I've had similar problem but since I'm in Australia it's a bit expensive to return H/W to US for analysis. But since our voltage is 240 I needed to get a converter from 120 to 240 for the firepod to work. BUt it was noisy so I got a AC to DC converter which complies with the firepod spec, it works well with 24VDC. Maybe it's worth while to try it if everything else fails.

[TubeGeek]

Gabster,

Any update on the power supply?

[gabster]

Folks...

The Pod returned from Presonus with "Problem Not Found" again after beeeing sent in the second time... I plug it in with hope.... The HUM was still present.

I took things into my own hands --- and I FOUND THE PROBLEM with the POD. And I FIXED it!

A detailed description with pictures will follow... First I want to talk with them :-)

Thanks,
GAbi.

[TubeGeek]

Kewl...I was considering opening mine but I figured because it is on warranty, why bother.

I am anxious to get rid of the hum...it drives me nuts.

Look forward to your instructions.

[gabster]

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:
http://www.gabtone.com/gablog/images/firepod/1.jpg

http://www.gabtone.com/gablog/images/firepod/2.jpg

2. Now... can you can see that S/PDIF socket? Can you see the metallic part that is between those two RCA connectors? BINGO!!!
http://www.gabtone.com/gablog/images/firepod/3.jpg

THAT IS THE CULPRIT!!!

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.

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

http://www.gabtone.com/gablog/images/firepod/4.jpg

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!
http://www.gabtone.com/gablog/images/firepod/5.jpg

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!

Cheers,
Gabi.
____________________________________
Gabriel Sound Garage - The color of tone...
www.gabtone.com
847 394 5091
Arlinton Heights, IL

[TubeGeek]

Thanks Gabi...I will be very happy when this is hum free. I will get into it tonight.

[gabster]

kool TubeGeek!

Tell us the results!

I will be doing this surgery on my friend's Firepod as well tonight!

Good luck!
Gabi.

[TubeGeek]

You da man Gabi:cool: :cool: :cool: :cool: :cool:

Thanks for checking into this and figuring it out. Presonus needs to give you a job!

It worked like a charm and mine is quiet as can be now.

[gabster]

Yeeehaaaaaw!!!!!!

if Presonus decides to make guitar tube amps.... maybe! heheheheh

Glad to hear you did it! Enjoy pure quiet sound!!!!

Gabi.

[vbrilon]

Hi, I just found this thread while googling for why my newly bought Firepod has a hum in it. Any chance you could repost the pictures so I could try to fix my own device?