Sub Phatty Hum

[Bald Eagle]

I'm getting a fairly loud hum from the Sub Phatty audio output jack. I have tried connecting to a Motu 896, a Korg M3 and directly to a powered monitor and still get the hum. I get the hum even when the Sub Phatty is powered off. The hum stops when i disconnect the power cord. The headphones are perfectly quiet in all configurations.

I don't know anything about ground loops other than reading bits in forums but could this possibly be a ground loop problem? I don't have to many options as far as where I can locate my gear and power sources. Someone told be to try plugging in the Sub Phatty into a ground loop eliminator and that into the power strip. Any thoughts or suggestions would be greatly appreciated.

[nofuturenocore]

Hello are you sure that you use Mono Jack and not a Stereo Jack ?

[Bald Eagle]

Yes, it's definitely a mono jack.

[till]

Please use all audio gear from the very same main socket. And be sure, that the fridge is not on the same fuse.
This hum is not normal at all for the SubPhatty or other Moog gear. So there might be something defective somewhere in your set up. Hard to tell what is causing the actual problem.

[nofuturenocore]

Ok and do you try to only plug the Sub Phatty in the electrical outlet you are using ? ( This is improbable because your headphone output work correctly and your other gear too but it's something to try.)
Sometimes Lights or other devices can cause this kind of problem but a part this I don't see, maybe a fabrication problem but coming from Moog I find this weird...
You never make a wrong connection between CV inputs and your sound card instead of the audio output or do you use CV higher than 5v or use an other power cords ?

About the ground if you use a 3 PIN ( Phase Neutral Ground (Don't know if it's called like this in English)) Outlet plugged directly into a corresponding Outlet this shouldn't be the problem but I don't know anything about US Outlet and I'm not Electrician so this is something to verify ( I got the European version of it ).

[Bald Eagle]

Thanks to everyone for the feedback. I have a solution that seems to solve my hum problem although I suppose it's really just masking it rather than properly correcting it at the source.

First I'll say a little more about my configuration. There is a double outlet on the wall on its own circuit from the breaker box. One of the outlets is connected to an APC UPS which has 5 battery backup outlets and 5 more that are just conditioned, not battery powered. I have the MOTO 896 connected to a conditioned outlet in the UPS. The second outlet from the wall has a power strip. I think its just a simple strip, not even a surge protector (yikes!!!). That power strip has the Sub Phatty and an extension cord which goes to a TV and cable box. And of course there is a mess of audio, midi, usb and other power cables all around it.

So all that being said my solution was an EBTECH Hum Eliminator Model HE-2-XLR. I can really crank up the volume and there is no hum or hiss at all. This device really works great.

http://www.ebtechaudio.com/hedes.html

I guess this will do for now but I will have to go back at some point to try to find the true source of the problem. There is not much I can do about the wiring as I am an apartment dweller so this hum eliminator box may be my only choice regardless of any other findings. Of course if anyone thinks that this box is a bad idea I would like to hear about it but an electrician did recommend it so I was assuming it is perfectly safe.

[Bald Eagle]

Just for a final update ... I have moved the SubP to its final resting place. I have a surge protector coming from the wall. Its on a dedicated circuit. There is an M3, an ink jet printer and of course the SubP plugged in to the surge protector. I still get hum. With the Hum Eliminator device Its perfect.

I did have my doubts about that device but I give it a thumbs plus for anyone having a similar problem.

[modoc_333]

Usually those things work to break a ground loop rather than filter hum. You need to figure out why you have a loop. Test it first by hooking it up all by itself. If you have a ground loop, it could be dangerous. You could also have a polarity issue. Maybe your Sub is wired backwards.

[Amos]

ground loops are so easy to get, especially if using USB, and or powered speakers, and or a computer audio interface... perhaps all of the above! all it takes is two paths to ground for your audio signal to get hum.

my point is just that "maybe the synth is wired backward" is probably the least likely explanation here; this is a common audio situation and one which the Hum Eliminator was invented to solve. Everything's probably OK here.

[Bald Eagle]

ground loops are so easy to get, especially if using USB, and or powered speakers, and or a computer audio interface... perhaps all of the above! all it takes is two paths to ground for your audio signal to get hum.

my point is just that "maybe the synth is wired backward" is probably the least likely explanation here; this is a common audio situation and one which the Hum Eliminator was invented to solve. Everything's probably OK here.

Thanks for the feedback Amos. I'm coming to terms with Ground Loop being a part of the musical audio domain. Another thing that occurred to me is that being an apartment dweller I have no control nor do I even know what wires lies on the other side of the wall that may be causing interference.

So like Amos said, this problems exists and they make devices to deal with it. The SubP sounds awesome.