[dsrviola]

I've never dealt with hum issues before, so forgive my ignorance. I've got hum coming out my speakers now that I've hooked up my new subs (a kit from Rythmik Audio. Quite nice) With my current set up, the only way I can run the subs is via their hi level input. There's no hum with the amps just plugged in and on, but when I connect the amps to the output from the main amp (tried via the speaker binding posts and via the amps binding post) I get hum. Sounds like a ground loop problem, yes? I've tried cheater plugs, and reversing polarity on the AC to no avail. Any ideas on how to track this down and eliminate it would be most welcome.

Thanks!

[Imperial]

So, you've built the subs yourself?
You could install dc blockers in them then... on the input. It could be a cap..
Or you could put a small transformer on the input, that could also do it.
Or you could "cut" the screen in you signal cable, if it has one. That is only connect the positive center pins...
Or you could make sure the screen on the ac cable to the amp is not connected to ground, thereby eliminating an
ac ground loop if that is the problem... Assuming this is okay with the amp in the sub... Ask Rythmik BEFORE doing this... 
ALWAYS try any of this with the volum at lowest setting, then slowly turn up...

Imperial

[dsrviola]

Yes, I built them with a friend.

Wouldn't putting a cap before the input create a high pass filter? And would I put it across the terminals or on each leg? It hums with just one of the legs (either + or - ) hooked up.

[Imperial]

Yes, I built them with a friend.

Wouldn't putting a cap before the input create a high pass filter? And would I put it across the terminals or on each leg? It hums with just one of the legs (either + or - ) hooked up.

Well, the Rythmic amps have 30K input impedance (line level input..), so using a 1 micro-farrad cap (Or parallel a pair of 0.47 micro-farrad caps for 5.6hz..) gets you
a rolloff of 5hz... your signal is down with 3db at 5hz...

Anyway, have you mailed Rythmik yet about this hummmmmm issue?
Maybe they have a fix for it.


Imperial

[Imperial]

Well...
You get hum from your main speakers, when using a pair of subs?

Er... Is the subs humming as well or just your main speakers?



You could also try using a 3 to 2 prong plug adapter on you subwoofers ac cords. That has been known to remove hum.
You could also remove you cable tv plug from its socket to see if this works... Yeah! That can be a source of groundloop as well in your powergrid!

If using a 3 to 2 prong removes the hum... the ground loop could be in your house grid... and that could mean you need to have an electrician to really remove this gremlin all together. That would of course be a last resort, because you then have got something wrong with the grounding in your ac outlets...

Imperial

[dsrviola]

I tried the cheater plugs all over the place (nothing improved), and the stereo (w/ subs) is on a dedicated circuit, so the satellite dish shouldn'timpact the system.

[Imperial]

You could try the subs on a different circuit breaker to see if this removes the hum...

Read this: http://www.psaudio.com/articles/hum.asp
Perhaps you see something there that makes sense.

Finding out where the hum is coming from is definitely best done "on site" as trying to guess the right scenario is difficult 

Imperial

[jules]

Could you give us a few more system details?

You're running the sub off your "main amp". Do you have a pre-amp?

jules

[dsrviola]

No preamp. Just out from the DAC into EVS Attenuators which are plugged directly into the amp.