Topic: This just in................

[Daryan]

It could also be oxidation on a capcitor or inductor, another guess though without being there to fool aropund with it.

[zowie]

The relation of the hum to the volume depends on where the ground loop is; if the loop is being casued at the amp or component, but can be constant or variable as you have seen.  Variable hum will come from the amp itself being the source of the loop, constant hum is generally caused by a component; but isolating either should cure it.  If you can turn the plug around (non-polarized 2 prong only) then give that a whirl.  If you have the 2910 connected to any other components, disconnect it and see what happens, you should be able to isolate it.

I think you have it backwards.  If the hum is coming from the component, adjusting the volume on the amp will make it louder or quieter.  If the hum is constant, it's got to be coming from someplace after the volume control.  It's not impossible, but I think it's not a good guess (without having seen the schematic) that there would be a ground hum problem that comes in at some point in the circuit after the volume in an integrated amp.  I guess we'll see.

Shane, try moving any other equipment at least a few away from the Jolida to see if something is possibly causing magnetic interference.

[cheshirecat]

I think you have it backwards.  If the hum is coming from the component, adjusting the volume on the amp will make it louder or quieter.  If the hum is constant, it's got to be coming from someplace after the volume control.  It's not impossible, but I think it's not a good guess (without having seen the schematic) that there would be a ground hum problem that comes in at some point in the circuit after the volume in an integrated amp.  I guess we'll see.

Shane, try moving any other equipment at least a few away from the Jolida to see if something is possibly causing magnetic interference.

Crap, yes you're right.

[shane]

Okay I tried this this morning.  I left the amp plugged in and turned on and then began unplugging evrything else around it until the humming stopped.  I have the amp plugged into the wall and a power strip into the same outlet which has my dvd, tv, & cable box plugged into that.  Nothing happened until I unplugged the strip itself.  The hum didn't stop but it did become less auduble.  Whachya think now?  Bad outlet?

Shane

[zowie]

Bring it to a friend's house.  If it's still humming, either teach it the words or return it.

[dnsacks]

shane - how many prongs does the amp's plug have?  2 or 3?

If it has 3, try using a "cheater plug" that allows a 3 pronged plug to be plugged into a 2 prong recepticle so you bypass the third (ground) plug and see if  that makes any difference --

[shane]

That worked.  Absolutely silent now.  What now?  Is this a permanent fix or is there something more I can do?

Shane

[dnsacks]

Shane -- this is unfortuantely NOT a permanent fix and you shouldn't run your gear in this manner.  However, it points to the problem likely being a bad/noisy grounding circuit in your house/on your outlet.  A substitute ground for this outlet/plug could fix the problem.  Such a ground can be made by directly wiring the ground wire to a water pipe/radiator pipe, etc. 

Do some google searching for "ground loop" (and as with any other high voltage electrical matter, be SURE you know what you're doing)

[cheshirecat]

You actually should be fine to run this way.  There really isn't any danger to you or your stereo, in fact some manufacturers spefically recommend this, like Plinus for example:

http://www.pliniusaudio.com/que/que.htm#09

"This occurs when more than one item in a system has its signal ground connected to the power ground. Circulating currents in this loop can give rise to a hum or buzz. In this case try a 'cheater' plug (no ground connection) on the power connection of the offending item. You should also try the ground lift switches."

I know cable systems generally have a separate ground to guard against lightning strikes and the like.  You could hunt around to see if there is something (maybe another tv or cable box) plugged into the same circuit that is also connected to the cable system.  Try disconnecting the cable from all TVs and such and see what happens.

[BobW]

It is debated by Audiophiles, but any electrician or electronics tech (hi ya !) with a few year's of experience will tell you that open grounds take you back to the safety standards of the 40's.  (not a good thing)
The JoLida has tube high voltage under it's hood.  Be VERY careful.

Grounded plugs are legal necessities and insurance requirements in most communities.
Bypassing them may be lethal and could void your homeowner's fire and liability coverage.
If the gear has an inherent wiring flaw, lifting ground may mask it, but the device is still defective.

What to do ?
Test the amp at another location or two to verify that it isn't defective, before the warrantees slip away.
If the amp is good:
Try a different power strip, in case it has the fault.  (You'd be surprised how may bad power strips there are, especially the "surge protector" type)

Use a VOM  get someone who is good with one (some electricians...) to verify that you have good wiring to your wall socket.
Search up "NEMA" for basic information.

Be very careful with ground-lifted gear.
The chassis may have a lethal voltage to ground, plumbing and heating systems, or other equipment.

FWIW, my opinions...don't run ground-lifted gear and and do not substitute a water pipe for a proper circuit ground.
lastly, test or have your household wiring checked.

+T for grief with new toys. It takes some of the fun out.
But you will get this figured out.
Break down the problem and eliminate a piece at a time until you find the culprit.

I had a very similar experience in a house where some fool buried a wall socket box that had leaky old cloth wiring behind some sheetrock.  I shut down circuit breakers until the bad circuit was found.
I then had an electrician run down the bad wire.

I ended up buying a power conditioner during the troubleshooting time, just to keep my sanity.
The conditioner isolated the gear from the circuit, yet allowed me to keep a circuit ground.

Good luck !  Be careful.

[shane]

Thanks for all the input guys.  I've narrowed it down to this outlet specifically.  I plugged the amp into another outlet via an extension cord and there is no hum.  I called a friend of mine (electrician for 30+ yrs and he's going to come over tomorrow so we can nail this down.  When I called him he started giving me the "its easy all you have to do is............".  That's where i come in with the "uh, that's why I'm calling you.  I don't do elctricity"  Thanks again guys I'll let you know how I make out.  in the meatime I'll continue to look and this extension cord running across my living room ands step over it everytime I go to the kitchen.

Shane

[Nick's Picks]

fucking ground loops!

there are things out there called "hum busters"...and what not that are supposed to be very effective on things like this.  I saw something very inexpensive in a parts express catalog for this as well.

My Martin Logans ...which as Electrostats needed to be plugged into the AC outlet...used to suffer terribly from ground loop hum

[cheshirecat]

I called a friend of mine (electrician for 30+ yrs and he's going to come over tomorrow so we can nail this down.

Did you end up getting this one resolved?  Any comment on what the problem was?  Might be helpful for others who encounter ground loop issues.

[shane]

I narrowed it down to the particular outlet I was using.  I have the amp plugged into another outlet via an extension cord and it works fine.  I have yet to work on the outlet yet because I'm gutting that room in about another month.  Once I do I'll post an update on wha tthe deal was with it as my buddy is going to be re wiring and replacing all my outlets, lights and switches.  So I guess an answer to your question is no.  But I'll keep everyone informed.

Shane