HUM dilemma Can anyone solve This one?

Hi bob - read your posts on hum and hope you can help my dilemma. I have lexicon dc-1 preamp, krell kav250a, ead powermaster 500 and all b&w nautilus speakers. i have a continuous hum, as long as the amps are on. The preamp can be powered off, have satellite only, and if that wire is unscrewed from the wall, the hum is still there. Use a Monster HTS conditioner, all shielded interconnects, and everything is plugged into one outlet. Had three dimmers associated with the same circuit, and switched all of them for top-of-the line lutron dimmers (at $70/each!), switching every dimmer on the circuit. In fact, I ran everything by high grade extension cord to a different outlet on a different circuit - none of which changed a darn thing! The only thing that changes the tone of the hum is increasing or decreasing the degree of dimming on the dimmers - any of them. They are all grounded properly and have the latest RF suppression according to Lutron. The other difference I notice is that the speakers powered by the EAD Powermaster 500 tend to emit a slightly louder hum than the two mains attached to the krell. but when one listens, I still hear the hum in the mains as well. I will try cheater plugs, but dont want the expensive equipment at risk, but what else can i do? the last thing i should note is that i have six halogen bulbs in the dimmer switches, all of which hum similarly when dimmed. i am told this is acceptable, but the loudness of the dimmed bulbs is quite noticeable. Any ideas? This is a real dilemma for me! When sitting in the room with everything off (lights, preamp, tv, all lights, everything except the two amps [which are always powered on]), I still hear the hum! It's just audible enough that it makes sitting in what should be a quiet room kind of annoying. One last note - just to let you know I'm not crazy - even my girlfriend has noticed the hum and she doesn't know much about audio at all. She even jokes how her $200 system has less hum than my $25k system! Please help!!

In need,
Try disconnecting ALL of your sources from your preamp. This means power cords and interconnects. See if this gets rid of the problem. If it does, add one source back at a time. First do the power cord into the wall and check that. Then connect the interconnects between the source and the preamp. EACH piece step BY step. This will tell you where the hum is coming in from IF it is source related.

If you disconnect the sources and it is still humming, try disconnecting one amp at a time. In other words, try the preamp and Krell and check results. Then try the preamp and EAD, etc.. If it does it with both amps, then just leave the amps plugged in with NO preamp connected. You've got to narrow it down as to where it is coming into the system and go from there.

I know that this can be VERY frustrating. I am currently in the same boat as you. I recently added a new DAC and i'm getting a VERY noticeable hum. While most of the reaction is between the DAC and preamp, i can plug the DAC directly into my amp and still hear the hum ever so slightly. Evidently, the DAC and that specific preamp just don't jive. Luckily, i have several of the same preamps, so i'm going to try swapping in a few others and see what happens. Who knows, i may have some leaky caps or ???

The weird thing is that changing power cords on the DAC makes a VERY noticeable difference in the pitch of the hum heard through the speakers. Who says that power cords don't make a difference ???? Sean
Hi Baz,
I completely agree with Sean, but please test PIN/RCA inlet on your preamp too; good luck!
Well, tried disconnecting things in sequence like suggested above, but this didn't work. I can't figure out if this is RF interference or a ground loop. The dimming effect on the tone of the hum (it changes with the degree of dimming) suggests to me this is somehow related to RF interference, but these new dim switches should at least have CHANGED the character of the tone somewhat. Installing the new dimmers really didn't help at all... still looking for suggestions!! Thanks! Baz
have an electrician you trust install an isolated/dedicated circuit in your home theater room. Isolated circuit / dedicated GROUND. Hope this helps Lee Ross
What Monster HTS? They overall are decent units for what they sell for, but there is better out there.
I definitely sympathize with you. I have a Lexicon DC-1 hooked in to a Krell KSA 200 for the front left and right and a Krell KAV 500 for the center and surrounds. Electricity is run through a Tice Power block. The front left and right are quiet as a tomb. The center on the other hand exhibits a noticeable hum whether the Lexicon is on or off. I've tried everything except the dedicated circuit.
Had a similar hum problem with my combination HT and audio system. Turned out to be the Krell 500 3 prong plug. Try a 3 prong to 2 prong “cheater plug” on the Krell. Worked for me…
I'll make some assumptions and some suggestions. I assume that you you do not have a dedicated circuit since you mentioned the dimmers are on the same circuit. A dedicated circuit (or 2) might help. Have you checked the polarity of your wall outlets? Have you gone to your electrical panel and turned all of the circuits off, one at a time, to see if another load on the system is causing the hum? Is the circuit for you gear run from a sub panel? If it is, you need to check that the grounds are bonded to the box and the neutrals are seperate and not bonded to ground. (the neutrals and grounds are only bonded together at the main AC entrance, from there out, they need to be apart) I strongly advise against "cheater" plugs. If this turns out to be a persistant problem, you may want to try a power conditioner with balanced 120V output.(60V+60V)
Kinsekd, I have a Krell KAV-500i that I am soon going to sell (I love it, but I no longer have a use for it). At the moment I am using it as a pre-amp only. I have noticed that when the "theatre throughput" button is engaged, there is a very distinct hum. This is on a two-channel system, I am not attempting to use it for surround applications. When that button is not engaged, the whole system is dead quiet..........
I don't have a dedicated circuit, and was going to try a cheater plug to see if it works. Why do people advise against it? The polarity checks as normal with the three pronged polarity checker. No reverse, adequate ground. Am I guessing that cheater plugs or a $1000 power conditioner are the only things that are going to help?

Can anyone explain why the dimmer switches still affect the hum to such a great degree even though they are supposed to provide superior RF suppression? Is it safe to say this is not RFI related? Thanks again... Baz
Mixing lighting and plugs on the same circuit is an industry no no.(Electrical construction) Who ever wired your house was not very bright. You may have a grounding problem at the panel itself. Or somewhere in the circuit. An unbalanced neutral or a neutral balanced on two hots can have an adverse effect. (This is a common practice in house wiring) Ballests in light fixtures create a lot of noise in circuits if applicable. A cheater plug defeats the ground completly. If there is ever a short to metal on your unit guess who becomes the ground wire. Think of your ground as a life jacket and never take it off. A good start is a dedicated circuit or two each with a dedicated neutral and isolated ground attached to an IG recptacle.
Hmmm.. Some responses make me wonder if everyone has read what I wrote above. I moved everything to a dedicated circuit by a high grade extension cord to a different outlet, on a different circuit, one without dimmers or even light switches! The tone/hum stayed exactly the same. That is why this dilemma is so confusing. There doesn't seem to be a common denominator anywhere... that is why i believe adding an isolated circuit will make this problem go away... any other ideas???? Thanks! Baz
There are those who believe that only the plug that connects to the wall outlet has to be grounded to provide protection for your circuitry. Use of multiple 3-pronged connecters into your conditoner or other intermediary components increases the chance of ground loop propagation.

Please refer to Michael Elliot's (Owner and designer of Counterpoint, now Altavistaaudio, electronics) recommendation:

Please note that Mike beleives that if yoru problem is a ground loop issue no matter how expensive your line conditioner is it won't eliminate it.
I hope this help your situation.

I had two sources of hums in my system: one turned out to be inside the amp itself (xformer was oriented horizontally facing the audio circuits and emitted electronic picked up by the audio circuitry). This was fixed by the manufacturer.
The second source was ground loop also modulated by a dimmer controlled lights. Reducing the number of 3-pronged connectors eliminated 90 % of the hum but I still have a very minor hum.

Baz I replied privately to your email inquiry, but it came back twice as "undeliverable". I then sent the same reply thru Audiogon emailer; of couse I dunno if it was received. If not then give me an email address that works OK?
Thanks bob. I'll check e-mail and try your suggestions. As for the other suggestions, nothing has quite helped yet. I'll let you know when I have time to disconnect the sources to the preamp and disconnect all the inputs to the amps and check it again. Thanks! -Baz
hi all -
tried cheater plugs and man, did that make a difference! i put cheater plugs on the krell and the ead powermaster, and the hum is only noticeable if i place my ears directly up against the center speaker only. from the listening position, it's imperceptible... must have been that darn ground loop again... thanks everyone! -baz
Now you've located the source of the problem. I would now encourage you to fix the root of the problem if possible. It sounds like you've lifted *all* the grounds in the system and that is NOT a good idea.
Actually, I only lifted the grounds in the two amplifiers. The preamp is still grounded... Is there any way to fix the main problem without having a separate dedicated line run? I already had everything plugged into the same outlet... a different power conditioner?? any ideas? thanks. baz
For what it's worth, I too have "Hum", in my system, but only when using my sensitive tube phono stage.

Finally traced it to my Monster HTS2000, despite NOTHING being "on", powered from it, (have my A/V gear plugged in to) when I unplugged the whole damn thing (Monster HTS) the hum vanished.
The ground for the cable TV entry at my place was attached to my neighbor's electrical system. Moving it to my side of the feed removed most of the hum and lowered the noise floor considerably. Using a cable ground lifter helped, too. Completely removing the connection between the CATV and stereo was the absolute solution and is the current set up. I also have to float the ground on either the amp or pre-amp to alleviate a different problem and hum. Floating the ground on the amp, which means grounding everything through the PLC, gave the best overall sound. The pre-amp sounded "drier" with its ground floated. So, now the amp has a cord with the ground wire disconnected at both ends (don't want the loose wire to play antennae). Still not comfortable with floating grounds, so am still looking into other solutions.
Denf - What do you use as power conditioning now? I too have a monster HTS but want to use something for power conditioning.

Fpeel - Cable TV can cause many problems and using a passthrough filter will certainly help rid that hum. Fortunately, I have satellite and no cable TV signal anywhere near the system. Thanks! Baz

I'm still using the Monster for my a/v sources, but again, I un-plug it when I listen strictly to my 2 channel.

I'm using the PS Audio P300 for my 2 channel "front end".
Two parts to the hum existed...

installed a dedicated 20A circuit, finally, and that significantly dimished the hum...
this allowed me to isolate each component better and determine what actually was causing trouble... once i got to the preamp, i touched the s-video cable going from dss to pre... this changed the hum... i unplugged the svid cable and the hum totally disappeared! i'm buying a new svid cable tomorrow and i'm sure that will make the problem go away... i think it was picking up rfi, because when i used my rf controller for the lutron radio ra system, i could hear the tone of the hum change significantly... that did it for me... thanks everyone!