Rotel 1066 and subwoofer hum-please help

[rd1bruce]

I have the 1066 and 1095 amp. When I connect my subwoofer(Martin Logan Descent) I get A noticable humm even with no signal being processed.What am I doing wrong? The sub offeres a few ways to be connected: 1.Left and right rca plugs
2 LFE plug
3. Sub in rca Plug
4. Sub out rca plug
The back of the 1066 has sub 1 and sub 2 preouts. I have tried connecting using just the individuale sub 1 and sub 2 and also using sub 1 as the left channel and sub 2 as the right channel. I get the hum both ways. With power to the subwoofer but no connections from the 1066 there is no humm.

PLease Help-
It's driving me crazy

Thanks

[skullmurdoc]

You should try to change your wire to see if this is causing your problem. Also make sure your cable is not touching a power cable or something like that. I had the same problem but with all my loudspeaker. The problem was interconnect that was passing too close of my power bar wich was causing interference.

Hope this help.

Frederick Richard

[Foxman]

I agree with skullmurdock, the only time I had a sub that had a hum it was because I had a bad cable. Also, I would not run the sub cable from both sub out 1 and sub out 2. Check your owners manuel for the sub and see if it matters that you use both left and right inputs. On my SVS it doesnt maettr, and it plainly states in manuel that unless I have a left and right out on the AVR not to use but one input on the sub.




You just can't fix stupid

[BKSinAZ]

In reference to your contection...Left and right connections are not needed. I myself would only use #4 (sub out RCA) There is no need for two connections to go into your sub. The single rca will do just fine. Submit a follow up on your problem to let us know what actually resolved your problem

[rd1bruce]

Thank for everyone's input. I am going to try all the above suggestions tonight. Will let you know what happens.

[skullmurdoc]

Yo rd1bruce,

Its been tree days now and you didn't tell us if you fix the problem or not. I cant talk for the other but I really want to know if we helped you fix your problem. If so what fix it ??? If not can we help you furter more, or did you just give up and trash your 1066. I hope not hihihihihhihihihihihihi.

Give us some update man !!!

Frederick Richard

[rd1bruce]

Sorry guys.
I had to leave town for a few days. Will be working on your sugestions this week end and will definitly get back and let you know how it goes.
Thanks Again

[rd1bruce]

Still have hum . I replaced cable and do not have it toching A power cord. The owners manual to the sub says to run a left and right channel for 2 channel music and run one cable to the lfe connection for home theater. I have tried both however still have hum. The strange thing is even with the power off to the 1066 & 1095 I get the hum.

[Kevin D]

Try a 3-prong to 2-prong cheater plug on on the power cord to the sub.. I wouldn't leave it on there, but it could let you know if you have a bad ground..

Kevin D.

[ckong]

Seem like a ground loop problem, pls goto this web-site:

http://www.epanorama.net/documents/groundloop/home_solving.html

[LEVESQUE]

Don't laugh at my solution, but I was having a hum with a Servo-15 + RSP-1066 and RMB-1095.

I bought 2 big slab of concrete, 3 inches thick each, put the Servo-15 on it...hum is gone... and the bass is tighter and less boomy.

For 10$, it was one of my best "tweak" 8)

BTW, the Servo-15 was on a woodfloor, thus the vibrating and the hum.

[BKSinAZ]

GREAT! I think I will do the same.......maybe an over sized marble tile or something that my wife will approve of.

ANYONE wana buy a wife?.....hehehehe

[sndtowne]

Hum is usually caused by a difference in ground potentials.

Give this a try - try breaking (disconnecting) the shield on the cable between your processor and your subwoofer cable and see what happens.




Bruce

[rd1bruce]

Thanks again guys. I will be home this sunday and will try each suggestion.

[sconcina]

I recently acquired a Rotel 1066 and instantly introduced hum into my system, just like you. Some rooting around pinpointed the root cause to a misguided decision by Rotel to have a two pronged plug for AC in. They could have been forgiven for that if there was a grounding lug on the unit, but there isn't.
That means that the receiver is not properly grounded in my installation, since I measured 0.2 V between GND and neutral at the plug. The Bryston amp has a ground lift switch and it worked better in the 'lifted' mode.
Out of desperation, and before I went out and purchased an isolation transformer, I took 12 AWG cable, plugged it into the ground pin of the AC socket and started touching the various interconnected chassis that should be ground. As soon as I touched the ground of any of the connectors on the back plate of the '1066 the hum was GONE. I then made a cable to make a 'professional' connection to the '1066 with a 3-prong AC plug on one end, fat cable in the middle connected only to ground on one end and to the shield of an RCA plug on the other. I plugged the RCA in an unused video in socket and the AC plug to an outlet on the same power strip as the '1066 and the amp.
Of course a word of caution when working around AC (even if around the ground/neutral portion). Always measure the voltage between the points you are about to short for ground loop cancellation. In fact I also measure current, to see if I am about to cause some problems somewhere else. If you see less than 1 V and less than 50mA, you are going to be OK.
Hope this helps !
Stefano