Rotel RMB 1095 Hum

Hobbyguy

Just got my Rotel 1095 today...hooked it up to my Yamaha RX-V2700 and Polk SDA-1Bs. With no volume there is a low hum. When the sound is up it is hard to hear the hum but during quiet the hum is audible. I tried connecting the amp to a different outlet...still hum. With the receiver off and only amp on there is a hum. When I disconnect the interconnects the hum goes away. Tried different RCA cables...still same hum. I don't have expensive interconnects but I am wondering if there is something wrong with the amp. Bought it used on e-bay. Or would better interconnects get rid of the hum? I recently searched for the same problem and one thread said that the 1095 has this hum....Does anybody know if this is true?

ben62670

You have a ground loop somewhere. Is the amp plugged in the same outlet as the AVR? Try that and see if the hum goes away. If you still have the hum try disconnecting all the connections from the AVR, and leave the RCA's attached to the amp. If it is gone you have something introducing noise to the AVR. Just keep plugging in connections one at a time till the noise appears. Cable TV can create noise too.

Hobbyguy

Thanks for the excellent trouble shooting Ben. I disconnected all power lines...tv, cable box. I have a antronix booster for the cable installed by time warner...cut power off. All power cords disconected even receiver, except amp....still hum. Disconnected cable from cable box and No HUM. Connected all power lines...no hum. Reconnected cable to cable box....hum. Anyway to filter this?
Thanks
Richard

Hobbyguy

Well I hope this doesn't put my amp at risk but it works. I plugged my three prong amp cord into a 2 prong converter and...No Hum...nothing...absolute silence!! If it is a ground loop then removing the ground prevents the loop.

ben62670

There are filters for CATV. I have an antenna, and have not had cable or satellite for years. Hopefully someone can recommend a good CATV filter. Using a cheater plug is fine in my book to eliminate hum. Just make sure the 3 to 2 is a tight fitting one. Is the power cord an IEC unit? You could just "extract" the ground from the cord:) Please try the filter route first. I am just listing options.
Ben

Hobbyguy

Well you are going to cringe....The amp did not come with a power cord...I found a power cord from one of my computers PSU and it fit perfectly (my PSUs are rated to 1000watts...it is from pc power and cooling). The Grounding adapter is from radio shack and it is almost a cold weld tight. I am currently looking for a nice MIT power cord to replace ASAP. I would prefer some sort of choke on the Cable....Any ideas anybody?
Richard

leroyjr1

Have you looked at signal cable power cords?

Hobbyguy

Haven't looked at that brand yet...but I did find:
http://www.zzounds.com/cat--2757
and
http://www.21best.com/21_best/electronic/security/video/filters/for_sale_.html
Both sound interesting....anybody try these?
Richard

Hobbyguy

I think the best answer might be:
http://www.audioholics.com/tweaks/connecting-your-system/ground-loops-eliminating-system-hum-and-buzz

It looks like I will need to buy a Cable TV ground isolator from Jenson