Help!!!! Hum in speakers McIntosh XRT30's and MC1201's

[hotlogic]

Hello everyone. I have a bit of a problem. First I will tell you what I have in my system.

Speakers: Pair of McIntosh XRT 30's
Amps: Pair of McIntosh MC 1201's
Pre-amp: McIntosh C 2200 Tube Preamplifier
CD/DVD: McIntosh MVP 861
Power conditioner/surge protector: Monster HTS 5100
Connections are all by high end Synergistic Research cables (balanced from pre-amp to amp).
HD Display: ReVox 50" Plasma

I also have a Xbox 360 elite and Motorola HDTV tuner hooked up but that was after I noticed the problem.

In the beginning: I designed my basement to have 2 seperate 12 gauge (20 amp) circuits which are for each of the McIntosh MC1201's. I also have 2 seperate 14 gauge circuits on the same wall. I plug everything else into the power conditioner, which only uses one plug.

One side is crystal clear and the other has a slight hum. The hum doesn't come out of the amplifier but from the speakers, mainly from the midrange/tweeter section. I switched the power cords, speaker cables, and interconnects but nothing changes. The hum doesn't get louder as I turn the volume up or for any other reason. I have turned off every other circuit in the house just to see if anything may be interferring, but there was no change. I unplugged everything from the system except the 2 amps, pre-amp, the dvd/cd player, and power conditioner to try to locate the issue, but nothing changed. Does anyone have any ideas. I thought about buying some PS Audio plug ins that turn the noise in the line into light. Has anyone used these for similar problems? Any help would be really appreciated. I spent to much time and money to have my system humming at me!!!!

 

[highfigh]

At some point, these guys need to realize that big amps should be run on 220/230VAC.

Unplug the input to the amps and turn the system on. The noise should be gone. For testing, plug both amps into the same circuit, along with the pre-amp and connect them together as you normally would. Connect the sources, one at a time. If the noise doesn't come back, add another source. If the noise starts when the sub is on, turn it off to see if it changes. It could be the power supply in that. If the sub is across the room from the rest of the system, unplug the audio cable from it and see if it changes. Chances are good that you have a grounding issue.

If you have resistance in the electrical ground, you can easily introduce noise. Bypass the Monster conditioner to find out if that's affecting it, too.

You already said you don't need to turn the volume up, so a source doesn't need to be playing, although you can. The amps won't draw more than the circuit can supply unless you crank it up, so don't worry. When the amps are idling or at low power output, you'll have nothing to worry about.

Did you run speaker or audio cables parallel to power wiring?

 

[TLS Guy]

At some point, these guys need to realize that big amps should be run on 220/230VAC.

Unplug the input to the amps and turn the system on. The noise should be gone. For testing, plug both amps into the same circuit, along with the pre-amp and connect them together as you normally would. Connect the sources, one at a time. If the noise doesn't come back, add another source. If the noise starts when the sub is on, turn it off to see if it changes. It could be the power supply in that. If the sub is across the room from the rest of the system, unplug the audio cable from it and see if it changes. Chances are good that you have a grounding issue.

If you have resistance in the electrical ground, you can easily introduce noise. Bypass the Monster conditioner to find out if that's affecting it, too.

You already said you don't need to turn the volume up, so a source doesn't need to be playing, although you can. The amps won't draw more than the circuit can supply unless you crank it up, so don't worry. When the amps are idling or at low power output, you'll have nothing to worry about.

Did you run speaker or audio cables parallel to power wiring?

In this case you need to consider you may have an amp or preamp problem.

Just plug in the power amp connected to the speakers. Do you hear hum? If yes, then switch the speaker connections at the amps. If the hum switches sides, your Mac amp on that side needs service. If it stays on the same side, you likely have AC or RF penetration picked up by that speaker cable. If no, then plug in the preamp, with nothing plugged in. If there is hum, then switch the preamp channels to your amps. If the hum switches to the other speaker, then the preamp needs service, or you have a bad connecting cable. If no hum, then add units one at a time to find the source.

Since this hum is in one channel and does not change with volume, I'm suspicious of either equipment failure, or penetration of AC, or RF from a speaker lead, feeding the interference through the negative feed back of that amp channel. Possibility three is a bad cable between pre amp and amps. I think it will prove to be one of those three issues in this case.

 

[highfigh]

At some point, these guys need to realize that big amps should be run on 220/230VAC.

Unplug the input to the amps and turn the system on. The noise should be gone. For testing, plug both amps into the same circuit, along with the pre-amp and connect them together as you normally would. Connect the sources, one at a time. If the noise doesn't come back, add another source. If the noise starts when the sub is on, turn it off to see if it changes. It could be the power supply in that. If the sub is across the room from the rest of the system, unplug the audio cable from it and see if it changes. Chances are good that you have a grounding issue.

If you have resistance in the electrical ground, you can easily introduce noise. Bypass the Monster conditioner to find out if that's affecting it, too.

You already said you don't need to turn the volume up, so a source doesn't need to be playing, although you can. The amps won't draw more than the circuit can supply unless you crank it up, so don't worry. When the amps are idling or at low power output, you'll have nothing to worry about.

Did you run speaker or audio cables parallel to power wiring?

If you have Cable TV, unplug the cable feed- they're notorious for causing noise problems. If that gets rid of the noise, you'll need an isolator for the cable feed. Also, Code requires that all Cable TV, Satellite and Telco service be grounded at the demarcation point, or as close to it inside the structure as possible. If done outside, connecting to the main ground, or a separate ground stake should be used. If inside, attaching a ground to the main panel or the water supply pipe where it emerges from the wall are recommended. IIRC, NEC Article 250 deals with this.

 

[Rickster71]

Hi hotlogic welcome to Audioholics.
It sounds like you have different ground potentials between your 20amp receptacles, and one of the 15amp circuits.
If you're able, or know someone who can; check the ground connections on the four circuits you're using.
It's a process of elimination to see which receptacle, or cable TV lead is the guilty party.

Your MC 1201's are well within the ampacity of your 20 amp circuits; no worries there.