This is a long post but it's only because I've read, done exhaustive testing, and had an audio tech and an electrician investigate and still have no solution. Any insights are welcome and appreciated.
The problem is a hum/buzz from my amp. The chassis itself -nothing audible through the speakers. It is a fluctuating hum that rises and falls in volume and repeats any time I have my television, proc and amp, and cable box on and the TV is on the same circuit as the rest of my gear.
The reason for not installing a separate circuit is that this is a rental. For now, I have an extension cord run to another circuit for the plasma. It's a Band-Aid. I would like to know what s happening, why, and how to resolve it so I can eliminate this as a possible cause of an audio related issue that I will not get into at this point.
Gear:
Integra DHC 80.3
Comcast Cable - hdmi through the Integra to the tv
Rotel 1095
Panasonic ZT60 plasma (using input 3 - not the ARC input - however the ARC input behaves the same)
Symptoms:
1. The Hum/buzz whether oscillating or constant appears not to be the plasma only, but a combination of the plasma and the cable box on the same circuit.
2. Removing the plasma from the circuit eliminates the hum.
3. Moving the cable box to a separate circuit, and keeping the plasma on the primary circuit with all the other gear "does not" eliminate the hum.
4. Lifting the ground on the amp or the tv has no impact.
5. When cable box and Plasma are on the same circuit:
a) TV on, Cable input selected on pre amp and cable box off - no hum
b) TV on, Cable input selected on pre amp and cable box on - hum is present
c) TV off, Cable input selected on pre amp and cable box on - no hum
d) powering off the cable box, powering off the tv, disconnecting the cable feed from the cable box, disconnecting hdmi out from proc to the plasma, and selecting an input source other than cable all eliminate the hum
e) While I know it had hummed with the BluRay player on in the past, I cannot replicate that now. It appears to be only the cable. Maybe user error- perhaps I failed to turn off the cable box in previous tests
What I've already done:
1. Had Comcast rerun the ground to the service ground rather than the little grounding rod they installed
2. Had Comcast disconnect all unused cable lines (they may not have gotten to them all under the house)
3. Bought a Viewsonic inline coax ground loop isolator
4. Tested with a receiver, cable feeding the receiver via optical and component video - receiver pre-outs to the Rotel. Same hum.
5. Tested with an older DLP I have. This tv operates fine on the same circuit. Difference being it's a DLP, and it uses a 2 prong polarized plug while the plasma uses a 3 prong.
6. Had an electrician monitor the draw on the breaker and with every component in the system, and everything in the room turned on, with music well above reference pushing all 5 channels and both subs, the draw was only 11-12 amps on a 15 amp breaker.
7. Replaced cable box
8. Replaced breaker
Considerations:
1. I've read that Plasma TVs can cause not only - but specifically toroidal transformers to buzz/hum. Has anyone reading this experienced and solved this?
2. Local Audio Pro suggested it may be a bad power supply in the plasma. I have a warranty but am reluctant to have the set disassembled unecessarilly as it's no longer in production and irreplaceable if damaged. I consider this a last resort.
3. Audio Tech recommended some power conditioners with isolation banks. They ranged $2 - 4k. Sarcasm aside, If I could afford a $2k+ power station (willingly that is) I'd just have bought a better processor. I hope there is another solution.
Again, any knowledge anyone is willing to share on this will be greatly appreciated.
The problem is a hum/buzz from my amp. The chassis itself -nothing audible through the speakers. It is a fluctuating hum that rises and falls in volume and repeats any time I have my television, proc and amp, and cable box on and the TV is on the same circuit as the rest of my gear.
The reason for not installing a separate circuit is that this is a rental. For now, I have an extension cord run to another circuit for the plasma. It's a Band-Aid. I would like to know what s happening, why, and how to resolve it so I can eliminate this as a possible cause of an audio related issue that I will not get into at this point.
Gear:
Integra DHC 80.3
Comcast Cable - hdmi through the Integra to the tv
Rotel 1095
Panasonic ZT60 plasma (using input 3 - not the ARC input - however the ARC input behaves the same)
Symptoms:
1. The Hum/buzz whether oscillating or constant appears not to be the plasma only, but a combination of the plasma and the cable box on the same circuit.
2. Removing the plasma from the circuit eliminates the hum.
3. Moving the cable box to a separate circuit, and keeping the plasma on the primary circuit with all the other gear "does not" eliminate the hum.
4. Lifting the ground on the amp or the tv has no impact.
5. When cable box and Plasma are on the same circuit:
a) TV on, Cable input selected on pre amp and cable box off - no hum
b) TV on, Cable input selected on pre amp and cable box on - hum is present
c) TV off, Cable input selected on pre amp and cable box on - no hum
d) powering off the cable box, powering off the tv, disconnecting the cable feed from the cable box, disconnecting hdmi out from proc to the plasma, and selecting an input source other than cable all eliminate the hum
e) While I know it had hummed with the BluRay player on in the past, I cannot replicate that now. It appears to be only the cable. Maybe user error- perhaps I failed to turn off the cable box in previous tests
What I've already done:
1. Had Comcast rerun the ground to the service ground rather than the little grounding rod they installed
2. Had Comcast disconnect all unused cable lines (they may not have gotten to them all under the house)
3. Bought a Viewsonic inline coax ground loop isolator
4. Tested with a receiver, cable feeding the receiver via optical and component video - receiver pre-outs to the Rotel. Same hum.
5. Tested with an older DLP I have. This tv operates fine on the same circuit. Difference being it's a DLP, and it uses a 2 prong polarized plug while the plasma uses a 3 prong.
6. Had an electrician monitor the draw on the breaker and with every component in the system, and everything in the room turned on, with music well above reference pushing all 5 channels and both subs, the draw was only 11-12 amps on a 15 amp breaker.
7. Replaced cable box
8. Replaced breaker
Considerations:
1. I've read that Plasma TVs can cause not only - but specifically toroidal transformers to buzz/hum. Has anyone reading this experienced and solved this?
2. Local Audio Pro suggested it may be a bad power supply in the plasma. I have a warranty but am reluctant to have the set disassembled unecessarilly as it's no longer in production and irreplaceable if damaged. I consider this a last resort.
3. Audio Tech recommended some power conditioners with isolation banks. They ranged $2 - 4k. Sarcasm aside, If I could afford a $2k+ power station (willingly that is) I'd just have bought a better processor. I hope there is another solution.
Again, any knowledge anyone is willing to share on this will be greatly appreciated.