Mono Block Ground Loop

[eth2]

Thank you Babadono.

It appears that there is something in the living room, or outside of the house on that side, that is causing the RF interference. Moving them to the den has all but resolved the issue. The amps sound wonderful without the distortion. So I guess the PA80/80 stays in the living room with the Khorns, and the PA90 goes to the Den with Cornscalas. VAC has offered to modify the PA90 to eliminate the possibility of RF interference. They are absolutely wonderful to deal with. You call and get the owner (Kevin) and if he can't fix the problem you get the head of the service department (Brent). I will be in Florida in a few weeks so I guess I will have it done. It does not matter if you own a 20 year old model or the new 90k mono blocks. It is like dealing with Mark or Bob who are also great, but unexpected with a big company.

[eth2]

Kaiser:

As your issue appears to be personal, I have PM'd you.

Edited April 7, 2014 by eth2

[eth2]

I am also finding that the interconnects play a big role in the RF issue. Long RCA cords increase the interference and shorter, higher quality interconnects minimize it.

[CECAA850]

You might have someone flip breakers while you listen to the noise so you can see what circuit is causing the problem. Once you find the circuit you can start narrowing down the culprits.

[eth2]

You might have someone flip breakers while you listen to the noise so you can see what circuit is causing the problem. Once you find the circuit you can start narrowing down the culprits.

Great idea! Thanks.

[Marvel]

3. Look for cable boxes that are attached to the room circuit. If you have one, try disconnecting the cable from the box.

My cable wraps over the feed to my house. It's awful. It was that way when I moved in, and I just haven't got around to getting them to run some new cable. (I know... good luck with that...)

Bruce

[Marvel]

Actually, I look like Cheney. I am often stopped and asked for my autograph. especially when I am in D.C. That is the real reason for the avatar.

No offense to you, but you would think it might be dangerous to look like someone who is hated by so many.

Bruce

[joessportster]

Actually, I look like Cheney. I am often stopped and asked for my autograph. especially when I am in D.C. That is the real reason for the avatar.

No offense to you, but you would think it might be dangerous to look like someone who is hated by so many.

Bruce

I don't hate Cheney, I hate all politicians EQUALLY

[eth2]

Actually, I look like Cheney. I am often stopped and asked for my autograph. especially when I am in D.C. That is the real reason for the avatar.

No offense to you, but you would think it might be dangerous to look like someone who is hated by so many.

Bruce

Short of plastic surgery, not sure what I can do.

[eth2]

I am a bit younger and a whole lot stronger than Cheney. And if I encounter someone who is bigger and stronger than me, I am VERY fast.

[eth2]

If all you have plugged in are the two amps with no other audio equipment, do you still get the noise?

Yes. In fact if the preamp is not plugged in the noise is worse. But as I said, I moved them to another part of the house and most of the noise is gone. I have tried tripping breakers one at a time, but that makes no difference.

[LarryC]

1. Look for dimmer switches somewhere in the area where you get the buzz.

I am not convinced that this is an RF problem -- in fact, in some ways it seems like airborne EMI, which is entirely different from RFI. It may be helpful to determine whether it is airborne, or comes through the house wiring.

EMI is suggested by the fact that the noise disappears when you move the offending speaks to a different floor. IOW, it might be caused by an EMI-generating source like an electrical service entry panel right on the other side of the wall behind the speaker. This is an airborne source. Moving the speaker might be the only solution. EMI is a 60-Hz hum with higher-pitch components. In my very limited experience, it does not change as you move around the room, and it only changes a little as you move wires (A/C, I/C's, etc.) in the vicinity of the speaker.

EMI likely enters the speaker through the crossover coils. I've heard of dealing with the problem by moving the coils outside the speaker!

RFI is suggested (to me) by the changing character of the sound. It will vary if YOU move around the room, or wires or components are moved by small amounts. It will contain higher-frequency components like radio signals, most notably, or hums or buzzes. I would certainly take VAC up on it's offer to shield their units. They may offer that because they know something. RFI seems to be an airborne affliction (local ham radios, etc.)

It almost seems like you're not paying attention to MDeneen's and my suggestion that you look for dimmer switches and make sure those are replaced with ones that don't cause buzzes in audio components. That's one of the good suggestions you've got here. I'm not sure whether they cause EMI or RFI, but replacing the guilty switch can solve the problem at once -- it did for me.

[NOSValves]

If all you have plugged in are the two amps with no other audio equipment, do you still get the noise?

Yes. In fact if the preamp is not plugged in the noise is worse. But as I said, I moved them to another part of the house and most of the noise is gone. I have tried tripping breakers one at a time, but that makes no difference.

Actually with power amplifiers without input level controls running them with nothing plugged into the inputs will result in noise, the RCA jacks act like an antenna floating in the breeze. The best way to determine if a power amp is making the noise internally is to short the inputs with shorting jacks. Any noise left after that is either internal noise of the amplifier or noise the circuit/tubes are picking up via the air. Once this is done and if it confirms the amps are quiet all by themselves then you add the preamp install the shoring jacks into the input chosen on the preamp with no sources attached to the preamp and so on until you find what is causing the noise...slow methodical is always best. Ground loop is almost never straight 60 hz hum and can often have a good bit of buzz along with it. Have 3 to 2 wire cheater plugs to try lifting devices from ground as you go...

Anything described as coming out of the mid horn or tweeter would not be considered hum. 60hz and 120hz Hum comes out of the woofer only. I work through this type f problem with

[babadono]

So the problem is the speakers(?) or their location in your house(closer to some source of interference). What I was going to suggest if the amps have RCA inputs is putting a shorting plug on the inputs. This document will help walk you through the process of finding your problem:

http://www.jensen-transformers.com/an/generic%20seminar.pdf

Please,please,please take 20 minutes to read this document. And like the author suggests write everything that you try and it results down. When you are on the fifth thing you try you will not remember the results of the first thing you tried. This is nothing against you personally it is just a fact about how elusive problems like this sometimes are. I have found when I try something and it makes an improvement it sometimes helps to undo it and make sure the problem comes back. That way you are not chasing your a$$.

I hate it when the laws of physics get in the way of our music enjoyment!

[eth2]

1. Look for dimmer switches somewhere in the area where you get the buzz.

I am not convinced that this is an RF problem -- in fact, in some ways it seems like airborne EMI, which is entirely different from RFI. It may be helpful to determine whether it is airborne, or comes through the house wiring.

EMI is suggested by the fact that the noise disappears when you move the offending speaks to a different floor. IOW, it might be caused by an EMI-generating source like an electrical service entry panel right on the other side of the wall behind the speaker. This is an airborne source. Moving the speaker might be the only solution. EMI is a 60-Hz hum with higher-pitch components. In my very limited experience, it does not change as you move around the room, and it only changes a little as you move wires (A/C, I/C's, etc.) in the vicinity of the speaker.

EMI likely enters the speaker through the crossover coils. I've heard of dealing with the problem by moving the coils outside the speaker!

RFI is suggested (to me) by the changing character of the sound. It will vary if YOU move around the room, or wires or components are moved by small amounts. It will contain higher-frequency components like radio signals, most notably, or hums or buzzes. I would certainly take VAC up on it's offer to shield their units. They may offer that because they know something. RFI seems to be an airborne affliction (local ham radios, etc.)

It almost seems like you're not paying attention to MDeneen's and my suggestion that you look for dimmer switches and make sure those are replaced with ones that don't cause buzzes in audio components. That's one of the good suggestions you've got here. I'm not sure whether they cause EMI or RFI, but replacing the guilty switch can solve the problem at once -- it did for me.

Larry,

I have done all the things that you and Mark suggested:

1. I disconnected the dimmer switches.

2. I went to the electrical panel and shut down each circuit separately and then shut them all down except for the circuit that the amp is on.

3. I used 3:2 plugs - absolutely no change.

4. I ran an extension cord to a far location in the house (different circuit) so that the amps would not be on the same circuit.

5. I did not move the speakers, I moved the amp and connected them to different speakers (K'horns are the ones that are buzzing and are on the second floor, and Cornscalas are the ones on the first level of the house)

6. As I said, unplugging the preamp makes a huge increase in the noise level. If I touch the grounding hub on the preamp it makes a small difference when the preamp is unplugged.

7. The VAC 80/80 has a very slight hum. It is sometimes almost nonexistent and sometimes barely audible. Same with the B&K ss

There are no motors (except for the refrigerator) that are operating. we have no neighbors so it could not be anything from their house. The circuit panel is on the other side of the house and three levels down.

I do not know what "cheater plugs" are but will get them if you tell me what to look for.

I REALLY APPRECIATE ALL YOUR HELP ... HONEST.

Thank you all!

[eth2]

Bobadano,

I will go through the document again as soon as I get home and try everything again.

Thanks

[babadono]

If all you have plugged in are the two amps with no other audio equipment, do you still get the noise?

Yes. In fact if the preamp is not plugged in the noise is worse. But as I said, I moved them to another part of the house and most of the noise is gone. I have tried tripping breakers one at a time, but that makes no difference.

Actually with power amplifiers without input level controls running them with nothing plugged into the inputs will result in noise, the RCA jacks act like an antenna floating in the breeze. The best way to determine if a power amp is making the noise internally is to short the inputs with shorting jacks. Any noise left after that is either internal noise of the amplifier or noise the circuit/tubes are picking up via the air. Once this is done and if it confirms the amps are quiet all by themselves then you add the preamp install the shoring jacks into the input chosen on the preamp with no sources attached to the preamp and so on until you find what is causing the noise...slow methodical is always best. Ground loop is almost never straight 60 hz hum and can often have a good bit of buzz along with it. Have 3 to 2 wire cheater plugs to try lifting devices from ground as you go...

Anything described as coming out of the mid horn or tweeter would not be considered hum. 60hz and 120hz Hum comes out of the woofer only. I work through this type f problem with

Don't forget the cables in this chain of troubleshooting. They can and do cause noise problems sometimes.

[eth2]

OK - I have once again gone through the steps.

I have replaced all dimmers with regular switches.

I have all circuits disable except the one in the living room; no change

I have also run a cord to another part of the house and turned that circuit on; no change

Interestingly, when I use either both 3:2 plug adapters or no plug adapters the hum is very loud. When I use only one 3:2 adapter it is still present, but perhaps 1/10th the loudness.

Flipping all breakers back on has no effect.

Turning the preamp on increases the volume of the hum buy by about 50%, but still far lower than with both plugs using 3:2 adapters or no adapters at all.

I have tried using different RCA cables without effect.

Increasing the volume on the preamp has no effect.

If I turn the right amp off the hum stops completely.

If I turn the left amp off it decreases markedly (but does not stop)

Edited April 8, 2014 by eth2

[beeker]

This is a very serious thread and i have to say once i got rid of my 901's everything started to click. I'm not kidding

[LarryC]

...and there is a loud amount of noise using either 3:2 or 3:3 plugs.

I think he said above that "Interestingly, when I use either both 3:2 plug adapters or no plug adapters the hum is very loud. When I use only one 3:2 adapter it is still present, but perhaps 1/10th the loudness." That is similar but not identical to my experience with my two Levinson mono blocs, where if I used a cheater plug on only one of them, the hum was completely eliminated. No effect from any other step taken.

Too bad that does't work that well here.

Edited April 8, 2014 by LarryC