Classe and B&K amp buzzing through speakers (1 Viewer)

[Eric_RP]

HELP!

I am experiencing a buzzing noise through my speakers. My setup is: Denon 3803 - Main pre-out (L & R) is split and input into 4 separate channels of my Classe CAV-180 to passively bi-amp my main speakers. Center pre-out is input to 5th channel of Classe amp. My surround (L & R) and rear surround (L & R) pre-outs are input to B&K AV5000ii amp with the 5th input capped with shorting-plug. With the system hooked up this way I get a buzzing sound out of my mains (mid and tweeter not the bi-amped separated woofer) and my center speaker. If I turn off the B&K amp (the amp is positioned directly on top of Classe on next cabinet shelf) the buzzing is greatly reduced to acceptable level.

I have disconnected everything and I don’t think it is a ground loop. I have a dedicated HT 20A circuit and I tried cheater plugs on both amps with no change.

I thought it may be something with splitting the main signal and inputting it to the same amp, so I tried switching inputs so the woofer output of my mains went to the B&K amp and the surround speaker pre-out went to the Classe with the rear surround remaining hooked to the B&K. Weird thing happened, the buzzing sound came from the rear surround speakers then??

I would like to figure out what is happening so I can enjoy for a while prior to possibly going to a dedicated pre-pro, B&K Ref 50 (I will need to save some cash to upgrade). If I upgrade to the Ref 50, with my current amp and speaker setup, I would use the RCA outputs for the woofer output and the XLR outputs for the midrange and tweeter I would not be splitting the signal and I’m thinking that that is the basis of my problem.

Please reply with any suggestions.
Thanks,
Eric

 

[Charles Gurganus]

"the amp is positioned directly on top of Classe on next cabinet shelf)"

I'd try to seperate the amps for starters. Have you tried disconnecting cable TV? (if you have that)

 

[Eric_RP]

Charles, Thanks for the reply. I have tried disconnecting the Cable TV with no change. I will try seperating the amps, I was wondering if the power supply of the amps might be influencing each other and the signal out to the speakers.

Any other suggestions?

Eric

 

[Charles Gurganus]

Eric, I'd bet moving the amps will make a difference. Make sure you don't have a stray speaker wire or RCA's touching.

 

[Ted Kim]

Since the hum changes location (speaker) depending on which amplifier you are using, this is tricky.


Have you checked your cable management? i.e. speaker wires should be spaced from interconnects and should not run parallel. If they must be in close proximity they should cross at right angles. Same thing goes with power cables and the interconnects.

 

[Eric_RP]

Thanks for the reply. I will separate my amps by at least another shelf and I will also check my cable spacing. I have tried to separate my cables from the speaker wire and power cords as best as possible, I have my speaker wires running directly down through the floor behind the equipment rack/shelfs and run through the basement to come up at the appropriate speaker. I have not had the problem before just running the speakers directly through the receiver or when I was only using the B&K amp prior to getting the Classe. I will also check to make sure the speaker wires do not run parallel with any cables or power cords. I have quite a cabling issue as I also have a DVD-Audio and SACD player running 6 cables each into a switch box then to the 3803.

Would the upgrade to the B&K Ref 50 likely have a lower background noise level especially using the XLR connections or will I have the same issue if it is an interaction between the amps?

Thanks,
Eric

 

[Charles Gurganus]

I don't think changing preamps will do the trick but you may also want to make sure the 3802 is not too close either amp as well. I know its a pain. You pretty much have to disconnect your entire system and start putting pieces together 1 at a time until you discover when the noise is picked up.....Pretty much an all day job. Been there and done that!

 

[Eric_RP]

Thanks Charles - My receiver should not be an issue as it is on the other side of a wall from the amps. I will disconnect the system this weekend to separate components and play around with moving them to different shelves. I was hoping someone would tell me that getting the B&K dedicated pre-amp would solve my problem, that way I could justify upgrading and spending the extra money sooner!
I just listened to my system as I was home for lunch and I did notice that the buzzing was only noticeable when no signal was being sent to the speakers. Even at low volumes with classical music the background noise was very low in the main speakers playing in stereo but was still noticeable from the non-active center. Maybe this is just as you suggested, I'm getting an interaction between the amplifiers especially as particular channels sit idol and their capacitors are fully charged.