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Help needed diagnosing new buzz in 2-channel system

skriefal

skriefal

Super Member
Just today I encountered a new, obvious buzzing sound through my speakers when listening to my 2-channel audio system. I've been unable to identify the cause and would appreciate any suggestions.

First, the system:
  • Juicy Music Blueberry Extreme (BBX) pre-amp (tubed)
  • JWN amplifier (tubed)
  • AR-XA turntable
  • Denon 2910 CD/SACD/DVD-A player
  • SAE tuner
  • Polk LSi15 speakers

What I've tried, in order:

  • Swapped in spare tube set into the JWN amplifier. Buzz remains.
  • Swapped in spare 6922 input tube in the Blueberry pre-amp. Buzz remains. I did not swap in a spare 12X4 rectifier or spare phono stage tubes, but I doubt that would help (read on...).
  • Swapped interconnects and power cables . Buzz remains. I didn't try different speaker cables, but I doubt that would help (read on...). Buzz remains.
  • Swapped speakers. Buzz remains.
  • Disconnected all audio inputs from the pre-amp (including one that could have brought in a ground loop from my Dish Network DVR). Only A/C power and the pre-out are connected at this point. Buzz remains.
  • Unplugged power cables from the tuner, CD/SACD player, and turntable. Only the JWN amplifier and Blueberry pre-amp are powered at this point. Buzz remains.
  • Lifted the A/C ground on both the amp and pre-amp (using "cheater" plugs). Buzz remains.
  • Powered the pre-amp from a different A/C outlet (with the help of an extension cord). Buzz remains.
  • Unplugged the pre-amp power cable entirely. Buzz remains. At this point the amp was powered and the pre-amp's pre-out was connected to the amp, but all other pre-amp inputs and outputs (including power) were disconnected.
  • Tested the JWN amplifier driven by a spare Carver pre-amp. Buzz is gone.
  • Tested the Blueberry pre-amp driving a spare amplifier. Buzz is gone.

The last two tests suggest that there is no problem with the JWN amplifier or the Blueberry pre-amp. But when the two are connected together a buzzing sound appears at the speakers... even with no other inputs or A/C power connected to the pre-amp.

I'll probably be changing the system around in a few weeks, and that may eliminate whatever is causing this issue. But I'd still like to answer what is going on here if I can.

Anyone have any ideas? Thanks!
 
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I've tried one more thing -- adding a ground wire between the pre-amp's ground post and the amp chassis (tried a few spots). No change -- buzz remains.
 
You have me completely stumped.

Maybe a ground solder point / pad between the interconnection of the pre and amp? Try wiggeling the RCAs while the combo is on and connected.
 
On the last 2 no-buzz tests, do you have good sound when source and speakers are placed back ? I am thinking about the RCA in & out of the 2 amps.
 
TLCW said:
On the last 2 no-buzz tests, do you have good sound when source and speakers are placed back ? I am thinking about the RCA in & out of the 2 amps.
Click to expand...

For those tests I tried with and without a source device connected to the pre-amp. No noise; everything worked as expected.

The noise seems to be present only when the Blueberry pre-amp is feeding the JWN amp, and it remains even if A/C power and all sources are disconnected from the Blueberry. This was not happening a week ago.
 
I also agree it is the connection ( IC cables) from Blueberry to JWN. Try to see if only 1 ( left / Right ) channel does buzz. I suggest use some simple interconnect ( say white / Red free stock cables) to try.
By repeating the 2 no-buzz tests to re-confirm the debug criteria along the way.
Just in case, do you have some heavy duty electric motors switched on nearby ?
 
It's both channels, and I've already swapped in a simple interconnect with no change. But I can certainly try another.

No electric motors, but there is a Vandersteen 2W subwoofer sitting a few feet away. And it wasn't sitting there a week ago. I did try unplugging that sub -- with no change -- but haven't tried moving it.
 
Swapping in another interconnect didn't change anything. Nor did moving the nearby subwoofer. Guess this will have to wait until I can do a more extensive rearrangement of my systems.
 
Since you still have 2 no-buzz setups, relax and listen to some music with any of these meantime. Be joy and try debug at free times.
 
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