Diagnosing a spitting/popping channel- need some help!


Did a search here and I think I am on right track, but might need some help here. Getting a sporadic spitting/popping sound sometimes in left front monitor speaker in a 5.1 setup.
I have the following signal chain:
  • Pioneer HT receiver
  • VAC Standard Preamp
  • Odyssey Audio Monoblock Extreme amps
  • Monitor Speakers are ACI Jaguars and there are dedicated ACI Subwoofers for each channel.


I use the Pioneer HT receiver L/R preamp outputs into the VAC preamp HT bypass inputs for when I use the TV so the Pioneer HT receiver amp sections are out of the chain for the L/R fronts.

Have done the following troubleshooting:



  1. I switched the preamp out L/R cables and the spitting/popping continued out of the same left front speaker (rather than switch sides).
  2. I turned off the Pioneer receiver completely and still get the popping.
  3. I assume that means it is not the Odyssey amp; and not the Pioneer so it must be in the VAC preamp?

Am I right in assuming it is likely a bad preamp tube in the VAC?

The VAC manual says it has the following two pairs of tubes in the Line stage:
2 x 12AU7 & 2 x 12AX7 (line stage)

Where/how do I start checking tubes?

Am I on right track here?
Thanks.
lkdog

Showing 1 response by stringreen

Tap on each tube with theĀ  end of a pencil....if you get the pop, clean the pins of the tube