[ctviggen]

I have a tube amp I use to run my center channel.  I plugged it in after months of room reconstruction.  There was a humming noise coming from the speaker.  The room now has many feet of low capacitance speaker wire from the equipment rack to the speaker.  Could the length of speaker wire cause the humming?  Or is there a tube bad in the amp.  I've been using another amp (digital) without any humming, but I'd like to try tube amp again.

Also, do you think I can use an automatic controller to turn on/off the amp?  That is, I'd turn on the amp with my remote using an electronic control and the on/off knob for the amp would always be on.

[avahifi]

Is your center channel tube amp a stereo amplifier?  If so, try using the other channel to see if the hum issue remains or not.

If you have long runs of speaker wires or interconnect cables, make sure they are not run in parallel with AC power cords for any long distances.

Please provide more details about your system and its connections so we can provide more accurate help.

Regards,

Fank Van Alstine

[ctviggen]

Thanks, Frank.  It's a monoblock chinese made tube amp (Cayin 860) that I bought when a single channel of my Bryston/Lexicon 5 channel amp wouldn't drive my VMPS RM30C center channel.  I also tried a Nuforce amp, which drove the speaker but I thought was too revealing (every pop or click was reproduced exactly).

If I run the channel using a channel of my receiver, there's zero noise on the channel.  I have the entire system on two hospital grade, isolated ground, cryogenically treated outlets.  Both 20A circuits on the same phase.  Cryogenically treated 10 gauge wires.  I installed this myself and had it inspected.

I'm using low capacitance, 12 gauge speaker wire run perpendicular (as much as possible) to AC lines, but again if I use a channel of my receiver to power the center channel, there is zero hum on the center channel.  There's a  ton of hum on the channel if I use the tube amp.

How do I know a tube is bad (this is my first and only amp)?

[avahifi]

To make sure that the hum issue is not being caused by some incompatibility between your source or interconnect cables and the suspect amplifier, please do the following:

Turn the amp off, disconnect the signal input cable at the amplifier, leaving the amp connected to the speaker.  Turn the amp back on.  Does the hum still remain?  If it does, it definately is a problem with the amplifier.  If the hum now goes away, the problem is with something ahead of the amplifier.

Does your tube amplfier have a bias setting method?  If so check that to see if it will bias set normally.  If it does not set properly, you likely have a defective output tube.

One further thought, does the amp have a three wire AC power plug?  You may be generating a ground loop betwen that amp and the other components.

Let me know the resuls of these tests.  Also, what kind and how many output tubes are used?

Regards,

Frank Van Alstine