Speaker Hum Question

Unless it's an SFL-1 pre or other with one tube, switch the tubes and see if the noise follows to the other speaker. If so, you might want to replace the noisy (microphonic) one. It's also very possible that one channel noise is a dirty tube pin contact, removing and replacing the tube, carefully, will usually clean the contact. Use a soft cotton cloth to handle the tube. In any case, the first upgrade I have always done with tube components is the tubes themselves. If you have "modern" tubes you are in for a treat when you try NOS or lightly used 60's and 70's vintage RCA, Mullard, etc. See NOS threads here and at Audio Asylum. AA won't do 3 letter searches though so you need to input type: 12ax7, 12au7, 7316, whatever. Hope this helps, let us know.

Duh, just noticed it's an Sonic Frontiers pre. Cleaning the tube pins still might help.

Andrew, I would have to say it is likely a grounding problem. I was getting a hum from my amp, even though I installed a dedicated line. Turned out to be my front porch light was not grounded, changed the fixture, made sure it was grounded, problem solved. Good Luck.

Andrewbuck,

I had a problem like this before. I had hum coming from one of my speakers. After hours of trying to figure out the problem I figured out that there was something wrong with one of my rca cables. I was using solid state gear. I hope this helps

You say that the hum is present with the pre in standby - this would tend to exonerate it, and everything before it. Try disconnecting the input leads to the power amp, then turn it on - if the noise is gone, it may have had something to do with the interconnects here. (Make sure the cables are not in close proximity to AC cords, then swap the leads right for left - if the noise moves with the cables, suspect a faulty wire/rca jack connection.) If the noise is still present, turn off the amp, reverse the speaker leads right for left at the amp, and power it up again - if the hum stays in the same speaker, you may have an AC cord too close to that cable. If the noise moves to the other channel, suspect the amplifier itself (possibly its input jacks). You could try using a substitute amp (borrow if necessary) to check this. (It is unlikely that a noise you describe as a "hum/buzz" could originate in the loudspeaker itself [driver, crossover], so its seeming presence at the tweeter only could point to the speaker cable in a biwire setup, but the super-steep crossover on this model could seem to produce the same effect when fed a noise signal above the crossover frequency.) And if all this sounds like too much hassle, well, this is what dealers are supposed to be for!