"Buzz" Coming Through Speakers

Plug in a component directly into the power amp leaving the preamp out of the loop and see if the buzz goes away. I presume you have no power conditioners plugged in.

Replace the dimmer switch with a regular switch.

You may try lifting all your cables off the floor, making sure no cables are touching one another, and crossing cables at a 90 degree angle -- not parallel.

In the past, changing the tubes resolved the problem. But not this time.

It appears that the line stage version of the SP16 uses three 12AX7's, and the version which includes a phono stage uses three more. Not sure which version you have, but in any event it may be worthwhile to try swapping the tubes around among the various locations in the preamp.

Regards,
-- Al

The first thing to do is verify that the preamp is indeed the culprit. To this end:

run the amp with no input- no interconnect cables attached. Is the buzz still there? If yes- its the amp, if no:

Reconnect the preamp. Do not have any other component attached. This is important- if a ground loop is causing this it can be coming from another component. Is the buzz present? If no, swap the interconnect cables left for right at the preamp end and see if the problem moves. If it does, the preamp is indicated. If it does not, its a cable.

If yes, in both channels: Try floating the ground pin of the AC power cord as suggested on this thread. This is for testing only. If this fixes it, you need to talk to the manufacturer about fixing the preamp's ground problem. If it does not, you need to talk to them about fixing the preamp- any number of internal faults can cause this.

Good Luck and please report your findings.