Speaker buzz with SS amplifier, input disconnected

Hi Brian- I had a similar issue with BAT monos a while ago. I would get a hum with the speakers connected and no input connected to the amp. Your amps were designed to run with XLR input and the amp will hum if there is no device plugged into the XLR inputs, so hopefully you have a preamp that has XLR outputs. IN the manual of your amplifiers, it states "In case you have a preamplifier with only RCA outputs, you can use the RCA input. Remember to plug in the XLR Terminator plug, when you use the RCA input. It connects the negative input to ground, making sure that the input is not “floating” with the risk of noise or oscilliation comming in to the amplifier circuits." So - connect the inputs of the amps with an XLR cable to the outputs of a balanced preamp and the noise should disappear OR use the RCA inputs to connect to the preamp and use the XLR Terminator plug as described and the noise should also disappear. I hope this helps.

The buzz is constant with balanced inputs connected or disconnected. I am using balanced cables between my VAC preamp and the Gamuts.
Thanks!......still buzzes, both channels but more on one side.

Did these amps have this problem from day one, or is this recent?

Do you have any other equipment near the amps that is on?

Do you have florescent lighting or light dimmers?

If you swap the physical position of the left and right amps, does the greater hum stay with the amp?

If you move one of the amps and speaker to another room, is the problem still there?

I'm trying to figure out if you might have electromagnetic pickup (radiated pickup). You can tell if it is radiated because when you move the amp around, the pickup will be greater or less.

Dimmers and florescent lights transmit higher frequencies that sound like buzz.

Power conditioning doesn't get rid of radiated pickup.

Possibly both amps are having electrolytic cap breakdown, but that normally happens one at a time on older amps.

Thanks for your thorough inquiries, Tom32.
The amps have had this problem from day one, for approx 2 months but is inaudible over the music...only between tracks etc.
Actually my equipment rack is removed from the amps and loudspeakers, with a 5 meter balanced IC between my VAC pre and Gamut M250 monos.
No fluorescent lighting or dimmers.
Yes, the larger hum stays with the amp and there is apparently no change with change of room (I used a monitor speaker in room #2 as the Blades are too big to move!
I think I will send them back to a Gamut for non warranty investigation/repair.....thank you to all respondents !

What I meant about moving it to another room was to see if a different AC branch of power or if a different electromagnetic environment caused a change. You should check everything before going through the hassle and cost of sending it back. Also the repair dude is going to be pretty puzzled if he gets them on the bench and can't find a hum.

But is sure does sound like a power supply hum to me.