persistent buzz/hum RESOLVED!

[tipatina]

My Smashup went to Bottlehead to fix hum/buzz. On turnon and with the first 15min of music its quiet but after this hum/buzz comes from both speakers audible from listening position. Not affected by volume control, input selection, shorting plugs, moving things around and even moving to a new room. I have reflowed lots of joints, especially anything I could find going to a ground.

[tipatina]

Follow up.  The Smash had already been to Bottelheadquarters once and cleared the inspection but since I still had the noise Doc and Eileen graciously agreed to take it back for another check. The Smash was dead quiet in the Bottleheadquarters system on extended listening. While it was there I was listening to the pass labs ACA monos being fed by Meridian Direct DAC and Macbook. Quiet. I unplugged one of the amps while the other was still on and same hum/buzz (both speakers even with only one amp on). This got me thinking that 1) it wasn't the Smash after all, 2) I have a ground loop. When I got the Smash back into the system same hum/buzz. I solved it by 1) reflowing grounds in the ACA monos 2) cheater plugs on both of the ACA monos, 3) ground wire from the Smash to the center screw of AC outlet, 4) 75 Ohm shorting plugs on the unused Smash inputs. Of all of these the 2 cheater plugs make the most difference. Now, dead quiet with incredible sound. Listening to Ron Carter Orfeu as I type. I realize cheater plugs aren't the healthiest solution but they are working. Thanks to Doc and Eileen for being so responsive and willing to help. I needed to get this figured out as my plan has been to have the Smash as the hub of my system for future builds (Kaiju next possibly)