[Stephan1310]

My new 4B-SST2 amp makes some mechanical noise/hum. The hum comes directly from the amp, my speakers are nicely silent. I disconnected all equipment (speaker cables, interconnects) only the amp attached to the socket and hum is still there. Took the amp out of the cabinet and put it on solid floor: still same hum after powering on. Then took the amp and connected to a different AC outlet on a different electrical group in the house: still same hum. The noise or hum is not loud, just audible from my listening position if the room is very quiet, easily audible if you approach the amp closely. I saw in another thread that the issue might be due to some transformer issue. What do you recommend? My dealer suggests to compare it to his 4B-SST2 and possibly send it to the importing company (Mafico here in the Netherlands) for check-up.

[James Tanner]

My new 4B-SST2 amp makes some mechanical noise/hum. The hum comes directly from the amp, my speakers are nicely silent. I disconnected all equipment (speaker cables, interconnects) only the amp attached to the socket and hum is still there. Took the amp out of the cabinet and put it on solid floor: still same hum after powering on. Then took the amp and connected to a different AC outlet on a different electrical group in the house: still same hum. The noise or hum is not loud, just audible from my listening position if the room is very quiet, easily audible if you approach the amp closely. I saw in another thread that the issue might be due to some transformer issue. What do you recommend? My dealer suggests to compare it to his 4B-SST2 and possibly send it to the importing company (Mafico here in the Netherlands) for check-up.

Hi,

The transformers are large and there is some mechanical hum but it should not be excessive. I would say comparing to the dealers unit makes the most sense at this point.

james

[bob stern]

The 4B SST (like most, if not all, Bryston amps) has a DC blocking capacitor (actually two back-to-back electrolytics) in series with the power transformer primary.  This prevents transformer mechanical hum caused by any DC offset in the AC power mains.

Does the 4B SST2 retain this DC blocking capacitor?

If not, a PS Audio "Humbuster" could be used to block DC in the AC power line.

[Fernar]

I got my 4BSST2 today - switching it on gives no hum of any sort - even put my ear near the amp and nothing..