Power Amp transformer hum - intermittent and increases and decreases in a few seconds

You are very welcome! That's what this site is for. Lot's of great people on here! I've been helped many times in the past and am grateful for that and for the chance to help others if I can. 

Tom

FYI, One of my many power amps, a Smart Theater Systems TA 242 ( which is actually a beefed up Hafler 220 by design, and very musical ), experiences the transformer hum ( toroidal, chassis only ), when I use my OTR microwave. Have not tried a cheater plug during these times, as it is always in rotation with others. Enjoy ! MrD.

Some {not all} toroidal transformers can buzz when DC is present on the power line.

My Son of Ampzilla 2000 has a faint buzz when my Canon printer turns on, and when my Keurig brews a cup of coffee.

Otherwise it is dead silent.

My Pass Labs XA60.5 never buzzes and it has Toroids.

don_c55826 posts

03-11-2019 4:16pm

My Pass Labs XA60.5 never buzzes and it has Toroids.

Just a guess because Pass Labs incorporates a DC blocker in their power amps.



Bryston does......
https://www.diyaudio.com/forums/power-supplies/161428-variations-dc-main-filter-buzzing-toroid-trans...




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Mechanical hum is not always the result of DC offset. I have some DC offset on my mains and even two DC blockers in series couldn’t eliminate an obnoxious hum in one of my amps.

Anyhow, I own the CMX-2 but found the Audio By Van Alstine Humdinger works far better. I had a bucking transformer that still hummed loud when plugged into the CMX, but it ceased completely with the Humdinger.