All transformers buzz and the changes you are hearing may be related to power line harmonics. HTH is correct about the windings vibrating not the core. If you own a smartphone, download a microphone app that records and displays the audible frequency; a number of them exist for very little $$. I'm guessing if it's 60 HZ it's mains related, if it's 120HZ or higher it may be power supply noise on the secondary winding of the transformer. In either case, it's likely not out of the ordinary.
Buzz coming from power amp - not through speakers
Hi, first post here. I just picked up a Harmon Kardon PA5800 off ebay. It sounds great, no issues there. However, the amp itself makes an intermittent hum/buzzing noise (ie, the sound comes out of the amp unit, not through the speakers). It fades in, peaks, then fades back out with a period of about 5-7 seconds. Sometimes it's not noticeable at all, but occasionally it's loud enough to hear even with a moderate volume level through the speakers.
Anyone have ideas? DC noise on the AC line? Basic service needed, ie new filter caps? (I'm a tube guitar amp guy, not even sure this type of amp has filter caps).
Anyone have ideas? DC noise on the AC line? Basic service needed, ie new filter caps? (I'm a tube guitar amp guy, not even sure this type of amp has filter caps).