What causes transformer hum
DC - either on primary or secondary side. On secondary easily avoided by using 2 bridges (if symmetrical rails are used), on primary there exist DC-filters.
The probably annoying noise aside it shouldn't do any harm.
Have fun, Hannes
PS: the mechanism behind turn on/off thumbs is also still unclear to me; I sometimes hear that different impedances on the balanced inputs can cause this (blame your preamp) or that the caps for both rails need different times to charge up. Maybe someday I have a satisfying reply to this
Actually, the transformer doesn't continue to hum. There is a hum when I initially turn it on that fades out within 3 or 4 seconds. Then it is quiet. At the same time there is an initial "thump" that forces my woofer and mid-range drivers to peak excursion in my passively crossed speakers.
rocco:
Could you please elaborate on "grounding issue"? What should I look for?
rocco:
Could you please elaborate on "grounding issue"? What should I look for?
jaycee:
I didn't add any additional circuitry to the amp and the leach amp doesn't have any sort of integrated "soft start" circuit. I did, however, add some additional line-level active filters at one point (a linkwitz transform and additional EQ), but I have since removed them. As I recall, the thump and buzzing started to occur when I removed those circuits, but all they were really attached to is the RCA inputs and I've restored the original connections just as they were.
I didn't add any additional circuitry to the amp and the leach amp doesn't have any sort of integrated "soft start" circuit. I did, however, add some additional line-level active filters at one point (a linkwitz transform and additional EQ), but I have since removed them. As I recall, the thump and buzzing started to occur when I removed those circuits, but all they were really attached to is the RCA inputs and I've restored the original connections just as they were.
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