50 hz, transformers, power amp hum

Archived from groups: rec.audio.tech (More info?)

I have read posts on this subject, but seen no real solutions:

I moved from USA to Germany two years ago. I brought along some audio
gear. I found a 500w transformer on ebay.de that gives me roughly 120v
and runs everything pretty much without a hitch, except for my Proton
D940 Receiver. When I first plugged it in, everything was fine. But
after awhile a 50 hz hum started coming from the speakers. At first I
experimented with reversing the power plugs of both the transformer
and the receiver. I was able to make it go away, but it always came
back. Now any changes in wiring don't produce audible effect. What I
find interesting is that what I am getting is a low level 50hz hum in
the speakers that is independant of the volume control, so it is not a
problem when I am cranking, only when I want to work at the computer
late at night, like now. Also, this hum seems to not affect preamp
circuits, as I can transfer audio from vinyl to digital without
picking up the hum, for example.

The transformer itself is audible even without load. That probably
points a finger, but I am wondering if this a problem without a
solution. I have often noticed audible hum in neighbors' stereo units.
Is 50 hz inherently harder to filter? Also, I brought a Hartke bass
amplifier which was dual voltage, 50/60. It works, but the unit itself
hums like mad. Interestingly, the hum does not come out of the
speakers significantly.

I do not know details of German house wiring and grounding
configurations, but it seems that it is single phase with one side
roughly 227v and the other neutral to ground. I measure no potential
between neutral, electrical ground, and earth ground (i.e. my steam
radiator).

I am running connected components some powered from the transformer
and others direct to the house voltage. This is probably a bad idea,
but no amount of fiddling seems to remove the hum from my speakers, or
add it anywhere else.

I suppose I could solve the problem by throwing enough money at a new
receiver or power amp, but I just like tinkering with problems,
solving them myself, and keeping my money. (Example: I drive a Saab
with 330,000km on it. It's still a great car!) Also, I like the
switching features on my Proton; separate listen and record out
selection, and pre-out and pwr-amp in jumpers. What new home theater
receiver has that?

Anyone know some details about hum, specifically in the 50hz range?

Robobass

Archived from groups: rec.audio.tech (More info?)

If you are getting the hum out of the speakers, and you do not have a
shielding problem from the interconnects, this means that the main filter
caps in the power supply have to be changed.

One test is to disconnect all the interconnects, and see if there is still
hum. If so, get the unit serviced.

The power transformer in the unit is most likely running hotter, because it
was probably designed to run on 60 Hz. It would not hurt to replace the main
filter caps with ones of a bit of a higher "uF" rating, if there is enough
physical space. An experienced technician should know what to do with this
problem.

--

Jerry G.
=====


"robobass" <lostfrom68jay@yahoo.com> wrote in message
news:ec311425.0406221528.79e5d081@posting.google.com...
I have read posts on this subject, but seen no real solutions:

I moved from USA to Germany two years ago. I brought along some audio
gear. I found a 500w transformer on ebay.de that gives me roughly 120v
and runs everything pretty much without a hitch, except for my Proton
D940 Receiver. When I first plugged it in, everything was fine. But
after awhile a 50 hz hum started coming from the speakers. At first I
experimented with reversing the power plugs of both the transformer
and the receiver. I was able to make it go away, but it always came
back. Now any changes in wiring don't produce audible effect. What I
find interesting is that what I am getting is a low level 50hz hum in
the speakers that is independant of the volume control, so it is not a
problem when I am cranking, only when I want to work at the computer
late at night, like now. Also, this hum seems to not affect preamp
circuits, as I can transfer audio from vinyl to digital without
picking up the hum, for example.

The transformer itself is audible even without load. That probably
points a finger, but I am wondering if this a problem without a
solution. I have often noticed audible hum in neighbors' stereo units.
Is 50 hz inherently harder to filter? Also, I brought a Hartke bass
amplifier which was dual voltage, 50/60. It works, but the unit itself
hums like mad. Interestingly, the hum does not come out of the
speakers significantly.

I do not know details of German house wiring and grounding
configurations, but it seems that it is single phase with one side
roughly 227v and the other neutral to ground. I measure no potential
between neutral, electrical ground, and earth ground (i.e. my steam
radiator).

I am running connected components some powered from the transformer
and others direct to the house voltage. This is probably a bad idea,
but no amount of fiddling seems to remove the hum from my speakers, or
add it anywhere else.

I suppose I could solve the problem by throwing enough money at a new
receiver or power amp, but I just like tinkering with problems,
solving them myself, and keeping my money. (Example: I drive a Saab
with 330,000km on it. It's still a great car!) Also, I like the
switching features on my Proton; separate listen and record out
selection, and pre-out and pwr-amp in jumpers. What new home theater
receiver has that?

Anyone know some details about hum, specifically in the 50hz range?

Robobass