Transformer hum - is it normal?

[PENG]

So the take home message is: Hell, no, loud transformer hum noise is Not normal.

I suspect the 6" rule could be acceptable by most.

 

[PENG]

Anthem MRX 300 AVR, ear on front panel and ear on the top panel over the (EI core) transformer (which was surprisingly hot...): no audible hum

I am not surprise, my MCA225 is hardly audible too, but don't be so sure about some of their other amps..oops...

Oppo BDP-83, ear ~1" from front panel (only part that is accessible): no audible hum

Those little ones are too small to make much noise anyway. Too bad I could hear the fan of my 95 (from a few inches away) though.

Sadly, one generally cannot expect solid engineering from the so-called high end...

(Obvious exceptions: McIntosh, Bryston, Boulder, Meridian, and like quality-focused firms.)

Exceptions? I just don't want to name any of the high end brands, including the ones you listed but I can assure you I heard some of them at within a few inches from the front plate. Yet I can hardly hear any of my Denon AVRs (especially the old 3805), AV7005 and the low cost and old Yamaha RX-V659 and the GFA-555.

If a unit's hum was audible from a foot away, no question that I'd return it.

Me too! I almost returned one, it was heard from about that distance, luckily that was the only bad one, of all the ones I have owned so far.

 

[algava]

They all hum because of alternating magnetic forces induced in the metal core, some more than others according to how well they were designed.
The human ear is definetly not the way to measure this noise and compare.
And I don't know who listens to their music 1 foot from the amp, it's more a matter of like/dislike, it should be more or less quiet.
I have never even thought about it and I've gone thru pleanty of cheepo and mid end receivers, I use to repair them for a living.
Al

 

[pcosmic]

They all hum because of alternating magnetic forces induced in the metal core, some more than others according to how well they were designed.
The human ear is definetly not the way to measure this noise and compare.
And I don't know who listens to their music 1 foot from the amp, it's more a matter of like/dislike, it should be more or less quiet.
I have never even thought about it and I've gone thru pleanty of cheepo and mid end receivers, I use to repair them for a living.
Al

The guy who took the stethoscope to an amplifier most probably needs some psychiatric treatment. (A stethoscope?!?!....facepalm).

 

[dananton485]

I just noticed yesterday a very quiet hum that emits from my receiver when it's powered on. It's coming from the transformer I believe. I assume this is normal but wanted to see if anyone else had noticed it on theirs.

This a cheap $400 receiver, but it has been connected to an APC power filter since new.

I know this post is old but I experienced a similar situation with my Integra 30.6. I previously had a Integra 20.4 but needed to replace it after the HDMI board went haywire. There is a current fix for this so I am keeping the 20.4 for my shop system if I get it up and running. Back to the 30.6 noise problem. The Integra 30.6 has an internal fan though the sound I heard sounded more like a transformer. In any case, I was able to resolve the problem by re-routing my power cable away from my speaker and audio cables. Think it picked up some interference. BTW sound was present even under mute or no source so it was definitely a power-up sound not from a source. I was able to hear the sound from 12 feet away from my normal listening position in the living room so it was definitely not normal though my wife didn't notice it when tv programming was on. She listens to it very low volume so I am surprised she didn't notice it before. Anyway, it is quiet now and since resolving the problem there is still a very very much lower hum which can only be heard by putting my ear near the case. I believe this is a combination of the transformer and built-in fan within the case hard to tell. I know for a fact that the unit has a fan because I took the case off and installed some passive heat sinks on the HDMI AV board CPUs. BTW probably didn't need to do this since it has an active fan but after my other unit went bad from what I understand the Integra Onkyo units HDMI board is prone to overheating. Looks like the manufacturer figured this out since the newer unit here has a fan in it when the 20.4 did not have a fan. Highly recommend installing heat sinks if you have an older ONKYO or Integra Receiver without the case fan. I guess you could install a fan too but from what I read the heat sinks seem to work well as a workaround once your rework the board.