Hum from Power Amplifier...is it normal ?

[admin_exported]

Hi there,

I have noticed an audiable hum from my Arcam P90 power amplifier when I get very close to it (standing with my ear at the same level), but I do not hear any noise from my Arcam A80 integrated. The hum is from the amplifier and not from the speakers. Is this normal ?

Cheers, Justin.

 

[Anonymous]

[quote user="Justin1970"]
Hi there,

I have noticed an audiable hum from my Arcam P90 power amplifier when I get very close to it (standing with my ear at the same level), but I do not hear any noise from my Arcam A80 integrated. The hum is from the amplifier and not from the speakers. Is this normal ?

Cheers, Justin.
[/quote]

It's transformer lamination buzz. Completely normal and nothing to worry about.

 

[Andrew Everard]

[quote user="Zoot Horn Rollo"]

It's transformer lamination buzz. Completely normal and nothing to worry about.[/quote]

But easily cured with a mains conditioner. ONLY KIDDING!!!!

But seriously, it shouldn't be making this noise, and once you hear it, it could become very noticeable when playing quite music - you'll hear it because you're listening for it. Now where have I heard that one before.

I have solved this problem in the past with a little judicious tightening of the transformer mounting bolt on some other amps, but then those had a big very obvious bolt-head sticking through the chassis, and responded to a little gentle spannerage.

I'd have a word with Arcam customer service and see what they reckon.

 

[Anonymous]

now dont go and stick a screwdriver in your arcam - just call them...

 

[Andrew Everard]

Wasn't suggesting putting s screwdriver inside - just tightening the transformer mounting from outside the case. if possible.

 

[Anonymous]

Thanks guys, I look to see if there is an easily accessible (external) bolt, but I shall also give Arcam a call.

Cheers, Justin.

 

[Anonymous]

[quote user="Justin1970"]
Hi there,

I have noticed an audiable hum from my Arcam P90 power amplifier when I get very close to it (standing with my ear at the same level), but I do not hear any noise from my Arcam A80 integrated. The hum is from the amplifier and not from the speakers. Is this normal ?

Cheers, Justin.
[/quote]

When you stick a large amount of magnetic (Iron core) material in a powerful (transformer coil generated) magnetic field, one might expect a little movement😉. As Andrew says, sounds like a bolt needs tightening.. a Lot of amplifiers have the bolt coming out the bottom of the case as toroidal (doughnut shaped) transformers are usually mounted by a plate that sits on top, covering the central hole and gripping the unit, with a big bolt that goes through to mount it on the bottom side of the case wall. As you tighten in you pull down on the plate which pulls the transformer body harder to the case wall (which will often have a kind of 'seat' for the transformer to rest in, rather than pushing right into the bare metal).

The short story is, if this bolt comes loose then the transformer is free to vibrate. Not a problem in itself but you just know it's gonna get on your nerves. Co-incidently. Some time ago I built my own amplifier which used a small toroid to power a 25w stereo integrated amp. In order to test the power supply load I stuck some resistors (not speakers) into the speaker terminals and whacked the volume up full. I was astonished that even though there were no speakers connected I could still hear the music... from the transformer..

 

[Anonymous]

Thanks for the info...although I haven't tried tightening anything up yet ... I did move the amplifier yesterday, to listen for the hum in a different part of the room (away from all the cables etc). Now that I have put it back I no longer hear the noise. To my thinking that exactly supports your suggestion (and Andrew's). Thanks for the help.

Justin.