Humming Bel Canto

[bemcsa]

I have just acquired a secondhand evo 4 and it seemed to be fine for a couple of days.

I leave it powered up, but it started humming quite loudly this morning when it had no signal going into it. I turned it off and on again and it has not happened again. I have noticed there is a low level hum from it all of the time (I assume its the transformer), is this normal or should it run silently?

It seems to be warm (not hot) all of the time and does not get much hotter even when playing loud. How warm should it be when not being used?

I am concerned about the loud hum this morning and would like to know if anyone has any suggestions about what may have caused it. The seller did say he would take it back within 7 days if there are any faults. I am obviously tempted to try and get him to honour this promise.

Any suggestions would be appreciated.

[penance]

I think the evo uses a toroid tx, these can hum with a les than perfect supply, i suspect that is what you are hearing.
As they are very efficient amps they wont get much hotter with use, although i cant say what the normal operating temp is.

[bemcsa]

but why should it start humming loudly for no apparent reason (about the same volume as when you first power it up and it hums for about a second just before the relays kick in - or shouldn't it do that either?) ..... getting paranoid ....

[penance]

I dont know about the power up sequence on a BC, but the hum suddenly happening could be due to outside influence on the mains.
Maybe try plugging it in a different socket?
Do you use any mains conditioning?

[bemcsa]

no mains conditioning yet, but its on the to do list (along with getting rid of those £1.99 interconnects that had to be pressed into service)

[wadia-miester]

Never had a Humming one whoo err!!!!!, earth loop maybe, are you running it in dual diff? balanced or SE?. Try a different mains socket/switch the pre-off see it goes/change the I/c's even for another set of cheapies see if it goes.
When it started humming, was ther fridge/cooker/kettle/emmersion on?
Start up sequence, click then slight umm for 2 sec's lights dip then ok.

[bemcsa]

I currently have 2 RCA jacks plugged into channels 1 and 3. The mono switches are in. One XLR/RCA switch is in the other is out. If I change the XLR/RCA switch configuration, I do get humming at the speakers, but with one in and the other out there is no humming at the speakers.

The humming comes from the amp itself, I guess the transformer. Usually it is quiet, you only really notice it if you get right up to the amp. I could well imagine this is normal, or should it be silent?

When it started humming loudly, the preamp was turned off, I did have the telly on which comes from the same mains spur, I guess something could have triggered it, but should it be that sensitive?

When it is powered up but not in use, should the amp be warm?

[smudge]

Hi

As you say the humming comes from the amp itself, the most likely culprit is the trany , in my experience of transformers it will only get worse over time, also i notice on their web site they quote a stand by power of some 20 watts.

Stuart

[Ya-Boo]

my Evo 4's been powered up 24/7 from day one as is my CDP , only time mine hummed was when using VDH first ultimate RCA which was a real shame because these are my prefured cables.

[bemcsa]

I have now tried powering up the amp with no speakers or inter connects plugged in and it still hums. I have tried a different power lead and plugging into different sockets. The humming is not that loud, but I would think that it should run near silent.

The humming seems to come and go, but there is something not quite right. I dont think it is influenced by any other electrical appliances as I tried turning most of them off.

I assume it does not need mains treatment or special power leads for silent running?

[wadia-miester]

Nope, every one I've owned, is stone quiet even without the toys, certainly no humming, never had a noisy tranny at all?
Just one question is the main power switch sticky?
Just plug the B/C in the pre and switch the pre on (with the i/c connected), but no signal, stick your lug hole in the speaker, what can you here?
How close are the B/C and the pre, as for temperature mine even when at warp 10 never gets above luke warm, virtually all the time its about room temp.
What speaker cable you using and where have you got bass jumpers set on the Herons?

[bemcsa]

The mains switch is not sticky.

With no signal and the pre connected and powered up there is a very quite hiss. There was a hum at the speaker when both XLR/RCA switches were in, but toggling one cured it.

I am using bi-wire to the herons.

The fact that it still hums when there are no speakers or i/c 's connected would suggest that the problem is not caused by an external source but the power supply in the amp itself.

It only gets warm, not hot, not even very warm.

One final stupid question, I assume the mains lead should have an earth?

[sideshowbob]

As as already been said, if it hums unconnected and the hum's coming from inside the amp, it's probably the transformer.

What do Bel Canto suggest?

-- Ian

[MartinC]

My power amp used to hum quite loudly when mine or my neighbours washing machine was on, in sync with when the drum was turning. The rest of the time it just has a very slight hum you notice if you put your ear up to it. None of the mains leads I've tried made any difference to this, and neither did my Trichord isolation transformer I tried briefly out of interest, although I never planned to keep it there. I was just thinking if the hum comes and goes at all it could be the result of some mains borne noise. I know the BelCanto is a big bugger, but would you be able to take it anywhere else (I mean a different house, work etc.) to see if you had the same problem there?