Strange Main hum on 250
Posted by: peteS on 08 August 2000
When I was moving my kit around this evening, I noticed a strange thing. If I turned the 250 on before the HiCap, I got a pretty noisy mains hum from the speakers. When I turn on the HiCap this goes away, dropping down to a very quite hiss. I've never noticed this before, but then I hardly ever turn them on and off! Anyone else noticed this - is it normal or is there something wierd going on?
Posted on: 09 August 2000 by Former member
The hum is caused by the 250 not having any fixed input. When the Hicap is off the pre-amp is off so the input to the 250 is floating around and hence the hum.
Cheers
Jason
Posted on: 09 August 2000 by Former member
Naim do recommend that power amps are turned off first and on last.
Simon
Posted on: 27 August 2000 by Clive B
I think the naim boxes just take it in turns to hum for a while. I guess it's introduced by distortion in the mains. But the best way to avoid any hum during power up is to leave it all on permanently! Not only does this sound best (Naim equipment enjoys a long warm-up time) but its also best on the electronics. You only really need turn it off when you go on holiday and during thunder storms (even then I usually take the risk and rely on the insurance!).
Regards, CB
Posted on: 27 August 2000 by Steven Phee
Clive,
just curious.... why is leaving Naim equipment on all the time better for the electronics? Does this mean switching it off when not in use would actually shorten its life?
cheers!
Steven
Posted on: 31 August 2000 by JosephR
For any separates system, not just Naim, the basic sequence is that you should turn on from the source first, and the power amp last. When shutting down, it would be from the power amp down to the source ...
