[marcosax]

Hi to all, I've just joined this forum because I have a problem with my beloved power amp.
I bought a second hand Bryston 4B-ST here in Italy 5 years ago ( date of manufacture May 1997, as confirmed by Brian at Bryston Canada when I bought it)
It’s been giving me many hours of great music, but lately (a couple of months ago) I noticed a humming noise coming from the speakers when no music was payed. I tried by lifting the ground with the switch in the back and the hum almost went away. I forgot about it, pressed by other, more important issues.

The other day, back from 20 days vacation, I turned on the amp and the humming is considerably louder.
Operating the ground lift switch reduces it considerably, but is still too loud. Obvious something is wrong.

The humming noise is coming (at equal volume) from both speakers and not from the unit.
Unplugging the balanced inputs from the pre (BP 20) doesn’t make any difference.
The amp can still play music which cover the humming.
I tried changing the power cord, also plugging it in another wall outlet to no effect.
I think the humming frequency is at around 150 Hz (I measured by ear, using a digital guitar tuner… so I could be wrong)

I live in Italy and I contacted both Bryston Canada and Italian importer and I'm waiting for a reply.

Does anyone know what could be the culprit and if it is covered by the warranty?
I read it could be due to faulty capacitors, but also that this should generate a 50 - 60 Hz hum. Mine sounds higher in pitch.

I'd also like to know if it's safe to keep using it or is better left turned off.

Thank you so much for any help you could provide

Marco

[marcosax]

Problem solved !!!
Triggered by James Tanner's post in another thread about Oscar Peterson, I approached my system rack in order to play a Telarc record of Mr Peterson (A Summer Night in Munich) when I tried agin to unplug the input cables from the pre, and this time the hum stopped !
I then checked the pre rear panel and noticed a RCA cable plugged there coming from my TV set. I unplugged it and NO MORE HUM!

Now it's dead silent!
Sorry for the trouble. I still can't believe how I didn't notice the hum stopped if input cables were unplugged...
Anyway... all is well what ends well !

thanks anyway and sorry for the trouble (but served me to know his forum existence !)

[rmurray]

  Glad the hum has gone, such a relief for sure. I have the 4B ST and after 15 years of daily use  it's still a great sounding and dependable unit. Anyway welcome to the Bryston group

[marcosax]

thank you, rmurray. It's been a great relief indeed!
My unit turned 18 in May and since I bought it (5 years ago) it only needed a bias adjustment because one channel was overheating.
Apart from that, perfect.

My setup is : 
Denon DCD 2010AE (to which an Airport Express is optically connected to feed the liquid stream from Itunes library)
Bryston BP 20
Bryston ST 4B
Dynaudio Focus 220

Everything bought second hand here in Italy from enthusiasts in forum markets.
It's my 'definitive' setup and I'm super happy about it!




 

[rmurray]

 I have the bp25 (remote model). I can say that these two units are a wonderful match to my JBL Ti120s. My source is the amazing BCD-1 all connected in balanced mode..............

[marcosax]

great setup!
My BP 20 is your BP25's little brother, as it should be the same unit but without the remote.

I connected pre and power with balanced cables too, although Mike Pickett of Bryston Canada wrote to me:
"As far as how best to connect it to your 4BST, there is no reason not to use balanced cables, all other things being equal. 
However, both types of connection use the same circuitry in both units, so I don't expect a significant difference in performance."

[redbook]

 Good to have a new member on board Macrosax, love your user name. The 4B ST is an amazing amp