'Breathing' hissing noise through one channel

[The Black Adder]

Hello there.

I've just turned my amp on and I'm getting what sounds like a 'breathing' hissing noise through one channel. Breathing as in a regular in and out hissing/crackling noise.

This is not amplified as it doesn't get louder via the volume control.

It started when I turned the input selector knob. It goes away then returns after 5 mins or so but it has happened without even touching the knob. Also it happens no matter which selection of input.

Has anyone had this with their valve amp or has any idea what it can be?

Regards
Joe

[lurcher]

Could be a noisy valve, or dirty pin. Or it could be a resistor breaking down. Those are the first things that come to mind.

[The Black Adder]

Hi Nick..

Brand NOS valves fitted today as I thought it was a valve on it's way out so I got me a full set of Mullards... I guess I need to arrange a trip up to Halifax.. lol Would that be ok?

Cheers
Joe

[lurcher]

Of course. Is the noise only one chan, or both?

[The Black Adder]

weirdly it was the left channel last week, this week it's the right... I'm getting a hum too in the channel.

[jantheman]

weirdly it was the left channel last week, this week it's the right... I'm getting a hum too in the channel.

Have you been moving valves around?
Hum could easily be caused by a valve, insulation breakdown between cathode or anode (can't remember which) and heater. Had this myself recently.....

[goraman]

That sounds like a dying valve to me alright.
Take them all out and spray the pins and sockets with deoxit,if it continues buy new valves.
My power amp has 12 tubes,I have been there.

http://store.caig.com/s.nl/sc.2/category.188/.f

If your pins and sockets are gold plated.
http://store.caig.com/s.nl/sc.2/category.292/.f

I just noticed your amp is an Audio Note PP, These amps can use foil caps made by Jensen.
I have heard some odd things happen with these caps before they fail.
If you have another complement of tubes that are known to be ok,replace them and reset the bias if needed and see if it protists, if it dose don't rule out the coupling caps.
Was that the EL84 kit amp? 10 or 12 watts out,Class A?

[The Black Adder]

Thanks chaps.

The valves are new, installed today. I've been discussing replacing the caps by Nick (Lurcher) too so I think that is on the cards.

I had a valve fail the day before yesterday on the problematic channel too hence a full NOS set.

I'll try and get some Detoxit too... you never know. Cheers for that! It's 12wpc... sounds ruddy nice too!

[jantheman]

Thanks chaps.

The valves are new, installed today. I've been discussing replacing the caps by Nick (Lurcher) too so I think that is on the cards.

I had a valve fail the day before yesterday on the problematic channel too hence a full NOS set.

I'll try and get some Detoxit too... you never know. Cheers for that! It's 12wpc... sounds ruddy nice too!

Was the channel problematic before the valve failed or did the problem arise after the failure????