Bare Knuckle Pickups Forum

Forum Ringside => Guitars, Amps and Effects => Topic started by: Ian Price on March 16, 2009, 07:35:07 PM

Title: Leaving amps switched on for a long time
Post by: Ian Price on March 16, 2009, 07:35:07 PM: Evening all,

Just realised that I've left my amp on standby for quite a few days (I think about 4). Does this have any effect on the amp/valves at all?

Cheers!

Ian.
Title: Re: Leaving amps switched on for a long time
Post by: AndyR on March 16, 2009, 08:03:34 PM: They must be really warmed up by now - must sound great :lol:

But honestly, I don't actually know whether this is good or bad. I did used to leave mine on all day at weekends when I was using it, just to keep it cooking ready for use...

(And my Vox Tonelab has been on for 2 hours now, keeping its valve warm, just in case I want a little go in a bit :lol:)
Title: Re: Leaving amps switched on for a long time
Post by: ailean on March 16, 2009, 08:34:10 PM: I don't think it will do any damage, you will actaully do more by turning the amp on and off, the hot / cold cycle won't help them.

I heard that Jimmi Hendrix used to keep his amps plugged into generators inside the trucks when he was on tour just to keep them warm. No idea if it's true though :)

(I'm assuming it's a valve amp, if it's not then better to turn it off but you won't do much harm keepign it on standby)
Title: Re: Leaving amps switched on for a long time
Post by: WezV on March 16, 2009, 08:35:45 PM: i am more worried about your carbon footprint ;)
Title: Re: Leaving amps switched on for a long time
Post by: 38thBeatle on March 16, 2009, 08:52:44 PM: I don't think you'd have done any harm leaving your amp on standby for more than a few hours( I have done it myself). As far as I know it is harmless as the heater is going but there is no high voltage ( amp techs on the forum may be able to say if I am talking cobblers). I am not sure though if leaving it for a few days is good though.
Title: Re: Leaving amps switched on for a long time
Post by: the_bleeding on March 16, 2009, 09:00:04 PM: does it still work?

if anything, you've just worn down the heaters a little. Since it was on standby, the tubes shouldnt be worn down themselves.
Title: Re: Leaving amps switched on for a long time
Post by: indysmith on March 16, 2009, 09:24:38 PM: My audio electronics tutor at Uni reckons that leaving a valve amp on standby for more than 5 minutes will do damage to the valves, as the heaters are on but no signal is getting sent through.
I'm not sure on the truth behind this, I've never experienced any adverse effects.
Title: Re: Leaving amps switched on for a long time
Post by: HTH AMPS on March 16, 2009, 09:25:43 PM: valves were designed for constant operation afaik, so you'll be alright there. switching them on/off (i.e. heating/cooling) has more of a negative affect on lifespan than leaving them running all the time.

transformers otoh I'm not sure about - they may get a bit hot, especially if the valves and transformers are upside down in the chassis causing the heat to go back into the chassis (like most old Fender amps).
Title: Re: Leaving amps switched on for a long time
Post by: martinw on March 16, 2009, 10:45:01 PM: Leaving an amp on standby (i.e. with heaters on and HT off) for very long periods of time, can in extreme cases cause cathode poisoning, the effect of which is a reduction in the emissivity of the cathode and in the efficiency of the valve.
That's the theory; in practise, I've never heard of this causing any noticeable problems.

Probably best avoided in any case. :wink:
Title: Re: Leaving amps switched on for a long time
Post by: jpfamps on March 17, 2009, 12:46:14 PM: Back in the day much equipment that used valves was left on permanently (broadcast, radar, studio etc). Many hi-fi punters leave the heater of valves in their amps permanently on (although often at a slightly lower voltage), so that the amp reaches optimum listen temperature quicker.

Turning valves on and off will cause your valves more stress than leaving them on standby. I would also agree that in a guitar amp, which won't be left in standby for ages, cathode poising is not something I would worry about

However, as stated above the heat dissipated into the amp may be a problem depending on how the amp is built.
Title: Re: Leaving amps switched on for a long time
Post by: martinw on March 17, 2009, 12:51:47 PM: Quote from: jpfamps on March 17, 2009, 12:46:14 PM

.......which won't be left in standby for ages, cathode poising is not something I would worry about

The OP stated that he left the amp on standby for 4 days. :wink:

There's a difference between on and at idle, such that conduction is happening, and on standby.
Title: Re: Leaving amps switched on for a long time
Post by: jpfamps on March 17, 2009, 01:15:53 PM: [/quote]

There's a difference between on and at idle, such that conduction is happening, and on standby.
[/quote]

Thanks for explaining this to me.
Title: Re: Leaving amps switched on for a long time
Post by: Pete24v on March 17, 2009, 01:16:31 PM: i though standby was nothing more than a mute? on matmaps anyway...
Title: Re: Leaving amps switched on for a long time
Post by: martinw on March 17, 2009, 01:25:50 PM: Quote from: Pete24v on March 17, 2009, 01:16:31 PM
i though standby was nothing more than a mute? on matmaps anyway...

On Matamps it is just a mute (signal ground), but on most amps, standby turns the HT off. Had this conversation with Jeff a few times! :)
Title: Re: Leaving amps switched on for a long time
Post by: HTH AMPS on March 17, 2009, 09:57:20 PM: you can run the heaters on reduced voltage in standby with a simple rewiring mod if you're worried about cathode stripping/poisoning...

http://www.freewebs.com/valvewizard1/standby.html
Title: Re: Leaving amps switched on for a long time
Post by: Ian Price on March 17, 2009, 10:02:02 PM: Cheers for the responses guys - the amp seems fine to me! Will remember to switch it off in future!

Ian.