Mike Reed
pfm Member
Funnily enough, yes; my latest purchase. It's a headphone amp. (Myryad), which, once you insert the live IEC plug, has only stand-by or on.
Valve amps: when and when not to leave on.
- Thread starter Brian S
- Start date
Funnily enough, yes; my latest purchase. It's a headphone amp. (Myryad), which, once you insert the live IEC plug, has only stand-by or on.
uncl_nigel
pfm Member
My Cambridge CXU bluray player only has a standby switch
My Quad 303 does not have a power switch
I turn it on&off on the wall, it gets quite hot upon the cooling fans, allmost like some valve designs - guess its normal, just owned it very short time
Tony L
Administrator
A 303 should not even get warm unless you are really hammering it driving an awkward load. I can listen to mine all night and it doesn’t get more than a degree or two above ambient room temperature.
I don’t understand your reference to cooling fans, the 303 has none.
PS My Leak Stereo 20 has no power switch either, like the 303 (and Quad and Leak tuners) it was designed to be switched by the preamp.
I don’t understand your reference to cooling fans, the 303 has none.
PS My Leak Stereo 20 has no power switch either, like the 303 (and Quad and Leak tuners) it was designed to be switched by the preamp.
davidsrsb
pfm Member
And probably turns off the main circuits with just a very small standby power supply
Something very wrong there, the 303 is a low idle current design and was often installed in a wood cabinet without much ventilation.
Tony L
Administrator
A little perspective: I spend a day a week running and demonstrating a period-correct replica of a 70 year old valve computer. A machine containing around 560 wartime-period valves and countless associated components that has been run several times a week for twenty years now. It does not catch fire!
Also, when was the last time anyone here went to a rock or blues gig that was stopped because the guitarist’s amp “caught fire”? You can rest assured anyone worth paying admission to see will be using valve amplification, and likely nice vintage kit too.
These things can happen, just as some solid state amps without adequate protection can ‘go DC’ on failure (and I know of one example that actually set someone’s speakers alight!), but it is again very uncommon.
Also, when was the last time anyone here went to a rock or blues gig that was stopped because the guitarist’s amp “caught fire”? You can rest assured anyone worth paying admission to see will be using valve amplification, and likely nice vintage kit too.
These things can happen, just as some solid state amps without adequate protection can ‘go DC’ on failure (and I know of one example that actually set someone’s speakers alight!), but it is again very uncommon.
uncl_nigel
pfm Member
It might be uncommon but when it happens in front of your own eyes in your own sitting room it is not easily forgotten!!!
The smell of burnt out electronics tends to linger in the room for quite some time after you have taken the wreck to be disposed of.
I have also had a computer PS catch fire at work after a power cut and the residual smell is quite similar and really unpleasant.
The smell of burnt out electronics tends to linger in the room for quite some time after you have taken the wreck to be disposed of.
I have also had a computer PS catch fire at work after a power cut and the residual smell is quite similar and really unpleasant.
Barrymagrec
pfm Member
I suspect he means cooling fins.
My limited experience of quad 303s is as you say, they don`t get hot.
Tigerjones
Bagpuss
I've got this really weird system with my hifi where I turn it on when I want to listen to it and turn it off when I don't. It never stays on overnight unless the cats fancy a late night session which is rare these days.
Arkless Electronics
Trade: Amp design and repairs.
/\ +1
The time that spectacular valve failure is most likely to happen is when you switch it on and the valves have just warmed up enough to start to operate.
IME 90% of such failures will happen then. All of this applies only to power amp output valves as valves in other places use lower voltages and more importantly are very current limited compared to output stages.
It is also, as you might guess, hugely dependent on the quality of the valves with NOS being generally the best (and I'll include the oft used Russian mil spec 70's and 80's valves in this) and the very worst being Chinese and E. European ones from late 70' to v early 90's. Worst I've seen with such crap ones as these is for both EL84's and GZ34's to last about 40 seconds before going bang... change valve for another, thinking it's a fluke... lasts 40 seconds then bang again. I've always stayed away from JJ valves due to extreme unreliability sometimes expressing itself in fireworks as well (EL34 in Marshall guitar amp actually melted the glass!!) but apparently they have much improved lately.
Tony L
Administrator
Would it be inappropriate to ask what amp caught fire and to what extent, i.e. what was actually flamable? Most valve amps are very solid steel boxes so one would hope any fire would be pretty self-contained, i.e. little more than a smoking resistor or whatever.
I remember using my first one as a monitoring amp when recording and really stupidly just putting it down on the floor under the mixer. When I came to pack up it was so bloody hot I nearly dropped it! The carpet had obviously blocked its ventilation. Shortly after its PSU caps leaked so it certainly didn’t like it! When used more sensibly they run at little more than room temperature all day long.
Seanm
pfm Member
This is much less reassuring than you might think!
uncl_nigel
pfm Member
SAC Glowmaster 88
Destruction of one channel's printed circuit board - the amp had to be written off.
This did not happen during switch on but during the playing of music.
Destruction of one channel's printed circuit board - the amp had to be written off.
This did not happen during switch on but during the playing of music.
Apologies, I meant fins
Quite warm over them and the block dividing them in the middle, perhaps transistors are in there ?
The amp is just back from a full service at Quad in UK
Arkless Electronics
Trade: Amp design and repairs.
Yes that's where the transistors are. 2 per channel and one more for voltage regulator. a Quad 303 should be virtually cold with no music playing.
Arkless Electronics
Trade: Amp design and repairs.
It's better that way IMHO as you can hover around it for the first minute while it warms up, with one hand next to off switch just in case!
Be especially wary of brand new valves first time they are used. This is the time they are most likely to go.
Tony L
Administrator
Never heard of it, but just googled and it looks to be made in Thailand and I can’t find a UK importer. Are you sure it was designed for UK 240V mains? A lot of grey-import stuff from the east is designed for 220V and will cook on UK mains.
I certainly don’t consider the countless stories of exploding eBay Ming Das etc to be any reflection on valve technology at all, more that using the correct mains transformer for the country’s mains is rather essential! 220V and 240V are two very different things.
Arkless Electronics
Trade: Amp design and repairs.
Very true. The crap valves that come standard with such things, plus el cheapo high voltage electrolytics used right up to their ratings, are an episode of the big bang theory waiting to happen as well... but without Sheldon! This is true even at 220V and with a 220V unit on 240V mains I wouldn't leave one on whilst going for a piss!