Moving valve amp after playing?

charleshaupt

Hi all ,the one guitarist in town goes ballistic on any one daring to help him move his valve amp after he played a gig.Apparently the amp first needs to "cool down"? Asking out of curiosity. Thanks c

guidothepimmp

I'm no authority on valveamps but well known local valve amp builder told me it should be ok to move it so long as it doesn't get chucked in theback of a bakkie and bumped hard.

Its because the valve filaments are more fragile while hot and could break if jolted

But wheeling it around and moving is fine. Btw.. cool down time is shorttoo.. 5 minutes isfine

singemonkey

I definitely prefer my amp to have about 2 mins at least before it's seriously moved. That's not the same as gently moving it a meter to the back so that someone else's amp can go in though. But I don't want to lug it and manouever it all over the place before the valves have cooled.

AlanRatcliffe

Many with more knowledge than I say the temp changes from hot venue to cold winter night can be bad for the valves. So I generally play it safe and wait a while...

vic

Hot valve amp....?

OK, how long does it take (after one has switched off your amp) to finish your drink, then pack away your axe, pedals and mic,... then finish your chat with some patrons and fellow band members, then waiting to get paid.....? surely long enough for any amp (even an AC30) to cool down "enough".

Charles, your guitarist is somewhat over-sensitive.... ?

Tokai-SA

Ag shame, valve amps are so sensitive. ?
The best idea is, whilst the amp is cooling down run out and buy it some flowers. ?

MikeM

Tokai SA wrote: Ag shame, valve amps are so sensitive. ?
The best idea is, whilst the amp is cooling down run out and buy it some flowers. ?

Yea, it's a price you pay for them sounding better than modelling gear :roflmao: :roflmao: :roflmao:

ThomasN

Wait a few minutes before moving it, just like its a wise idea to wait a while before dropping the standby after putting the power on. The harder the valves re pushed during a performance, the longer it will take to cool down.

I remember the older Alpha Romeo vehicles often had owners with cracked engine blocks after driving the cars hard, pulling into their garages and immediately turning off the engines without letting them idle for a while.

Same principle.
New tubes can be flippen expensive. :-[

vic

ThomasN wrote: Wait a few minutes before moving it, just like its a wise idea to wait a while before dropping the standby after putting the power on. The harder the valves re pushed during a performance, the longer it will take to cool down.

I remember the older Alpha Romeo vehicles often had owners with cracked engine blocks after driving the cars hard, pulling into their garages and immediately turning off the engines without letting them idle for a while.

Same principle.
New tubes can be flippen expensive. :-[

I have here a Vox AC10 which started its life in 1965/6. This amp has seen many many hours of gigging ....those long 4-5 hours gigs....it hasn't got a standby switch... and guess what ? it still has its original Mullard valves...all of them.....and it's still fully operational. So it's obvious that the quality of the tubes is a real determining factor.

Funny you should mention the old Alfas ?.....I had a late '60's model GTV in the early '70's....trick was to fast-idle the engine for about 5 mins in the morning to warm it up properly before driving hard because the block and top were of different alloys with the potential of uneven expansion..... with the result that the top gasket sometimes blew. This led to loss of water and water getting into the oil...this again caused over heating of the engine and resultant warped tops and blocks.... ☹ Alfa remedied this later by providing gaskets with steel linings around the ports.
But the biggest headache was the unreliability of the mechanical temp regulator between the radiator and engine....this thing would get stuck, not allowing cold water into the engine with catastrophic over heating of the block...oh my....So we would remove this culprit....but now it would take at least 15 mins to warm the engine up...LOL !

Gearhead

My 2c in this thread go towards some thermodynamics thoughts (although I must say MikeM's funny). If these tiny little parts inside our valves are fragile, they also do not contain a lot of stored energy as heat. Meaning the valves cool down fast enough, not even close to big massive car engines.
The only thing I can think of that heats up more during longer sessions is the amp chassis, which actually is the one part doing the cooling down of those tiny little parts (vacuum is a very good thermal insulator). This means you can actually check if the amp is ready to move: as soon as the outside has cooled down.

ThomasN

Vic wrote:
ThomasN wrote: Wait a few minutes before moving it, just like its a wise idea to wait a while before dropping the standby after putting the power on. The harder the valves re pushed during a performance, the longer it will take to cool down.

I remember the older Alpha Romeo vehicles often had owners with cracked engine blocks after driving the cars hard, pulling into their garages and immediately turning off the engines without letting them idle for a while.

Same principle.
New tubes can be flippen expensive. :-[
I have here a Vox AC10 which started its life in 1965/6. This amp has seen many many hours of gigging ....those long 4-5 hours gigs....it hasn't got a standby switch... and guess what ? it still has its original Mullard valves...all of them.....and it's still fully operational. So it's obvious that the quality of the tubes is a real determining factor.

Funny you should mention the old Alfas ?.....I had a late '60's model GTV in the early '70's....trick was to fast-idle the engine for about 5 mins in the morning to warm it up properly before driving hard because the block and top were of different alloys with the potential of uneven expansion..... with the result that the top gasket sometimes blew. This led to loss of water and water getting into the oil...this again caused over heating of the engine and resultant warped tops and blocks.... ☹ Alfa remedied this later by providing gaskets with steel linings around the ports.
But the biggest headache was the unreliability of the mechanical temp regulator between the radiator and engine....this thing would get stuck, not allowing cold water into the engine with catastrophic over heating of the block...oh my....So we would remove this culprit....but now it would take at least 15 mins to warm the engine up...LOL !

I think there's a huge difference between the vintage tubes and say... the KT88's and EL84's fitted into high gain amps found today no?

vic

Gearhead wrote: My 2c in this thread go towards some thermodynamics thoughts (although I must say MikeM's funny). If these tiny little parts inside our valves are fragile, they also do not contain a lot of stored energy as heat. Meaning the valves cool down fast enough, not even close to big massive car engines.
The only thing I can think of that heats up more during longer sessions is the amp chassis, which actually is the one part doing the cooling down of those tiny little parts (vacuum is a very good thermal insulator). This means you can actually check if the amp is ready to move: as soon as the outside has cooled down.

The temperature inside a tube should be high enough to allow electrons to " boil off "from the filament......1000 plus degrees C is reported. So the temp inside the tube is very high but as soon as the amp is switched off (as you say) the tube cools down fast due to the small surface area of the filaments, etc. and the rapid movement of cool air around the tubes. The chassis is lukewarm compared to the valves.....no comparison really....

a Vacuum is not a good thermal insulator at all......the glass of the tube is a very good thermal absorber.....Infrared radiation (heat) travels through a vacuum the same way as visible light does......eg. the sun's heat (IR waves) travels through 150 million kilometers of almost perfect vacuum to reach earth in about 7 minutes.

AlanRatcliffe

Correct me if I'm wrong, but the "vacuum" inside a valve is inert gases, rather than a hard vacuum.

Chocklit_Thunda

Alan Ratcliffe wrote: Correct me if I'm wrong, but the "vacuum" inside a valve is inert gases, rather than a hard vacuum.

In gas filled tubes, discharge tubes and cold cathode tubes. The others have a hard vacuum. Not sure which one the amps use though.

vic

Alan Ratcliffe wrote: Correct me if I'm wrong, but the "vacuum" inside a valve is inert gases, rather than a hard vacuum.

For audio use (as in amps) it is indeed a "huge" vacuum (hard vacuum). One does find gas filled tubes (probably an inert gas, and in some cases mercury vapour) for some electronic applications....but even here the pressure is slightly negative.

Gearhead

The point I'm trying to make is that a filament cools down quickly from halfway its melting point (roughly) to a couple of hundred degrees. It then is able to withstand low-g movements. As Vic pointed out, this cooling down is because the high temperature metal radiates heat through infrared. From, say, 200C downward this does not do a whole lot anymore and from 80C downward the main cooler is conduction through the attached wiring going into the amp chassis. Radiation goes up by absolute temperature to the power of four.
Yes some tubes are not entirely vacuum but my statement was about pointing out that after the small hot tube parts have cooled down to, say, 80C, the glass is going to be less of a coolant than the copper everything is attached to. In fact the reason why the tube does not cool down fast anymore is that the copper is about the same temperature, also above 60C (too hot to touch). I'm sure no one here will argue that a bottle of gas will conduct heat better than copper. If you want to make a bet about the insulating qualities of hard vacuum (for any heat transport except radiation), please state what we bet about?

Long story short: If you want a simple rule about when it's safe to move your amp: when everything you can touch (without electrifying yourself) is not too warm to touch. Bulbs, case parts around air vents etc.
Another rule of thumb would be: after one or two beers. Or: after the cab and the guits are in the van. After the missus has said it's time to go. When the barman switches the bright lights on. When the chicken wire in front of the stage no longer stops the empty bottles of beer. Etc.

MikeM

I've had an amp of mine knocked over while on and there were no problems. I'd personally not be too worried. If it was such a big deal, I'm sure we'd all have heard horror stories ?

joel

singemonkey

Gearhead wrote: The point I'm trying to make is that a filament cools down quickly from halfway its melting point (roughly) to a couple of hundred degrees. It then is able to withstand low-g movements. As Vic pointed out, this cooling down is because the high temperature metal radiates heat through infrared. From, say, 200C downward this does not do a whole lot anymore and from 80C downward the main cooler is conduction through the attached wiring going into the amp chassis. Radiation goes up by absolute temperature to the power of four.
Yes some tubes are not entirely vacuum but my statement was about pointing out that after the small hot tube parts have cooled down to, say, 80C, the glass is going to be less of a coolant than the copper everything is attached to. In fact the reason why the tube does not cool down fast anymore is that the copper is about the same temperature, also above 60C (too hot to touch). I'm sure no one here will argue that a bottle of gas will conduct heat better than copper. If you want to make a bet about the insulating qualities of hard vacuum (for any heat transport except radiation), please state what we bet about?

Long story short: If you want a simple rule about when it's safe to move your amp: when everything you can touch (without electrifying yourself) is not too warm to touch. Bulbs, case parts around air vents etc.
Another rule of thumb would be: after one or two beers. Or: after the cab and the guits are in the van. After the missus has said it's time to go. When the barman switches the bright lights on. When the chicken wire in front of the stage no longer stops the empty bottles of beer. Etc.

Yeah. This is cool. But practically speaking you're not taking a big risk after, essentially, half a beer. Yeah, the tubes might be still warm to the touch, but they won't be scalding. And we are talking low g movements. We shouldn't be tossing our tube amps around as it is. What you're saying is getting it 100% safe. On a coolish night, a couple of minutes and the tubes are already waaaay below their operating temperature.

shawnv

Vic wrote: Hot valve amp....?

OK, how long does it take (after one has switched off your amp) to finish your drink, then pack away your axe, pedals and mic,... then finish your chat with some patrons and fellow band members, then waiting to get paid.....? surely long enough for any amp (even an AC30) to cool down "enough".

Charles, your guitarist is somewhat over-sensitive.... ?

Waiting to get paid if you are playing at corner house in 4ways should give you an entire month... I guess thats enough cool down time ey.