Keeping Tubes warm ona cold day......

[gators81]

Played an outdoor show the other night and noticed that my amp (Messa Boogie Dual Calibre) had almost no low end on it. The temp outside was in the low 40s. Can the cold affect the tubes by not allowing them to warm up properly? Is there any way to keep the tubes warm?

[MikeH]

I don't know if you've ever played outside before, but I've noticed that guitar amps tend to sound like they have a lot less low end in big, wide-open spaces where the sound has nowhere to go but 'away'.  That's a lot of drummers use extra heavy sticks when playing outside, other wise it sounds like they are playing on a kids toy drum set.

[gators81]

I have, but never that cold. I live in Orlando, Florida so we don't get much really cold weather. The place we played was wide open.

[Johan]

the filament inside the tubes heat up to around 800-900 degrees Celcius( around 1500F)...a 40F or 80F ambient temperature makes no differance..
your loss of low's probably has more to do with lack of solid walls and floors around the amp ( place your amp in the corner and blast away to see the differance it makes...)
j

[gators81]

Thanx.....next time I will try to find a corner to place the amp in. 

[SonicVI]

Seems like an amp would have better low end in cold air than warm air. The denser cold air should be able to transmit sound better. It's probably a negligible amount though.

[jkokura]

Do you use an open of closed back cab and was it miked or left to fill the space on it's own? If there's nothing to deflect the sound, only the forward moving sound waves from your cones will end up being heard, so using a closed back cab, or even better, putting a small deflection wall behind the cab will help out a lot.

[petemoore]

  Amazing how cancellations, concentrations and even consumption of waveform / frequency / amplitude, changes with the venue changes.
  They ask me: "Why would the room matter?'' like it's a statement of logic.

[amptramp]

Electrolytic capacitors tend to drop in capacitance when they get cold.  Your amplifier may show a reduction in low-frequency response, especially if it uses electrolytic cathode bypass capacitors.  An outdoor venue also has a much difference acoustic load than an enclosed space, so you can get both electronic and acoustic effects.

[GibsonGM]

even better, putting a small deflection wall behind the cab will help out a lot.

You'll find that if you had a 'backer' such as a piece of plywood behind the amp, you'll reflect more of your low end outwards towards the crowd.  Otherwise, outdoors just stinks for sound control!!

[gators81]

There was nothing but open space behind my amp.The amp is a combo with a partially open back. The stage was pretty much just a covered area with no walls. If I had known what to expect there I might have brought a piece of plywood to stick back behind the amp. Worst part of the gig was the layer of dew over all our equipment at the end of the set.

[gators81]

Thanx for all the info.

[mac]

thermionic emission is given by richardson law,

j=const*T*T*exp(-W/k/T)

google for constant value, the minimun energy W needed to extract an electron from the metal surface and boltzmann constant k, and do the math, ie, compare j at T=273K and T=300k.

mac