Amp left on standby

  • Thread starter Thread starter TelePaul
  • Start date Start date
The reason tube amps have standby switches is so you can leave the settings alone on your amp and axe between sets. If you turn the amp off, when you turn it back on to start playing again there will be a warm-up factor of up to a minute or so (while the tube filaments get hot) before you can get any volume. If you leave the amp on bet\ween sets, all sorts of noise and feedback can occur.

So somebody (Fender?) invented the standby switch. This (at least with the older Fender amps) leaves the filament voltage on, but disconnects the rest of the amp from its B+ supply voltage. See schematic (go to Schematics and Layouts, then Bassman or Bandmaster):
http://www.ampwares.com/ffg/

So when you get back on stage to start the next set, you pick up your axe, flip the standby switch on, and you're ready to make noise immediately at the same settings that you left.

The tubes will light up and be hot while it's on standby. It won't hurt to leave the amp on or in standby for days or months at a time, although some components may have their lives shortened minimally, and your electric bill may be a little higher. :)
 
I don't have anywhere near the gigging hours of Lt. Bob, and don't own the array of amps that he does, but other than that my experience with tube amps echoes his.

All of my musical career I have used tube amps for my guitars. I have done some pretty intense gigging that involved both long gigs with amps left on (some with no Standby function at all) for hours, and then doing it again for several nights in a row. Gigs in the blazing summer heat with no shade. Gigs with the temperatures dropping into the '30s (f).

A well-designed tube amp is designed to run forever at its nominal operating temperature, and as Lt. Bob said, as long as there is adequate ventilation, an amp will not suffer from being left on other than minor tube wear.

I have never suffered a tube amp failure, period. Had a couple of main power switches that needed replacement, and of course retubing when it's necessary.

In fact, the only amps I have seen quit working are solid-state FOH amps that go into thermal-protect mode when it gets a bit too hot, like being in direct sunlight on a hot day.

YMMV, but I think a decent tube amp is like a tank.
 
boingoman said:
I believe I will.:D

Why of course?
Click to expand...


when you engage the high voltage line.. also refered to as B+ it cannot help but increase the current flow through the tube... the heater current which can be on the order of 1 amp per tube doesn't change... but the active parts of the tube at idle can be considerable... a single pair of 5881's running at say 450 volts and putting out 50 wts uses 30ma per tube... if it's at 300V it's @40ma and at 600V it's @20ma... aand that's all at idle...
 
dementedchord said:
when you engage the high voltage line.. also refered to as B+ it cannot help but increase the current flow through the tube... the heater current which can be on the order of 1 amp per tube doesn't change... but the active parts of the tube at idle can be considerable... a single pair of 5881's running at say 450 volts and putting out 50 wts uses 30ma per tube... if it's at 300V it's @40ma and at 600V it's @20ma... aand that's all at idle...
Click to expand...

Word- I'll be curious to see how many actual degrees it adds- the plate's bigger surface area means it's actual temperature will be lower, and it's color (ie not glowing) indicates this as well. And if this extra heat raises the temp of the amp as well, since the tubes are outside the amp in a lot of cases. The point I was edging towards is that the extra heat by itself isn't a reason to use the standby switch. :)
 
dementedchord said:
when you engage the high voltage line.. also refered to as B+ it cannot help but increase the current flow through the tube... the heater current which can be on the order of 1 amp per tube doesn't change... but the active parts of the tube at idle can be considerable... a single pair of 5881's running at say 450 volts and putting out 50 wts uses 30ma per tube... if it's at 300V it's @40ma and at 600V it's @20ma... aand that's all at idle...
Click to expand...

30 mA isn't much compared to 1 A.
 
dementedchord said:
when you engage the high voltage line.. also refered to as B+ it cannot help but increase the current flow through the tube... the heater current which can be on the order of 1 amp per tube doesn't change... but the active parts of the tube at idle can be considerable... a single pair of 5881's running at say 450 volts and putting out 50 wts uses 30ma per tube... if it's at 300V it's @40ma and at 600V it's @20ma... aand that's all at idle...
Click to expand...

Are we talking about class A amplifiers? Or is the "B+" referring to class AB or such?
 
vadoom said:
Are we talking about class A amplifiers? Or is the "B+" referring to class AB or such?
Click to expand...

B+ is high voltage DC that flows to the plates of the tubes. It serves two basic purposes, to drive the plate more positive than the cathode, allowing current to flow, and serves as the carrier of the output signal. The name B+ is from the time when the DC for tube devices was often provided by batteries. The A battery was for the filament, the B battery was for the plate voltage, and, if used, the C battery was for the grid bias. B+ is also called HT, for High Tension.
 
hang around and learn alot....so in stand-by mode the B+ is off? and the amp is cooler?...and when turned back on the tube(s) filiments heat up to play...is this correct?

I was wondering. Because if I wanted my amp to be quiet I'd turn down my volume knob on my guitar making sure I was on clean channel. Which is what I do with no standby.
 
No, in standby, the tubes filiments (6.3 VAC or 12.6 VAC or DC heaters) are always on.
 
Track Rat said:
No, in standby, the tubes filiments (6.3 VAC or 12.6 VAC or DC heaters) are always on.
Click to expand...

That's what I figured as well, since you leave the amp in standby while it "warms up" - if the tube filaments were shut off and cooled down every time you put the amp in standby, there would be no need for standby :)

Normally I do the same thing as the last poster when I am playing through my Blues Junior, which has no standby switch - turn the volume to 0 with the guitar plugged in, and let the amp sit for a while. Unfortunately that's the only option in that scenario.

As for leaving your ampon standby all night, I maaaay have accidentally done just that myself last night :eek: I was playing, put it on standby with the intention of coming right back to play, and when I got sidetracked doing laundry, totally forgot about it. Since there are other lights blinking or steadily on other equipment when I go to bed, I thought nothing of it :)
 
You must log in or register to reply here.
Back
Top