LED prob.

[JimRayden]

So I hook up a LED and a tube filament to the same supply. For a test, I used a 9V battery. If the socket is empty, the LED lights right up. As soon as I put the tube in, the LED shuts off and the filament doesn't light up either. In the pedal, these will be connected to a wall wart, I used the battery for just testing. Is it possible that the battery can't supply that much current needed for the filament and it'll work just fine with the wall wart plugged in?

Thanks for any help or humorous comments.

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Jimbo

[GibsonGM]

I haven't worked much with tubes, but don't they require 12V to function? Like, 12AX7 = 12 volts?  I can't really picture what the circuit is like from your description, either.  Is there any combination that lights the filament? I'd say it definitely is sucking current, and the LED just isn't getting enough to light. 

[JimRayden]

12AX7 works on both 12.6 and 6.3V depending on how you wire the filaments. I've wired them in parallel, so they're pulling about 300mA at 6V. I was testing it out with a 9V battery (it does no harm if I do it for a short period of time), so the tube must have pulled 450mA. The LED was in parallel with the heater and with a 2k2 resistor.

The filament doesn't light up with the battery at all, even without the LED. Is it possible that 450mA is to darn much for the battery?

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Jimbo

[The Tone God]

The filament doesn't light up with the battery at all, even without the LED. Is it possible that 450mA is to darn much for the battery?

For a 9v battery hell ya its too much. 300mA is the running current needed. Filaments pull ALOT more current on heat up. Way more then the battery can supply. The poor battery just gives up under the load of the filaments starting.

Andrew

[JimRayden]

Okay, I'll just leave it alone and hope for it to fire up (not literally though) with a wall wart.

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Jimbo

[RaceDriver205]

The poor battery just gives up under the load of the filaments starting.

Do you have a car, JimRayden? 

[JimRayden]

The poor battery just gives up under the load of the filaments starting.

Do you have a car, JimRayden? 

Yeah, but I have not yet had the chance to investigate its electrical systems, as I'm currently more absorbed in audio signal processing than automobiles and their odds and ends.

So to put shortly, I do not know what you're hinting to. That the startup can drain the car's accumulator pretty fast, especially when you're struggling with it on a cold winter morning? Yeah, that's common knowledge.

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Jimbo

[zpyder]

Car = big ol' 12 volt battery - Might a device which can supply enough current to crank an engine supply enough current to heat up a 12AX7?

cheers,
zpyder

[JimRayden]

Car = big ol' 12 volt battery - Might a device which can supply enough current to crank an engine supply enough current to heat up a 12AX7?

cheers,
zpyder

Oh, I thought he was comparing the heater of a tube to the starter of a car.

Actually it'd be cool to power up a tube (or even just a stompbox) from a car battery. Just for the darn fun of it. Damn you, now you got me thinking about making my gig rig portable and running on a buch of car batteries.

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Jimbo

[zpyder]

[The Tone God]

Actually it'd be cool to power up a tube (or even just a stompbox) from a car battery. Just for the darn fun of it. Damn you, now you got me thinking about making my gig rig portable and running on a buch of car batteries.

In the old days car radios were tube based. The tube filament ratings were setup up for running from car batteries and alternators.

Andrew

[JimRayden]

Actually it'd be cool to power up a tube (or even just a stompbox) from a car battery. Just for the darn fun of it. Damn you, now you got me thinking about making my gig rig portable and running on a buch of car batteries.

In the old days car radios were tube based. The tube filament ratings were setup up for running from car batteries and alternators.

Andrew

I'm aware of that but I wasn't talking of measly 2W radio power amps, I was talking about a full-blown live gear.

Could anyone calculate, how many car batteries it would take to give a decent 2-hour gig? For the sake of keeping the amount of batteries under control, let's make it indoors. No, I'm not trying to pull it off, it'd just be a cool - and useless - thing to know.

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Jimbo