Low Voltage "space charge" tubes and designs

[Brymus]

Someone posted this at SSguitar.com its really quite interesting and has lots of useful links.
Rick will get a kick out of these ,I never heard of them before.But apparently AES has some of them.
http://www.junkbox.com/electronics/lowvoltagetubes.shtml

Tubes designed to operate with 12V on the filaments AND the plates.For car radio designs should make nice pedals too.

[amptramp]

You may want to check out this thread:

http://www.diystompboxes.com/smfforum/index.php?topic=79069.0

and this site:

http://www.sophtamps.ca/mambo/index.php?option=com_content&task=view&id=25&Itemid=37

Space-charge tubes (and the whole family of 12-volt car radio tubes) are simple to use and provide some distortion as they are.  The second site uses 600 ohm transformers to match the 800 ohm output load rating of the 12K5, but if you can find a 70.7 volt line transformer with a 6.25 watt setting, that is an exact 800 ohm match.  You can use transistor-type capacitor voltage ratings with these tubes.

[brett]

Hi
strange as it may seem, at 12 V the 12AU7 high-voltage tube seems to behave the same as the low-voltage 12U7.  I don't know why.  Maybe it has to do with its much higher than average capacity for carrying current (which is why it can be used as a power tube in low wattage amps such as the Firefly).  Gain is low, however (5 to 10, as compared to 20 or 30 when run with 200V on the plate).
cheers

[Chrome Dinette]

I have successfully used 5840 and 7327 submini tubes with 24 volts on the plate, and as low as 5 volts on the filament.  In fact, I built a small tube preamp for a friend to mount in an archtop guitar, and I made a large psu to go with it that put 39 volts on the plates and 6.3 volts on the heaters.  My friend thought it was too big and I ended up buying a premade switching supply from Jameco and sticking it in a Hammond box, to which I added power cord, fuses, leds, etc.

I have also used 12bh7's with 24 volts on the plates and heaters(2 tubes in series).

archtop tube preamp:

http://www.vimeo.com/3747038

dual 12bh7 oscillator(with link to original schematic on some other forum):

http://www.youtube.com/watch?v=67_C_lVa7ZA