Starting point for tube preamps

[swinginguitar]

i'm looking for some general information on incorporating preamp tubes into stompbox designs. can anyone point me to some good tutorials?

some specific question:

1) for a dual triode like the 12ax7 - is each side typically used as a separate gain stage (1 feeding the next), or are they ganged some way, or even just one side used?
2) could one side of a 12ax7 be used for a gain stage, and the other for something else (such as a driver for an oscillator)?
3) what's involved as far as voltage/transformers/rectiifiers/power supplies for preamp tubes? sources for parts?
4) is it a big deal to incorporate all those parts into a pedal enclosure? (radial/seymour duncan/blackstar/et al do it, so i assume the transformers wouldn't be on the magnitude of a tube power amp)

[panterafanatic]

1) You can use both as gain stages, or in parallel for a different tone.
2) You're better off using both as gain stages and a MosFET to drive whatever follows it.
3) I buy isolation and filament transformers from Antique Electronics Supply, you should be able to get multiple preamp transformers from there. A standard 1n4007 rectifier will more than suffice.
4)You can fit it into a large case, a BB C or DD would probably be well served. Remember to plan it well. How far acks and pots go into the enlcosure, where your recitifier and filer caps will be placed. Tube socket placement, ect ect

[puretube]

Lot of guys don`t like pre-amp (triode) tube stuff...
they seem to prefer sending their tone thru dozens of pn/np junctions
and then castrating it to 0.7 or o.3V,

and then megablasting that via their tube-pre-amp equipped tube-powerfliers...   

[swinginguitar]

any pros/cons to using external transformers? (for example like the tonebones @ 15v)

[panterafanatic]

I wouldn't use 15v DC over a 9vDC for the simple fact that these aren't opamps, the full power supply voltage won't matter as much over that 6 volts. Unlike going from 5 to 12 volts for an IC, a tube preamp could much more benefit from a supply of say 50 to 100volts, staved plate designs won't give you that tube-ey sound as much as increasing the B+ would.

This also makes it a little less hassle to worry about having the current for the heaters sine you can specifically buy a transformer with a 12v or 6v heater windings in addition to the higher voltage winding.

You can get interaction between the transformer and signal circuit, but a well planned layout will make such interactions negligible.

[GibsonGM]

http://www.valvewizard.co.uk/