I am here recommending a general design of a power-tube saturation pedal for everyone to implement - companies and hobbyists. Most similar products are unfocused and try to do too much and end up being overdesigned and overpriced. What the guitarists need more than anything now is a very simple, single-function pedal packaged in a totally traditional way as a distortion pedal. Use an EL84 power tube driving a resistive or RLC load in a stompbox configuration with Distortion, Level, and Tone controls (3 controls total), 1 In jack, 1 Out jack, a power cord, and 1 footswitch. That's all, no more. List price: $175. It does not have preamp distortion. Push the price down, down, down. No power switch. No fuse, no anything. Strip out all possible parts.
This web page is the design spec and invention announcement. I will start designing this with the AX84.com DIY crowd including Chris Hurley.
You can get a great single-coil neck pickup tone and a great double-coil bridge pickup tone, at any volume, using this chain:
eq pedal 1 (smile for single-coil neck, frown for double-coil bridge)
overdrive (for single-coil neck) or distortion pedal (for double-coil bridge)
eq pedal 2 (moderate smile curve)
tube power amp <--
dummy load <--
eq pedal 3 (V curve)
solid-state power amp
I've gotten the same great sounds with any decent tube power amp (usually from a combo amp) combined with any power attenuator used as a dummy load (Power Brake, Power Soak, Hot Plate). I just use the Spk Out of the power attenuator, with high attenuation, as a Line Out, feeding EQ pedal #3.
There might be slightly less dynamic depth than when the saturating power tubes directly drive the guitar speaker, but the general idea works as well as the Guytron/Van Halen 3-stage amp configuration -- which is to say, very well and conveniently, and flexibly. Every guitarist should have a power-distortion pedal.
I recommend you try the same chain, and when you confirm that it works very well to produce classic power-tube response at any volume, package the tube power amp and dummy load together. Don't include a cab-sim filter; assume that the chain ends with an actual guitar speaker. I intend to upload sample clips to http://www.mp3.com/distortionvalve and add samples to the Amp Tone reference and test input CDR I'm making.
See also powertubesatpedal.htm.