Should that Zener be other way round or is this the right direction?
Btw, what difference would it make to use 100uF instead of 470uF in parallel with the Zener?

Maybe I'm going to use some sort of input/output connectors for PCBs so I can easily swap the tonestack before or
after the microamp and see which works (sounds) best.

Now about my power supply. I need +/- 18V for the power amp, 12V for channel switching relays and 9V for preamps.
Would it be ok to use this schematic: http://www.generalguitargadgets.com/pdf/ggg_bipolar_ps.pdf
and add 12V regulator between the 18V and 0V rails and also 9V regulator between 12V and 0V?

Something like this:

Hey, I came up with this block diagram showing features I want from this amp.
I think master volume would be really usefull for controlling the overall volume,
unless the power chip circuitry has it's own volume controll.

Thanks for your post Phil!

Those soundclips of your PhAbbtone and DDC are great! That's something I've been looking for.
And yes, I mostly play metal but that's why I'm going to build the Dr. Boogey preamp for my distortion channel 

I wonder does the PhAbbtone work as a "stand-alone" preamp or do I need to put some clean booster circuit after it (in case I want no distortion and don't want to use the DDC)? What I'm trying to tell is:

guitar > PhAbbtone > clean booster?? > power amp   OR JUST   guitar > PhAbbtone > power amp

I was thinking if  it's possible to put a bypass switch between PhAbbtone and DDC so I could have CLEAN sound and switchable distortion sound in same channel?

I'm planning to build my first guitar amp and I would really use some help getting my schematics etc. right because I'm a beginner in electronics. So, basic idea is to have 2 switchable channels: clean and distortion (2 different preamp circuits) both with versatile tone controls. The power amp could be somewhat transparent so that it would not affect too much to the tone and sound itself, I'm trying to leave that for the preamp section. This amp is going to be sort of a practise amp so it doesn't need to push out tons of watts, say 10..50W would be ok for driving my 1x12" cabinet loaded with 8 ohm Celestion Vintage 30 speaker.

So far I've thought to use gaussmarkov's Dr. Boogey as a distortion channel. I really like those soundclips found on youtube about this pedal. And what comes to the clean channel I'd like it to be as clean as it can but slight overdrive is not bad at all when cranking up the volume as long as there is enough headroom for clean sound. One option might be MXR micro amp clone + some tone stack attached to it.
For example Marshall style tone stack would be nice:
http://www.beavisaudio.com/techpages/blocksfragments/Marshall_Guvnor_Tone_Stack.gif

I looked into ROG's Tonemender but it didn't somehow convince me. I'm using EMG 81 and 60 active pickups and mostly 60 for cleans so the clean channel should be quite clear and a bit tight, no loose bottom end although the V30 is fairly bright itself.

Do you guys have any suggestions for the clean channel? And of course for the power amp which I have no idea at the moment.