From the voltages you listed, it would seem that T4 collector is connected to T6 base, as you have the same voltage listed for them.
But T4 collector should go to T6 emitter, so once again the voltages listed are questionable.

Thanks so much Loudthud!  I swapped those JFET leads and we now have audio!  Thanks to everyone who contributed to this thread!

Quote from: Umlaut on Today at 03:18:58 AMGK schematics are an extremely useful resource on how to bias and design jFet gain stages, btw. Most if not all of their guitar amps from the late 70s on (and a lot of their bass amps) feature jfets in one form or another.

So much to learn, so little time... 

Yes, bipolar supply. Look for Gallien-Krueger 200RG model (and similar very early 80s models) schematics to see where that particular gain stage originates : ) they use J113, but for these particular applications, depletion mosfets behave like jfets.
That stage CAN be built to single supply, but then we'd have to tinker with an additional Vref, and since I am running the whole preamp on bipolar, there's absolutely no need to go down that rabbit hole.
GK schematics are an extremely useful resource on how to bias and design jFet gain stages, btw. Most if not all of their guitar amps from the late 70s on (and a lot of their bass amps) feature jfets in one form or another.

That's an interesting idea you've got there. Say, are you running those LND150's at +/- 15V? Am I reading the circuit diagram correctly?

Thanks a lot. I really appreciate your help and support. I'll keep you posted on my progress.
M.

Yes, I did use 2N5089. I tried 2N3904 but it did not work as well
BC550 should give you a similar result to 89s though.
Bear in mind that I tinkered with it for less than 1h, so it was a bit of a summary test.
As for the voicing, I'd say marshall-ish with a raw, unfiltered edge to it. Into the right amp it can sound quite nice (think Black Sabbath, Pentagram, etc), but I prefer a bit more filtering and tone-shaping. While it sounds quite full and "amp-like" (not a term that I like, but...), and it has a nicer feel than your standard boss disto-box, I would still be partial to other multi-stage pedals like the AMT Legend ones, for example (check on FSB for schematics).
Oh, I tested it on the clean channel of my Peavey Bandit silver stripe, low input and bright switch off, which is an amazing pedal platform IMO.
Yesterday I was fiddling with a distortion circuit of mine which is quite similar in its topology and voicing, but using LND150 depletion mosfets. To my ears, they sound much more pleasant than BJTs in this kind of cascading gain stage circuits. I will probably post it at some point in the coming days, as I am pleased enough with it to share it 
Again, breadboard and see for yourself! lotsa fun can be had with this circuit, whether you tinker with the values or not.

Hi Guys
Sorry - i don't hang out on this forum very much as i must confess, i am a tube amp fanatic ;-)
The blue dots are where i removed the link wire and the green wire connects to the chassis ground.
One of life's great mysteries is why the only place i could find the schematic for a tube amplifier was on this - a solid state amplifier forum !
Anyway, sorry for the extremely late reply to this thread - i can always be found lurking on the freestompboxes.org forum or you can always email me (while i am still living) baja002steve@gmail.com
cheers to all
bajaman

.2V? My cheap meter probably.

Hey, Umlaut.
It's great that you've been able to breadboard and play it. Thanks a lot for all your input. It's going to save me, and possibly others, some time.
My parts came in this afternoon and I'm looking forward to breadboarding it myself, but it's going to have to wait a bit. Hopefully, no longer than two weeks.
Oh, and I found some BC550's the other day. I might give them a whirl too.

I also have a couple of questions:
1. Did you use the 2N5089 transistors?
2. Now that you have some hands-on (and ears-on) experience, how to would you describe the voicing of this preamp?

M.