ROG-like hiwatt pedal help

[tcobretti]

I'm trying to put together a schematic to convert this preamp into a pedal.

http://www.drtube.com/schematics/hiwatt/hwpre1.gif

Questions:

1)  What does the horseshoe shaped resistor/cap combo in the top left corner do?

2) If I'm simulating the brilliant channel, do I need to include the right half of the second tube?


3) How is the output section going to work? I'm not really sure what to do with the drain side of the last two jfets (tube 4).


4) Are there any gotchas that are going to complicate this project?


I'm pretty new to this stuff and figured this would be a good way to learn, so any advice would be appreciated.

Thanks,
travis

[maximee]

Sorry, I can't help you with your questions...
But... I'd go with the "normal" channel instead of simulating the bright channel... I have a DR504 head, and the bright channel is just way too bright for me (and all my friends who played through my rig)


If you need someone to A/B the difference between your pedal and my amp let me know...  

[tcobretti]

Ok.  Thanks for the advice.  I've never actually played thru a hiwatt so I may ask you to A/B it once it's done.

[Craig V]

Might I suggest modeling the pedal after the CP103.  That is what Townsend uses - great for the Live at Leeds tone.

[petemoore]

You can probably mod that bright channel to be more usable, probably a simple revoicing of the input cap on the volume knob...I don't know but to say I did a mod to Ch1 of my MkII 50w, now, instead of barking and biting when hit with anything except the softest input, it just growls instead...it changed  from almost complete uselessness, to being used all the time.
 Someone helped me figure that one out, and called it: "Oh, that 'spike in the forehead' high end that amp is known for", which described it very concisely.

[tcobretti]

I'd like to build the CP103, but haven't found a schematic.  I'm hoping the DR103 is similar, and since this preamp is the basis of so many hiwatts it seems like a good place to start.