The "Big Sho"?

[JOHNO]

  Been messing around alot lately with the big muff and doing all of Yun's mods and those other mods. You guys know the ones i mean. In stead of putting Yun's rocket boost in front of the muff I thought I'd go for a SHO. So anyway it sounded unreal, heaps of sustain. So i was at the pub thinking and drinking and it struck me. What if I take out the input stage of the muff and insert, you guessed it a SHO. pmsl. So I just did it on my bread board and it too sounds unreal, although it hisses like a tiger snake on heat. So I'm guessing that the output impedance of the Sho doesn't match the input impedance of the first gain stage of the muff. By the way i hooked the Sho directly to the 1uf cap after the sustain pot. Anyway just thought I'd let you guts know what i was doing. Any thoughts or math problem's would be greatly appreciated
                                                   Johno

[Ripthorn]

This sounds like a cool idea.  I have never built a big muff, but if this works out, it just might be enough to get me to do one.  I know, it sounds like a sin that I have never built one.  Never built a fuzz face, rangemaster or valvecaster either, though, so no biggie.

As for the hiss, there may be an impedance mismatch or you just might be boosting some background noise so much that it comes on through really loud.  Just make sure to keep us posted as this sounds really cool.

[Toney]

 It's extremely easy to stuff up a BS170 with poor handling or too much heat. Delicate little things, they are...
What does a damaged but still functioning BS170 in a booster sound like? Answer = Hissing like a basket of snakes. I have found this out the hard way...
I would audio probe the SHO stage before I did anything else.

[JOHNO]

Thanks toney i didnt know that fact about the BS170, ill check it out tommorrow as its past midnight at the moment. I just figured that if i had damaged it the SHO wouldnt work at all. Anyway this thing is as loud a box full of crickets. I stuck a 39k resistor between the SHO and the 1uf cap of the gain stage of the muff and that dropped the volume a bit. Even if it is noisey ill still find a spot for it in my rig. Hopefully i can sort out the hiss.
      Thanks Johno

[JOHNO]

You spot on champ. Just hooked up the Sho directly to the amp and it hisses. So i guess i've damaged the fet. I was so careful with too. I dont have an earth strap so do I just earth my self the a water pipe or what?

[Ripthorn]

I would just use a socket for the fet.  That way there is no soldering heat to damage it and electrostatic damage is kept to a minimum as well.

[JOHNO]

It is in a socket. I put it in after i finished the board to test the circuit and then took it out again while i boxed it up. But i guess ive shorted it some how. I did grab the legs of it with a pair of pliers to bend the legs out so it would fit in the socket easily. Im tipping thats when ive buggered it.

[JOHNO]

Well ive got this up and running. Tried a few different tricks, like changing the 10m resistors in  the Sho circuit to 1m but it lost gain. I did lower the the value of the 39k resistor to 10k and its sounds good, lets a bit more drive through. Might try going even lower, say 1k. Put a new fet in it but didnt stop the hiss. It hisses at high gain levels on the Sho but ive read the sho is like that.  Well it doesnt have the sustain of a complete muff with a Sho in front of it, but it is a pretty good sound IMO. Well thats about it for this, hope someone else tries this thing out. Ill post some clips when i get around to it.
                               Cheers Johno.

[petemoore]

 Rubber gloves...
  Or don't touch it, use an insulated alligator clip to keep a 0.0v maximum potential by connecting across the three transistor pins, haven't looked at the data sheet, something like the G/D or G/S voltage max is a 20v thin sheet of glass, you can easily generate static electricity which can charge to way over that.

[JOHNO]

Thanks pete, this morning when i put the new fet in i used the plastic of a ciggarette pack, seemed to do the trick. By the way for any one interested in building one of these im pretty sure it can be built on a standard BMP board. im just going shopping to get a 1mm drill bit to to finish an old muff board i have lying around and ill lets you's know.