how does the first solid state guitar amp sound when adapted to being a fuzz?

[pinkjimiphoton]

freakin' SWEET, that's how it sounds...

all germanium, from hint of dirt to fuzzy goodness.

here ya go, the venerable kay 704 guitar amp adapted as a fuzz.
link to schematics/vero at the ultimate guitar site are in the video description if ya diggit.

here ya go:

[GibsonGM]

Good deal, Pinkjimi!  Amazing what you can do with this old stuff and a little ingenuity, huh? 
Sounds pretty cool; you could use that for recording and whatnot.

Thanks for putting that together )

[pinkjimiphoton]

it was a lot of fun, but it was something someone else came up with, i just kinda tweaked it until it worked fairly well.
i may have to mod it some to get the noise down, it's pretty noisy!!

[Davelectro]

Wow. That sounds amazing.

[pinkjimiphoton]

here's my schematic, with the mods i made to jim's circuit (what i actually built):



i didn't bother with the vibrato.

here's jim's schematic. he has the presence circuit going to the outside of the output cap, seems risky to me.
i just tied it to b+ at the node of the q2 collector and the resistor feeding it from b+, seems to work still, and no dc on the output.



this is the original amp for comparison. all germanium. these were really warm sounding, tho not particularly loud til ya hit the 35 watters.



here's a pcb of jim's original circuit, this isn't what is in the video tho. i had to tweak it some, as original it just needed more cojones.

this also has the presence circuit tied to the output. i don't reccomend it. caveat emptor. you can omit it if you want, or tie it to ground. seems to work that way too.




here's the vero i cobbled together. check the nodes first if you wanna build it just to be sure, as the original vero i'd worked up had two mistakes on it that required a little judicious jumper action. the mistakes should be rectified on this, but ya never know....



here's a couple pix of my actual build. messy. gotta box it. it had a bit of debugging and modification, so it's not pretty..









th th that's all, folks...

[midwayfair]

What's this? A Jimi schematic on a computer, not hand-drawn? 

[italianguy63]

Hope you are feeling better Jimi!  Does not look like it affected your energy!  Keep up the good work!  MC

[GibsonGM]

here's a couple pix of my actual build. messy. gotta box it. it had a bit of debugging and modification, so it's not pretty.. Wink


What, I'm not the only one whose proto-builds look like that??!   

[pinkjimiphoton]

thanks guys.

i noticed the schematic he asked me to use was still a bit wonky...

this is what i built, and i know it works. (minus the tremolo)

[psychedelicfish]

Sounds great! I'll have to make myself one some time. I'll probably use positive ground and PNP transistors because that's all I have.

A couple of things I noticed:
1. The 2u2 cap between lug 3 of the gain pot and the base of the second transistor is drawn backwards.
2. The gain pot (in yours and the original schematic) is wired backwards from what I'd expect. This means that the first transistor will be heavily loaded when the gain control is turned down. I think you said at one point that it doesn't really sound good until you turn it up? That could be why.

[pinkjimiphoton]

good catch ed, i'll revise it.
the original circuit was pnp.

i didn't check the polarities of the caps, my bad! i just put in the minor circuit change with the presence controls and boosted up the gain a little bit.

[LucifersTrip]

thanx for keeping up the germanium experiments!

[kingswayguitar]

me likes
wow 5:20 - 5:30

[pinkjimiphoton]

thanx for keeping up the germanium experiments!

dave, this would probably work great with pnp, too.

i have the audio designs fuzzound project getting close to ready too, russ rutledge and jrod have been working on it with me and we have
so many variants that all work and sound good it's insane.

again, there was probably a mistake in the one that was on ebay, it was either built wrong, or more likely serviced wrong at some point.
anyways, i built one with all poly caps, and sockets for the battery pos/neg so i can run it either way, and there was zero discernable difference.

as long as the ge's are in the magic ballpark, say 30% tolerance from 100, it's gonna work.

i gotta give props to gus smalley here too, cuz without some of the stuff he's shown me recently, i don't think i could have pulled this off.

invader jim is working on this again over at the UG forum, he's having problems with q2 overheating. i'm thinking it's a biasing problem, this circuit will motorboat if you put too much bass in.

it sounds most excellent with a .1u cap in parallel (up to 470n i tried) completely changes the character of the breakup. but if you dime the gain pot, it will motorboat.

last week i built 5 "new" (for me) ge circuits, and i have three more in line for after the group gorge/ hollowdaze festivus thing.

i'm gonna TRY to spec out regularly available transistors (si) that work well TONEFULLY in this and the other circuits as well, that way as long as the ge's gain is right if ya put 'em on a switch you can have the best of both worlds.