Anyone Interested ?

[Dragonfly]

Ive got a really cool little pedal that was given to me by a friend that found it in a pike of stuff in his music store...its by a company called "Audioworks", and the pedal is called the "F.E.T. Distortion". Its a really good sounding overdrive/distortion that seems to work pretty well with a variety of amps/guitars....

anyway....i dont have time to trace it out (pretty busy lately), but i could probably post top/bottom board pictures and some values if you guys are interested in working out the circuit....

let me know if you want to do this...i probably wont have time to post pics till wednesday...

Andy

[spudulike]

Go on, worth a look and maybe RE

[stm]

Sure, please post the pictures when you can 

[roknjohn]

Dragonfly you stumbled on to what I would consider one of the best kept secrets I know. A friend of mine had one of these years ago, and I have it traced out somewhere. If I can find it in the next week or so I'll try scanning it and posting it.

I have tried many times to find information on the web about this pedal, and never had any luck. If memory serves me correctly, it was a grey colored pedal. Kinda smooth and creamy sounding overdrive, could get a little thick but not over the top. The standard 3 knobs: Drive, Tone, and Level.

Built a clone some years ago, traded it to someone, and never got around to building another. Think it had MPF102 fets in there. Would be interesting to try with other fets.

[roknjohn]

 Well it didn't take to much effort to locate the schematic. Sorry about the layout of it, was one of my first attempts at transferring circuit to schematic. Shoulda went back at some point and cleaned it up. Anyway here it is.


http://i25.photobucket.com/albums/c57/roknjohn/Audioworks.jpg


Sorry for using link, but can't seem to get ATTACH PICTURE to work. This should be accurate, as I stated I did make a clone using this schematic years ago.

[Steben]

reminds me of a Fet muff with extra treble cut feedback caps.

[lexluthier]

I have a few of these, I really dig the thick, midrangey sound. Here are some gut shots. The PCB's are really cheap. Been actually thinking of making some more heavy duty clones, as these are kind of fragile.

[Rob Strand]

A list of cap values (and some record of the pcb locations) is required.
Also the pot values and the tapers.
There's also a few resistor values that are obscured by the caps.

[thermionix]

Looks very MXR-ish in construction.  I like how they filed all the solder joints.

[Rob Strand]

Yeah, construction looks MXR.

Almost done.
The pot wires are wrapped tight and I can't see where they go.
Have to keep a lot in my head to guess what goes where.

It's got input output buffers and JFET switching.
4-stage JFET  (sort of a Muff arrangement)
EQ  - looks a bit funky

[thermionix]

Where were these pedals made?  I've never seen pots like those in anything.

[Chugs]

Looks like it may be quite similar to the Washburn A-D3.

[Rob Strand]

Where were these pedals made?  I've never seen pots like those in anything.

Audioworks "F.E.T. Distortion" pedal
Designed by Henry Karn in the early 1980's
(Traced unit approx 1984)

Looks like it may be quite similar to the Washburn A-D3.

Great stuff Chugs!
Yes that's pretty much it.

There's a few differences in the finer points:
- (obvious) The switching ckt uses a 4069.  And the LED has it's own declick cap.
- The buffer is DC coupled to the first JFET.
   So maybe the 1M resistor on TR5 is a lower value on the Audioworks
- Cant see the 15k on TR6 gate..
- There's no 47pF's on the last two EQ stages.
- The power supply uses 220R not 100R
- One resistor feeds both +ve opamp inputs on the last stage.
- The Audioworks clearly uses two different JFETs types which have different pin outs
  The JFET switches follow a J111 type pinout and the Audio JFETS follows a BF244/BF245 pinout.
- The unspecified source resistors are 10k  (maybe one I can't see).

Given there's quite a few unknown values from the photos I can't comment on the part values.
The resistors I can see match-up well.   The cap sizes I guessed are in the ball-park of the Washburn.

[I could merge in your values and post the schem but I don't have an image account.]

[Rob Strand]

OK I used tiny pic.

[j_flanders]

Designed by Henry Karn in the early 1980's

You get more hits (and info) for "Kern" instead of "Karn".

Given there's quite a few unknown values from the photos I can't comment on the part values.
The resistors I can see match-up well.   The cap sizes I guessed are in the ball-park of the Washburn.

A handdrawn schematic was posted in reply #4: http://i25.photobucket.com/albums/c57/roknjohn/Audioworks.jpg
I re-uploaded to tiny pic in case you couldn't see it because of a photobucket issue:

[Rob Strand]

You get more hits (and info) for "Kern" instead of "Karn".

Thanks.

A handdrawn schematic was posted in reply #4: http://i25.photobucket.com/albums/c57/roknjohn/Audioworks.jpg
I re-uploaded to tiny pic in case you couldn't see it because of a photobucket issue:

Cool thanks.

I can see it aligns with my trace a bit better.

I can also see two differences:
- The first stage isn't DC coupled to the first opamp.
- The switch connection and part around the 220k resistor is slightly different.
- The input cap is smaller than the Washburn.

I was fairly certain about the DC coupled stage.

Maybe someone can cast some fresh eyes over those parts?

[Rob Strand]

- OK regarding the switch.  My V1.0 schematic has an error.  The side of the cap C20 that goes
to pin 13 and the 4k7 resistor should connect to ground.

- Regarding the DC coupling of the first stage I can't see anything.

Opamp pin 1 ->  big long jumper -> fairly clear track to a single resistor.
Other side of that resistor goes to place where there is an unused hole,
one resistor connection (R8), one cap connection (C5) and the gate (Q3).
There is only one unused hole and no other corresponding hole where a cap
could go.  Even though the parts are a little obscured on the component side
of the board.  There just no place for a cap in series with R7.

[italianguy63]

I have a dumb question.. 'cause I'm dumb.  In the 1st schematic.. on the LED circuit..  D4 and D5 have opposite polarity.. How does that work?

MC

[duck_arse]

D4 is a zener, it will conduct "while the battery volts is good", and doesn't when it's too low. same as boss uses in many places.

[antonis]

Are you sure about R14/R15 values, Rob..??

It seems to me that 10/11th of signal is "lost"...