Fairfield Circuitry - The Barbershop (gut)

culturejam · Post by **culturejam** » 20 Feb 2009, 15:23

Happened to see this over at TGP. Here's the original web site:
http://www.fairfieldcircuitry.com/B.html

Unfinished box with letter stamp markings.

Went fishing for a gut shot at TGP and got the pic that is attached.

Couldn't get the other side, unfortunately. But somehow, I'll bet that BajaMan can guess the circuit by looking at the traces.

fairfield · Post by **fairfield** » 20 Feb 2009, 22:21

I'm tempted to post the schematic to save you guys the trouble...

Instead I'll give you a hint, it starts with a common source N-channel JFET and ends with a NPN follower.

culturejam · Post by **culturejam** » 20 Feb 2009, 23:24

That was fast.

Thanks for hint. That's mighty nice of you and demonstrates a high level of professionalism and maturity.

letsgocoyote · Post by **letsgocoyote** » 21 Feb 2009, 00:33

very nice guts. i love gutshots not for the reversal sake but i jsut love to see how other people are building pedals

briggs · Post by **briggs** » 21 Feb 2009, 00:42

OK, so we have a 10KA (log) drive control and a 10KB (lin) Sag control with a 100KA volume control at the end of the circuit. I'm guessing the 10KB sag is adjusting the collector bias for the NPN and the 10KA is setting the gain of the Jfet stage running into the NPN?

analogguru · Post by **analogguru** » 21 Feb 2009, 01:21

and what is with the other two transistors between - in a fuzz-face similar configuration ?

analogguru

fairfield · Post by **fairfield** » 21 Feb 2009, 02:25

The 100k log is Drive and the 10k log is Volume. Indeed about the 10k linear, but Sag is also adjusting the bias of other transistors. Who said there was nothing between the first and last stage?
The plot thickens.

Don't get too excited about this circuit. Like so many others, the schematic doesn't explain why it sounds good. I was wondering...

Who here would enjoy receiving a newly purchased pedal with printed schematics in the box?

analogguru · Post by **analogguru** » 21 Feb 2009, 02:33

Hey cool !!! .....retro-style..... kay, maestro, shin-ei.....

analogguru

culturejam · Post by **culturejam** » 21 Feb 2009, 06:24

fairfield wrote:Who here would enjoy receiving a newly purchased pedal with printed schematics in the box?

I'd enjoy receiving it. Now how's going to newly purchase it?

soulsonic · Post by **soulsonic** » 21 Feb 2009, 06:54

letsgocoyote wrote:very nice guts. i love gutshots not for the reversal sake but i jsut love to see how other people are building pedals

Me too... most of the time I could care less what the actual circuit is other than in the most general sense... ie; what the basic topology is.

briggs · Post by **briggs** » 21 Feb 2009, 10:44

soulsonic wrote:
letsgocoyote wrote:very nice guts. i love gutshots not for the reversal sake but i jsut love to see how other people are building pedals
Me too... most of the time I could care less what the actual circuit is other than in the most general sense... ie; what the basic topology is.

Most of the values speak for themselves when looking at familiar circuits, I too enjoy seeing the topology...

So we've got 4 semiconductors. Jfet -> Gain Control -> 3 NPNs with adjustable bias.

sergedeep · Post by **sergedeep** » 21 Feb 2009, 11:32

I must say I like the looks of that pedal. I've been considering to give metal stamping a try as well. Is it as easy as it looks or can you teach us what you have learned when doing it?

fairfield · Post by **fairfield** » 21 Feb 2009, 15:53

The circuit is 2 cascaded common source amplifiers, into the follower. The Sag is affecting the bias of all 3 in a strange way. The fourth is a MOSFET used as circuit protection.

Currently I don't include the schematic with the pedal. I've been considering it for some time now, just haven't gotten around to it.

The stamping is easy, once in a while I miss and smash my fingers but it's worth it. Just make sure you do it on a sturdy surface.

rbstep · Post by **rbstep** » 21 Feb 2009, 16:50

count me in to receive a pedal.

Whoismarykelly · Post by **Whoismarykelly** » 21 Feb 2009, 16:53

I ordered one late last night. Should be cool

soulsonic · Post by **soulsonic** » 22 Feb 2009, 05:48

I like the curvy lines on the circuit board artwork.

briggs · Post by **briggs** » 22 Feb 2009, 12:11

soulsonic wrote:I like the curvy lines on the circuit board artwork.

It reminds me of old Electro Harmonix boxes. I like the little hand logo too. It's good to see some decent quality for once, and at a seemingly reasonable price for some hand assembled goodness. What parts are being used? Decent quality resistors and Caps? AND it looks like we have at least something semi-original! Woooooo

Dirk_Hendrik · Post by **Dirk_Hendrik** » 22 Feb 2009, 19:18

soulsonic wrote:I like the curvy lines on the circuit board artwork.

i don't know wether I like em from a professional perspective. It does surely match the term "artwork"

RnFR · Post by **RnFR** » 22 Feb 2009, 19:33

i like the pcb and ribbon for the switch. seems like a very good idea. i was going to see if i could make a pcb or find something like that on line. looks like it would definitely take away from the tangles surrounding a 3pdt, and it still gives you some leeway as far as mounting the board in the box. i.e. it's not necessary to remove the switch for repairs.

and i like the art!

--------------

what are those 12 large solder points for on the right of the pcb?

DWBH · Post by **DWBH** » 22 Feb 2009, 20:12

RnFR wrote:what are those 12 large solder points for on the right of the pcb?

Those are the audio jacks' solder pins.

Fairfield Circuitry - The Barbershop (gut) [traced]