FET Dream distortion pedal schematic

[mdroberts]

Hi All,

We had some inquiries recently about FET Dream pedal, which we haven't made for several years.  That prompted me to release the schematics and design files for non-commercial use: https://github.com/Cause-Effect-Pedals/FET-Dream

FET Dream was a transparent, smooth distortion pedal with a lot of versatility in the distortion... reminiscent of Dumble tones.  I've left our original website up for historical context.  If you want to check out sound clips: http://cepedals.com/clips.html

Not selling anything anymore... just hope this helps out the community!  This site is how I got started building my own pedals in the first place.
-mark

[mdroberts]

I found the hand-drawn schematic of the little circuit used to characterize the jFETs.  In production, the J204 FET was used.  The calculations done to bias the Fetzer jFET stage are in the spreadsheet posted under design files on github.

[nerdbot]

This is cool! I remember looking into this pedal years ago and liking the sound of it. Maybe I'll try building it sometime. Thank you!

[idy]

The second transistor can be either BJT or JFET? What is the thinking on that? Since it's a buffer you didn't need another selected JFET?

Very cool design. Nice selection of tone control, assymetric clipping elements.

[idy]

I guess the lower output impedance of the BJT is better before the tone "stack?"

[mdroberts]

IIRC we had convinced ourselves that the FET Follower would have worked fine, but I do prefer really low impedance there and prefer emitter follower myself (and saved populating a couple components). We had the option of populating either, and a ton of 'bad' jFETs that we could have used 

[mdroberts]

Very cool design. Nice selection of tone control, asymmetric clipping elements.

Thanks, we put a lot of work into both! 

• Tried lots of combinations and orientations of the clipping elements to optimize for the range we wanted to see (keep it open and transparent, not overly compressed like a zen drive, popular at the time).
• The tone 'stack' included a teeter-totter inspired 'Girth' (mostly bass cut) was applied pre-distortion so you could avoid smearing mud everywhere in the distortion. The peaking low pass filter for 'Lean' was essentially a Dumble-like mid-boost. The FET stage was considered part of the tone 'stack' since it gave the player the option of introducing more 2nd harmonics, pre-distortion, by digging in.

[Vivek]

Thank You Sir !!!!

[Vivek]

Are the SPICE files available ?

Thanks

[Mark Hammer]

Aren't you FET Dream folks also based in Ottawa?

[Mark Hammer]

Aren't you FET Dream folks also based in Ottawa?  I think we met once, at one of those local guitar shows that Darwin organizes

[Rob Strand]

Not selling anything anymore... just hope this helps out the community! 

Very generous to release the schematics.

[mdroberts]

Aren't you FET Dream folks also based in Ottawa?

One of us is in Ottawa (Mark), the other was in Mississauga at the time.  We could have met.

[mdroberts]

Are the SPICE files available ?

Thanks

Hi Vivek.  I have spice files... whether they are useful or not is the big question!  I can't get these to run on my system anymore, they were on a PC that was disposed of back in 2012!

It looks like we started simulating a 'FET Dream' back in November of 2008.  Prior to that there was a lot of work with Dumble tone stacks (I was busy creating schematics of various Dumble iterations on TAG at the time).

By the end of January we were just doing some sims we called 'doppelgangers' where we duplicated the FET Dream several times with different pot settings to get an overall image of the tone capabilities in the stack.  By then however we had several prototypes of the pedal and much preferred working with the real thing to finalize what we went to production with.

So here's two files... the very last .asc I could find and a PDF of an earlier Doppelganger output.  IIRC we had toned down [sic] the stack quite a bit since earlier tilting filter and peaking filters had been quite hairy! 

Sorry I can't help you more than that!  It will be up to you to find library elements etc. and try to figure out how to get them working again.

-mark.

PS It looks like I still can't upload files so I put them in a directory on GitHub: https://github.com/Cause-Effect-Pedals/FET-Dream/tree/main/LTSpice

[Mark Hammer]

Aren't you FET Dream folks also based in Ottawa?

One of us is in Ottawa (Mark), the other was in Mississauga at the time.  We could have met.

I think it would have been at a show at the Brookstreet Hotel.  Does that ring a bell?

[mdroberts]

I found the hand-drawn schematic of the little circuit used to characterize the jFETs.  In production, the J204 FET was used.  The calculations done to bias the Fetzer jFET stage are in the spreadsheet posted under design files on github.

The original Fetzer test jig came from a .diy layout on RunoffGrove site, which I've just found:

[box]

Hi All,
Some interesting lecture regarding FET:
http://users.jyu.fi/~loberg/FYSE400slides/LECTURE4FYSE400.pdf
Very nice circuit.Congratulation ,
Regards,
box

[KarenColumbo]

The second transistor can be either BJT or JFET? What is the thinking on that? Since it's a buffer you didn't need another selected JFET?

Very cool design. Nice selection of tone control, assymetric clipping elements.

Ha! I thought I'd use both and it's some sort of "transistor clamp" - shows the abyss of my ignorance, i guess

[mdroberts]

Ha! I thought I'd use both and it's some sort of "transistor clamp" - shows the abyss of my ignorance, i guess

Those populating options can be confusing on the schematic!  Just needed to have them for generating the layout.  Also needed to remember to short the appropriate potentiometer pins when building them too.

[KarenColumbo]

Ha! I thought I'd use both and it's some sort of "transistor clamp" - shows the abyss of my ignorance, i guess

Those populating options can be confusing on the schematic!  Just needed to have them for generating the layout.  Also needed to remember to short the appropriate potentiometer pins when building them too.

You bet I'll try to get it working