Looking to build low parts Jfet Buffer/Boost - need ideas?

[chumbox]

Hey All

I want to build an all in one Jfet buffer with a boost control. Ideally low parts count and wondering if there is a way it can be done with one Jfet that runs as a unity buffer but you can then dial boost on top of that? Any ideas, thoughts or reference schematics appreciated. Hoping to stick in a 1590A with a switch ultimately.

Thanks in advance!

[Elijah-Baley]

It could be useful:
http://www.seymourduncan.com/tonefiend/wp-content/uploads/DIY%20Club%20Project%203%20v02.pdf

[Kipper4]

Buffer or booster?
Buffer = unity gain
booster= booster

build a fetzer and use a series resistor to ground from the 100k output so it only goes down to unity?

http://runoffgroove.com/fetzervalve.html

[Elijah-Baley]

[...]
build a fetzer and use a series resistor to ground from the 100k output so it only goes down to unity?
[...]

I could wrong, but do you mean that with that mod the Fetzer it is not anymore an attenuator? And we can do this mod to any booster?

[Kipper4]

Try it on the breadboard

[Elijah-Baley]

Cool, nice trick! And maybe I need it.

[chumbox]

Love this idea Kipper

[KarenColumbo]

have a looksee here
http://www.albertkreuzer.com/electronics.htm

[blackieNYC]

Only the J201 version of the Fetzer has 13dB of boost.  that's plenty for "solo level" under the right amplifier circumstances. The other Fets aren't enough - see the bottom of the fetzer page.
Maybe the Omega would be better - more gain for driving the hell out of a dirt pedal.http://runoffgroove.com/omega.html

The Albert Kreuzer site looks cool.  But the Tillman preamp is only 3dB of gain IIRC.

[Elijah-Baley]

This is very interesting: http://www.muzique.com/amz/mini.htm AMZ Mini-Booster mu-amp

[chumbox]

Just stumbled across this schematic and it appears to run at unity when off and then become a boost when on by attaching the boost wiper, using similar to idea to Kippers without an volume pot at the end it appears.  Nice design.

[Ben N]

It could be useful:
http://www.seymourduncan.com/tonefiend/wp-content/uploads/DIY%20Club%20Project%203%20v02.pdf

Useful, esp as a beginner project, but kind of ass backwards, IMHO.

[antonis]

Just stumbled across this schematic and it appears to run at unity when off and then become a boost when on by attaching the boost wiper, using similar to idea to Kippers without an volume pot at the end it appears.  Nice design.

I agree but it definately isn't a low parts design for a single FET ... 

[antonis]

Maybe I get something wrong but a buffer is a device which acts ONLY as impedance "isolator"...

If we use a booster (which adds gain) and lower it's output we have an amplified - attenuated signal in which we've kept Vin/Vout ratio to (almost) unity but we've already alter it's waveform..
(We shouldn't consider it "buffer" anymore..)

We can go much closer if we use a booster with variable gain (lowest setting to unity) taking in mind the restriction for relative low R_D value (for low output impedance) and signal's phase reversal..

Or use an op-amp in non-inverting configuration..