A jfet npn boost DESIGN

[Gus]

The following is ONE way I would build a J201, high hfe NPN type boost.  I picked a J201 because it seems to be posted about a lot at forums
You could use different JFETS and adjust the circuit values
Note what it kind of looks like
The Jfet drain biases the NPN this allows the removal of an number of parts
tone control is mild just removes the high end peak
R2 will need to be adjusted for BOTH the JFET and NPN Bias points
Voltages are a suggestion they should sound good
you can add an output volume control
Using a Jfet allows a high value gate resistance so you can use even higher values if you want
I picked the R10 and R7 values for the parallel resistance they appear to the guitar
The bass roll of at higher gains is to help with not overdrive the speakers at low frequencies
This is done by adjusting C2 value
Sim is with the 10K tone(R5 and R6) set for treble
C1 connects to the tone control wiper

EDIT
I have a 2N5457 sim some values are changed

I saw posts about a certain booster so I searched for the schematic.  When I looked at the schematic I found on the web(I don't know if the schematics are correct I have not seen the effect myself to trace the circuit) I wondered why it was designed the way it was?
I then simplified and adjusted the circuit one way I would build it.
What effect do you think I searched for?

[Derringer]

I like the way you biased the NPN .. and that you essentially have a hi-z in and low-z out from this block

[Gus]

I like the way you biased the NPN .. and that you essentially have a hi-z in and low-z out from this block

This circuit has selectable hi -z or low-z in and is more predictable with biasing
http://www.diystompboxes.com/smfforum/index.php?topic=99139.0

You do not need JFETs for hi-z, you can add a tone section and/or a gain control.

[kingswayguitar]

i like. lately i've enjoyed direct coupling transistor stages. particularly for biasing p-jfet which require a high gate voltage.

http://www.diystompboxes.com/smfforum/index.php?topic=96999.msg844340#msg844340

[pinkjimiphoton]

looks great gus, to me anyways..

this is kinda a redesign of the "echoplex" booster?

i own two echoplexes, they most assuredly aren't boosters...lol... i haven't really paid much attention to these cuz to me it seems like internet hype.

i know that tony krank guy redid 'em too, and runs his with a charge pump. claims it makes a difference.

they are FUZZES. they have very little to do with an echoplex in my opinion.... a whole lot of hype people buy into. all the plex does is buffer, not boost,
and if ya put one in a TB bypass  loop switcher, off or on barely even colors the sound.

not ranking on you, gus, just the whole thing to me smells of bull feathers, ya know?

i'm  saving this to add to my "to do" folder.. there is way too much crap in there, i've got close to 40 gigs of schematics and layouts at this point.

thanks for another great circuit!

[Gus]

I simed the first gain stage of a  EP3 from a schematic I found in a groove tubes book I have.
It is different than an EP boost(if the schematics on the web are correct)

[fuzzo]

I had a similar idea with the addition of an Germanium PNP transistor after the JFET (followed by the buffer) . All three DC coupled.

the only annoying is the trimmering of the JFET 

[tca]

The good thing of your design is the decoupling of the bias voltage (includes R2) and the gain control (C2 and R9), similar to your other circuit with a +-9V power source. Thanks for sharing.

[Gus]

This a a link with one of the schematics
http://revolutiondeux.blogspot.com/2012/01/xotic-ep-booster.html
Note the tone control part in the modded section is the same except I direct coupled the stages I simmed other values in the tone section IMO the sim looked the "best" with the values selected.  I wonder if the selection was by ear or done with math at the link.

You need to keep the base current in mind when direct coupling stages like this, too big a value and you have a larger voltage drop and a greater difference in drain to emitter voltage.  I would have liked to a use 20K or larger value tone control for more range, HOWEVER  the voltage difference from drain to emitter would be greater.

In the sim I posted you can disconnect C2, R9 for a little less gain

You can reduce R7s value and increase R8s value and adjust C3 value for the highpass.  This adjustment has issues because as it act more like a voltage divider input volume control

With circuits it is often the set of compromises you will accept that determine the design

[Gus]

removed images

[tca]

^ Why?

[Gus]

I realized I did not want to give away free design advice this might help/start a company so why should I help?

I am thinking I might start to remove all of my sims and schematics only a few people seem to pay attention anyway.

[tca]

I realized I did not want to give away free design advice this might help/start a company so why should I help?
I am thinking I might start to remove all of my sims and schematics only a few people seem to pay attention anyway.

It seems a contradiction in terms... but I do get your point. I guess its time to make your own

Cheers.

[FiveseveN]

It's really sad to see some people's unscrupulous, lazy "business models" affect the comunity this way. I just wanted to point out that you can make it slightly harder for assholes to steal your ideas by posting them in the Members Only subforum.

[mistahead]

Its a shame that the average punter can't tell the difference between someone with my skill level, nicked layouts, and a mate who can airbrush/etch, and someone who is actually quite clued in.

I would hate to see the guys I've learned, and learn, from quitting the scene because of some little C-scrapes with no respect for the community and the IP.

Then again every time I see a new poster asking about layouts I do a bit of searching and usually find a Boutique pedal C-scrape-guru advertising a limited run of the box - maybe we should have a competition for tracking down and exposing these cases!

[Bill Mountain]

That's a shame.  I love your circuit designs.

[pinkjimiphoton]

gus, you make some of the coolest designs out there, toneful, useful, cool...

please reconsider. i realize your point is valid, and i stand by ya whatever you choose. just hate to see that drastic of a measure.

i'd love to try and build this, i just haven't had time to do much lately...life keeps getting in the way, gotta make hay while the sun shines.

your stuff is as good...or better...than the commercial SHIT out there. hate to see it go away.