Orange Tiny Terror Jfet conversion

[Domin]

Hi! I tried to convert this schematic into Jfet one with 3 gain stages and buffer before volume and tone control but gain stages have too much gain. Is there any way to lower it? I biased it to cca 1/2Vcc but even first stage distorts and its not clean

[antonis]

I tried to convert this schematic into Jfet one

Just by replacing tubes with JFets..??
(in the mean of no resistors/caps values alteration..??)

[temol]

Hi! I tried to convert this schematic into Jfet one with 3 gain stages and buffer before volume and tone control but gain stages have too much gain. Is there any way to lower it? I biased it to cca 1/2Vcc but even first stage distorts and its not clean

What JFETs? Yo can try to lower the value of the 22u  in the first stage. Or remove the cap completly.

T.

[Domin]

I tried to convert this schematic into Jfet one

Just by replacing tubes with JFets..??
(in the mean of no resistors/caps values alteration..??)

Im new into it so im just trying

[Domin]

Hi! I tried to convert this schematic into Jfet one with 3 gain stages and buffer before volume and tone control but gain stages have too much gain. Is there any way to lower it? I biased it to cca 1/2Vcc but even first stage distorts and its not clean

What JFETs? Yo can try to lower the value of the 22u  in the first stage. Or remove the cap completly.

T.

I removed all of them but at max settings it lacks gain

[temol]

I removed all of them but at max settings it lacks gain

Start with a first stage only, not all.
What models of transistors are you using?

[GibsonGM]

Go look at Jack's JFET boosters at the AMZ site, linked at the top of the page here.   I think you might be able to do some kind of limited bypassing to get the gain you want.

Perhaps a 1k pot with a cap (wired as variable resistor) to ground in parallel with the source resistor...try simming it up or breadboarding!  Literally a pot in series with a cap, say 1u or 10u, to ground.   Pot wiper is connected to one of the outer lugs.   I played with a J201 boost doing this for a minute in LT Spice and it worked, but have to run out soon.   

The value of the pot and cap are going to depend on what the final design is using for source resistance, and whether you want a 'full bandwidth' gain control or something more like a treble boost.  Once you find your 'topology', you build it on breadboard and try it out.

[Domin]

I removed all of them but at max settings it lacks gain

Start with a first stage only, not all.
What models of transistors are you using?

2SK117, they are from aliexpress so not that great but all of them have more gain

[Domin]

Go look at Jack's JFET boosters at the AMZ site, linked at the top of the page here.   I think you might be able to do some kind of limited bypassing to get the gain you want.

Perhaps a 1k pot with a cap (wired as variable resistor) to ground in parallel with the source resistor...try simming it up or breadboarding!  Literally a pot in series with a cap, say 1u or 10u, to ground.   Pot wiper is connected to one of the outer lugs.   I played with a J201 boost doing this for a minute in LT Spice and it worked, but have to run out soon.   

The value of the pot and cap are going to depend on what the final design is using for source resistance, and whether you want a 'full bandwidth' gain control or something more like a treble boost.  Once you find your 'topology', you build it on breadboard and try it out.

Ok ill try that, thanks

[antonis]

Ok ill try that, thanks

And, of course, omit all those 68k grid stopper resistors..
(use them only in case of high-pitch oscillation, due to Miller capacitance, experience..)

https://www.diystompboxes.com/smfforum/index.php?topic=94071.0

Topic related to JFET high distortion..
https://www.diystompboxes.com/smfforum/index.php?topic=126575.0

[GibsonGM]

Yes, make the 'grid stoppers' a lower value or omit them       Limited bypassing is used often in tube preamps. 

The gain control in a fuzz face is also usually done ALMOST the same, but you should have that kind of gain control in parallel with the JFET source resistance.  I hope I'm being clear enough that you understand...

[antonis]

I hope I'm being clear enough that you understand...

Don't professional painters draw schematics, Sir..??

[GibsonGM]

Have to run, wife needs me to drive her to work. However, I DID put something together!  This should give the idea.
An internet search would probably find more info on how this is done. (pot value, etc).

[Domin]

Have to run, wife needs me to drive her to work. However, I DID put something together!  This should give the idea.
An internet search would probably find more info on how this is done. (pot value, etc).

Yes I understood it, im gonna try it today Ill give you info

[antonis]

https://www.runoffgroove.com/fetzervalve.html

https://sound-au.com/articles/jfet-design.htm
(Art 3. A Typical JFET amp design..)