J201 JFET - fabulous friend, sneaky foe (comment/discussion)

[PRR]

I remember being over at Ampage forum when Aron said he was going to start his own forum. I guess that was around 2001-2002?...

Aron had a "page" before a forum. Back in the 20th century!
https://archive.ampage.org/threads/1/open/000934/Re_Arons_Stompbox_Page_has_moved-1.html

[Rob Strand]

Do a search in the "First Stompbox Forum" archive and it will show that the J201 was in widespread use on this forum (at its previous site) several years before Don decided to change out the 2N5457 for the J201. I would contend that the J201 popularity came from here instead of his revised article that came along a few years later. 

Jack, that is absolutely the case!

I remember being over at Ampage forum when Aron said he was going to start his own forum. I guess that was around 2001-2002? Anyway, yeah I built quite a few of those J201 based circuits that people were presenting here. They were coming out of the woodwork back then. I still use some of those circuits today.

Jack was the one who introduced the mu amp to guitar pedals.   He may have also been the one that introduced the J201 to guitar pedals at the same time.   I would have to trawl through the archives (Aron's and/or mine) to confirm it.

Aron had a "page" before a forum. Back in the 20th century!
https://archive.ampage.org/threads/1/open/000934/Re_Arons_Stompbox_Page_has_moved-1.html

And yep, Aron (and Jack, RG) have all had their stuff up on the web from the very early days of the web.


https://www.muzique.com/amz/mini.htm

"In 1995, my site went live on the Internet and became the second guitar effects and schematics site to be available! The first site was called the Leper's Abode and it has since disappeared, leaving my web site as the longest continuously available DIY guitar effects site on the Net. "

[Paul Marossy]

I remember being over at Ampage forum when Aron said he was going to start his own forum. I guess that was around 2001-2002?...

Aron had a "page" before a forum. Back in the 20th century!
https://archive.ampage.org/threads/1/open/000934/Re_Arons_Stompbox_Page_has_moved-1.html

Hmm... I guess I actually got involved here after that happened. I think he still hung out sometimes at Ampage too? I'm not sure... was a long time ago now! I just know where Aron started from. I remember the forum moved once or twice too.

I chuckle when I think back to the Ampage days. Someone would make a post there about having figured out the Fuzz Factory, provide a schematic and Z Vex himself would reply with things like "another mangled schematic". lol

I only remember the exact day I made my first working guitar FX because it was the same day my firstborn entered the world (Oct 20, 2001). It was from info I got at this forum and I chased my tail for several years after that building all kinds of stuff, none of which made me a better guitarist... but my sound is hella better now. 

[Rob Strand]

J201, 1998/1999

I didn't dig too hard but there was an old thread from Oct 1998 (on Jack's message board?) discussing Jack's FETMuff.

- The original version of the pedal from 1998 only specified 2N5457's.

- Somewhere along the way, perhaps in the text on Jack's site he may have specified an MPF102
  as an alternative.   Jack regretted it because people had trouble with the device to device
  variations - which is the reason for the thread.

- In the same thread it looks like Jack suggests using a J201 to someone with limited JFET sources.

Here's a 1999 version of the circuit which has the J201 as an option - it seems to be an update which occurred between 1998 and 1999.

https://www.tremolo.pl/Efekty/FET/Fetmuff.gif

In 1999 there's quite a few J201's in use.
In 2000 there's plenty -  "everybody's doing it"

I don't have enough info on the Booster at my fingertips (only go back to Feb 2000 version with J201)

[POTL]

Hi all.
   I remember my first pedals, which I started building 7 years ago (maybe even earlier). The first was Big Muff, the second was Fuzz Face, and then I got to know the world of J201.
   Yes, I remember those thoughts that the pedal sounds like a real amplifier (haha no), and how cool that it is enough to take the original circuit and replace the tube with j201 and adjust it correctly (yes, yes, again not true). Then search for different circuit, J201 as amplifier, Mu Amp, SRPP, combinations of these solutions. I compared it to Zvex Bor/distortron/JHS Charlie Brown and found j201 to be better.

But the moment came and I realized that I want to make circuits meaningful and understand how they work. Then I realized how many shortcomings of J201 and other Jfets.
1) Limited stock. Jfets very quickly begin to distort the signal, give stronger compression, work worse with dynamics (attack with the right hand and volume knob). BJT, Msofet, Op Amp are better, as they are limited only at the extreme points of the supplied power, these devices are closer to lamps in this parameter.
2) Biasing, we know that lamps can be biased cold (cold clipping) or hot (standard). BJT, Mosfet, Op Amp, can also be biased differently, Jfet are much less flexible and have a smaller tuning range, I would say that they cannot or is pointless to use in Cold clipping mode.
3) Constancy/repeatability/stability. Tubes, BJT, Mosfet, Op Amp are stable, we just install them in the finished circuit and everything works, Jfets do not. yes we can use Mu Amp and SRPP but their sound is very different from single cascades and IMHO limited in flexibility.
4) Clear sound Tubes, BJT, Mosfet, Op Amp have a large headroom, Jfet can have this headroom 10 times less (and many times the difference is even greater). we live in the 21st century and many people use active pickups and preamps built into the guitar.
5) BJT, Mosfet, Op Amp are readily available in dip packages, Jfets are mostly in smd. Another significant drawback, during the design.
6) The gain of Jfets is also lower than that of Op Amp, BJT, Mosfets.

Let's forget that Jfets is the holy grail (no) and think coldly, why are we still using it years later and with so many disadvantages and alternatives that do its job better? Amplifiers on Jfet outdated? I think yes. Phasers on Jfet deprecated? definitely Do you need Jfet? I doubt it very much. perhaps there is a need to use it as a switch. hardly more.

[POTL]

[FSFX]

Interestingly, in many decades working in electronics, the only place that I have ever seen J201s used extensively is in DIY guitar pedals. The manufacturers probably still continue to manufacture them (well the SMD version) just to satisfy the hobby market and DIY pedal builders who seem to consider the J201 is the holy grail of JFETs and the only JFET to use for everything whilst excluding or ignoring all the other fine JFETs still being manufactured.

From this thread it seems we can gather a bit of history as to how this runt of a JFET managed gain favour with pedal builders and be considered the only device to be used, even mistakenly in such circuits as phasers, analogue switches, tremolos and other applications where its high on-resistance, low Idss and low Vp make it quite unsuitable and a very poor choice of device.

There are places where it is a good choice. The J201 is great for what it was originally intended which is 'low level audio', however, I would not call guitar level signals 'low level' like microphone signals. But then that does mean it is pretty much guaranteed to distort a guitar level signal which is probably what overdrive and fuzz pedals are meant to do anyway.

Probably the only real plus point about it compared to many other JFETs is that its Idss and Vp is so low that it runs quite happily from a 9 volt battery taking very little power supply current whereas a lot of other JFETs require to run at higher currents and voltages for optimum performance.       

[anotherjim]

Is there something akin to J201 hidden in the back of electret mic capsules?

[FSFX]

Is there something akin to J201 hidden in the back of electret mic capsules?

Most definitely. In fact the TF202 is a device made specifically for electret mics and it has very similar characteristics to a J201 at the bottom of its characteristic range with very low Vgs(off) and Idss.

http://www.unisonic.com.tw/datasheet/TF202.pdf

[Rob Strand]

Is there something akin to J201 hidden in the back of electret mic capsules?

There's a whole heap of them. You will find the JFETs for electret microphones have very low IDSS (and low VP).  The IDSS is less than half of a J201 and are generally sorted into two or three groups.
(some examples: TF202,TF218,TF222,TF246,TF252, TS788, 2SK3373, 2SK3536)

It's exactly why electret microphones have *<* 500uA specs (not *=* 500uA like most people assume).

[anotherjim]

^Thanks, I see from the datasheet the mic JFETs include a gate bias network attached to the source. I've wondered how they did the bias.