which jfet matcher do you use (think is most reliable)?

[tabbycat]

have just got to the stage where i want to learn why, when and how to match jfets.

was looking in the utliities section and there are three flavours:

regular http://tagboardeffects.blogspot.co.uk/2012/07/jfet-matcher.html

greatly improved with ic http://tagboardeffects.blogspot.co.uk/2012/07/greatly-improved-jfet-matcher.html

and greatly improved without ic (supposed to be more accurate but everyone seems to have had trouble with it). also in the above link.

which do you use?

and re the ic version (looks most likely) is there anything else that will work as well as the tlc2262 that i might have kicking around?

[PMowdes]

I have tried to make both the IC and the improved MKII but neither seemed to work for me, which is a massive pisser for such a simple layout.  Think I am missing something because I think I managed to smoke a few trannies in the process.

 In the end I just brought some pre matched 2n5952's from DasMusikding.

Word of caution.  Don't buy matched sets from china.  I brought two matched quad sets and they all came in the same bag unmarked and I couldn't sort them out, FFS!!!!

[Frank_NH]

I've built and used this one.  It works great - all you need is a voltmeter (DVM) to read the voltages as indicated.  Note that Idss is inferred from a voltage measurement.

What you want to do is to make a log (or use a spreadsheet) with two columns of numbers:  Vp (V) anmd Idss (mA).  Take your set of set of JFETs and label each with a piece of whice masking tape.  You may choose simple letters: a, b, c, d...  Measure each one and record the measurements along with the label ID on your log.  Now when you go to use them you can note the Vp and Idss readings for the particular JFET.

Another approach is to rough sort the JFETs according to Vp, Idss measurements.  Usually, if the Vp for a two JFETs is close, so is Idss, so you can sort all JFETs within a certain range of Vp and put them in a bag together, labeling the bag accordingly.

Note that if Idss or Vp are way off from the spec for the JFET, it's a bad part and you should dispose of it (lest you use it by mistake later).

By measuring my JFETs I have been able to avoid trimmer pots for builds like the Wampler Plexidrive.  Mainly, it's just good to know what you have so that there will be no surprises.

[motterpaul]

I am pretty sure I ended up with the IC one, but I also had a LOT of problems getting these to work consistently.  The best the is the DCA Pro tester (cost about $150).

I have noticed you posting a lot about FETs, but I guess it is because you have been doing phasers. I have had almost no trouble using them for overdrives, surprised how easy it was.

Anyway - good luck and keep trying. You might have gotten a bad batch.

[tabbycat]

thanks for the recommendation and advice, frank. i made the one you posted last night and going to play with it over the weekend. will use your logging method and see how i get on.

basically i have made a handful of cab sim things that require jfets (ampegulator uses eight i think, ginger four or five, etc) which means i need to be able to work out:
a) if any are dodgy (or troubleshooting will be impossible) and
b) getting values to within recommendations for them to sound good.

if i can't build something that sounds better than an anybrand £30 stomp, there isn't much point. am not building for love of building but for love of good sounds, so being able to optimise results through getting values tight is a skill i think i need to learn, otherwise i'm just wasting my time and effort on building junk.
having had a forced break from building it has made me decide to get a bit more serious about what i build. having less energy and concentration means i need to focus on building less but build better.

so getting my act together re properly evaluating core components is a good place to start.

[tabbycat]

hey paul, thanks for the thoughts.

i remember readling the greatly improved thread and it mentioned how many people had trouble with it, so thought i'd ask for a recommendation before going for one. maybe try the one frank suggested above if the ic one doesn't go. alas i don't have $100s for test equipment so making my own will have to do for now. next test kit buy will be a cap tester, but that's a luxury not an essentail for me atm.

re the fets, as just mentioned to frank, have a handful of cab sims all fet hungry, and i think how good they sound will depend a lot on getting the fets right. i have a few from fuzzdog, which i am sure are good, and bag from china which may be good or junk, but only sorting will tell. and i think it's a good skill to learn.

have never built a phaser (have a behringer small stone clone and joyo phase90 clone, both cost less than £20 and sound great). unless i can find a pcb i stay away from big modulation vero builds (ada, etc). just too much for me. massive builds and potential troubleshooting nightmares. have never sorted jfets for modulation yet. my clone theory and mrx flanger clones came with trimmers which i still have to bias properly but seem to work well enough to get good sounds out of with amateur tweaking.

if you have built drives with and without matched fets, what difference has it made to your drive builds to match the fets? big or minor?

[j-pee]

hello,

I'm so grateful for this topic, and for this superb circuit...

I modded it a bit:

#1
added two switches, one ON/OFF, and one A/B (2P2T)


#2
used a 6 pin IC socket.. for transparency...

#3
then, of course, like all beginners, I had to add some LEDs...
1 for ON/OFF indication, and one for "mode" indication... A or B setting


and I LOVE IT...