The best J201 out there

[caspercody]

Has anybody found a really good J201 manufacture? I have been ordering the Fairchild ones from Mouser (512-J201), but need to order more, and I am wondering if anyone has found one they have ordered that are really good?

Thanks

[R.G.]

Can you define what "really good" means?

Cheap? High gain? Low gain? Consistent gain? Consistent anything? High voltage standoff? Specific/high/low/consistent Idss/Vgs/gm? Sounds good?

... oops... "Sounds good" means clean? distorted? crunchy? low noise? more/less treble/bass? ...

[Derringer]

get the ones that go to eleven ...


Seriously though, I'd be surprised if there's a particular "brand" of j201's out there that a group of people prefer. With tubes people seem to be more brand specific ... and I'm still on the fence about that too.

But with silicon .... it's silicon. Get a batch, get some trim pots, and sift through different ones to see if one sounds better than the other.  And I haven't yet reached a stage where I've actually A/B'd jfets against each other to find the 'perfect' one. I haven't built anything that required me to match them though either.

[Paul Marossy]

I don't see how a J201 from a certain manufacturer is going to be any better or worse than a J201 made by another manufacturer. They're both made to the same specs in very similar environments.

The only difference I could see is in the price tag because one manufacturer can get away with it because of their name and/or reputation while the other may not be able to do that.

[aziltz]

so far they've all just 'worked' for me.  i dont think i can tell the difference even if i swapped.  maybe if i have 2 identical boxes and A/B'd.

[petemoore]

  They're all at least a little different.
  So are the appliciations they go into.
  Jfets' tend to vary all over the map that way, even J201's.
  Best you can do is pick a design or application that isn't particular about 'which Jfet' or hand sort through to find what you need in the available stocks.

[dschwartz]

I´d think that consistency is the only feature that may vary between brands...not sure though.

[Paul Marossy]

I´d think that consistency is the only feature that may vary between brands...not sure though.

Maybe. But the spec sheets are pretty loose on some things. As long as they fall within those specs, they did their job.

[Ben N]

I´d think that consistency is the only feature that may vary between brands...not sure though.

Well, I'd suspect that inconsistency is what is common to them all. But I'd sure be please to be proved wrong.

[caspercody]

I just wanted to see if anyone has had more bad builds using one type of J201 than another.

I have built the Thor (have issues with high pitch noise), the Dr Boogey (rebuilt it using shielded wire and helped to get rid of some high pitch noise), Sweet Thing (no problems), BSIAB2 (no big problems, alittle high pitch noise),and Big Daddy (no problems). I think I have used all the same J201s, but have noticed the ones I have built with the most trimmer pots are the ones with the noise issues. Some say to bias to 4.51v, and some say to bias to 5.5v. And I know it all comes done to what I hear, but I am to anal about getting them to work at the voltages that the builder has recommended.

All of these builds I have used the pcb layouts from ROG, or GM, or GGG. And used shielded wire.

Thanks for all the replies, and great project designs!

[dschwartz]

i mean, by the way fets are made (etching silicon and glass or something like that) i suppose some manufacturers can achieve better etching than others, just like some diyers etch boxes better than others.. Or if their fet selection for each model is more strict, i dont know..

i dont think different brands should sould different though, fets are fets..

[liddokun]

I agree, especially because j201's, like many other components are manufactured in the millions, so I doubt they'd have time to check them all. Maybe certain manufacturers have stricter manufacturing guidelines/procedures? I highly doubt that, since they're selling each one for a couple cents.

[petemoore]

  Yupp...sensative little buggars, pretty much have to build the circuit around them or test them to work in the circuit...
  Or have it where it doesn't particularly matter.
  Like you Cody, I built batches of Jfet stuff like it didn't matter, and found out it all starts mattering...real soon. I didn't get all that lucky and recall those trimpots being haggardly to work with, I opted for lots of Jfets in 'this' socket, and a 10k trimpot with maybe a 47k or...whatever I was looking for collector resistor [so the adjustability would be between 47k and 57k], finding a Jfet that biased where I wanted the resistor to be, ok maybe a 20k pots then...I ran out of Jfets too fast.
  If you're altering the Drain resistors between say 6k8 or 110k...well...the circuit starts taking on a new look and sound...
  I like the Mu Amp for that reason, worth the extra Jfet per stage, once in...always worked...1 Minibooster covers my Minibooster needs...
  Prof Tweed, 18, English Channel, can't even remember all the others...I had over 100 Jfets.

[dschwartz]

i agree..mu amps are my basic building block nowadays. You can hear different fets sounding different, but not as different as using a trimpot.

[alanlan]

You should be asking:

"I bought 10 J201's from the same manufacturer - which one sounds best"

i.e. they are so variable anyway, it's hardly worth looking at differences between manufacturer.

Having said that, there's quite a possibility that certain manufacturers parts have a slightly different spread of characteristics within the spec for the device.  How that translates to better is difficult to know without actually measuring the given characteristic.

It's a job for someone else, I'm not that keen.

[caspercody]

Petemoore, what do you mean about adding the mu amp? Is there a way to adjust the projects I made (Thor, Dr Boogey) to get rid of the high pitch noise but keep the voltage around the spec?

I am looking at making the Plexizer, JCM800, and Diezel but want to make sure I fix (or better understand) the reason about the noise on the other projects first. Both of them work great, just when I have the bright switch on or off (I cant remember right now which setting) and the gain between 10 and two on the Thor, or if I have all the pots maxed on the Dr Boogey that I get the high pitch noise (it probally is commonly called oscillation).

[Jered]

  On your builds with noise issues make sure you have all your JFET gates grounded with a cap in the pF range. You can also parallel your drain trimmers/resistors with caps, but this will change the tone.

[caspercody]

I will try this, any suggestion on what pf size to start with?

[slideman82]

Try Mullards or Telefunkens 

[petemoore]

Petemoore, what do you mean about adding the mu amp?
  You set the 1 Jfet up to bias the other one, holds bias real nias that way, in fact you can take the supply voltage way up or down, try different Jfets...pretty much do anything you want with it.
  A bit more to wire up, but the stable, easily repeatable 'pure performance' is worth the 'extra' trouble.
  ...Of course YMMV, it's my belief that you'd have to like the sound of a Mu amp and that might take some cow-time [moo joke here], picking tranny's and...
  Basically it distorts a little bit or slightly, boosts, the input impedance is that of a Jfet, I hope I"m not misquoting...Jack reported the Minibooster's current driving capability could sometimes use some help, that's a 3rd transistor [buffer].
  I really like the 1rst stage as tube or Jfet, simple Jfet jobby seems to do great work there [1Q], not picky as long as it makes ''quality'' boost.
  When I started getting into the >2 transistor Jfet builds, the trimpot, the JFet and who knows what else conspired to create a great disdain for working with multi-Jfet circuits. I'm not purporting to say these circuits can't perform reliably, just that I had consistant troubles getting them to do just that, I wrote 'too unstable' and went on to realize I like being not that picky as long as:
   "the truck has truck tires, the engine works great", 2 valves per cylinder is fine...for a truck.
  or
  "The racecar has extremely round racing tires, the engine is right on the verge of failing most of the time, and the final gearing if not each of the ratios has been fitted to the course, the whole car is balanced and competes with or beats it's clone".
  Talkin' electronics is not as easy as talkin' ''tracks roads cars'', we know the difference between a huge and very light load, road and racetracks, I can't describe or even envision the 'track'' of someone elses signal path, especially if there's not extensive and complete discovery of the signal path...even if every pot value and speaker name were designated, all settings included...well that never happens.
  try 2...Ed did.