JFET

[Axmanjr]

Ok, so I went to Fry's Electronics today and was gonna buy some JFET201. I did find JFET transistors, BUT they were all labeled differently.  I didnt see JFET201- but I saw a bunch of N-channels, P-channels, radio-this, and audio-that....  So my question is, what's the difference with all of these JFETs?  What does each type do? :?:

[jrc4558]

If they're all field effect transistors (FET), they all do pretty much the same thing. They amplify signal. the labelling would be J201. You can also use a more common 2N5457 or SK117 or MPF102. Browse web for datasheets, select the apropriate parameters for your applications.

[ErikMiller]

If you were at Fry's, I'm guessing that their stock was all NTE, which are not sold under the industry standard part numbers.

NTE sells "equivalent" parts under their own part numbers, such as NTE458 for their "equivalent" to the J201. I put the word in quotes, because a lot of the time, what NTE thinks is equivalent, you or I might not.

I built the classic Tillman buffer using NTE's 458, and it worked all right, but a couple of years later, I got hold of some actual J201's, and it sounded MUCH better with one of those in it. Tillman himself does not recommend the NTE for that project.

As for what all the different kinds of JFET's do, well, a basic electronics book can describe it better than I.

What are you seeking to construct?

[Jered]

Axmanjr,
   Just order some J201's from Steve at Smallbear, you'll be glad you did.
Jered

[gez]

low and medium power audio or switching is basically what they're used for.  

Some have higher transconductance than others, some switch faster than others, some guarantee a minimum drain current others a certain range for cut off on the gate.  

Did I mention gate capacitance?

[MarkB]

Erik - that's the second time in a few days that someone mentioned the Tillman buffer/preamp..

Any idea if that circuit is good for using as a preamp for an acoustic?  My wife's aunt has a magnificent Collings acoustic - and wanted me to build her something to juice up the 'plugged in sound' a bit..
"-)

[WGTP]

I just changed out some J201's for NTE458's in a MuAmp/Srpp and they have more gain.  There are also J202's that seem to have more gain than the J201's.  The MPF102's at RS have less gain.  That's the only ones I have tried so far.  

[RDV]

Any idea if that circuit is good for using as a preamp for an acoustic?

I think it would. Here's the link.
http://www.till.com/articles/GuitarPreamp/index.html

Regards

RDV

[Axmanjr]

Thanks everyone for your replies!

ErikMiller- you're right, they were all NTE.  This gave me a very big headache.  I was looking for a JFET201 for the modified EA Tremolo build found on GGG's website.  So basically, you're saying that if I can stay away from NTE, then I should?  

I also noticed at Fry's that it was difficult to find certain transistors (such as 2N3904...) since they are not labeled as such!

[Hal]

why doesn't the Rat Shack have _any_ JFETS or MOSFETS.

they anger me.

[Tim Escobedo]

Keep in mind that JFETs are ALL OVER THE PLACE. Even the same types.

I have three different types of J201s, from Fairchild, Siliconix, and Central Semi. You wouldn't know they were the same parts, from the way they behave. Even from the same mfgr. and presumably the same batch, you can't really count on them behaving the same, depending on the circuit, too.

[smoguzbenjamin]

I used an NTE 458 in a runoffgroove EA tremolo and it works fine :?

[MarkB]

Hal -
I've found MPF102s at RatShack...
but generally - I've given up..
order em from Steve
"-)

[ErikMiller]

Erik - that's the second time in a few days that someone mentioned the Tillman buffer/preamp..

A sign that building one is your destiny. :-)

I sure do like mine. A nice little thing to have about the studio for running directly into the mixer or rack effect.

Any idea if that circuit is good for using as a preamp for an acoustic?  My wife's aunt has a magnificent Collings acoustic - and wanted me to build her something to juice up the 'plugged in sound' a bit..
"-)

In its simplest form, there's not much gain. I think he mentions a way to jack that up, though.

If it's juice you seek, my suggestion is for the much-lauded AMZ MOSFET booster.

[ErikMiller]

In my book, NTE's stuff is what I'd use if nothing else were available.

It's priced way too high, and I can never be sure about the true compatibility. I don't like their proprietary part numbering either.

Radio Shack does sell a useful MOSFET, the IRF510. It can be pressed into service in the AMZ MOSFET boost (with less gain). Also, they sell the MPF102 JFET. When I breadboarded an Anthony Leo/EA Tremolo, the MPF102 worked fine.

Radio Shack also sells 2N3904's.

Fry's used to be a good place to find components, but less so these days. Like Radio Shack, they've discovered the easier bucks to be had in consumer electronics.

Also, I think not all Fry'ses are equal in what they stock. The Palo Alto, CA and Sunnyvale, CA ones may still be okay for components. Haven't been to them in a while, but years ago, they were still great.

It's funny, these big places seem to be quickly backing away from selling components, and then we have Small Bear swamped with more business than he really wants.

My years working in corporations showed me how clueless businesspeople can be about maintaining a steady niche-market cash cow. I've seen great products and brands destroyed due to the notion that SHITloads of money must be made or none at all.

Freehand, anyone? Farrell's Ice Cream? It's not enough to be steadily profitable, ya gotta be able to flog it until it's dead.