Harbinger j201

[Jmilla]

Are the tayda crappy ones ok since it is a singe jfet or do I need to track some down from a better dealer?

[midwayfair]

Actually, since the Tayda ones aren't usually real J201s (or just very out-of-spec), they might work BETTER.

The J201 in the Harbinger is an input buffer, and it's a source follower. A FET will create clipping as soon as a signal exceeds its Vp (for how to actually measure that value on any FET, check here: http://runoffgroove.com/fetzervalve.html#11); you can observe this by measuring the source voltage on the FET. Plug in one with low Vp and you'll have a low source voltage even with a big resistor (10K is fairly large), but plug in one with a higher Vp and you'll get a higher source voltage. The higher source voltage corresponds with extra headroom.

One thing you can keep in mind is: IN general, the more gain a FET is capable of producing, the lower the Vp will be, and the easier it will be to clip the FET. J201s are pretty much the top of the gain range for FETs.

I use MPF102 for my input source followers when I don't want clipping; they're not very expensive, they have the right pin out, and they're not hard to get ahold of. The source voltage on them with a 10K will be about 3-3.5V, which is pretty high. (In fact, I haven't been able to get higher even with other FETs.)

However, I'm going to suggest you get your FETs from a better dealer regardless, simply because you'll be able to use them in other effects where it matters more without wondering whether they're actually suited to the purpose. It's not like Tayda's cheaper than anyone for their FETs anyway ... they cost as much as Smallbear. It kind of takes some balls to price known unreliable/out-of-spec FETs like that.

[Jmilla]

Yeah I noticed the price is similar, and since I have to get a few things from smallbear anyways I'll get them there.

[midwayfair]

Yeah I noticed the price is similar, and since I have to get a few things from smallbear anyways I'll get them there.

I've been tossing in 10 FETs of the three most common types I use (2N5457, MPF102, and J201) into my orders from them, building up a tiny stash slowly without feeling too much of a hit. You might also pick up some 2N3819 while you're there -- those were ROG's suggestion for input buffers, but beware that the pin is different.