Several different versions of the same JFET, which one is preferred?

Started by hillio, January 02, 2008, 09:13:30 PM

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hillio

Mouser stocks 4 different kinds of J201's, all all pretty close in price except 1.  The only real difference I can see between them is that they all have different drain currents and in some cases power dissipation ratings.  For example,  There are three different 'types' of J201's that cost $0.14 each. The first two have drain currents of: 0.2mA to 1mA, and the third is 80mA.  All three have power dissipation ratings of 625mW.  Can anyone tell me which of these three would be best suited for use in pedals, and why?   Also, there is one other type that Mouser stocks that costs $0.21 each.  It has 8mA drain current, and 325mW power dissipation.  It this one any better than the other three?  Does lower power dissipation equal less noise?   I have seen J201's listed on some other websites as "Low Noise" JFETs and the cost is 3 - 4 times higher than ones I mentioned earlier.
These things are so cheap that cost really isn't the issue. But as you all know, more expensive doesn't necessarily mean that a particular component is 'better', or better suited for a given application.  I would just like to know how the differences between the components I mentioned, and how those differences would affect the sound of products such as BSIAB2, Thor,  Pepper Mill, the Insanity Box and any other FET based OD pedals.

I apologize if this topic has already been covered elsewhere, but I haven't been able to find specific information about what I mentioned in the post.

Thanks


petemoore

Can anyone tell me which of these three would be best suited for use in pedals, and why?
  Yes, the one that biases in the circuit in question.
  Beyond that, the one that edges out the others for bias and sound.
  After that, I havent' researched the differences in Jfet's J201's or otherwise except the NTE458's were consistantly the highest gain Jfet's I've had/heard/heard of, only thing about them is they are the one exceptiion in the types/brands mentioned so far that I wouldn't particularly recommend for SB usage..but that was in a circuit I built, not exactly a wide or accurate testbase for conducting extensive interviews on Jfets...not that conducting such tests would be of any real use...not sure.
  It is worth it to test say a small handful of Jfets if you have say 3 or 4 x 1 Jfet gain stages chances being very good to find 4 suitable candidates, but with just 4 chances are fair to middlin' that one of them may refuse to bias under the shown bias conditions...depends on the Jfets // depends on the circuit.
  I tried to find jfets that wouldn't bias in Mu amps, and noticed tonal differences...
  But for Jfet gain stages, J201's, and *2n5457's are generally great candidates to have spares of because the Vgsoff varies so much from one Jfet to the next, wide variations from j201 to j201, same for 5457's, mPF102's, etc.
Convention creates following, following creates convention.

hillio

Thanks for the info.  That pretty much answered my question.  I've been meaning to put together that little JFET matching circuit from GEO , but haven't gotten around to it yet.  I've been wanting to test a bunch of MPF102's to see if any of them showed similar characteristics to that of a "good" J201 or 2n5457, mostly because I can get bunches of them at a nearby Radio Shack.

Thanks again.


Krinor

Just buy a fair amount of each type, put sockets in your circuit and experiment. You won't regret it. It's actually quite fun. Almost like tasting good wine. Minus the hangover.  ;)