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Projects => Tech Help - Projects Page => Topic started by: copachino on October 24, 2014, 10:44:05 PM

Title: low gain j201 as buffer??
Post by: copachino on October 24, 2014, 10:44:05 PM
hi, i have a bunch of j201 maybe fake from tayda and im just wondering if they can be used for a buffer in the ruby amp
Title: Re: low gain j201 as buffer??
Post by: jubal81 on October 24, 2014, 11:01:35 PM
Bad idea. It'll distort like crazy.
Title: Re: low gain j201 as buffer??
Post by: copachino on October 25, 2014, 12:14:18 AM
Quote from: jubal81 on October 24, 2014, 11:01:35 PM
Bad idea. It'll distort like crazy.

so they are useless?
Title: Re: low gain j201 as buffer??
Post by: jubal81 on October 25, 2014, 12:17:35 AM
Quote from: copachino on October 25, 2014, 12:14:18 AM
Quote from: jubal81 on October 24, 2014, 11:01:35 PM
Bad idea. It'll distort like crazy.

so they are useless?


I threw mine out. You can test them and try to use them in an overdrive, but keep your expectations low.
Title: Re: low gain j201 as buffer??
Post by: copachino on October 25, 2014, 12:42:32 AM
Quote from: jubal81 on October 25, 2014, 12:17:35 AM
Quote from: copachino on October 25, 2014, 12:14:18 AM
Quote from: jubal81 on October 24, 2014, 11:01:35 PM
Bad idea. It'll distort like crazy.

so they are useless?


I threw mine out. You can test them and try to use them in an overdrive, but keep your expectations low.

already did, but no luck, i have to leave them on the garbage then
Title: Re: low gain j201 as buffer??
Post by: Rockhorst on October 25, 2014, 10:07:11 AM
They might be good in an AMZ mini booster type circuit. There are two J201s connected in an SRPP setup. Only the lower one (in the classic schematic) needs to be a JFET, the other (upper) one is just a current source and could be a BJT, even a germanium, if I'm paraphrasing Jack Orman correctly. I'm not saying it will work out, but try your low gain JFET together with a high gainer in a mini booster circuit (or it's derivatives, like BSIAB2 and the Dirty Little Secret). Use sockets and swap them round. Might sound good.
Title: Re: low gain j201 as buffer??
Post by: midwayfair on October 25, 2014, 03:34:38 PM
Yeah, don't throw them out.

There's a use for almost everything.

J201s distort when the input signal exceeds about 0.5V to 1V. Even if yours are low gain, they will probably distort easily if you put them last in line in a JFET overdrive. You can also use them as output buffers in distortion effects -- distorting a buffer is typically softer distortion, and a JFET will also sound softer than a BJT.

I agree with Rockhorst -- the SRPP is a great idea, since it boosts the gain so much more than the standard minibooster. http://www.geofex.com/Article_Folders/modmuamp/modmuamp.htm

They'll also work just fine in many effects that use similar mu-amps, in situations where getting as much gain as possible isn't critical. You could use them in my Clipper Ship overdrive, for instance. In that effect, the signal is clipped before the SRPP below the input threshold for FETs anyway, and the output volume is so high that you don't need anything remotely as high-gain as a J201 regardless.

Finally, they're still useful as switches and potentially as variable resistors. (I believe that the J201's original intended use was as a switch.) So you can use them for the FET in the Stage Fright, Sharkfin, and Lowrider, or as the variable FET in the Bearhug or perhaps an EA tremolo (depending on what the gate-drain resistance measures).

What I'd do is test them in a booster circuit against known good FETs, and sort them accordingly.

I'd offer to take them off your hands, but I don't think the overseas shipping is really worth it and I already have a bunch of FETs, but you could always toss them up in the PIF subforum.