Author Topic: Soulsonic JFET bias  (Read 676 times)


  • Electron Doctor
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  • Jason - Evergreen State
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Soulsonic JFET bias
« on: May 04, 2015, 04:36:34 PM »
Interesting thread going on at FSB about JFET circuit designs. Soulsonic posted a biasing setup that looks really interesting - the point being you can set the DC bias with minimal effect on the AC.

Here's a link to the thread

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  • Jon P
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Re: Soulsonic JFET bias
« Reply #1 on: May 04, 2015, 05:38:53 PM »
I don't really feel like jumping in a fsb thread, but:

There is nothing you can do to not have JFETs have variable gains.
Positive voltage on a gate will alter the signal level just like baryon the drain or source voltage
Who gives a crap about 'variable drain loads' in most pedals? We're talking about a couple k at most for j201 and a few hundred ohms for 2n5457s. And if it's followed by another stage it's dividing against a 1m resistor, which is an imperceptible amount of division.

I don't see a clear enough advantage to warrant a 66percent increase in resistors and the need for more filtering caps to make the Vb approach how quiet and stable GROUND is.
Myself's music & things I make: My band: PCBs of my designs from: (Bearhug Comp & Cardinal Harmonic Trem); (Hamlet+ delay & Blue Warbler envelope vibe); Snow Day OD/Flabulanche: