aion 3408 Manual - Page 5

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BUILD NOTES

Setting bias trimmers

Turn the trimmers so that the drain ("D" pad) of the JFETs measure 12V, measured with a multimeter

(red probe to "D" pad and black probe to ground).

This is just a guideline, though. You can tweak the trimmers to fine-tune the circuit to your liking. The

bias affects the total gain of the circuit, so you can make it a little cleaner or a little dirtier than stock.

J201 usage

The J201 transistor is very popular in DIY pedal designs, but was discontinued in TO-92 through-hole

format several years ago and is becoming very scarce. Genuine parts are getting expensive and many

counterfeits have entered the market.

The MMBFJ201 is a SMD version that is still in production. On the PCB, two outlines have been included

for each individual JFET, one for TO-92 and one for SMD (called SOT-23) right next to it. Make sure you

only use one or the other—don't put both a through-hole and surface mount part in the two Q1 spots.

J201 adapters

Many DIY builders are intimidated by the small size of surface-mount parts. Aion FX offers

pre-soldered

J201s on adapters

so they can easily be used as through-hole parts.

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