Aion Draco (Dr Boogie) JFET Bias

faramir

faramir

Member
Built an Aion Draco Dr Boogie clone. Only issue I ran into was biasing the 4th J201. I could only get it to 5.8v with the trimmer turned all the way up. The others all could easily get 4.5v. Any ideas on why this might be? My guess is a bad J201, possibly damaged by me during install? I used a soldering iron at 700 deg F and they are SMD's installed straight to the board by me. I got them from Stomp Box Parts. Not sure how easy they are to damage or how they would behave if I did.

Despite this it actually sounds pretty good though its a bit staticky-fizzy sounding at some settings. Hoping fixing that bias issue will help. Definitely sounds better at 18V (I did the bias at 9).
 

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faramir said:
could only get it to 5.8v with the trimmer turned all the way up. The others all could easily get 4.5v. Any ideas on why this might be?
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sometimes this just happens.
recently, ive breadboarded a JFET distortion circuit which also called for 50K trimpots, but i found one of the JFETs couldn't achieve a bias range that i was satisfied with. so i just swapped the 50K trimpot for a 100K trimpot. this solved that issue.

i suspect (guess) if you tried a 100K trimpot for that position you'd be able to bias it down lower.

faramir said:
sounds pretty good though its a bit staticky-fizzy sounding at some settings.
Click to expand...
try it into the FX return of the amp to bypass the preamp (usually sounds better this way)
faramir said:
Definitely sounds better at 18V (I did the bias at 9).
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agreed.
 
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