Author Topic: Sparkle Boost bias problem - Can't get voltage low enough  (Read 1020 times)

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Sparkle Boost bias problem - Can't get voltage low enough
« on: February 19, 2006, 06:12:52 PM »
Dragonfly's Sparkle Boost: http://aronnelson.com/gallery/album18/SPARKLE_BOOST_LAYOUT

The good news is the ciruit works.  I have sound in both switch positions, volume and gain pots both work, and at max vol/gain i have a much louder and distorted sound. 

But, I am trying to bias the NTE458 transistor in the Sparkle Boost, but I can only trim from a little more than 9 volts to right around 7 volts.  I am taking this reading by placing the black probe of my DMM on the ground strip, and the red probe on the transistor D(rain) strip, past the trim pot.

The NTE458 packaging is confusing about the pinouts, but forum posts indicate you look at the flat side of the NTE458 and left to right is D, G, S.  This is how I have it installed.

As far as I know, I have made no subsitutions to the circuit.  This is only my second build, so I am very new still.