Watt Sucking Fireball Amplifier

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Watt Sucking Fireball Amplifier

“The Watt Sucking Fireball amplifier illustrates a wide use range of Linear Systems JFETs and matched bipolar transistors. It has an all JFET front end using a (Differential-Cascode-Transimpedance)™ amp driving a resistor loaded differential current to voltage gate driver; a lot to say in one sentence. Though simple in overall design concept, the goal of this design was to prove out an all N-channel JFET amplifier having almost no intermodulation distortion using a linear low loop gain signal path and minimal feedback. The output JFETs are vertical Power JFETs made by Sony in the 1970s. The vertical C7 driver FETs were my own fabrication in 1994. But that’s a whole other story. Though the debate rages on, audio is always AC so capacitors selected well are valid, and Nelson Pass said so. This input diff stage has capacitor coupled sources, as does the output stage driver. Independent current sources set preamp quiescent voltage matching. Independent current sources make output zeroing simple via a differential current steering integrator to balance gate drive current sources. Output JFETs are negatively biased gate to source and thus balanced to zero the output DC voltage. Linear Systems single & dual JFETs and Matched bipolars are effectively used in the entire bias management system. 

The DCT (Differential Cascode Transimpedance)™ preamp was invented for the Linear Systems 2009 Burning-Amp Festival Demo.

Following founder John Hall, I have been designing discrete transistor and JFET circuitry with Linear Systems parts since their first year of founding in 1987, and before that, Micropower Systems, much of it in Semiconductor fabrication machine instrumentation. Discrete Music amplifier design is now a 60-year continued preoccupation.” - J Kirkwood H Rough