The rest of the design features two black plastic control knobs with silver tops and clear plastic collars, two smaller black and silver knobs, eight black plastic pushbuttons and a red power indicator light. The output matching transformer at 600 ohms was a UA-5002 (later improved to UA5002A) with a split secondary, a tertiary winding for negative feedback to the final line output circuit, and a separate emitter winding.Ĭovering up all this electronic wizardry was a brushed aluminum faceplate with blue paint around the Weston meter. The output amp circuit was similar to the preamp, but followed by a 2N3053 bipolar transistor operating in Class A. The original 1968 design by Bill Putnam used an input transformer at the industry standard 600 ohms resistance (Peerless, later UTC), a T-pad resistive attenuator to drop the input voltage, a FET acting as a voltage variable resistor to control gain, followed by a bipolar transistor as a preamp (the famous 1108 circuit with a Darlington pair). Digital Adapters & Miscellaneous Cables.
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