Quad 303 Monobloc Power Amplifiers

I converted this pair of Quad 303s (serial #31789 & 31792) to monoblocs by removing a channel from each one. The power supply & output coupling electrolytics have been replaced with ELNA Cerafines for significantly improved performance. They have also been fitted with a gold RCA plug & 5-way binding posts making it easier to connect them to non-Quad gear.
The 303 is considered by many to be the best solid state amplifier that Quad built -- particularily if you are driving Quad ESL 57s. Around this neck of the woods they are often used as the 2nd amp in a biamp situation with an Advent 300, or NAD 3020/7020 as the midbass amp.

The monobloc conversion ensures maximum channel isolation for optimum imaging and doubles the size of the power supply available for each channel as well as providing a seperate, less stressed, regulator on each channel. With one less driver board in each amp, there is less heat generated with more open space for it to radiate into increasing reliability.
Rated at 45 w/channel in stereo, they should put out slightly more as monoblocs. Increased power, though, is not the reason the conversion was done, but improved quality.

These are very fine sounding power amplifiers.

Next mods would be to rewire the amplifier for improved sonics, and if real serious would rebuild the driver boards with better parts, and replace the output transistors with uprated 2SD733s.