30 Watt Original Version
The first of this series were thirty-watt and pure class A, as reviewed in Hi Fi Choice in 1998 by Jason Kennedy. They used two KT88s and two 6SN7s in each channel, which were configured as follows; first stage directly coupled to a concertina phase splitter, capacitor coupled to a dedicated driver stage, capacitor coupled to the output stage. Overall feedback was applied, as well as local loops. Power supply HT was via two GZ34’s, and large choke for extra smoothing.
60 to 120 Watt Versions
These amps were quite a different breed from the latter. They had four KT88s and three 6SN7s in each channel (later versions had 2 6SN7s and one ECC34). The front-end circuitry was very similar to the 30-watt versions, but the output stage was grid biased and driven by cathode followers. They could be biased to give between 60 and 120 watts! Power supplies HT via solid state, capacitor, choke and capacitor. Time delay circuit for HT, approx. 40 seconds.
Some of the original Copper amps [including the one above] have now been brought up to the latest specifications, with larger mains transformers fitted, higher quality components including power supply, and bypass caps etc, and all versions are now fitted with the new’ and Excelent all-round performing Tungsol KT120/150 power valves, which means these amplifiers can now be set to give up to 50 watts [per channel] of pure class A power…