Preamps
CPR1 comprised of 4 gain blocks, 2 RIAA disc and two line. The blocks were discrete longtail pairs followed by an op-amp. Line stages had jFet muting.
This PCB was used in the kits and 510 preamplifier.
CPR2 comprised the same 4 blocks and muting. Each block comprised a discrete current feedback amplifier. This PCB was used in the kits and 610 preamplifier
Pre-Preamps
MC1 was a complex disc pre-preamp utilising an array of 9 discrete transistors.
MC2 was a simpler open loop symmetrical common emitter design, using two low Rb transistors in push-pull parallel.
MC3 The same as the MC2 but with a capacitance multiplier PSU section.
MC4 was a similar design but for solely battery operation