Another opinion on Counterpoint Amplifiers

[Gepetto]

I spoke with Mike way back and he told me they had to match up the mosfets and bought thousand piece lots to do that. It might even be true.

But there is nothing to balance them and they won’t current share properly if not matched.

They also did an extended burn in to keep drift under control, and would occasionally replace a mosfets that was hogging current.

This is why he developed his upgrade at Alta vista. He replaced the output boards with a different design. I never heard these.

But it is important to know he always lamented counterpoint tying his hands so he couldn’t build what he truly wanted to build. He had to compromise on design and component choices to meet price points. He didn’t have that at Alta vista and the sales prices reflected that.

Unlike bipolar transistors (negative tempco on the B-E junction), MOSFETs share current naturally when parallelled (positive tempco on the D-S junction, Rds increases as they heat up). However, parallelling MOSFETs can lead to oscillation issues and damping resistors are needed to kill any parasitic oscillations that may occur that are associated with the G-G-G interconnect wiring inductance and the relatively large G-S capacitance of each MOSFET.