HP 410C Amp - Improved

This is cloned version from the user 1audio

A little background- The HP 410C was introduced in 1963 and in production through the 1980's. While obsolete in many ways they are still useful for servicing vacuum tube electronics. There are quite a few still in service. There were two generations of the internal circuit board. The first had a vacuum tube and an optical chopper assembly. The second had a discrete opamp with 2 Jfets for the input. This is a replacement using a CMOS opamp. I plan so share the design and etc. for anyone who can use it. Its not intended for commercial use.