What is it?

This is a kit consisting of a tiny circuit board, some male-to-male machine pin strip, some capacitors, and a decent-quality modern operational amplifier in SO-8 package to replace Hitachi's proprietary HA1452W IC, which seems to be a dual externally compensated opamp with (possibly?) offset trimming capability. Like two mediocre NE5534 knockoffs in a single package.

The HA1452W is a non-standard 14-pin DIP package from the era of non-standard opamps, circa 1977. It is found in some vintage audio equipment from Hitachi, Pioneer, and probably others.

This kit allows you to replace it with a modern ultra-low-noise part for enhanced performance.

It comes with gold-plated male-to-male machine pin strips, a socket, an lme49720 (aka lm4562) opamp in so-8 package, a 100nf C0G power bypass capacitor in 1608 package (big enough to hand solder), and a pair of 22pf through-hole ceramic capacitors which can be used to short ultrasonic signals to unity gain, which may prevent oscillation (cheap insurance that can't hurt the audio quality).

Why did you make it?

I have a 1978 vintage Hitachi HCA-6500 "control amplifier" that always sounded dull and noisy and wanted to improve its sound quality. I am unaware of any other opamp adapter for this particular nonstandard part, so I designed and tested my own.

What makes it special?

While I am confident that there were certainly technicians in the '80s who were able to suss things out and replace the ha1452w with a better or more standard part, to my knowledge this is currently the only option other than replacing it with a NOS, used, or re-badged original part.