Starting in the ’50s, they’d figured out how to start miniaturizing components. “Couplets” and “printed electric circuits” started showing up in equipment around then. These components were combinations of several resistors and capacitors in a single package.

Like most components from that era, they do start to go bad over time – although you can’t exactly run down to the local Radio Shack and buy a Centralab PC-191 or a Sprague TC-24 anymore.

So, sometimes it’s necessary to roll your own.

Those two boards replace a set of tone control circuits in the EICO HF-81 amplifier. A little bit bigger when made with discrete components, but not too bad! These will be much more reliable, too.