By request: Any appetite for/chance of a "vintage electronics measurement and discussion" section?

[restorer-john]

Both restored and untouched would be interesting. Restored because it tells how good it was when it was new. Untouched because it tells how most people would experience it at home. Also if a test of an untouched amplifier shows some issues it may provide a rough guidance of what to expect when buying such a vintage device, what to look after when trying it at the sellers place or at home. Audible ques etc.

There's everything in between untouched and restored.

A simple repair under warranty in 1976 could be have been factory parts or a bodge. A unit could have gone in for one thing which was fixed and several other manufacturer service department updates might also have been performed. Or not in the case of an untouched unit that never saw a service department.

Unless you know the actual history, the only person who can tell if something is 100% original with no factory or otherwise mods, is someone who goes over the amp with a magnifying glass and a lot of knowledge, checks date codes, crosschecks substitutes from S/Ms etc. Even within a model run, especially with the higher power, more expensive receivers/amps, components changed and upgrades/downgrades were made.

I can say that after testing many identical models of amplifiers is that the variations in performance between perfectly functioning (restored or not) examples is small. Characteristics baked into units are predictably repeatable. Minor noise/hum and THD differences are always present. Channel balances and FR differences are always there. But the basic power outputs and characters of the amplifiers remain as they were when designed.

But often, I see absolutely head-scratchingly silly design decisions and I will fix those flaws to improve the unit. Ones where a component is an order of magnitude out, resulting in poor bass response for example.