I once possessed and evaluated a professional version of the Philco scratch
eliminator: factory rack mounted. With its winking eye green tube pacing
the contents passing through, it provided a delightful visual spectacle,
especially in a darkened room. Notwithsanding Ken Carpenter's superbly
performed sales pitches on Bing's Philco shows, it was an acoustic horror.
Bandwidth changes called attention to the noise instead of giving a
listener's ears and brain the chance to adapt to it.
There was another version: designed to interface with a
complete Philco (presumably high end) system. In addition to the audio in
& out, it accessed its power from the system.
I think that the interface was via a round octal socket. I had one, but am
not sure that I'm conjuring up the right image in 'my mind's eye'. It had
a second cable that connected the
filter's chassis to a small & attractive control panel that would've been
mounted in, on or near the system's cabinet.
As with the "pro version" I had no schematics. I presume that
Philco buffs would have them.
Having no Philco (or any other old set) with which to test it, I avoided
the temptation to try to see if it was operational.
I'd offered it on eBay perhaps 2 years ago (for a give away
I-don't-want-to-discard-it price & there were no takers.
I'm not being coy: I don't recall if I saved or tossed it. If anyone's
interested in it, then contact me directly & I'll check
Art (Shiffy) Shifrin