Tube EQ Blonder-Tongue Audio Baton from 1959

This is an all tube-based multiple band-pass filter. I just tested it with my TerraSonde Audio Toolbox (a testing device much like an Audio Precision machine) and it is working perfectly well. A couple of the dials, the barber pole ones, toward the bass frequencies, are a bit stiffer toward the bottom of their turn than the other ones. However, this is strictly mechanical.

It has all of the original tubes and it passed my frequency sweep tests almost perfectly, which is surprising given the age of this unit. There is a slight high-frequency rise when the unit is inline.

The video is of the unit for sale. The SoundCloud file is the actual unit with white noise passing through it. I recorded this today, the day of posting the advert on Reverb. I step through each band-pass filter, starting High to Low.

]  <-- Jack Endio's write-up on these (with extra links).
<---Eric Barbour (aka Capt. Metasonix) wrote a little about it.