Pre-amplifiers for vintage Grass polygraph. 7DAC uses (2) 12AU6 red tip Telefunken tubes (present). *1966* Telefunken <> diamond medical tubes work, date code: U 9116201.

Some knobs missing, parts not missing. Polygraph units totally untested. Lot: 8.

Combined shipping available: fill cart with all items you want from my store, click "purchase," then click "request total from buyer." A revised invoice will be sent to you that reflects the lower price.