In over forty years of collecting, I have seen/heard of a handful. Of that handful, I have owned three and still keep one. These were stereo phono stages, which could also be wired for Tape Head or Mic input. They are a bit tight inside, but can easily be refined/upgraded. Tube compliment was one ECC83/12AX7 and two, triode connected EF86s. EQ was similar to many of the vintage 12AX7 preamps...