The Longhorn is a phono cartridge, and we have not figured out how to stuff vacuum tubes into one of these yet.

If you mean the phono preamp, it does not use 6N1P tubes. It uses 12AX7 tubes, JJ Electric ECC83s versions at this time.
The 6N1P tubes (Sovtec brand) are used in the line sections of the hybrid Ultra preamplifiers and DAC, and the vacuum tube Transcendence Eight preamp.
The 12AX7 tube is optimized for high voltage gain, necessary to follow the RIAA feedback loop correctly. The 6N1P tube is optimized for high current gain, very useful in driving real world loads. Each has their useful applications.
Regards,
Frank Van Alstine