Mount Cyanide (818) Preamp

Projects > Mount Cyanide (818) Preamp

Made for the Jensen 918 Op Amp (gar918, BLU-18), the Mount Cyanide 818 Mic and Instrument Preamp caters to the low impedance input and feedback network that Deane Jensen spec’d for his original 918 op amp. Jensen, Cinemag and Lundahl Transformers footprints in all positions – with an option for Pikatron in the instrument direct input. Microphone input features the relay-controlled PHD circuit of phantom, pad and polarity. The unbalanced input automatically switches to a D.I. circuit and runs the signal through a third transformer allowing direct recordings for guitar, bass, synth or drum machine. A total of 3 transformers in the signal path makes the 818 an excellent preamp for instrument tracking. An output fader allows you to drive the transistors and transformers harder for saturated tone while maintaining optimal recording level.

*Please note that the instrument input will only work with unbalanced connections. For balanced, use the mic input and engage the pad.


Discrete Op Amp Options

  • BLU-18

  • gar918


Auto-switching Transformer D.I. (unbalanced only)

  • Jensen JT-DB-EPC
  • Cinemag DBX
  • Lundahl LL1935
  • Pikatron UP3096M

Input Transformers

  • Jensen JT-16PCjr
  • Cinemag CMMI-2C
  • Lundahl LL1570

Output Transformers

  • Jensen JE-123s (vintage models routinely pop up on eBay)
  • Jensen JT-11E Series
  • Cinemag CMOB-3 or CMOQ-3
  • Lundahl LL1517

Additional stuff

  • Choice of Grayhill gain switch or standard Alpha rev log pot
  • Output fader is a simple Alpha dual pot. There is space (but not a footprint) for balanced t-pad attenuator
  • Illuminated pushbutton switches

Currently available as a bare PCB ($15) or fully assembled.

More info available at–