Hybrid Balance Mu-Stage preamp with subminiature tube

This is a new made preamp – Hybrid Balance Mu-Stage.  Dual triode medium gain subminiature tube like 6N16B-V, 6N18B-V, 6N28B-V, 6111, & 6021 etc… can be used.  The choice of submini tube is due to its low noise and good microphonic effect. 


  1. Hybrid (Mosfet + Tube) mu-stage design with full balance at input and output
  2. Supply voltages: +128V, +59V, -69V and two 6.3V DC – all regulated supply
  3. Tube biased at about 1.5mA at about 60V plate voltage
  4. Mosfet IRF710 as Source Follower biased at about 7.5mA
  5. Gain about mu of the tube, about 20 to 40 times
  6. Non feedback design and thus tube may need to match for gain.
  7. Tube can be replacable using IC sockets, the submini tube is first soldered on 8-pins leads and then inserted into IC socket.

FFT measurment:

FFT Balance Mu Preamp

Update new photo on Jan 3rd, 2011 …..

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