Musical Fidelity B1 doubts


I'm restoring an old Musical Fidelity B1 amp. I've found some pics and schematics in the web, but it seems that my model is quite different: apparently it seems to be a very first version, or even a pre-series unit (serial # 00049)

Especially, I have not found any pot able to adjust the bias current (see pictures). Moreover, R40 and R46 resistors have never been mounted. The only adjusting point is a 2K trimmer mounted at R30 place on right channel only , I suppose to allow a preset balance between the two channels.

No way to balance the DC output and to adjust the bias?

Many thanks in advance, Paolo


  • Musical Fidelity B1 b.jpg
    Musical Fidelity B1 b.jpg
    680.3 KB · Views: 124
  • Musical Fidelity B1 c.jpg
    Musical Fidelity B1 c.jpg
    606 KB · Views: 119
Thx Huggygood,

I've had a look at that post, unfortunately I have not found any mention about my (pre-series?) model.

In fact, my amp works somehow but with no chance to actually control the DC offset (currently not so big, but not null, 50-100mv with no load applied) and the bias current.

I wonder if it would be possible to modify my circuit in order to allow those adjustments