CSPP With Vertical-Fet 2SJ18

[frankln]

See this amplifier
http://www.ne.jp/asahi/evo/amp/CSPP/2SJ18.htm
somebody know the working principle of this amplifier and knows me explain?
The trimmer should be set as?
V-fet: what will be happening here?

 

[Elvee]

It is a semiconductor variant of the "circlotron". You can redraw the supplies, output stages, ground and load in a different order to understand what's going on.
VR2 & 3 set the Iq and VR1 sets the DC offset.

 

[frankln]

thank you Elvee.
can you recommend a procedure for adjusting the trimmer?

 

[Elvee]

Obviously, you should adjust Vr1 to get 0V at the speaker terminals.
For Vr2 and Vr3, it is less clear: they both have a similar effect, and I don't quite see the purpose of biasing the current source with a FET. Anyway, you should adjust them to get the recommended quiescent current.
Somebody else may be more inspired than I am.

 

[frankln]

thanks for the information.I have four 2sj18 (and they were not cheap) and I would try to build this amp possible without burning them

 

[Elvee]

Start with VR2 at its highest resistance, and VR3 at its lowest. This will give the minimal current possible.

 

[frankln]

Start with VR2 at its highest resistance, and VR3 at its lowest. This will give the minimal current possible.