jc’s DA100 amp

so here is one of these jc morrison circuits in action: the silbatone RI-25, a WE437A–Ed–DA100 amplifier:

the (principle) schematic for the amplifier part, three direct coupled stages. the current sink in the input stage allows for a resistor biasing this stage and a level shifting resistor (just above the mosfet), without losing gain:

the power supply. some well-known jc tricks, like tube diodes that provide slow turn-on of the voltages and dampen the spikes of solid state diodes; chokes in the ground leg of the pi filter. a new trick is chokes before the rectifier: AC chokes, no air gap needed.

combining both schematics above we see that we are missing B+2 from the first one. jc says forget about the resistor in the DA100 kathode circuit and instead there is a bias supply between that kathode and ground, with the main B+ closing its own direct current loop between the top of the OPT and said kathode.

I was happy to see the pic above that proves that the tube diodes are sported at the back, instead of hidden under the hood, because the two pics below were obscuring the fact:


ps: yes, all schematics published with jc’s enthusiastic consent. no, I do not mind it is the version without the part values. we would be lucky to own one of these tube types, let alone the combination. so I-cannot-design-a-circuit-but-I-can-built-it jockeys need not apply. those who can design would make up their own minds about every part anyway. the architecture is fully there in the schematics and the choice of tubes is a choice of ingredients by an amp designer. ‘it is just like cooking’ says jc…