- Jun 9, 2010
- Newhall, CA and Corpus Christi, TX
I am curious the hear an answer to this.
If an amp is designed to be isothermal (meaning, all bias-affecting parts--VAS, drivers, Vbe multiplier, and outputs are closely coupled) then you can set it once when cold and forget it. Oh, and if the Vbe multiplier is a truly constant-voltage design, too (which takes a few more parts than the basic version.)
Basically, don't try to extend experience with one amp design to another amp design. Also, don't try to extend experience with one amp type to another amp type. Vidar, Magni 3, and Loki Mini all share a very similar gain stage. Vidar has to be biased with a constant-voltage Vbe multiplier and potentiometers, whereas Magni 3 and Loki Mini can get away with a couple of diodes and no pots. Why? Because one design has a much larger output stage, with very low-value emitter resistors. The others have smaller output stages, more closely thermally coupled to the diodes, and larger emitter resistors.
Horses for courses. Want to learn more? Start with Bob Cordell's amplifier design book.