I am just getting into learning the solid state end of thing, as my main area of interest has been valve guitar amps. I have found vacuum tubes to be way more intuitive learningwise, and really feel as if I'm a rookie again now that I am trying to give solid state a go.
I am currently going through bob Cordell's power amp book, and find that the Vbe multiplier is causing some head scratching.
I understand the basic concept of using the Vbe drop of the transistor to create the desired voltage at the collector end of the voltage divider. What is confusing me is exactly what voltage this is referenced to.
Let me ask this another way. On page 42 of bob's book, the basic amp schematic shows a 10ma current source hooked up to the +35 rail feeding the collector if the VAS transistor, who's emitter resistor is hooked to the -35v rail. The spreader is in series between them as seems to be the usual arrangement.
If the spreader wasn't there, what would the voltage be here? I feel it is intended to be at ground, or at least close for the spreader voltage to be correct on both ends, but even that doesn't quite work in my head. I see how the positive end is going to be correct, but shouldn't the negative end of the spreader be the same, only, negative? I just can't make it work in my head, and not being able to understand what the voltage would be at this node if there were no spreader makes it hard to even know where to start.
What am I missing here?
I am currently going through bob Cordell's power amp book, and find that the Vbe multiplier is causing some head scratching.
I understand the basic concept of using the Vbe drop of the transistor to create the desired voltage at the collector end of the voltage divider. What is confusing me is exactly what voltage this is referenced to.
Let me ask this another way. On page 42 of bob's book, the basic amp schematic shows a 10ma current source hooked up to the +35 rail feeding the collector if the VAS transistor, who's emitter resistor is hooked to the -35v rail. The spreader is in series between them as seems to be the usual arrangement.
If the spreader wasn't there, what would the voltage be here? I feel it is intended to be at ground, or at least close for the spreader voltage to be correct on both ends, but even that doesn't quite work in my head. I see how the positive end is going to be correct, but shouldn't the negative end of the spreader be the same, only, negative? I just can't make it work in my head, and not being able to understand what the voltage would be at this node if there were no spreader makes it hard to even know where to start.
What am I missing here?