Solid State Guitar Amp Forum | DIY Guitar Amplifiers

Howdy folks, i was just surfin the rickenbacker site and i got this cool schematic ,,it looks neat and simple so i decided to included here for anybody interested.
if anybody knows how this amps sounds like let me know.
any explanation about the D1 D2 D5 D6 Q4 Q6 C4 is appreciated
,,have fun

here is the schematic

D1, D2: voltage reference for the constant current load: Note that the base of Q3 is tied to potential which is 26 V (supply) minus two times the voltage drop of a diode. The emitter voltage is one diode forward voltage drop higher than this, thus current over R5 is constant: about 0,65V/220R. You remember how constant current helped in the case of bootstrap? This is a more linear way to do it - less dependent on signal frequency or slightly varying rail voltage. Stuff around Q4 is another constant current source, which uses the same voltage reference (but for reliability is separated by a resistor): It basically replaces the bootstrap.

D5, D6: Just an ordinary rectifier configuration for center-tapped transformers. (CT is grounded).

Q6 is a voltage amplifier (common emitter). It is loaded by the biasing diodes and the constant current source. It is fed by the differential stage and buffered by the emitter follower Darlington stage. You see that the output (taken after the buffer) connects to the differential input stage and thus the amount of feedback is defined by R8, R17, R7, R6 and C5. This feedback arrangement is similar to non-inverting opamp configuration. The whole circuit IS practically just a high power, discrete opamp: The high open loop gain of the circuit is tamed to low closed loop gain by using feedback.

...Oh yeah, C4 is a "Miller" capacitor that provides local negative feedback for Q6. It ensures that gain drops to unity at high frequencies. Its function is to prevent oscillation.

http://www.uoguelph.ca/~antoon/tutorial/xtor/xtor4/xtor4.html

I suggest you get yourself a good analog electronics theory book since any respectable one should cover the theory concerning a similar circuit. For serious learning about amps I suggest you search for books from Randy Slone or Douglas Self.

thnx teemuk for this explanation
i would consider a book but its so hard to find such books where i live.
thats why im goin for the net.
if you know some free ebook i can download it would be great.
thanks again