Thanks Richard for your effort. You have first version with the RC over VAS emitter resistor. Latest version is simulated only, not real test yet.
BR Damir
That looks very good
How can you replace a VAS emitter resistor with a diode?
What resistor value do the Diode have with the current used in your schematic?
Will you make a 100W@8 ohm edition of you fine amplifier?
That looks very good
How can you replace a VAS emitter resistor with a diode?
What resistor value do the Diode have with the current used in your schematic?
Will you make a 100W@8 ohm edition of you fine amplifier?
Diode dynamic resistance at the VAS bias current is very low and here diode just add 0.65V about to the VAS emitter voltage. The VAS bias current has very little influence on it.
To make 100W/8 ohm version just remove one pair of the drivers and corresponding output pairs. What is missing is a layout for it.
Maybe those plots can explain why this amp measure so good and sound good in the same time at all power levels. These are output HEXFET currents at different wattage, 1W, 10W and 100W on 8 ohm load, simulated of course. Last plot was expanded around zero current to show that behavior better.
Damir
Damir
Attachments
I never considered to make single side pcb as this asks for to much compromises and will degrade quality of the amp.
From first PCB batch I've ordered I sold two pairs and the rest I used. For the moment there is no PCB offered, maybe after summer if there is going to be interest.
Very nice Toni,
I suggest you to start to solder from the input. You can test input part separately then together with VAS and if all works correctly the rest is simple.
You can measure the voltage drop on the Q2, Q14 emitters resistors and if there to much differences (matching not perfect) it can be corrected by changing one of the input CCSs (R4 or R7) current.
BR, Damir
Please share your schematic for the matching, I am currently building a hfe and vbe matching tester, similar to your with the same construction techniques. Great Minds Run Together...
Attachments
Voila ... a bit off topic. I do not want to pollute Damir's thread. So if there is more interest maybe you open a new thread.
You need up to 3 multimeters with USB support to automatically read the measured voltages. Schematic is pretty useless without homebrew PIC software and homebrew pc software (perl script to control relay board and read and convert raw voltages from USB multimeters).
BR, Toni
Attachments
