This one should be sufficient, even for both channels :
SK 47/75/SA
Yes, this amp is pretty simple but it sounds very good. The way it is done gives a very honest sound. With more idle you can make the sound slightly warmer.
SK 47/75/SA
Yes, this amp is pretty simple but it sounds very good. The way it is done gives a very honest sound. With more idle you can make the sound slightly warmer.
thank you for pointing that out... indeed collector current is too low for the 2SA 2SC parts.... will need to buy some D44 D45.
Now regarding class B operation, How can I be sure I have enough overlap to minimize crossover dist ? I know feedback will smooth things out but is it possible the transdiodes are not enough to fully open the ops transistors ?
Now regarding class B operation, How can I be sure I have enough overlap to minimize crossover dist ? I know feedback will smooth things out but is it possible the transdiodes are not enough to fully open the ops transistors ?
Due to the lower Ft of the D44/45 parts you may need to enlarge C6 the miller cap. Experiment with 100p to 1n
if needed.
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It is possible to enlarge the PSSR by splitting the 12K (R5 current setting resistor) in 3k + 6k + 3k, then from the 3K-6K end 6K-3K connection add a capacitor (100~470u) to Vcc/Vss. To add all possible housekeeping, add a diode in parallel to the capacitor K to Vcc, A to 3K-6K and A to Vss, K to 6K-3K. These diodes will empty the capacitors when shutting down. The capacitors also will function as a soft start.
P.s. 3K(2.7K) and 6K(6.8K) will be fine.
P.s. 3K(2.7K) and 6K(6.8K) will be fine.
As i said, the structure of the output stage does not need much idle.
In Douglas Selfs book i found an optimum value of only 15mA.
So first build it and then measure the idle over the low value resistors at the output.
If the sound you get is too " monitor " like you can ramp up the idle up to 150mA.
Watch the cooling profiles not to get too hot.
In my build i used the D44/45 pair and the miller cap was big enough.
Anyway, as Frans said, you can raise the miller cap if you have stability issues.
That makes the amp a little bit slower though. My build goes aprox. to 200kHz -3dB.
In Douglas Selfs book i found an optimum value of only 15mA.
So first build it and then measure the idle over the low value resistors at the output.
If the sound you get is too " monitor " like you can ramp up the idle up to 150mA.
Watch the cooling profiles not to get too hot.
In my build i used the D44/45 pair and the miller cap was big enough.
Anyway, as Frans said, you can raise the miller cap if you have stability issues.
That makes the amp a little bit slower though. My build goes aprox. to 200kHz -3dB.
What is 'super' about this regulator, why the zeners in parallel? what are the 1N4184's doing, are the BC's not a bit small for a soft start, or is there some other purpose (that I fail to see)
What is 'super' about this regulator, why the zeners in parallel? what are the 1N4184's doing, are the BC's not a bit small for a soft start, or is there some other purpose (that I fail to see)
The zeners and the diode form the voltage reference.... the setup aims for lowish impedance and temp compensation.
The transistor and the cap before the reg form a cap multiplier.... it works, I have used this for +- 15v in my cdp..... powering the output opamps....
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