Question about different gnd's on a specific amp

[Ermac]

Originally posted by AndrewT
Hi,
R20 passes ~6mA to the VAS
R22 will start to turn on the protection transistor ~8.5mA.

That means the VAS current can vary by +-2.5mA just as the protection transistor starts to turns on.

R22 should be split into two equal halves, maybe 24r each.
The protection transistor base should be connected to the junction of the split emitter resistor.
Now the VAS can pass 16mA just as the protection transistor starts to turn on.
This gives a VAS range of +10mA & -6mA around the 6mA Iq.

Protection transistor ???
Which one?

[Ermac]

Originally posted by taj
I recognize it too. It's from one of Randy Slone's books, not sure which.

..Todd

You're right! It's design #11.4 in his book.

Are his designs worth to build... or just hobbies?

[AndrewT]

Q17 is the VAS protection transistor.

Driver transistors should not be used for Q5, 6, 7 nor 8.