What do you think about this Amp

[bostjancek]

Hello !

What do you think about this 50W/8E Amp - it's worth to build it ? Do you sugest any modification ?

 

[mikeks]

Hello !

it's worth to build it ?

No...Both gain stages are not optimised for high gain at low distortion....

Even worse, the output stage employs a simple current limit...Which limits output current when it isn't necessarily required, and doesn't when it is needed....Bad!

 

[bostjancek]

Thanks for your oppinion !

Cheers

 

[amplifierguru]

Yes,

I would not operate a BJT amp (unless dedicated to a known load) without at least 2slope SOA VI limiter. that could be fixed with 1 more resistor,2 diodes and a couple of small c's for lagging.

Mikeks could do it in his head I'm sure?

rest of the cct is pretty ordinary but functional.

 

[darkfenriz]

I wonder what is 6.8k||0.1u for.

 

[amplifierguru]

Hi darkfenriz,

The 6K8//100n is to equalise dissipation in the diff'l pair, as the other one is cascoded and not seeing full rail voltage. Matching the dissipation helps minimise DC drift.

Greg

 

[darkfenriz]

my question was rather why not casode the second diffy transistor or use a zener?