biasing 1176 into class A

[syn]

Apologize for my ignorance. I'd like to change the given line amp into class A darlington output in oder to be capable to drive heavier loads...also would like to speed it up, it is on a slow side a bit as it is now...
I like the way the compressor (sidechain) acts though...

any ideas welcome

thanks

 

[Svart]

From what you've done it looks like you're trying to copy the big bloke output stage?

 

[Samuel Groner]

Well, what load do you expect to drive..? And what do you mean by higher speed--higher slew-rate?

Samuel

 

[syn]

@Svart
bigbloak does come to mind but only as the output transistor type. it is a great op amp, but i'm not sure i like its V bias-ing (4diode string). if i go into this i'll do adjustable V bias for it. i've stated that already under 3. :wink:
@Samuel
around 75-100ohms with as little imd and thd as possible and yes i mean higher slew-rate (higher speed), or maybe i should look into VAS current-sourcing in order to improve that... distortion quiet quickly builds up
if adding the output gain and it is multiplies of 3rd harmonic which makes it quiet ugly...

 

[Samuel Groner]

For such low loads you'd probably want somewhat lower emitter resistors if full output swing is needed.

I doubt that there is any easy way to improve distortion considerably; the basic topology with a single-ended input is just not very well-suited for that. I'd add a dedicated driver, seems to be simpler...

Samuel

 

[tv]

What about something very simple:

replacing the diodes with a red 5mm LED, bypassed by a 1uF ~ish cap ?

(if you want to go fancy, use the BLUE one )