As i felt like a deep unjustice to not even mention Lars's old design once in a decade, I start this topic with its schematic as it was once published on Olive audio.
It was the first high power amp i built, even modified it for use with complementary fets which is simply done by removing t14 and r29 and replacing all n channel tarnsistors with P channel ones, reversing the source resistors place of course .It worked flawlesly on a pcb i'd be ashamed to post...At the time there were the Holton amps in vogue, but having built both i was convinced that Lars's Zeta was the better one. it worked very well from +-90v to +-9 v .using only one pair of transistors and +-35v supply makes for a very good home amplifier .
As i don't find any explicit ban for posting its schematic anywhere i'll do it.
It was the first high power amp i built, even modified it for use with complementary fets which is simply done by removing t14 and r29 and replacing all n channel tarnsistors with P channel ones, reversing the source resistors place of course .It worked flawlesly on a pcb i'd be ashamed to post...At the time there were the Holton amps in vogue, but having built both i was convinced that Lars's Zeta was the better one. it worked very well from +-90v to +-9 v .using only one pair of transistors and +-35v supply makes for a very good home amplifier .
As i don't find any explicit ban for posting its schematic anywhere i'll do it.
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there's a 10k ohm resistor there limitting the current...you can probably make it smaller for lower V supply. I used bd139/140 at the time.also used bf423/bf422 instead of some 2n5550 /5401 as i didn't have them...used a lot of transistors from scraped CRT tv sets at the time,15...16 years ago.i might still have the pcb somewhere...can't remember exactly what fet transistors i used...probably irfz9640/640...
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Thank you for the Zeta....my first nostalgia Amp on Diyaudio. How much bias current recommended with two pairs at 45 Vdc? Thank you.
I have no idea...I don't think it really matter with fet transistors unles you're going to use it with all 6 output pairs on 2 ohms loads at max V supply. I'd simply use it with one single pair of final transistors on 8 ohms quality speakers and it should work very well as is. For years ai craved to rebuild it but for some reason i never got back to it.
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