JamJar: an HPA-1-inspired power amp

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James Solomon wrote the same things in July 1974. But since his article was in a professional journal for degreed EEs (IEEE Journal of Solid-State Circuits), for the most part only degreed EEs are aware of its existence. Bob Cordell's book quotes from it extensively, perhaps because Cordell himself is an EE with a long and storied career at Bell Labs. You know, the place where they invented the transistor.

link to Solomon

Don't be scared: the Blameless power amplifier is just a great big opamp. So is the HPA-1. So is the Hitachi. Same design principles throughout.
 
Pico,

Please could share some basics(general) of you regulator, so we may prep.

I would like to start a pre-amp thread after that.

Jam

I might post it in the thread I started before I went MIA and post it here.
Just give me at least another day just to be sure it can't be significantly improved further, I am currently running out of ideas to try.

Well I am sure it still will be tweakable for further incremental improvements, but apathy sets in at some point.
 
Today's toon............
 

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Hi Jam,

No, they're just flipped around to make wiring easier. The top (from left to right) is driver, cascode while the bottom is cascode, driver.

Of course it would have helped if I had given you guys the schematic. :eek:

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There was an error in the bias spreader, though. It still had the decoupling capacitor from the single-ended-VAS Beefcake.

Fixed version:

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Also you could put a 2 ohm trim pot connected to the sources of the jets and the feedback loop to adjust the sound to your liking.
1 Ohm source resistance on each jet is virtually zero degeneration and you get some adjustment.
If you didn’t want to add it you just put in links.
It will make the amp pcb way more versatile and give people more options for tweaking.
 
I see. The Oppo is a rather poor sounding example of an ESS ES90x8PRO evaluation board, IMHO. No wonder to play with the sound of amps in that case.
DACs can be far better sounding. Rather than amps, DACs are more of the focus of my audio hobby. At least for now :)
Jam knows since we live in the same town and visit regularly.

Anyways, if you or anyone else is interested in really good DAC sound, maybe we could find an appropriate place to talk about it.
 
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