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In Reply to: My "Jim McShane" Citation II is on it's way back home!! posted by Julien43 on May 11, 2007 at 14:09:26:
Stock circuit upgraded of modded?
Follow Ups:
I want to point out a couple things that others haven't touched on:1. I DO NOT alter the basic circuit topography. I can, I know how, in fact I know that Stu (Hegeman) himself was working on one particular change - but the circuit is a masterpiece, and I feel it would be like painting a mustache on the Mona Lisa!
2. I will not make new holes in the external chassis.
3. I do not remove or reduce the amount of NFB. People who do remove or reduce the loop NFB (or the short internal loops) don't really understand the circuit IMHO.
4. As Eli Duttman has said to me, "if Stu was alive today he'd be happy with what you do with his amps". That's the greatest compliment I could ever be paid.
and can attest to the results.Jim discusses all the updates to the Citation on his web site. Each adds clear performance improvement over the earlier stages.
I do not consider these *modifications*, however, which implies changes in the original circuit topologies. Reason here is that he takes the original design and uses slightly larger values of caps in the power supply - due in part to the fact that they were not available for the price points 40 years ago that they are today. Then he improves the grounding scheme of the original production as well as removing problematic parts like the selenium rectifiers that can cause really bad problems *when* they die.
We're fortunate to have a person so devoted to this particurlar series of high quality tube reproduction to be counted among us.
Cheers,
Jim's mods stiffen the PS smoothing caps superior modern parts, replace the coupling caps with superior modern parts, replace the selenium rectifier, add a soft start circuit and greatly improves the grounding schemeI didn't have the outputs strapped for triode or any other changes to the basic design
Julien
"There's someone in my head, but it's not me"
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