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RE: HK Citation 2 rebuild questions

Posted by Jim McShane (D) on April 19, 2015 at 15:57:55

In Reply to: RE: HK Citation 2 rebuild questions posted by Ping on April 19, 2015 at 07:57:58:

I'm bowing out after this - think what you like.

On guitar amps - I supply tubes to some of the smaller "boutique" amp makers out there. A LOT of them use TONE CAPS such the very popular Sozos that were not even around in the old days. And besides, they are not seeking fidelity; they are seeking a tone that is often based on deliberately induced distortion.

Why did I say I designed 3 amps (actually one was a preamp)? Because you asked and though I don't consider it relevant I wanted to answer your inquiry.

Why do I say what I say about Stu Hegeman? Because I HAVE communicated with a couple of today's designers who DID speak personally with Stu before he died and who HAVE told me that what we do with the Citation gear is terrific and in keeping with the original design intent he had. Now if they are lying to me then I'm off base, but I don't think they are.

BTW, he WAS limited in some of what he could do. There was a very low frequency oscillation in his prototypes that he struggled with, and he wasn't able to do exactly what he wanted to "fix" it because he had to have a design ready for production in short order. Also, I'm told by people who knew Stu that he felt that an ultralinear configuration may not have been the best choice for the amp, he preferred pentode mode. He was pushed by the sales guys to get the amp to produce very low distortion while putting out as much power as possible. The specs of the amp were a key part of the advertising pitch. Stu was a recording engineer, he wasn't a "specs" guy, so some design conflict was probably inevitable.

A quick thought about power supply capacitors - they and the semiconductor diodes were two of the most expensive small components in the amp. I'm not even sure they could be had in the day, but with the heat under the hood of the Cit II chassis I cannot imagine that Stu would not have used 105 C rated electrolytics if they were available at an affordable price. Nor would he have failed to utilize the other attributes of modern capacitors such as compact size, long life, low ESR and DF, and the myriad of other highly desirable characteristics offered today. FYI, MANY of the developments in these capacitors (and diodes) came about as the result of the switched-mode power supply and the constant demand for improved performance at less cost in less space. None of that development was present when the Deuce was deigned.

The diodes and capacitors? Please search out and read Rick Miller's 1990 (IIRC) design-changing Audio Amateur article regarding diode noise performance and the early 80s Walt Jung and Richard Marsh article "Picking Capacitors". You'll see how products not available to Hegeman made/make improved performance possible. Rick's article demonstrates using sound science that diodes like the top hats and even later pieces such as the 1N4007 sounded NOTHING like a tube rectifier due to the presence of relatively large amounts of PN burst noise generated by the minority carriers (holes) moving across the junction. That noise is completely absent from vacuum diodes (and Schottky diodes) as there is no mechanism to generate it. And it is only present at greatly reduced levels in modern fast/soft recovery diodes.

As far as mentioning what I did about the amp I sent to Phil Palombi... it is only relevant because I find that he and his comrades in the world of jazz (Phil was a classically trained bassist BTW, so he brings a lot to the table) have the ability to hear music far better than I do. So I value his opinion more than mine for that reason, and because he has no bias towards it like I may have. I did not mention that based on my reputation a number of other very well respected listeners have sought "McShaned" Citations. Dick Olsher (formerly of Stereophile and other respected publications, now writing for The Absolute Sound) sent me a Citation II amp to do for him. Sadly the core amp he sent was totally destroyed by UPS during shipping, and that project never came to fruition. My friend Dr. Norm Thagard, CNN expert correspondent, space shuttle astronaut, and audio design associate of Nelson Pass uses EIGHT "McShaned" Citation IIs in his home system. You can read about the special preamp Norm designed to drive all the amps in a back issue of AudioXpress.

At CES a few years ago a cable maker used his "McShane/Citation" at the show, and he got some amazing comments - here's just one:

""... a cable competitor, (name removed to protect the innocent and guilty), came by on a scouting mission. His interconnects start at about 6 times what our line tops out at, but he was very interested in our design and wanted a good listen. We played "freedom in the groove" for him and he said "this sounds very nice" and I started talking about the bang-for-the-buck factor with the $2k (McShane/Citation II) amp and $1k speakers and he stopped me mid sentence. "It sounds very nice at any price" he interrupted."

There's more, but no kidding - doesn't it seem like maybe there is SOMETHING worthwhile going on with these amps??

Finally, I never "attacked" you, but if you took it as an attack because as I stated before THE PREPONDERANCE OF EVIDENCE points in a different direction than your thinking it is certainly regrettable. I am sorry you took it that way, but only you can decide how to react to what I posted. Maybe I should not have said "facts", I should have just said "the preponderance or weight of empirical evidence". So my apologies for not defining my position more clearly and less controversially.

Edits: 04/19/15

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