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In Reply to: Citation II posted by Triode_Kingdom on March 18, 2007 at 21:29:32:
So you are saying what here? It can't work well? The Cit II is no good?Look at the marketing material of the day (you can see a 1961 brochure on my site if you want). There was no mention of UL or "distributed load" except in the spec sheet where it describes the output section in just a few words.
I'm confident the choice was made for performance reasons. There is virtually nothing about a Cit II that followed the trends of the day, there's no reason to believe the UL output was an exception to that.
Follow Ups:
> I'm confident the choice was made for performance reasons.Which of HK's product specifications improved as a result of applying the UL technique? If the answer is "none," and if you're correct that this wasn't market-driven, then perhaps it was just an excercise in innovation. Engineers do that sometimes.
"Which of HK's product specifications improved as a result of applying the UL technique?"Improved as compared to what? If there was EVER a "clean sheet of paper" design the II was one of them. And H-K wasn't U/L across the board. The Cit V was a true pentode amp (and it's marvelous!).
"If the answer is "none," and if you're correct that this wasn't market-driven, then perhaps it was just an excercise in innovation. Engineers do that sometimes."
Sure, that happens in a lot of fields.
But in addition to the published material, I've had the honor of speaking with people who were personally well acquainted with Stu before he passed away. They tell me to a man that he was absolutely driven to make the finest amplifier in the world. He could have chosen triode, pentode, U/L, whatever. He had free reign. He chose U/L. And really, by 1959-1960 U/L was hardly an innovation, it had been around for 5-6 years.
There was only one design and one construction compromise in the Cit II that Stu made anyone aware of - and it wasn't the ouput stage.
1. Construction - It had to be buildable by an average Joe - the huge majority of those amps were kits.
2. Design - Stu was not able to resolve a 1 Hz oscillation in the Cit II the way he wanted. He ended up using a different approach to solving the problem than he wanted because he ran out of time to work on it. The amp was scheduled to begin production, and he simply had to use a less elegant solution than he preferred.
With the benefit of way more time and much better parts than he had, I've been able to eliminate the 1Hz oscillation without applying Stu's fix. I must tell you, his fix may not have been as elegant as he wanted, but it is totally inaudible - and fixes the problem.
In light of all this, do you still believe he used U/L just as a marketing gimmick, or just to prove he could??
> In light of all this, do you still believe he used U/L just as a marketing gimmick, or just to prove he could??Please don't misquote me for your own purpose. You said earlier that you are confident the choice was made for performance reasons. To that, I asked which of HK's product specifications improved as a result of applying the UL technique? I was of course referring to HK's previous/parallel, non-UL power amplifier products and circuitry. If you have no definitive answer to this question, then I think it might be difficult to demonstrate that the basis for designing a UL output stage was performance-motivated.
One last issue here. You wrote in two earlier posts:"The popularity of UL had as much to do with marketing as anything else."
And later:
"If the answer is "none," and if you're correct that this wasn't market-driven, then perhaps it was just an excercise in innovation."
In my reply I wrote that "In light of all this, do you still believe he used U/L just as a marketing gimmick, or just to prove he could??"
That was not a quote, I was paraphrasing what you said. In light of your actual quotes above, do you think I paraphrased inaccurately or inappropriately? I apologize if I did, but I really don't think that's the case. Other viewers of this post can decide for themselves I guess.
You weren't misquoted - your actual quotes are in my post so there is no possible way to misquote you. No way."You said earlier that you are confident the choice was made for performance reasons."
Yes, and that was based on a number of different things as I said.
"To that, I asked which of HK's product specifications improved as a result of applying the UL technique? I was of course referring to HK's previous/parallel, non-UL power amplifier products and circuitry."
There was VERY little in the Cit II that was common to any earlier H-K stuff. No other H-K product up to that time had used that tube set, those OPTs, the multiple loop NFB, the low impedance power supply, and so on. What is it about "clean sheet of paper" that you don't understand? Do you really want to compare the Cit II to an A-300?? It's ludicrous.
If the change to U/L was the only change (or the only significant change) then your narrow-focused question could be answered. But there really is no H-K product to draw a direct comparison to!!
It doesn't mean anything, but since you seem intent on having some sort of answer (relevant or not), here is a quick list.
Compared to prior H-K designs, the Cit II...
1. Had octaves wider bandwidth
1a. Had an OPT resonant frequency in the 450K area! This made a lot of other things possible in the design.
2. Had much higher RMS and peak power
3. Had lower THD at a given power output
4. Had lower hum and noise
5. Had a higher damping factor
6. Used much higher total NFB. Used lower loop NFB.
Properly implemented UL will show better open loop performance than pentode as regards bass distortion and load tolerance, with a relatively small penalty in efficiency. Compared with triode, it will have less Millering (hence better OL bandwidth and a better spreading of the poles making feedback more stable) and markedly better efficiency. Some of these things will show up on the spec sheet (power), some won't (LF distortion, load tolerance) but will be audible. Your Procrustean restriction to the spec sheet alone is curious and telling- do you really think that all design virtues are contained therein?The two key words are "properly implemented." Slap a cheap piece of shit transformer in and you'll have grief; the best topology for shitty transformers is probably Circlotron.
disclaimer: My own design choices do not include ultralinear. But in the past I've built UL amps with excellent performance, so it's not beyond the capabilities of a DIYer.
> Properly implemented UL will show better open loop performance than pentode as regards bass distortion and load tolerance
Ahh, semantics. Very good.
they hapeened to have a U/L tap? ;-)
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