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In Reply to: That sounds similar ! posted by cheap-Jack on March 19, 2007 at 09:41:35:
Thanks, c-J, that is just the sort of comment I've read from a number of people who have tried UL and didn't like it. I believe the ST-70 was designed by one of the founders of UL, if not actually its inventor, so one would think that his UL product should be as good as it gets. (I know the ST-70 front end was mediocre but, hey, we can't all be good at everything!)Yet if, as you say, the ST-70 sounds better in triode mode, then why did he use UL? Could it have been a matter of pride in his own topology, or lack of appreciation of good sound, or commercial pressure to provide more power than triode mode could give?
Follow Ups:
Hi.& was later popularized by David Haflter & Herbert Keroes in early 1950s.
I thought he designed guns for Wyatt Earp? - just kidding ;)Yes, I know what you're saying, that was why I tried to choose my words carefully. However, the fact remains that nothing much came of the idea until, as you say, H & K came along, found out more about it, calle it "Ultralinear" and popularized it.
The question still remains in my mind: Why did Hafler, of all people, design and build a UL amp that sounds significantly better in triode mode? (I'm not speakinmg from personal experience; I've never even seen a Dynaco amp, but you're not the only person who has reported a similar finding.)
Hi.I don't know why this shared O/P load topology was so called "Ultra-linear". Technically, it is sorta kinda a blend-up of a pentode efficieny & a triode low-distortion transfer.
If you compare a U-L transfer chart, you will see the transfer traces look like a very distored triode transfer curve, kinked in a way towards a pentode curve. The curve forms of course change per the tapping percentage on the primary of the O/P iron.
Although commonly it was 43%, but Mullard used 20% & LEAK used 50%.
Both Peter Walker of QUAD, & Williamson objected using the term
"ultra-linear" & preferred the more appropriate terminology of "distrributed load", to which I concur.Put asisde the O/P power efficiency being much better than a trioide, which IMO, is the objective of U-L design, its transfer curve clearly told us it can't outperform a triode's linearity.
So why called it "ultra linear"? I scratched my head on this terminology. IMO, it could be a marketing tactics, who knows?
c-J
Hi ,
Mullard used 20% taps for higher output power or 43% for minimum distortion . Leak designs used 43% screen taps , they also used series resistors between the screen and screen taps in an attempt to reduce distortion . Williamson never advocated ultra linear in the original 1947 article or the later 1949 addendum published in Wireless World . Later designs which were based on the Williamson input stage and driver did . Quad 2 topology is somewhat different to UL , the load is split 90% to the anode and 10% to the cathode , no screen taps at all , this supposedly provides a low output impedence with pentodes with far greater power efficiency than triodescheers
c-J, where did you find it? Please share it!
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