From whatever I have searched so far I have only found good things said about UL as to how it combines the best of both the triode and pentode. Sometimes authors hurriedly mention that critics of UL believe it also brings with itself the worst of both the triode and pentode, and they just leave it at that without going into the trouble of explaining it.
I would like to know what drawbacks exactly are we talking about ?!
I would like to know what drawbacks exactly are we talking about ?!
percy said:
Well obviously, because they can't. Hey, can you explain to me why patch cables supposedly sound different? No? I don't blame 'ya.
[Edit] If you want my scientific opinion, it's a good way to compromise between distortion and power. A little global NFB is usually necessary to bring Zo down, which also reduces distortion to better levels.
If low distortion is the goal, a pentode amp with as much open-loop gain as possible will serve you well. Mind the phase shifts and get a very good OPT...
Tim
Re: Re: What's wrong with UL anyway ?
But then the purists will hound you and burn you at the stake!
If I may hazard a guess as to why some people don't like UL, it may be because it reduces the open loop gain (by lowering the output stage gain), thus reducing the amount of available feedback. But there is more local feedback around the ouput stage, so this isn't really a huge problem. Or maybe they just don't like the "sound"
Sch3mat1c said:
But then the purists will hound you and burn you at the stake!
If I may hazard a guess as to why some people don't like UL, it may be because it reduces the open loop gain (by lowering the output stage gain), thus reducing the amount of available feedback. But there is more local feedback around the ouput stage, so this isn't really a huge problem. Or maybe they just don't like the "sound"
I suspect one reason UL has failed to gain universal "approval" is because it's just too easy a solution for some people's taste. Compared with pentode mode, UL avoids having to provide a separate screen grid supply; it produces less THD but still retains a large proportion of the power capability of the tube; it has lower output impedance, i.e. better damping; and the load impedance is much less critical. Another reason is probably because it is a compromise: the "purists" prefer DHTs and the power mongers prefer straight pentode/beam tetrode.
Personally, I'd like to try UL. The reason I don't use it is just because my OPTs don't have the necessary primary taps. I'd also like to try cathode feedback, which, I suspect, would be at least as good, but I have no suitable winding for that either.
Personally, I'd like to try UL. The reason I don't use it is just because my OPTs don't have the necessary primary taps. I'd also like to try cathode feedback, which, I suspect, would be at least as good, but I have no suitable winding for that either.
Dare I say it, it's impossible to take someone's opinion on matters of tube audio if you don't know what camp they're in. From what I can tell, you've got three types of people:
1. Ones who feel tubes sound better than SS but only when using the best designs that produce the lowest distortion (ie: all distortion is bad). Tubes that have the best frequency response and dynamics are sought after and preferred - not ones that sound nolstalgic and "tubey".
2. Ones who are after a classic warm sound and don't mind if their music has rolled off bass/treble or lacks dynamics. These types go crazy over expensive NOS tubes.
3. Ones who believe in voodoo. There's even these guys on the SS side. They bless their speaker cables with holy water, use power cables of sufficient gauge to supply a city block (never minding the condition of the wiring in their walls, main panel and all the way back to the utility transformer), leave tubes outside in the sun to absorb photons which makes the music sound brighter (I'm making this up), think they can hear the difference between brands of RCA cables, etc.
I will definitly say, if you take advice from the wrong person, you won't end up with your system sounding the way you want it to. I personally think ultralinear sounds good. But I also don't consider being told my tube rig "sounds like very high end solid state" to be an insult.
1. Ones who feel tubes sound better than SS but only when using the best designs that produce the lowest distortion (ie: all distortion is bad). Tubes that have the best frequency response and dynamics are sought after and preferred - not ones that sound nolstalgic and "tubey".
2. Ones who are after a classic warm sound and don't mind if their music has rolled off bass/treble or lacks dynamics. These types go crazy over expensive NOS tubes.
3. Ones who believe in voodoo. There's even these guys on the SS side. They bless their speaker cables with holy water, use power cables of sufficient gauge to supply a city block (never minding the condition of the wiring in their walls, main panel and all the way back to the utility transformer), leave tubes outside in the sun to absorb photons which makes the music sound brighter (I'm making this up), think they can hear the difference between brands of RCA cables, etc.
I will definitly say, if you take advice from the wrong person, you won't end up with your system sounding the way you want it to. I personally think ultralinear sounds good. But I also don't consider being told my tube rig "sounds like very high end solid state" to be an insult.
Percy: In a properly-balanced output stage, even harmonics are mostly cancelled regardless of the topology. Sad as it is to say, Ray's take is probably the closest. If you can get a copy of Crowhurst's "Understanding Hifi Circuits," he digs into the technical plus and minus of each output stage topology in great detail. Some of what you're looking for can also be found in the Mullard tube manual.
I guess I'm in the 4th category, since none of the three that Powercntrl mentioned describe me at all.
I guess I'm in the 4th category, since none of the three that Powercntrl mentioned describe me at all.
Sy,
my understanding about even-harmonics and output stages is that the even order harmonics produced IN a P-P output stage (i.e within the stage itself) are cancelled but the ones coming in from preceeding stages get amplified just like any other.
I guess I'd count myself to be in category 1.75 .
I will pull out the crowhurst book now...
my understanding about even-harmonics and output stages is that the even order harmonics produced IN a P-P output stage (i.e within the stage itself) are cancelled but the ones coming in from preceeding stages get amplified just like any other.
I guess I'd count myself to be in category 1.75 .
I will pull out the crowhurst book now...
You have to realize that EVERYTHING you read in the "high-end" audio press is mindless rambling. And, no, that's not an opinion. That's a matter of fact. I visit the Stereophile web site from time to time, mostly for kicks. And I haven't read an article or feature where the author doesn't contradict himself at least once. They will bend everything to fit their agenda. It's impossible for any reasonably intelligent person to take anything on that site seriously. I don't know about grade school, but it wouldn't pass muster in high school. At that age you are expected to grasp the fundamentals of reason and logic.
Lets get a few things straight. There's as much difference between various tube amps as there is between some tube amps and solid-state amps. Tube fans simply can't tell a tube amp from a solid-state amp in a blind test.
In other words, hoping for an explanation is futile. There is none.
Lets get a few things straight. There's as much difference between various tube amps as there is between some tube amps and solid-state amps. Tube fans simply can't tell a tube amp from a solid-state amp in a blind test.
In other words, hoping for an explanation is futile. There is none.
phn said:
Hoo....laying down the gauntlet on this lot.....actually I agree with the first point 100% all is brainwash.....but I can tell the difference between tube and solid state amps. The tricky I'd admit but an UL cathode biased stage and true class A v.s a good solid state amp is competition......but the tube sound has a freer bass and the timbre harmonic of the symbals with a brush gives it away. As someone else mentioned quote...< solid state amps with piles of nfb; sound as flat as a pancake..lifeless>.
more anon ??
GEC <audio amplifiers preamble> dated march 1979 ,
MO valve Co Ltd Brook Green works, London.
richj
percy said:Hmm...I was atleast hoping to see some more technical discussion. atleast one post that mentions something about the amount of even/odd harmonic distortion as compared to other output topologies(triode, pentode, se, pp). and ofcourse how it sounds as compared to those.
http://www.lundahl.se/claus_b.html
and,
http://www.lundahl.se/claus_b_se.html
Answer - Not Much
I like Ultralinear.
Its faster, better pace, rhythm and attack than triode mode
Its lower output impedance than pentode mode and therefore requires less feedback to achieve a good damping factor.
Harmonic Distortion is less than either Triode or Pentode Mode
Intermodulation Distortion is less than Triode or Pentode Mode.
These last two items tell me its more linear than Triode or Pentode mode and rule 1 for any feedback design is make it as linear as possible BEFORE applying feedback.
AND not insignificantly - it sounds lovely and is simple. My very first valve amp project was an Ultralinear EL84. Its still one of my favourite amps - the whole glorious 10W per channel of it.
My current project is a 30% Ultralinear plus 10% Cathode feedback design using VDV2100-CFB/H Toroidal Output trannies.
Cheers,
Ian
I like Ultralinear.
Its faster, better pace, rhythm and attack than triode mode
Its lower output impedance than pentode mode and therefore requires less feedback to achieve a good damping factor.
Harmonic Distortion is less than either Triode or Pentode Mode
Intermodulation Distortion is less than Triode or Pentode Mode.
These last two items tell me its more linear than Triode or Pentode mode and rule 1 for any feedback design is make it as linear as possible BEFORE applying feedback.
AND not insignificantly - it sounds lovely and is simple. My very first valve amp project was an Ultralinear EL84. Its still one of my favourite amps - the whole glorious 10W per channel of it.
My current project is a 30% Ultralinear plus 10% Cathode feedback design using VDV2100-CFB/H Toroidal Output trannies.
Cheers,
Ian
I don't know what the disadvantages of UL are. Some folks (Brits mostly) believe that loading the cathode nearly equally with the plate (distributed load a la Quad) is better, although the rarity of these amps may prove otherwise. By the way, UL output stages have plenty low enough output impedence so that more feedback isn't necessary, except for scope jockeys competing for "clean" sine wave performance.
Furthermore, reduction of even order harmonics only works for sine wave signals (do the math), which may explain why push-pull amps really don't sound as non-euphonic as we are supposed to believe they do.
John
Furthermore, reduction of even order harmonics only works for sine wave signals (do the math), which may explain why push-pull amps really don't sound as non-euphonic as we are supposed to believe they do.
John
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