875c93f4   
   From: IanIveson.home@blueyonder.co.uk   
      
   Patrick Turner wrote:   
      
   > I see New Sensor is putting out Tungsol KT120 tubes whch   
   > bias like   
   > KT88 but have Pda = 60W.   
   > I read a few forums comments and I guys are happy with the   
   > new tubes.   
   > BUT, they will cost a bomb. About twice the price of a   
   > 6550.   
   >   
   > And when I saw the anode curves for the KT120 it was all   
   > horrible to   
   > look at.   
   >   
   > But then these curves had quite irregular shapes to part   
   > of them and   
   > look like they were drawn up by someome who does not know   
   > what they   
   > are doing. Plus the voltage range over which the tubes   
   > were tested to   
   > get the curves did not extend to the max Ea and max Eg2   
   > which are both   
   > +650Vdc. So I whoever made the tests and drew the pictures   
   > does not   
   > have a very good test set or the experience of those   
   > genuine people of   
   > the 1960s who spent their lives testing tubes.   
      
   Or has a better test set and/or greater knowledge. Or knows   
   how to test but falls short of the standards set in the 60s   
   for genuinely fiddling the results.   
      
   > The new tube seems aimed at guitar people who like rugged   
   > tubes and   
   > where the distortion does not matter; in fact the more THD   
   > the better   
   > as long as nothing clips.   
      
   Er, not quite. If distortion were the only objective they   
   would use transistors.   
      
   > The KT120 looks like the the insides simply have a 35%   
   > taller plate   
   > structure and taller bottle than a KT88.   
   >   
   > So with a taller plate there is more area to get rid of   
   > heat hence the   
   > improved Pda. But what about the rigidity of the longer   
   > cathode tube   
   > and the alignment of grid to cathode spacing? With extra   
   > length there   
   > must be more tendency for the hot structure to bend or   
   > sway with   
   > disatrous results.   
      
   Just what I thought. There are quite a few modes of   
   vibration...side to side, up and down, and rotation about   
   three axis, each for lots of bits relative to lots of other   
   bits, etc. etc. All in all, however, we have the impression   
   that long thin things, including "pin ended" beams like   
   bridges or joists, are weak or floppy. If they compensate by   
   making the grid support rods thicker, they risk changing the   
   characteristics of the valve perhaps. Maybe they use modern   
   material to make stiffer thin structures despite the change   
   in aspect ratio. Or maybe they just make everything longer   
   and hope they recoup the investment before anyone notices   
   they sound bad and fall apart in no time.   
      
   >   
   > The Electro Harmonix KT90 had Pda of 55W and looks just   
   > like a   
   > KT88/6550 but with taller plate but straight sided glass,   
   > like an EL34   
   > which has been fed steroids for a year. Initially, the   
   > KT90 were a   
   > reasonable buy because the price wanted was only a bit   
   > more than a   
   > 6550. But that seemed to change.   
   > Seems to me New Sensor is again "stretching" the KT 88   
   > upwards even   
   > more than they did with KT90.   
   >   
   > But if a 6550/KT88 is $30, then when stretched upwards, it   
   > should only   
   > cost for the extension in height of 35% so $40.50, not $70   
   > being   
   > talked about.   
      
   Ah, but not if they've actually solved the problem of   
   retaining stiffness. Maybe they've used an exotic   
   titanium/carbon nano-tube composite for the grid support   
   rods, so they're twice as stiff and half the weight. Or they   
   just put the price up because there are fewer rich people   
   now, but each of them has more money.   
      
   > Two KT88,6550 will cost less than one KT120 and the Pda of   
   > the two   
   > KT88/6550 = 84W,   
   > and so a quad of KT88/6550 are going to beat the pants of   
   > a pair of   
   > KT120.   
      
   As would a hundred EF96. But you need to include the cost of   
   extra bases, wiring, bias provision, heater current, chassis   
   work, and the general perception that fewer, bigger valves   
   are better.   
      
   > But for those that must have the latest gizmo, you know   
   > where to go to   
   > spend up.   
   > But don't expect any more power or fidelity than you are   
   > getting now   
   > with KT88/6550.   
   > The curves I could see do not indicate any more anode   
   > voltage swing is   
   > available if you just switch to KT120. Are the curves as   
   > good as for   
   > the NOS KT88? I don't think so.   
   >   
   > Many makers are already pushing their luck by running 6550   
   > with Ea too   
   > high and RL too low.   
   >   
   > There seems to be an absurd trend where there is never   
   > enough power,   
   > even with so called hi-fi amps they are set up in nearly   
   > all class B   
   > working with low load and high Ea to get the sales figures   
   > and to hell   
   > with the idea that for hi-fi about 50W max is all that   
   > should be ever   
   > asked from a pair of KT88/6550.   
      
   Something to do with modern speakers in big rooms maybe. The   
   room size of the average audiophool is much bigger now.   
      
   > I found the Sovtek small bottle 6550 and KT88 were   
   > excellent value for   
   > the price. The guts of these didn't change when the bottle   
   > size   
   > increased for the Electro Harmonix name range. OK, It was   
   > all a   
   > marketting ploy eh, to get away from the old association   
   > of Sovtek and   
   > the evil empire of the Soviets and USSR. I wonder how Mike   
   > mathews is   
   > getting on with the Russian Mafia boyos who tried to put   
   > the squeeze   
   > on him for a rouble or three. Maybe Mike needs the money,   
   > but then we   
   > could all say that.   
      
   Erm, logic has never been you're strong point. Why wait for   
   the collapse of the "evil empire" before changing the name?   
   The Soviet Union, and several of its dominions, had a   
   reputation for the mass production of primitive but famously   
   tough and serviceable engineered goods, such as tanks,   
   rockets, planes, cameras, machine tools, and valves.   
      
   "Soviet" was a very successful fashionware label here. It   
   had a kind of heroic ring to it. They did, after all, win   
   the war against Fascism.   
      
   Incidentally, the UK's new Conservative government is   
   pushing the idea of soviets to replace parts of local   
   councils, but they don't use the word, obviously. For   
   example, they reckon they can get parents' commitees to set   
   up schools. It would be cheaper if it worked, but naturally   
   it won't, and in some of the more sordid suburbs, the   
   results wouldn't be what we might hope for anyway. I guess   
   the idea is just one of many imaginative ways they are   
   finding to blame the poor for the shit we're in. It's a lot   
   easier to take £1 from 60 million people than it is to take   
   £60m off one rich bastard.   
      
   Meanwhile, since I'm digressing, that's my pension washing   
   up on Florida beaches.   
      
   Perhaps we should all call it a day and make digital stuff   
   instead. You argue that energy profligacy is OK because   
   there aren't many valve amps in the world, but that's a   
   typical capitalist fat cat argument if ever there was one.   
   By the same token, they'll be able to keep their useless   
   powerboats and private jets when the proletariat are forced   
   to ride bicycles to save the planet.   
      
   Except we can't make digital stuff, because the active bits   
   are so small we can hardly see them and certainly can't   
   solder them. Shame coz, being so short, I guess they're   
   pretty stiff.   
      
   All in all, if you're wondering where valve technology is   
      
   [continued in next message]   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)