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Thread: What are the best 6550/KT88 tubes for 2011?

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    What are the best 6550/KT88 tubes for 2011?

    I am looking to buy an octet of power tubes for my bass amp. I have not been using any of these recently and was wondering which ones were the most reliable and which seemed to have the best sound. Thanks, B.

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    I've been doing a lot of research on new KT88 & 6550's and I believe you may want to go with KT88's.
    Many long time, old time and hard time users running them in high plate voltage amps have provided great input and it's come down to either Winged C's or JJ's for sound and durability.
    I planned to buy several quartets in the near future for my Marshall Majors and Model T.

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    Noodle of Reality Steve Conner's Avatar
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    6550s and KT88s are not quite the same. The 6550 has more "outer mu" and so likes to run with a lower screen voltage. It may not be as happy as a KT88 in an ultralinear circuit like the Major.

    That was historically the case, anyway. The reissue 6550s and KT88s might share the same innards.

    I personally liked the Russian "Tung-Sol" 6550 reissues, but you won't go far wrong with the JJ or Winged C tubes.
    "Enzo, I see that you replied parasitic oscillations. Is that a hypothesis? Or is that your amazing metal band I should check out?"

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    I do like the Russian Tung-Sol 6550 RI's which are in one of my Majors and I've also tried them in my 1st gen Model T, not quite like the original GE Tung Sol but very close I will say...

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    Thank you, I am putting these in my Peavey Classic 400 bass head.

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    Does any one know what the differences are between the RI Tung-Sol and the regular Sovtek?

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    Replacing tubes in my 1969 SVT

    I'm also in the market for replacing the 6 power tubes in my amp. Are there any other vintage SVT users out there that have feedback on this subject? Mine has been modded to use the 6550's. I've been leaning toward JJ's because I have heard they sound great but are not consistant/dependable...?

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    I have read the same, but my experience has not matched that. I buy my JJ tubes from Bob at eurotubes.com. I have had no problems with the pre or power tubes I've purchased from him, but I'm admittedly not a high volume user, so take that for what it's worth.
    -Mike

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    Noodle of Reality Steve Conner's Avatar
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    Quote Originally Posted by MstrB View Post
    Does any one know what the differences are between the RI Tung-Sol and the regular Sovtek?
    I've got a few of each. Different shape bottle (the Tung-Sol is coke bottle shaped, the regular Sovtek 6550WE is a plain cylinder) and better quality construction (Tung-Sols feel nicer, thicker glass, more getters, no rattles) as far as I can see. The guts look the same apart from that.

    If you want different guts, the only other choice is the Winged C or JJ, I guess.
    "Enzo, I see that you replied parasitic oscillations. Is that a hypothesis? Or is that your amazing metal band I should check out?"

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    I've had few issues with the EH 6550 or KT88. They sound good and have lasted, so I continue to use them, rather than going "uptown" with another pricier New Sensor reissue from Tung-Sol, Gold Lion, etc.
    John R. Frondelli
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    'If you want different guts, the only other choice is the Winged C or JJ, I guess.'
    I think that chinese made 6550 and KT88 are available, branded Gold Lion and Valve Arts. Pete.

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    Winged C's vs JJ's

    A friend recently put these two to the test and mentioned the Winged C's (SED?) did not hold up when higher voltages were applied? Maybe for 100w users that is ok. Since I'm looking specifically for my SVT , I'm guessing JJ KT88 would be best unless I hear more opposition? Also..... are the blue and red glass just for looks and function the same? Does JJ make gold pin kt 88 and are those better as well?

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    Old Timer km6xz's Avatar
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    How was the amp set up that failed with Svetlana Electron Device 6550's? From my experience they are the most rugged of the tubes sold as 6550 but also most expensive. Their wholesale prices just went up again.
    There is so little data on any of these tubes, just opinion and rumor that flipping a coin will likely be as useful as asking how a brand of tubes are since most brands are different labels, and prices, not different tubes. There are only a few plants making 6550 style tubes a couple in China, 2 in Russia and 1 in Slovak Republic, and 100 brands sold for vastly differing prices of those same 5 plants. There has been no new developments in 40 years in glass tubes so don't expect any breakthroughs with any. The companies selling tubes are marketing, not R&D facilities. Buzz words, claims of magic mojo and killer tone are all hollow, backed by nothing but marketing hype, particularly the reviews of tubes by sound. How a tube performs in your SVT will be determined more by the way the amp was serviced than by the tubes selected. When you hear of people needing tubes often in them, the tech is more responsible than the factory that made the tubes. If not set up well, it will go through tubes of any brand.

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    Senior Member Pedro Vecino's Avatar
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    I've tried many SVTs (Classic, Vr, II pro, etc.) with different tubes. With 6550 Svetlana sounds more musical than with 6550 Sovtek (deeper and wider. With more dimension and better overall balance). Matching is important, and Groove tubes and TAD offer better matching than original Ampeg equipment (6550 Sovtek).
    The JJ KT88 through Groove Tubes sound more solid/rocky but it is a matter of taste. They are also mechanically stronger and more stable electrically.
    Even with small differences in plate current between them, itŽs desirable to measure and distribute them as symmetrically between sides.
    A good selection of preamp tubes is also important. I always use in the driver circuit good ECC83/82Žs. Philips, Mullard, RT or other NOS tubes. You'll get more musicality/dimension and without the premature compression of 12AX7A Sovtek and 12AU7EH or similar.
    Regards

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    Old Timer km6xz's Avatar
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    I might be a little dense but what measurable trait(s) of a vacuum tube result in "deeper and wider. With more dimension and better overall balance" of sound?
    The comment is doubling troublesome due to the range of circuits it is made about, which they all have one element in common: they are intended to be distortion generators.
    What test set up did you use, and what methodology was employed to ensure objective tests? After 50 years of dealing with tubes and other active devices, I have never been able to reproduce test results similar to yours. What am I missing?
    nickb, Beefcake and flyingdutchman like this.

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    The Sovtek & the SED sound different when installed in the same circuit...just like the SED6L6GC sounds different to a Sovtek 6L6, & a Sovtek KT88 sounds different to an EHKT88, or a SED KT88. Whether this is because the tubes themselves are responsible for the difference, or whether the circuit conditions themselves (ultimately changes in plate voltage & or plate current) account for the difference, is moot. If just changing the tubes results in a change in overall sound, when all other factors remain as equal as they possibly can, perceived differences can be attributed to the tubes.

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    Quote Originally Posted by km6xz View Post
    I might be a little dense but what measurable trait(s) of a vacuum tube result in "deeper and wider. With more dimension and better overall balance" of sound?
    The comment is doubling troublesome due to the range of circuits it is made about, which they all have one element in common: they are intended to be distortion generators.
    What test set up did you use, and what methodology was employed to ensure objective tests? After 50 years of dealing with tubes and other active devices, I have never been able to reproduce test results similar to yours. What am I missing?
    are you suggesting that unless it shows up on a test, it doesn't exist?

    put another way, are you saying that all tubes sound the same?

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    Senior Member Pedro Vecino's Avatar
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    km6xz, IŽm not interested in offending, but 5000 guitars and 3000 amps, perhaps? :-)
    I've been working exclusively with sound for guitarists (lutherie and amplification) for 32 years. My best tools for testing the results are the ears and play the guitars.
    I dŽont know what is a thyratron or a RF triode. I'm not interested because they dŽont sound (I supose) but I distinguish between an SVT Classic with 6550 Sovtek or Svetlana playing with a Jazz Bass or a Warwick Corvette, and the owners of the amplifiers as well. There is no mystery.
    I have very clear what is the timbre (not well explained anywhere. At least I've never seen). Certainly is not a little ball that rolls up and down through the tube charts. It is far more complex than this.
    I dŽont understand what is intended replacing the auditive perception with instruments outside the ears and contact with the instrument and "see" the sound graphically. Faced with a poor sound I can never tell a musician, "the oscilloscope shows it well". I who have to play with the equipment and demonstrate that obtained. It's that simple.
    This is a very old fight. The ear needs education and sensitivity, and does not fall from sky or given away with university degrees. Is obtained through continuous contact with the music and instruments composing a method.
    The effect of a "crystallized" lacquer on an instrument or the effect of a truss rod with a lot of tension (even getting a straight neck) it can be understood using the same system: observation, method and deduction.
    I dŽont try to convince anyone. Only expose my observations if they serve someone.
    The quality of my English, certainly not.
    Regards

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    Noodle of Reality Steve Conner's Avatar
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    Yeah, surely we can all agree that the different tubes can generate different distortion harmonics. That's the cool thing about them, differences in internal construction give differences in tone, like with guitar soundboards, organ pipes, saxophone reeds, whatever.

    I wish people would allow their ears to be informed by common sense a bit more, though. Even the slowest audio tube has a flat frequency response to several MHz. It can only shape the sound by generating harmonics when driven hard, it can't act as a filter. Put another way: It doesn't shape existing harmonics, it makes new ones.

    And, often it's just the different gains and plate impedances of the tubes that affect the sound, by interacting with the speaker damping, presence controls, etc. If you hear a difference even at low volumes, it's almost certainly for this reason.

    3000 amps doesn't impress me. I've built stuff that delivers pulses of 7000.
    "Enzo, I see that you replied parasitic oscillations. Is that a hypothesis? Or is that your amazing metal band I should check out?"

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    Old Timer km6xz's Avatar
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    Sure there is a difference when plugging in any tube into an amp, even if the same type, and often the exact same tube. All it takes to generate a different spectra is a gain change or player feedback difference. But what happens when a test is normalized, where the gain is tweaked slightly to compensate for the difference when installing different tubes? When a tube is described as having certain properties, without addressing the more significant factors such as level, and slight differences in signal, playing position, ear placement and other real world factors that swamp any minute differences in spectra distribution, something is either very illogical or someone is deliberately conning his audience.
    Just putting the level at a slightly different point on the F-M curves will have more impact on perceived differences than what a tube can contribute.
    Just putting a different tube in a socket without normalizing the system gain negates any validity of a listening test that ascribes subjective traits to a tube, power cord, speaker wire etc. A slight adjustment of gain or EQ depending on the circuit details, with a couple degrees of knob rotation to equalize the gain of an amp between tests would blur or negate any perceived differences. That has been tried many many times and the golden ears usually fail to correctly identify a change.
    Why would someone not try to reduce the variables that is needed to see if there really is a sonic difference? Because the results do not support the claims if proper tests are done.
    In your example of just tossing in a new tube and declaring one of the sample sets sounds better or "dimensional" is silly in the extreme. An analogy would be to observe that it takes 17degrees of steering lock to make a right center to center turn in your old car and noticing that 17degrees misses the center in a F1 racer. Reason and logic would suggest results are not what that test predicts.
    There are so many factors that swamp any contribution that a tube could make, that remain uncontrolled in typical claims of sonic traits of particular tubes, that such a person attributing the real or imagines difference to the tube is just bizarre and whacky.
    When water falls from the sky, some people claim not only that the god of water is crying but also claims that she is crying because of some action by humans. Others see rain as being reasonable and predictable results of repeatable conditions, and requires no magic or claims of supernatural or knowing the intention of deities. Both of these cases are more logical than people claiming the magic they do for tubes, power cords or other smoke and mirrors attributed to anything dealing with sound.
    Removes the variables that are uncontrolled and golden ears time after time fail to support their claims. That is pretty suggestive that nothing is really magical going on that defies physics, because what is claimed is not real.

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    km6xz wrote: "But what happens when a test is normalized, where the gain is tweaked slightly to compensate for the difference when installing different tubes?" Then you're not just changing the tube. If one brand of tube cannot be biased to run the same plate voltage & current as another (considering a datum, obviously when assessing lots of tubes of the same brand, you will end up with a bell curve, that will undoubtedly have some overlap with another brand) then that tube will typically perform differently. If you are adjusting other factors to compensate, then you are not simply assessing potential differences between tubes.

    It's like saying "all paint is white...if you want pink, then add red, if you want light blue add some dark blue, you want green add yellow...but really all paint is the same".

    "Why would someone not try to reduce the variables that is needed to see if there really is a sonic difference? Because the results do not support the claims if proper tests are done." Please point me to these "proper tests" with data & methodology. By altering other criteria, you are increasing variables, assuming that the only thing you have changed is the tubes & that is what you are trying to detect...it doesn't reduce variables.

    If you have one amp, one guitar one cord, 2 sets of power tubes that's all you need to determine whether there is a difference.

    "When water falls from the sky, some people claim not only that the god of water is crying but also claims that she is crying because of some action by humans. Others see rain as being reasonable and predictable results of repeatable conditions, and requires no magic or claims of supernatural or knowing the intention of deities. Both of these cases are more logical than people claiming the magic they do for tubes, power cords or other smoke and mirrors attributed to anything dealing with sound. " It doesn't matter at the end of the day why it rains, you still get wet. Even a child can tell the difference between dry, wet & very wet....or are they trying to con us too. I'm sure that we'd all get equally wet if the rain is "normalised"...y'know in a "proper test". Next time it rains I'll drop you a line & you can tell me from 2000 miles away how wet I am getting ;-) Or, perhaps I'll trust my own judgement, or that of another individual undergoing the same experience.

    Why suggest magic is involved, we're tallking about simple, repeatable, relative AB testing. You repeatedly refer to "claims" & offer counter claims, whilst providing no more tests/data/evidence than anyone else. Shit, or get off the pot...produce your test data.

    I don't percieve tubes to have a magical, or even a particular character when considered on their own. They need to be installed into an amplifier & fed a signal from a musical instrument to be put in any context...you are as aware as anyone else is of the difficulty of making products with EXACTLY the same properties in everyday mass production, therefore the potential for difference always exists.

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    Noodle of Reality Steve Conner's Avatar
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    Quote Originally Posted by MWJB View Post
    If you have one amp, one guitar one cord, 2 sets of power tubes that's all you need to determine whether there is a difference.
    Well, that's testing which of the two sets of tubes your amp likes most, not testing the tubes themselves. The conclusions you draw don't necessarily apply to everyone else's amps. And that's assuming you're able to put aside any personal feelings you might have about the tubes and listen with an open mind.

    I think most of the tests Stan mentions were done in the hi-fi field. A hi-fi amp can have 10x more negative feedback around all of its tubes than a guitar one, which acts to minimize the differences. I'm sure if you built a small single-ended test rig with no NFB, you could easily tell the difference between a 6V6 and an EL84 say, in a blind test. But between a Mullard EL84 and a Sovtek one? Who knows.
    "Enzo, I see that you replied parasitic oscillations. Is that a hypothesis? Or is that your amazing metal band I should check out?"

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    Yes, I agree Steve. But that's a real world scenario. most amp owners are just going to change the tubes, for a set that look nice & meet their budget...nobody is going to realisticaly change every perameter in their amp to ensure that the new tubes exactly match the alternatives in every respect, especially as data sheets are not alway available & not all perameters can be determined.

    I also agree that a tube that is deemed as desirabe in one application may be less so than another...I also agree with km6xz that playing style & dynamics are very relevant...but I would be cautious about suggesting that tubes of the same broad designation are indistinguishable. Especially as you, in another thread, seem keen to distinguish between military Russian tubes and their US/EU designations as if they are different items. Why suddenly is that different for the Mullard EL84 and the Russian 6P14P-ER?

    I also agree that the differences that are often heard are down to secondary criteria, but they're still real. A good example is my Triumph Leo, I did have a Phillips 6BQ5 in there, great. Recently I replaced it for a JJ that just happens to draw less plate current, this effect is clearly audible, not least in the fact that the tremolo is now vastly more pronounced (virtually unuseable). Is the difference because one is a Phillips & one a JJ? Probably not the bulk of it, the difference is because the tubes draw different idle currents & run at differing plate voltages...if simply changing the tube causes that difference, then ultimately it is the tube that is responsible, whether it knows it, or wants to be, or not. No one is realistically going to start subbing transformers on a cheap SE practice amp to make sure that their new $10 tubes sounds as good as their old one. You change the cheap part, that isn't hard wired. Any difference that follows the tube may justifiably be attributed to that tube, if not to all tubes of that brand.

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    ...sorry, the real world intervened for a moment there....where were we?

    Steve wrote: "And that's assuming you're able to put aside any personal feelings you might have about the tubes and listen with an open mind." Well, if I think a certain tube will meet my needs, say a KT88, I buy several pairs, all graded for repeatability, and then get on & listen to them at the same plate current in a fixed bias amp (at "whatever" in a cathode biased amp). I have already paid for all of them, there's no motive for preferring one over the other. If someone replaced a burned out set of tubes in one amp, with a new set from a different mfr, a week (hell, even a day) since they last turned the amp on, without the opportunity to do a quick A/B test, then sure...I'd be skeptical about any claims too.

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    Noodle of Reality Steve Conner's Avatar
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    Well, I guess I agree with those points too. But I still have an issue with subjective reviews like the famous ones by Derek Rocco of Watford Valves, where he claims that such and such a tube has such and such a sound. The sound of a tube is like the sound of one hand clapping. You can't hear it, all you can hear is the sound of the tube in some circuit, and that depends just as much on the circuit as the tube itself.

    The 6P3S and 6P3SE are different. They were Russian tube designs that got rebranded as 6V6, 6L6, 5881 etc because they happened to have characteristics that were kind of similar. I don't think the Russians intended them as copies of the Western tubes.
    "Enzo, I see that you replied parasitic oscillations. Is that a hypothesis? Or is that your amazing metal band I should check out?"

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    Derek does at least attempt to put the tests in context, I don't believe he's out to mislead anyone. He does stand behind his products & genuine quality issues are dealt with quickly & under warranty, matching is as close as you'll see from a tube vendor. Yes, I agree with the "one hand clapping" analagy...the tests are, at best, of limited value. I take them with a pinch of salt.

    "The 6P3S and 6P3SE are different. They were Russian tube designs that got rebranded as 6V6, 6L6, 5881 etc because they happened to have characteristics that were kind of similar. I don't think the Russians intended them as copies of the Western tubes."

    That's probably the case for all the Russian tubes, it was pretty much the case for many tubes...the Tung Sol 5881 (NJ) springs to mind. But, with the investment from New Sensor, is it still the case? I'm not ruling out a degree of "name plate engineeering" (especially the cunning visual similarities with NOS products), perhaps in some cases the boxes might be the biggest difference (e.g. Sovtek KT88 & EH6550 in the ST bottle?), but I'd be wary of assuming that they are all "the same", or different to NOS 6L6/5881 in general...I have had situations where a cheap Russian, even Chinese, tube outperformed NOS/other current production in every aspect (& the reverse)...but if a Russian tube sounds enough like a 6L6/5881 (if not necessarily identical to its NOS namesake) hasn't it earned that name?

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    I might be stating the obvious here, but it's all conjecture until you actually hear and play it, whether it is tubes, speakers, pickups, guitars, or any other instrument and/or accessory. Marketing hype is carefully crafted to sway you in a particular direction, but in the end, it's what all works for you. Sound/feel and reliability come first. Brand name really doesn't matter.
    John R. Frondelli
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    Couldn't agree more John.

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    No, I was referring to different tubes of similar measured spec, in this case 6550's. If it does not have similar characteristic to a defined standard or patent filing, it should not have the same designation.
    No, I did not suggest normalizing by changing components but to make minor adjustments to the amp....tone controls and volume settings. Or are those arguing that settings have to stay the same possibly never change their amp settings? How did they decide on those settings in the first place if not by taking the whole system as system and adjusting to most pleasing. Wouldn't it make sense to do the same thing with different tubes?

    The wild unsupportable claims about openness, dimensional, spacious etc, are just not rational when comparing similar designed tubes. If it is not similar, it should not carry the designation. But even comparing two different designs of tubes, one might be going to be closer to the compromises made by the amp designer. But another amp might be closer to optimum for the second tube type. But where does "openness, constrained, dimension, fast" come into it...they don't.
    If someone likes their settings, and their brand of tubes, that is fine, but to name a tube superior due to sound traits of the tube is off the deep end, as what happened with the OP asked for advice what was best for 2011. A few people reported their opinions of reliability which is also valid if the sampling is large enough to be representative. But then a few people went off into the ozone talking about new age'y sort of ethereal traits of tubes that just was hogwash and is salesman or religious fanatic talk. It is one thing to like a brand of tubes but another to claim traits that are not part of the realm of things tubes can control. No one knows the amp the OP has, its condition, his playing style, the environment it works in etc, all of which are more influential in sound character than anything tubes can impart.
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    Quote Originally Posted by km6xz View Post
    But then a few people went off into the ozone talking about new age'y sort of ethereal traits of tubes that just was hogwash and is salesman or religious fanatic talk. It is one thing to like a brand of tubes but another to claim traits that are not part of the realm of things tubes can control. No one knows the amp the OP has, its condition, his playing style, the environment it works in etc, all of which are more influential in sound character than anything tubes can impart.
    i dunno man.

    the BAGA is not a particularly unique amp, honestly. no real tricks. just big iron and lots of glass and a circuit i thought would produce the best results.

    but i'll be damned if i can find tubes with the same magic as those 2nd gen ei kt90s that i popped in there in the late 90s.

    TRUST me, i've tried.

    those good old sovtec 5881s could easily handle the specs, but they sounded like a wet noodle. the ONLY thing they had going for them was availability/price.

    i tried svetlana (real svetlana) el34's. they too handled the 620v on g2, but they had no sparkle.

    and we're talking BRAND NEW tubes vs. a set that were over a decade old.

    so if one tube's construction can have so much more mojo than another, why can't one brands version of a given tube type?

    does an el34 with 20% more gm still count as an el34?

    does a beam tetrode, say 6550, in which the screen grid aligns precisely in the shadow of it's control grid still count as a 6550? even when no other manufacturers versions do?

    can you hear the difference between the secondary emission of a gold plated g1 vs one that isn't?

    yes, these things are testable, and measurable, but it doesn't mean that someone who is doing reviews would have access to the tools necessary to do so.

    does that invalidate their opinion?

    for me, as long as someone uses subjective terms to describe a subjective impression, i've got no issue with it. i agree that extrapolating results is often done when it never should be. i agree that snake oil has made people a lot of money based on something without any demonstrable merit.

    but i also have space in my paradigm for those things which i either do not understand or i am not privy to.. and i cannot merely dismiss those things out of hand.

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    But then a few people went off into the ozone talking about new age'y sort of ethereal traits of tubes that just was hogwash and is salesman or religious fanatic talk. It is one thing to like a brand of tubes but another to claim traits that are not part of the realm of things tubes can control. No one knows the amp the OP has, its condition, his playing style, the environment it works in etc, all of which are more influential in sound character than anything tubes can impart.
    The problem is that there aren't words in the English language to describe different sound characteristics - so one does their best with what's available to try to communicate that. It's not about magical properties - there are real physical reasons behind why something sounds the way it does - but how do you communicate how something sounds in words?

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    Thank you, I understand what you are trying to say. B.

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    Thanks, I agree with you on these points. I have just had a lot of trouble with New Sensor power tubes shifting their bias point while on the probes. Have not had that problem with JJ or Svet. Since I need a matched octet for this amp the investment is significant.

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    618
    fwiw, i have found matching to be of little to no significance when talking about big power output stages with multiple parallel tubes.

    in fact, i've found matching in general to be an overrated criteria for choosing tubes. (basically i balance each side's total q-currents +/- 10% and call it done.)

    jm2c
    ken

  35. #35
    Member mhuss's Avatar
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    Zombie thread alert!

    I know this will produce anecdotal vs. statistically valid data, but which brand of KT-88s have proved reliable for you in the past couple of years?

    I have a JJ KT-88 which gassed out (white snow globe) after 1.5 years of intermittent/light use in a practice room (Fender PS300), and the head was not not physically on top of the bass cabinet. It's only travels have been across the room between my workbench and the amp side. (Anecdote #1 )

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