el34 test data ...... good?

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by samwheat, Sep 18, 2005.

  1. samwheat

    samwheat Member

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    I've got my eye on some el34's .... the test data results are:

    43.2/5760
    42.8/5800
    43.5/5690
    42.9/5640

    as measured in mA and umhos

    Are these new?

    Also where can I find this data on tubes?
     
  2. John Phillips

    John Phillips Member

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    Without knowing exactly what the test conditions were, those numbers are completely meaningless except to know how well-matched the tubes are - which those do appear to be... less than 2% spread on plate current and less than 3% on transconductance - and even then you can't be sure they're more than a rough guide.

    They're measured at a particular combination of plate voltage and bias voltage - which might be completely different from what you're going to use. If you're not buying from a reputable tube reseller who will guarantee matching under guitar-amp conditions, any figures like that (especially obtained with a 'tube tester', which don't run the tubes at anything like the voltages in a guitar amp) are just numbers, and I wouldn't base a buying decision on them alone.
     
  3. samwheat

    samwheat Member

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    plate voltage of 400VDC, -36V bias after a 12 hour burn-in
     
  4. John Phillips

    John Phillips Member

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    That's at least a guitar-amp voltage (a little low, most 4-tube amps operate in the 450-500V range) and the figures do sound OK at that.

    Still very hard to tell if they're new or not - is the seller claiming they are?
     
  5. samwheat

    samwheat Member

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    supposedly nos RFT's ...... they sold already

    I saw a transconductance value of 12.5 mA/V on a data sheet ..... do you multiply that at the plate voltage do check if the tubes are new?

    any links on where this can be explained?
     
  6. John Phillips

    John Phillips Member

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    You can't tell if the tubes are new from the data.

    It may not matter anyway... old-production tubes often test better than both the spec and new-production tubes - which they will outperform and outlast in many cases, even when they're quite used.

    It comes down to whether you trust the seller's description and pricing. Personally I use used old tubes exclusively (I get them cheap and test them myself in real amp circuits) and don't worry about test data as long as they work well. I've had a grand total of one fail in a gig situation in fifteen years :)... although I've thrown out a large number that weren't good enough to use in the first place.

    I'd be very wary of buying tubes from any source other than a reputable tube dealer, BTW - certainly when any claims are being made about their condition.
     
  7. samwheat

    samwheat Member

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    why do nos tubes last longer? ...... better material and workmanship? ...... better vacuum? ......

    what should I look for in nos tubes?
     
  8. John Phillips

    John Phillips Member

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    They last longer and are much tighter in spec to the original design parameters because quality was higher at every single stage of production - back then, tubes were used in critical applications such as military and aircraft systems, and were made in much larger numbers in American and European factories where quality was more important overall than cost; factory testing was thorough too.

    Now, they're made as cheaply as possible in Eastern Europe and China, for a non-critical fringe market, and the economics mean they have to get away with passing as many as they can. There simply isn't the quality control built in at every stage - if you haven't seen some pics of some examples of Chinese-made tubes you'd probably be shocked at how badly-made they can be.

    Unless you can afford to buy a lot and take your chances (many sold on the web are not as 'new' as they're supposed to be, and many may also be ones that didn't quite make the grade back-then too - they were far better, but still not perfect, and many were still rejected after manufacture, some of which probably got out into the market), you're best going to a respected NOS reseller, such as Lord Valve or KCA NOS Tubes (Mike of KCA posts here as 'Blue Strat').
     
  9. samwheat

    samwheat Member

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    i wonder how many EL-34's are manufactured each year

    what are the chances that western electric will make guitar tubes? ......... don't they make just 1 tube line?

    I'd rather pay nos prices for new tubes and be content with my tone but that's really not the way the market is ..... its flooded with cheap junk geared to the christmas shopper for a 12 yr old

    OTOH, I bought some jan ge, brimar cv4004 and tungsram preamp tubes and it was like night and day compared to new jj/eh stuff ...... i was all of a sudden a better player
     
  10. Blue Strat

    Blue Strat Member

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    Not much chance of Western Electric making guitar amp tubes unless people are suddenly willing to pay $100+ per tube.

    The only tube they're not making (actually, the company is/was called Westrex I believe) is the 300B, a high end audio tube which sells in the $300+ (probably higher by now) range.
     
  11. TheAmpNerd

    TheAmpNerd Member

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    They were. However the inside scoop was then when Westrex bought the WE name they also bought the Kansas City works plant.

    That said, they also got all the tooling, WIP inventory,
    ALONG WITH All the original WE 300B tubes that magically
    appeared in a ware house or two. From what I recall, though they had to move the plant to Arkansas, for
    some reason.

    I worked with some of these WE folks at Dallas Works.
    That was before TYCO bought them, stole the pensions,
    and shut down the only American Plant to win
    the Deming Award for Quality. They had excess
    capacity in China. OH and some of the Tyco guys
    are getting 25 years in the big house.

    Like anything that was made from Western Electric,
    it was made to LAST and NOT break nor wear out;
    if it did, the compnay lost money. Either on a
    house call, business call etc.

    Now things are so cheap if it breaks, just buy a new one.

    Of course, that assumes unlimted resources. Once the
    oil is gone, plastics prices will soar again. We'll probably
    get back to making things last again.

    Give it a few decades or centuries....your guess is as
    good as mine.
     

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