Sovtek 12AX7WA vs Sovtek 12AX7LP

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers T' started by Ken, Oct 10, 2003.

  1. Ken

    Ken Member

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    What are the differences in tone you might hear between these two tubes in a amp's preamp section?

    Thanks
     
  2. Taller

    Taller Silver Supporting Member

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    Anywhere is everywhere and nowhere is nothing.
  3. Ken

    Ken Member

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    Thanks! Great info:)
     
  4. myles111

    myles111 Member

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    Ken,

    These questions are answered on my GAB website and in my 200 page downloadable tube primer that has all the factory tests on these tubes and more.
     
  5. hipfan

    hipfan Supporting Member

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    You might want to check Rivera's website too. They use the Sovtek "LP" tube (as opposed to the LPS) in some of their amps due to some kind of power supply design quirk. The LP is a slightly different tube than other 12ax7's, and it's explained somewhere on the Rivera website.
     
  6. myles111

    myles111 Member

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    hipfan ...............

    If you check with Paul Rivera, he may mention that he and I are sort of close. I am somewhat familar with his amps.

    Paul's amps used DC heaters which are much quieter and more costly than more common AC heaters. The issue with the LPS, is that in some amps, AC or DC heated, the spiral element for the heater in the LPS can actually cause more hum rather than less.

    As a side note, almost all tubes use a helix heater, and I have found the LPS tube to be no quieter than other tube designs.

    From my last factory LPS test:

    Average Output/TC 1.2 1557
    High mA % 1.4
    Low mA % 0.9
    Average gp 0.0186
    Average gain 83.71
    Tolerance Range 41.7%

    Basically, the output current on these in the last batch was great, but their spread in quality was a bit on the broad side (know and trust your tube vendor). The gain was is low on these, lower than the average of today's 12AX7s by the way.

    If these are older stock from a vendor, earlier batches were even worse:

    Average Output/TC 1.0 1505
    High mA % 1.5
    Low mA % 0.6
    Average gp 0.0182
    Average gain 82.69
    Tolerance Range 75.0%

    Output in current was down, and the quality spread and inconsistency was about as bad as it gets. The gain was even lower than the later batch.

    Hope this was of some help.
     
  7. scottl

    scottl Gold Supporting Member

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    Ken, the WA's are the worst sounding 12ax7's I have heard.

    My Fuchs sounded great with the JJ/TEsla 12ax7, the Ruby Chinese 9th Generation (most gain of all of them), the Electro Harmonix, and the EI Gold pin. All tubes were tested and guaranteed by Mike at KCA.

    I can't comment on the LPS but why bother when the others sound good.....

    Scott
     
  8. hipfan

    hipfan Supporting Member

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    Hey, that's cool with me!

    Thanks for the good info on the tubes.
     
  9. myles111

    myles111 Member

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    Scott ....

    The WA makes most amps sound as if a blanket was placed over the amp. The WA's are good current drivers, but like you, I do not like them in any tone generation or gain stages.

    Sovtek is coming out with a new tooling WC. So far this tube in my first factory tests of these, they are pretty darn amazing. I do not know when they will be released to the public, but if the 100 samples I went though follow through to production, they will be a cool contender in the 12AX7 market, and probably at the same price as the WA or WB (that is now gone).

    The test results on the new unrelased WC:

    Output TC Gain
    Averages 1.1 1273 87.55
    90.8% 79.6% 87.5%


    High TC 1370 85.63%
    Low TC 1190 74.38%
    QA tolerance TC 11.3%

    High mA % 1.2 100.0%
    Low mA % 1.0 83.33%
    QA tolerance mA 16.7%

    High gain 92.31 92.31%
    Low gain 83.75 83.75%
    QA tolerance gain 8.6%

    ........................

    The last WA batch:

    Average Output/TC 1.1 1278 90.83%
    High mA % 1.5 125.00%
    Low mA % 0.8 66.67%
    Average gp 0.0154
    Average gain 82.99
    Tolerance Range 58.3% 58%


    As you can see, a big difference.
     
  10. myles111

    myles111 Member

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    hipfan ..............

    You are more than welcome.
     
  11. scottl

    scottl Gold Supporting Member

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    Myles, numbers look better for sure.... How does it sound though... Isn't there some intangible tone magic with tubes???

    Also, many amp guys tell me unmatched inverters are ok. You say otherwise. They say that the design totally doesn't need matched triodes and that it means nothing. Have you heard this??? Fwiw, my Ruby 12ax7 was 100/100 on box so I used it in the driver slot.

    Scott
     
  12. myles111

    myles111 Member

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    Scott -

    The WC sounds much more open and airy than the WA.

    On matched vs unmatched phase inverters .... there is always argument on this... maybe talk to some high end audio guys.

    When folks in guitar amps say that the circuit is balanced, ask them how that takes into account the time differences between the two sides, not just the voltage or output.

    There is a lot on this subject in my Tube Primer, downloadable off my website.
     

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