The mystical world of tubes

Discussion in 'Amps and Cabs [BG]' started by BassikBrad, Jun 9, 2020.

  1. BassikBrad

    BassikBrad Bass Face Brad Supporting Member Commercial User

    Mar 28, 2018
    New Mexico
    Endorsement: Mozztronics. Lusithand
    I am an avid lover of tubes.

    But they baffle me.

    Is there anyone, out there, who has considerable knowledge of the technical reasons
    why, differing tube brands sound different but have identical frequency response measurements ?

    And I don't mean just the gain level differences, or the tales of spiritual enlightenment
    when listening to tube amps after a few puffs of wacky baccy.

    All sensible words of wisdom will be received with much excitement, enthusiasm &

    Stay safe my friends, it's not over yet.
  2. Wasnex


    Dec 25, 2011
    You might want to post some of the traces you have taken that show near identical frequency response, and then describe the differences you hear.
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  3. BassikBrad

    BassikBrad Bass Face Brad Supporting Member Commercial User

    Mar 28, 2018
    New Mexico
    Endorsement: Mozztronics. Lusithand
    Good idea, I will later in the day !
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  4. seamonkey


    Aug 6, 2004
    Placebo effect
    If the devices measure the same, they will sound the same.
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  5. I’m sure there’s more wisdom to follow but I suspect it has to do with the way they interact with the tranny and compress and react to other components of the circuit.
  6. Just curious, what is your preamp tube lineup with the Reeves ? I have an interesting story with this.
  7. bassdude51

    bassdude51 "You never even called me by my name." Supporting Member

    Nov 1, 2008
    Central Ohio
    Seems like the most coveted tubes are the NOS from the 50s and 60s that were made in the USA and Europe. And yes, you are so correct! "The mystical world of tubes."

    It's so crazy that here we are living in the 21st Century with unbelievably advancements in electronics and tubes are still the best for amplification! Maybe not the most practical but still the best for sound.
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  8. micguy


    May 17, 2011
    That's only true if you actually know what to measure - a simple frequency response measurement, for example, misses some important things.
  9. seamonkey


    Aug 6, 2004
    Restate: If measured correctly, two devices that measure the same, will sound the same.
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  10. I found that the coveted Mullard ecc83 in V1 and V3 made my amp sound very honky in the upper mids.
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  11. micguy


    May 17, 2011
    Close - in many cases, close enough. As someone who's designed a lot of audio gear, there are things (especially when you have adaptive DSP in the loop) where you can't design exhaustive enough bench tests to make this statement. In those cases, one of the measurements we have to do a lot of is...listening tests (carefully controlled). Matter of fact, even when something is simple, and you'd think that objective tests would suffice, we always do some listening tests - it's really never a good idea to assume that your bench measurements are good enough.

    While listening tests are the hardest tests to do right (the humans involved are highly non-linear devices), they are, at the end of the day, for may of our products, the test that matters - every other test is ultimately in support of the customer's experience.
  12. abarson


    Nov 6, 2003
    Santa Cruz
    If that's the case, you've got a Mallard, not a Mullard.
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  13. Im talking in my Reeves C225 with my bass and Reeves cabinet. Not home stereo. I also found the same with some Telefunken 12AX7 from WG.
  14. seamonkey


    Aug 6, 2004
    Double blind listening tests by both trained and untrained listeners can be part of the measurement. Measure first, then DBT. If they measure the same and sound the same then maybe your extra measurements are redundant but no harm done with extra measurements.
    Sascha Erni likes this.
  15. iiipopes

    iiipopes Supporting Member

    May 4, 2009
  16. beans-on-toast


    Aug 7, 2008
    We all hear differently. A set of golden ears can help in the process.

    Brain scans while listening may provide the ultimate tool for evaluating audio. Good progress with portable brain interfaces and data interpretation have been make. It’s humbling how little we know.

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  17. bucephylus

    bucephylus Supporting Member

    Aug 18, 2002
    Central Ohio
    Vacuum tubes are designed and built to engineering specifications, which do NOT include details about particular constructions (nor spectral dispersion characteristics). They were initially designed as electrical switches (somewhat a curiosity at the time), and put to use as signal modulation / amplification devices during WWI. [A side comment is that the tube industry was directly enabled by the government investment in the factories to make the tubes in time of crisis. This is a generally unrecognized economic platform dynamic, in that government has paid for the major infrastructure that led to every single significant economic platform since the Civil War. Ayn Rand proponents mainly ignore this fact.] Anyhow, the various kinds of tubes that subsequently developed were generally designed for radio and television (CRT) specifications, in various stages of the required circuitry.

    The use of tubes in MI amplification is relatively “new“ (starting in the 1950’s); and has mainly piggy backed on tube specifications intended for other applications; in which, the harmonic details were more or less irrelevant. So, tubes have been designed primarily to meet engineering specifications (IEEE) and for production advantages / low cost. Within any engineering specification for a given tube, there are literally dozens of different engineering designs But, to my knowledge, there are zero tubes designed specifically for use in MI amplification.

    Enter musicians, who tend to scrutinize details. And, a careful ear will distinguish between tubes of different designs. But, I would be surprised if the same could be said for paying audience members. Tubes are one of those kind of fun things to check out, which do affect our sound; but, which generally don’t matter much, if at all, to the folks who are paying to hear you play.

    BTW, here is a link I like for the 12AX7 family of tubes:
    Last edited: Jun 9, 2020
  18. jthisdell


    Jun 12, 2014
    Roanoke, VA
    I certainly cannot explain it but the differences do exist. The Tube Depot has a good comparison for different tubes. I have a Valve Caster OD pedal with a 12au7 in it and I wanted to be able to have more control of the gain before going into OD. Another TB Member posted about the Gold Lion tubes and according to Tube Direct this would have less gain and more warmth than the Sylvania in it. So I took a leap and yes, the Gold Lion does perform as advertised and I am happier with the pedal.
  19. iiipopes

    iiipopes Supporting Member

    May 4, 2009
    Indeed. I'll take the dog's opinion any day over most human ears.
  20. Rabidhamster


    Jan 15, 2014
    “Identical frequency response measurements”
    Nobody measures so accurately that you could even know that. Even if they did, it wouldn’t be feasible to test every unit to that level of accuracy.
    you can have a “total frequency range” of 20hz-20khz and have loads of dips and peaks in that range. Two makers can say “yes, 20hz - 20khz!” And that’s accurate But that’s not the whole story.

    very few items in the world are actually identical. The best you can hope for is “within spec”.

    A spec sheet can tell you “ideal” characteristics, but in the real world “ideal” is never reality, so you have natural variance.

    I actually can’t think of anything that doesn’t have some amount of variance.
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