So, I learned something about my tube amp today, and a tube amp question

Discussion in 'Fred's Barcalounge' started by radd, Nov 7, 2019.

  1. Ricochet

    Ricochet I Bleed Orange

    Nov 13, 2009
    Monkey Island
    When was the last time you bought tubes?? :D
     
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  2. wabash slim

    wabash slim Friend of Fred

    Age:
    70
    Feb 10, 2010
    lafayette in
    It could also be due to the new tubes being closer in spec to the bias point. All performance tolerances vary. As it's a Class AB amp, a matched set of output tubes should be used. It's an imperfect world, and tubes are 100 year old tech, so there easily could be an issue with the tubes. Glad you had some that worked for you.
     
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  3. Waxhead

    Waxhead Country Gent

    Aug 30, 2014
    Australia
    ahh 12 months ago :)
    Prices have gone up I see but Doug still has many 12ax7 preamp tubes around $10-15 each

    http://www.dougstubes.com/preamp-tubes/12ax7-ecc83-7025/sovtek-12ax7-wa.html

    http://www.dougstubes.com/preamp-tubes/12ax7-ecc83-7025/electro-harmonix-12ax7.html

    Power tubes are always more expensive but Doug presently has these Sovtek EL84 for only $12.50 . Great price on an excellent power tube.

    http://www.dougstubes.com/power-tubes/el84-6bq5/sovtek-el84.html
     
    Last edited: Nov 8, 2019
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  4. ruger9

    ruger9 Country Gent

    Nov 1, 2008
    NJ
    Different power tubes of the same type (6V6 in this case) can sound different, especially if the amp isn't re-biased when you switch them. But I've NEVER had new power tubes (re-biasing or not) be different enough that I had to adjust my pickups. The amp controls maybe one notch here or there, but never the pickups....

    BTW- with that amp under a table like you have it (I have a similar setup), and against a wall, that will increase the bass response.... altho putting on your little riser might help negate that, but amp placement can definitely play a role in low-end frequencies...
     
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  5. Bertotti

    Bertotti Country Gent

    Jul 20, 2017
    South Dakota
    Microphonic tube, I have not had a booming one but it is possible microphonic combined with the right resonant frequently and bias could easily been the perfect mix for you issue. I haVe pulled noisy tubes and they have never worked in another amp so I tossed them. My last set of xxx head tubes failed. Turned her on warmed her up hit one big chord and after the initial attack silence! The threw them all out and put in new. Tubes can do some frustrating things at times!
     
    Last edited: Nov 8, 2019
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  6. stevo

    stevo Country Gent

    May 1, 2012
    Atlanta
    And unless the bias is way way off, I've never seen bias make a big difference like that.
     
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  7. DaddyDog

    DaddyDog Country Gent

    Sep 18, 2011
    Mississauga, Canada
    To learn more about tube amps, look for a podcast called The Truth About Vintage Amps. It's related to The Fretboard Journal. Terrific info from a guy who has been fixing tube amps for decades.
     
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  8. ruger9

    ruger9 Country Gent

    Nov 1, 2008
    NJ
    Which is why I said...


    ;)
     
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  9. stevo

    stevo Country Gent

    May 1, 2012
    Atlanta
    I deserved that. :D

    I guess I was trying to highlight the extremes. I've swept my bias pot from one extreme to the other and it never made much if any difference in tone.
     
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  10. Ricochet

    Ricochet I Bleed Orange

    Nov 13, 2009
    Monkey Island
    My last 3 amps were solid state... I'm just saying.:D
     
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  11. ruger9

    ruger9 Country Gent

    Nov 1, 2008
    NJ
    I'm surely digging my Roland Blues Cube Artist... (altho that didn't keep me from buying a Bad Cat soon after :D )
     
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  12. radd

    radd Country Gent

    Dec 27, 2017
    Santa cruz

    Love my Roland Blues Cube Stage. However, I have found that my Strat and Tele sound simply glorious through my Princeton Reverb. I think Fender tube amps love single coils.
     
  13. radd

    radd Country Gent

    Dec 27, 2017
    Santa cruz
    Something else different with the two new power tubes. I would get occasional crackling that would come and go. That is gone. I gotta think one of, or both, the tubes were bad
     
  14. wabash slim

    wabash slim Friend of Fred

    Age:
    70
    Feb 10, 2010
    lafayette in
    In the '50s, most tubes averaged between $5 and $10, with some even cheaper. Tubes were used in all electronics, and were common and available. You could find them at the grocery and drug stores. Now, they're niche items, only used by audiophiles and guitarists. Prices aren't that bad, considering.
     
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  15. Waxhead

    Waxhead Country Gent

    Aug 30, 2014
    Australia
    yeah agree Bertotti :)
    I've seen bad tubes make all kinds of weird noises that surprised me - buzzes, screams clicks etc. Extreme boomyness is no surprise to me.
     
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  16. stevo

    stevo Country Gent

    May 1, 2012
    Atlanta
    Thanks for that! I've been listening and really enjoy it.
     
  17. Bertotti

    Bertotti Country Gent

    Jul 20, 2017
    South Dakota
    Even minor bias adjustments on some amps. A teacher I got a couple lessons from has a Marshall, he was a huge AC/DC fan, so he had whichever Marshall did it for that. But it had no clean headroom at all. I took a meter to it and Cooled off the bias a bit. Not much and honestly I can’t remember how much I changed it but the tone change was dramatic. He was happy because now that doggone Marshall had a very good clean tone and with a bit of Knob tweaking still got his AC/DC break up and more. I just remember it was a very minor change in bias.
     
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