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Will new tubes help a circa 1980 Bassman 135?

Discussion in 'Amps and Cabs [BG]' started by lastnerve, Jan 27, 2012.

  1. lastnerve


    Jan 27, 2012
    I'm just trying to clean up the sound of this old Bassman 135.

    I've only used it about 3 years out of the last 30. I've never replaced any of the tubes, and now I'd like to see if I can get rid of some of the fuzzy, farty sound.

    I'm not at all smart about tubes; I don't know which of the tubes might be trashing the sound or which ones would be worth replacing. A local amp shop said they could improve the sound "dramatically" for about $300. I don't think the amp is worth that much of an investment.

    I've searched this forum for some help on this but I couldn't find what I was looking for.

    Anyone know of any threads or tutorials on performance improvement of old tube amps?
  2. Tubes do indeed wear out much like the soles of shoes.

    Usually the power section tubes are first to go with a loss in high end, and a gradual power loss.....and an increase in fuzz.

    Pre-amp tubes last longer, but do wear out as well. Replace the power tubes first, see how it sounds. If still fuzzy, change pre-amp tubes.

    As for a difference with new tubes: a crisp presence and better overall clarity.....some increase in volume.....but not huge!......more like cleaner head room before overdriving....fuzz.

    Always used matched power tubes! They "pull" equally on the transformer and increase the life of the tubes and transformer!

    Also, bias the tubes once they are installed! This is crucial! It's like setting the idle on a carburetor! It will increase tube life and give a cleaner tone.


    Hope this helps!

  3. will33


    May 22, 2006
    The original tubes may be just fine as they have low hours on them, although a tech may want to get their paws on them anyway, they were built better than todays. If it's been sitting that long, a good cleaning and a cap job likely are in order. Gonna have to take it in somewhere.
  4. Tim1


    Sep 9, 2005
    New Zealand
    The sound that you describe as "fuzzy,farty" is the sound that I have always associated with this head when it gets loud and runs out of headroom. If it is doing it at lower volumes also then it could be a capacitor, tube.....
    I would get a decent tech to look at it first before spending 300 bucks on tubes.
  5. otherclef


    Aug 10, 2011


    30 year old filter/bypass caps... change and go from there.
  6. RickenBoogie


    Jul 22, 2007
    Dallas, TX
    +1 again- take it in to a good tech and have it looked over. The tubes may well NOT be the problem. And even if they are, or partially are, chances are it needs a re-cap and certainly re-biased. Tech-Time.
  7. lastnerve


    Jan 27, 2012
    Thanks to all of you. I guess taking it to a tech would be the best thing.
  8. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    The speakers are more likely culprits than the tubes, with the power supply caps a close second.
  9. johnk_10

    johnk_10 vintage bass nut Supporting Member Commercial User

    Feb 16, 2008
    Thousand Oaks, CA
    John K Custom Basses
    the first thing that i'd look at is the amp's bias and how much current the output tubes are pulling.
  10. lastnerve


    Jan 27, 2012
    Geez, I hope it's not the speakers. I'm running it through a new Genz-Benz Neo 2x12 (4 ohm, 600 watts).

    I read in another forum that the original Sylvania tubes are superior to the tubes available today, so I'm gonna wait until I have a tech check it out before replacing them.

    This amp seems to be well regarded as old tube amps go, so I plan on making the most of it. I'll report back after I have it checked out by a tech.

    Thanks to all.
  11. allsidius


    Mar 6, 2006
    I had my 78 Bassman 135 retubed with a matched quartet from Tube amp doctor. It completely transformed the amp, it now plays so well that I had 3 offers to sell out of 3 professionals that hired it. Note that I use it for passive bass, it is not a good guitar amp.

    I run the amp through an old 412 Fender pyramid cab, fitted with Celestion G12T-75s, it plays so good it is amazing. I use an old P-bass and a Jazz, as well as a Rick 4003. The sound is classic 70s hard rock ala Machine Head. Just to be safe I just got a spare head. I see a lot of guys don't like the 412 cab, but that must be the cheapo 30 watt original woofers. Fender never put bigger elements in than the amp was supposed to deliver. Beef up the speakers and feel the difference!
  12. JimmyM


    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    Old Fender cabs suck for volume and fart out way sooner than the Ampeg cabs of the day, but they do have good tone when run at reasonable levels. The heads, however, are quite nice if a little different from the Ampegs. Glad to see you got your amp transformed...totally worth the money IMHO.
  13. allsidius


    Mar 6, 2006
    I think a lot of the flaws of the cabinet has to do with the underpowered original elements. The 4 G12T-75 together can take 300 watts, while the old ones probably took less than half. I considered the Celestion bass elements, but I found they were quite similar in frequency response and cost much more. In large pub settings I can't play any louder, If needed I use a DI box to beef it up.

    Forgot to add: I hate 15" for bass, they are far too "boomy" and ill defined in my experience.
  14. Tim1


    Sep 9, 2005
    New Zealand
    :meh: Can't let that comment about fifteens being "boomy" go by without a response, allsidus. Modern fifteens are a very different beast to the cabs of the seventies. My Bergantino 215 is very tight and punchy with plenty of useable top end extension, and I recently acquired a GK115 neo which again lacks boom but has plenty of punch. I tend these days to use fifteens more than tens, for their even response across the frequency range.

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