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DB 750 microphonic preamp tubes part 2

Discussion in 'Amps and Cabs [BG]' started by ajb, Sep 26, 2006.


  1. ajb

    ajb

    Mar 20, 2005
    This is the second thread I've started on this issue. The problem: The preamp tubes in my DB750 are microphonic. Tombowlus suggested that I get a gramma pad to cut down on the sound vibrations from the cab (directly underneath the amp), and I did. The gramma pad has made a noticeable improvement.

    But I still get some ringing from time to time and I think I just want to get a new set of preamp tubes. I noticed that Tombowlus mentioned in wnother thread that he tried Telefunkens on his db 750 with great results, so I'd like to give them a try as well. I respect his opinin and figure I can;t go wrong with the Telefunkens.

    So: Where do I get Telefunken preamp tubes for my DB750?
     
  2. ajb

    ajb

    Mar 20, 2005
    No one knows where to get Telefunkens? Come on, help a guy out! Tombowlus, are you out there?
     
  3. tombowlus

    tombowlus If it sounds good, it is good Gold Supporting Member

    Apr 3, 2003
    North central Ohio
    Editor-in-Chief, Bass Gear Magazine
    I got mine at www.dougstubes.com. Doug Preston is great to deal with, and I encourage you to contact him directly via e-mail or telephone.

    Tom.
     
  4. inazone

    inazone

    Apr 20, 2003
    Colorado
    I have the same problem in my db750 and went through the same with my db680 pre. I use a gramma pad as well and have never "tossed" arround my gear. It seems to me the stock tubes go bad in about a year (YMMV).

    I put Tung-sol tubes in the db680 and they have worked great for the last few years, Im going to do the same in the db750.
    Lord valve has them for about $15 each.
     
  5. I've experienced this with my DB659 as well. What is funny about it is they were NOS tubes that I received from Aguilar and when I replaced the stock tubes, it sounded horrible!

    I put the old tubes back in and it was all good again. I have never verified that those tubes were in fact microphonic because I did not have another tube pre to try them in.

    Tube preamps seem very sensitive to me. They sound great but you really have to make them happy for you to be happy LOL!
     
  6. SubMonkey

    SubMonkey

    May 3, 2004
    Denver, CO
    just some dumb questions...

    A fellow just looking in on this thread might get the idea that this is somewhat common (dare I say problematic) in this line of amps....

    do they use the same or similar pre-amp boards, could they (the PCB boards) be better supported ? any idea what the cause may actually be ? (used tubes sold as NOS ?)...

    I own none of the forementioned gear, I'm just wondering for my own benefit.

    SM
     
  7. One might draw that conclusion, based on this and a few other recent threads. I suspect that the ratio might be a bit lower than it appears.

    I've found Aguilar design and construction to be well above the norm. These "issues" probably do relate to the tubes themselves. In terms of supply and demand, companies are sometimes forced to switch suppliers or manufacturers to sustain production. A switch to a new supplier and a bad batch of tubes might test fine but not exhibit problems "in the field" for a while. My best guess (FWIW etc.) is that we're seeing the result of something along these lines.
     
  8. Hey Andrew, this is a little off topic... Just dropped in to visit your bass blog... very cool my fiend!

    LR
     
  9. Fiendish indeed! ;) Thank you for the kind words! I had some spare time this summer, so... those pages are the result.
     
  10. LouisV

    LouisV

    May 19, 2006
    mill valley, CA
    Just for the rec, my DB750 was also popin' & generally being tube-noisey. This is after over year of workin' hard in various clubs being quickly moved off the stage to make room for the next band or to go home. the beast also did some studio weekends running non-stop for 10-12 hours at a stretch, all without a sneeze... So after reading these posts, i called Doug at Dougs Tubes, & thank you Mr Bowlus! Doug was great to do business with! I called him on Thursday, we talked tubes, & I had the tubes in the amp on Saturday (1 Telefunken 12aX7, 2 Tung-sol 12ax7s, & 1 Amperex 12au7). The beast sounds (IMHO) totally clean (not only free of tube noise, simply clean tone!) & dare i say "better than ever!" Thanks for the tips! I also highly recommend visiting Dougstubes.com when it's time to change.
    (sorry for the long-winded post)
    louis
     
  11. bongomania

    bongomania Commercial User

    Oct 17, 2005
    PDX, OR
    owner, OVNIFX and OVNILabs
    There are also, for those who like to experiment, silicon rings you can buy which wrap around the tubes to reduce vibration noises. Here's one seller.
    [​IMG]

    As far as whether they actually help... I don't know yet, but I got some to fit 12AX7's which I will be trying out. Could be voodoo hype, could be very cool, we'll see.
     
  12. seamonkey

    seamonkey

    Aug 6, 2004
    headlight o-rings are high temp silicon. I bet they're a lot cheaper.
     
  13. tombowlus

    tombowlus If it sounds good, it is good Gold Supporting Member

    Apr 3, 2003
    North central Ohio
    Editor-in-Chief, Bass Gear Magazine
    I'm glad that you had a positive experience! Doug has always been a pleasure to work with. :)

    Tom.
     
  14. Primary

    Primary TB Assistant

    Here are some related products that TB members are talking about. Clicking on a product will take you to TB’s partner, Primary, where you can find links to TB discussions about these products.

     
    May 18, 2021

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