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Tube problems - demeter HBP-1

Discussion in 'Amps and Cabs [BG]' started by rick1906, Nov 21, 2006.


  1. rick1906

    rick1906

    Jun 6, 2002
    SD
    My rig consists of a Furman tuner/power conditioner, Crest CA-6, and Demeter HBP-1. I have owned the Demeter pre for less than a year now but I will be replacing the tube again for the second time. The preamp is very noisy until I change the tube. But then after a couple of weeks or so, it becomes noisy again. What could be the problem? I carry it to church every Sunday, so could transporting it cause the problem? I try not to bang it around much, but it occasionally happens.
     
  2. Jim Dombrowski

    Jim Dombrowski Gold Supporting Member

    Jan 16, 2002
    Colorado Springs, CO
    2 suggestions:

    - Send the preamp to Demeter, or have it checked by a competent technician . Perhaps there's something internal that's causing the tubes to malfunction.

    - Perhaps the Furman unit is not operating properly, and causing the problems with the preamp.
     
  3. Something strange going on for sure. Can you elaborate some on the kind of noise you are hearing...hiss, crackling, popping, or other?
     
  4. Jim Dombrowski

    Jim Dombrowski Gold Supporting Member

    Jan 16, 2002
    Colorado Springs, CO
    Also, you didn't say what tubes you are using. Perhaps you're just having bad luck with tube life, although preamp tubes should generally work for many years.
     
  5. chadds

    chadds

    Mar 18, 2000
    I went through 3 Tung Sol reissues in my BBII before I found one that didn't gurgle and spit. Though they all sounded amazing the final one is silent.
     
  6. Arthur U. Poon

    Arthur U. Poon

    Jan 30, 2004
    SLC, Utah -USA-
    Endorsing Artist: Mike Lull Custom Basses
    IMO call Demeter (805)461-4100 and get it in asap for repair before your warranty expires.

    Sorry for the long post:

    I guess I'd been using my HBP-1 for about 6 months and it suddenly started making a screeching noise. The noise wasn't constant and I couldn't figure out what was causing it. Sometimes it would happen after the unit had been in use for a few sets, other times it would happen shortly after powering it up. It was very frustrating because I was gigging alot at the time. Thinking it was probably a faulty tube I bought a replacement EH12AX7 from my local music store. Even after I replaced the tube the screeching noise persisted. I put it's original tube back in, got in touch with Demeter, and sent it back to them. I was told a few of my jacks were faulty, (I think they said they were cracked), and the tube was microphonic. Since I've had it back, it's worked flawlessly. IIRC, they were really quick in repairing it and getting it returned to me.

    As far as trying different 12AX7's are concerned, I bought a few NOS GE 12AX7's, but to my ears the difference in sound wasn't that noticeable from the stock EH12AX7. Actually, one of the GE tubes I bought was microphonic right out of it's box. I'm quite happy with it's sound using the stock EH12AX7.

    If you reugarly send a feed into the P.A., you may want to consider paying Demeter to replace your stock D.I. with the Jensen D.I. that they put into the VTBP-201S preamp. According to the HBP-1's manual, phantom power in excess of +48 volts can cause damage. I believe Tommixx had a few drivers damaged as a result of a P.A. board's phantom power feeding back into his HBP-1. The Jensen D.I. wasn't an option when I bought my preamp, so I bought a Jensen equipped Radial D.I. box as a precaution. Had a Jensen option been available, I would've gladly paid extra for it at the time I purchased my preamp. -Just a thought.

    I hope everything turns out 100%
    -Art
     
  7. rick1906

    rick1906

    Jun 6, 2002
    SD
    I am hearing all of the above...

    I've used the stock EH12AX7, two JJ Electronics, and now I'm back to another EH12AX7.
     
  8. Jim Dombrowski

    Jim Dombrowski Gold Supporting Member

    Jan 16, 2002
    Colorado Springs, CO
    Arthur Poon: Do you know if the Jensen DI from Demeter is available with adjustable output level (as opposed to the push-pull switch on the HPB-1)?

    Jim D
     
  9. Arthur U. Poon

    Arthur U. Poon

    Jan 30, 2004
    SLC, Utah -USA-
    Endorsing Artist: Mike Lull Custom Basses
    Hi Jim, I'm not sure. But I remember Pickebass had the mod done. Shoot him a pm, I'm sure he'll know.

     
  10. Pickebass

    Pickebass Supporting Member

    Jul 12, 2004
    San Antonio, TX
    GET the DI. Personally had bad luck with JJ tubes. Purchase multiple tubes and had problems. A telefunken tube sounds really nice in this head
     
  11. J.Wolf

    J.Wolf Supporting Member

    Apr 29, 2003
    Asheville, NC
    Contributor- Bass Musician Magazine
    I didn't like a telefunken in my HBP-1, but I really liked a Sovtek 12AX7LPS.

    Bummer about the wierd noises. +1 on calling Jim and seeing what he has to say. Also I would try a few more tubes before shipping it off. Its a longshot, but you may have just had some bad tubes.
     
  12. rick1906

    rick1906

    Jun 6, 2002
    SD
    Guys, thanks for all of the suggestion. It does appear to be bad tubes. I just changed it, and the preamp is as silent as it has ever been. Hopefully, it will last a while.

    I don't play through a PA much but I would like to get the DI mod. Does anyone know if it is a quick turnaround? That's the only preamp I have now.
     
  13. Pickebass

    Pickebass Supporting Member

    Jul 12, 2004
    San Antonio, TX
    Turnaround time was not the best. It took about 6 weeks if I remember correctly. If it's not something you need to do, just buy a good DI. I had it done because I was going thru a PA all the time
     

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