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Aggie db750 / Whappo Jr. not sounding right

Discussion in 'Amps and Cabs [BG]' started by JimmyT, Nov 28, 2004.


  1. JimmyT

    JimmyT Supporting Member

    Nov 28, 2004
    Seatlle
    Hello TB'ers - first timer; please be gentle :) Upgraded gear about 3 weeks with Aguilar DB750 and Whappo Jr. Sounded very good up until yesterday when tone went dull - kind of muted with perceived loss of overall range & clarity, and strange hissing rattle sound in tweeter at certain notes (consistent as note sustains - fairly loud), mostly in upper register of my 4 str Alembic Spoiler. Have not run head past 12:00 - gentle use at home practicing. Any ideas on where you would start to isolate the problem (other than contacting AG and Aguilar - in process). Could it be anything in the head? Hope not - bought used. Strange in that the tweeter doesn't seem to rattle with my SWR 350x head or GK800RB, but those have much less power and the cab still just doesn't sound right. BTW - changed the battery in the Alembic and put new strings on right away - problem still there.

    Thanks for any thoughts - I promise to contribute along the way for others after I get my selfish needs taken care of!
     
  2. IvanMike

    IvanMike Player Characters fear me... Staff Member Supporting Member

    Nov 10, 2002
    Middletown CT, USA
    bummer - see if you can try the aggie with other cabs, my $ is on there being an issue with the head.
     
  3. it could be a tube problem. if the cab responds like it should when used with a different head.
     
  4. NJL

    NJL

    Apr 12, 2002
    San Antonio
    both Aguilar and Accugroove have great service, they are only a phone call away!

    :)
     
  5. JimmyT

    JimmyT Supporting Member

    Nov 28, 2004
    Seatlle
    Thanks for the replies. First, found Mark at Accugroove and Dave at Aguilar to be very responsive, helpful and friendly. How nice is it to have the owner answer the phone directly. I hope they will be able to continue the great service as they grow.

    To update in the event this helps someone else - I plugged directly into the poweramp in on the back of the DB750, and the sleigh bell kind of sound disappeared. Looks like a preamp tube; sound is there in the tweeter when you simply tap on the faceplate of the amp as well. New preamp tubes are on the way. I'll let you know the conclusion.

    Thanks again - both are fantastic pieces of gear.
     
  6. NJL

    NJL

    Apr 12, 2002
    San Antonio
    i'm glad it's working our for the better!

    btw, if you ever need me to baby sit your rig, just let me know!!!

    :D
     
  7. JimmyT

    JimmyT Supporting Member

    Nov 28, 2004
    Seatlle
    It was the preamp tubes all right. Some new Russian made goodies, and voila: she's back, she's black and she's got a plan to stick it to the man. You hear that preamp tubes should last a long time, so I guess there's always an exception...

    One quick question - you can't tell by looking at them which one was bad. I don't want to chuck those that are good; I guess you would take them to somebody who has an appropriate tester?
     
  8. IvanMike

    IvanMike Player Characters fear me... Staff Member Supporting Member

    Nov 10, 2002
    Middletown CT, USA
    i woulda swapped them out one by one (you still can) to help identify the culprit(s). I'm really glad things worked out so easily and cheaply for ya. that is one K/A rig you got there.
     
  9. JimmyT

    JimmyT Supporting Member

    Nov 28, 2004
    Seatlle
    Thanks bro - I will. BTW - my son loves your "Mandy" icon.

    Be good
     
  10. J.Wolf

    J.Wolf Supporting Member

    Apr 29, 2003
    Asheville, NC
    the DB750 has four tubes I think. One is a preamp tube, one is a cathode follower tube, and the other two are for the EQ. When I had mine, I had a tube go bad, and I replaced the preamp (gain stage) russian tube with a telefunken 12ax7. That was the best thing I could have ever done for that amp! It totally came to life and sounded much better than with the stock tube, and the stock tube sounded pretty darn good to begin with. Of course, I then forgot to remove that tube when I sold it (read: DOH!) Someone got lucky.
     
  11. JimmyT

    JimmyT Supporting Member

    Nov 28, 2004
    Seatlle
    Thanks! I've kept myself from being any more than a plug and play guy for years - would be great to know a little more. Posts like yours help. Yes, 4 tubes in the 750 (I thought they were all considered preamp tubes) (3) 12ax7 and (1) 12au7. If you don't mind, do you remember the chain? If I'm facing the amp with the hood open, from right to left are the 12ax7's and as it turns the corner the 12au7. Which one is the gain stage and why is one of them have the metal shield (the 3 hole) over it? Why did you sell yours? Hernia? What did the Telefunken do for your ears? Again, thanks for the tip and the education.
     
  12. J.Wolf

    J.Wolf Supporting Member

    Apr 29, 2003
    Asheville, NC
    jeez I think I remember.. The one with the shield is the preamp tube, and the one behind it is the cathode follower tube. The two along the front panel of the amp are the EQ tubes. I hope I'm right about the functions of these tubes, I remember looking under the hood with an amp builder/tech buddy of mine and that was his opinion. I tried a bunch of tubes as preamp tubes, 5751, EH 12ax7, EH 12ax7lps, JJ Tesla, and some others, and when we popped the telefunken in there it was like whoa!! Really articulate and smooth and lots more information and detail in the mids that really gave the sound a distinct richness, and made it sound more 3D. Damn that was a nice sounding combination, but..... (and there usually is a but) they can be really pricey, and there are alot of fraudulent or used ones out there for sale, so be careful and buy from someone who is reputable and trustworthy. I hear lord valve is a good guy to buy from. not sure how to contact him though.

    I have some accugroove cabs, and the DB750 was a killer match for them. The clarity of those cabs and the depth of the sound always brought out the best of that amp, and vice versa, and you know it has the wattage to get any cab singing!!

    Anyways good luck, and I do suggest contacting Aguilar to pick their brain about tubes and which is which, in the off chance that I'm incorrect about my description, which may very well be. Happy listening
     
  13. Dr. PhunkyPants

    Dr. PhunkyPants Guest

    Aug 11, 2002
    USA
    I thought one of the four in the DB750 was for the DI. Not that I'd know, since Fedex destroyed the one that was supposed to be mine.
     
  14. J.Wolf

    J.Wolf Supporting Member

    Apr 29, 2003
    Asheville, NC
    perhaps you're right. I don't have my manual any more. I am almost positive that the one beneath the shield is the gain stage tube, switching that one would have the most affect on the tone.