Preamp Tubes? - Who, What, When, Where, Why, and How?

Discussion in 'The Workbench' started by joshuaaewallen, Jan 29, 2009.

  1. RiverRatt

    RiverRatt Well-Known Member VIP Member

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    No, the connectors leads on this thing aren't anything like the ones on my handheld meter. I was expecting banana plugs but these are a lot better quality. They look like they would have a solid outer ring and a banana plug or smaller in the middle. There's also what looks like an old serial-type connector.

    If you could find or build a pair of test leads for it, I'll bet it would still work. It might need calibrating but it's built like a tank and it seems to be in good condition. It has this cool NASA Apollo era look to it, like a huge red LCD readout and more plugs on the front than a telephone switchboard. It has handles on the front corners like older rack gear.
     
  2. MM54

    MM54 Well-Known Member

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    That does sound good, leads couldn't be that hard to come by for it. What's the model number again (so I can look it up)? The sort of industrial-used-to-be-high-tech look is quite my thing as well :D

    I have a hand-held meter that the probes have a solid outer ring with the banana plug in the middle, you can't use the leads on jacks that don't have the space for them, but I've used regular banana plug leads on it before and it seemed to work just fine.
     
  3. RiverRatt

    RiverRatt Well-Known Member VIP Member

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    I can't get to it right now. I've got to get ready for work and it's buried under a stack of debris. I'll check it when I get home this evening.
     
  4. sccloser

    sccloser Well-Known Member

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    Just dropping by to say that I am still alive. :D
     
  5. Captshiznit

    Captshiznit New Member

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    Hi thanks dude,

    I've done some reading got some preamp tubes on the way. Really good link will check it out.

    Preamp tubes I got if you are curios 2 Tung sol's for V1 and V2 a JJ EC803s for v3 and a Sovtek LPS for V4

    Will also probably mix them about but that's the idea so far.

    Will also take some pics of my old marshall tubes for guys to ID I really wanna know what they are so I can also maybe throw them into my tube mix. :D
     
  6. RiverRatt

    RiverRatt Well-Known Member VIP Member

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    Always good to know Vic! :wave:

    I was just thinking I haven't seen Cody or Joe hangin' out much either. Glad that Josh is getting a post or two in.
     
  7. Drake

    Drake Member

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    Wow, what a great thread. They should make this one a sticky!
    Anyway, other than my vintage marshalls, I am working on a new project, and could use some advice.
    I am up grading a vintage Ampeg B25 Bass amp. It currently has new JJ tubes in it and the tone is very "mid-Range". I need something to pull the bass back out of it. Also, it has a hum to it. All the caps have been replaced, good cables etc...so. I read on here that some preamp tubes could cut hum. Which ones would be best? It uses 12ax7's and a 6cg7.
    Thans for any advice!
     
  8. MartyStrat54

    MartyStrat54 Well-Known Member

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    Are you saying that you had a hum before changing tubes? If it was there already, I suspect a ground or lead dress problem.

    Try swapping your 12AX7 tubes around and see if the hum changes. If so, it is a tube problem. Just because you got new tubes doesn't rule them out.

    You probably would be better off with a Tung-Sol in your V1 slot.
     
  9. MartyStrat54

    MartyStrat54 Well-Known Member

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    The hum could be coming from your power tubes as well.

    Does your V1 tube have a metal shield on it? If not, is the tube socket the kind that you can put a shield on? This may help a little as well.
     
  10. Drake

    Drake Member

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    Yeah, the amp was serviced when I bought it, then my tech re-serviced it and said the hum was there before he worked on it. It does have shields on it already. Im getting ready to dump the JJ's for a set of Shuguang KT88's. Ill try the tung sol 12ax7 in v1
    ps...what is a lead dress?
    thanks
     
  11. Drake

    Drake Member

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    I figure the lead dress is the covering for the power (lead) cable, duh. Yeah, we replaced the whole thing and put a modern three prong ground power lead in.
     
  12. mickeydg5

    mickeydg5 Well-Known Member VIP Member

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    The subject is an Ampeg B25; What type of JJ power tubes are in there right now?
     
  13. Drake

    Drake Member

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    I had my tech rework it for KT88's. I know that is not stock. We also took out the rectifier tube and went solid state...better for bass than a sag tone (good for guitar)
    makes a bass muddy. The pre amp is 12ax7 and one 6cg7. Its had a cap job too. Basically, not much left of the original design LOL Even put in a cooling fan....hot rod!
     
  14. mickeydg5

    mickeydg5 Well-Known Member VIP Member

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    Plot thickens.
    Did the tech say whether or not the hum was there prior to rebuilding for KT88 tubes?
    Was the power transformer swapped out? If so, what brand & model?

    I do not want to ask too many more questions because we are in a preamp tube thread.
     
  15. RiverRatt

    RiverRatt Well-Known Member VIP Member

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    I revisited a guy I've bought from in the past today. He brings out boxes of tubes and insists that they are the ones I've already looked at, but then I find surprises like these. I don't think I would have overlooked these.

    [​IMG]
    L-R: Tungsram, Amperex Heerlen, Amperex Heerlen with Bugle Boy logo intact (YAY!) and an unknown 12AX7, possibly Hitachi. It has a seam that runs all the way from bottom to top on two sides, like the bottle was two pieces of glass joined vertically.

    The icing on the cake:
    [​IMG]
    Like I said, I'm on a EL84/6BQ5 roll lately. L-R: Sylvania, Unknown W. Germany (looks like Russian 6P14P), Sylvania, G.E., G.E., and a Mullard EZ81. If the rectifier tests good, I'm not going to have much of an excuse not to put together an 18 watt clone.
     
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  16. MartyStrat54

    MartyStrat54 Well-Known Member

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    Nice find on the tubes, especially the Bugle Boy. Is the date code still visible on it?
     
  17. RiverRatt

    RiverRatt Well-Known Member VIP Member

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    Yeah, Delta2K2. I can barely make out the bottom of the type code. It looks like I65. The other Amperex without a label is a couple of years newer than that. You can read the date code fine but that's the only thing left on the tube. I just gave it a 30 minute test drive in the VM and it sounded good.
     
  18. sccloser

    sccloser Well-Known Member

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    Good score!
     
  19. 66 galaxie

    66 galaxie Well-Known Member VIP Member

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    Wow, nice score Alan!
     
  20. Drake

    Drake Member

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    No, the PT was not replaced.
     

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