Homemade tube preamp/amp head questions

Discussion in 'Amps [BG]' started by J03YW, Dec 22, 2012.


  1. J03YW

    J03YW

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    Hey, I was in my great grandfather's basement and my grandpa got very excited just as my dad grimaces and has to leave out of fear what's going to happen.

    My HAM Radio loving grandpa just found a box of vacuum tubes & components. My father had been hiding from me that his dad has a whole stockpile of tubes laying around. Currently I have a BG250 that I just got and a crappy crate amp. Here lies the question: What should I do, to what, with what, and how? I kind of want to make a real nasty tube preamp that just has a gain knob and run it into either of the amps to my liking. I'd put 1/4 inch jacks on it, and use 3 12AX7s on it. Anyone have any ideas? I'd rather make a simple preamp than make a power amped head, instead my idea is to use my bg250 for cleanish lows (it already has tubedrive, i figured.) and my crate as a kind of hybrid dirty for top end, using my homemade preamp. Thoughts?
     
  2. JimmyM

    JimmyM Supporting Member

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    Good thought, I guess, but parts ain't cheap. And I'd do some research on what's all involved in doing it. But I'm all for someone who wants to learn how to do stuff like that.
     
  3. RickenBoogie

    RickenBoogie

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    There are tons of various vacuum tubes, but most of the ones used an MI amps, are not the same as those used in Ham radios. Then there's building the preamp, which is not a beginners project. You should start reading some Electronics books, and see what you can learn. Have fun with it.
     
  4. J03YW

    J03YW

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    the advantages of having a HAM radio grandfather: he has every part under the sun and the knowledge to make a very nice amp. He makes these radios every day and knows what he's doing. I'd like to ask you if 3 12ax7s and a gain knob would be enough to make a very raunchy preamp, or if i should change what kind/ number of tubes i should use. thanks!
     
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  6. will33

    will33

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    I admire your enthusiasm. Unfortunately, it isn't that easy to make this stuff people make that we can plug into and sound good. Not to be discouraging in any way, I say "do it", but, much research and learning is needed.

    I'd start by getting numbers off all the tubes you have there, searching them, and taking inventory. And don't let anybody talk you out of them, at least until you know what they all are. Then go from there.....
     
  7. J03YW

    J03YW

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    He has the tubes necessary as well as the ability to build a preamp. i plan to learn from him while making it
     
  8. J03YW

    J03YW

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    all right
     
  9. Mr. Foxen

    Mr. Foxen

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    Easiest starting with a cloned preamp, so you know roughly what you are going to end up with, that way you know it is an error if it sounds rubbish, rather than just how it sounds. Fender type tone stack and an gain stage would be a good start.
     
  10. B-string

    B-string Gold Supporting Member

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    Just picking a number of tubes means nothing. With just a gain control your idea of three dual triodes would be just a waste of glass. Two at the very most would be needed and chances are one half of the second will go unused.
     
  11. will33

    will33

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    It blew my mind when I learned that tubes even had halves. Like a 12ax7 is like 2 tubes in one.:bag:
     
  12. T-Bird

    T-Bird

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    Hi.

    One great place to start is the http://www.ax84.com/ .

    Unless You're doing something extremely, insanely hot, 1 12AX7 is all You'll need, 2 for a simple "EQ".


    A pre-amp is about the best introduction to the world of tubes, kudos for choosing that instead of the usual "I WANNA BUILD A SVT".

    +1 for copying a proven pre-amp design, Febder Bassman circuit for example is a breeze to make.
    SVT pre isn't that hard either.

    I only wish I'd had a grandpa or pa like that when I was starting out, would've reduced the amount of OOOPS! incidents quite a bit.

    Do rememer though, SAFETY FIRST.
    Even though You don't necessarily have as dangerous voltages there as in a power amp, you'll still be able to fry the nerves on your fingers.

    Regards
    Sam
     
  13. J03YW

    J03YW

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    thanks, i'm sure my gpa's wallet will appreciate this
     
  14. J03YW

    J03YW

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    I'm kinda trying to make a 25/50 watt amp a bit (read: a helluva lot) louder/make it a kind of bastard-hybrid with this preamp without adding a power section cause i don't want to hurt myself. is that plausible?
     
  15. fdeck

    fdeck Supporting Member

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    Well it's cool to have someone to learn from. For now I suggest learning as much as possible, and an idea for an actual project might just jump out at you. Your grandpa can show you how the audio circuits work in basic receivers, which are conceptually the same circuits used in music gear. This would give you a good head start on understanding tube bass amps.
     
  16. B-string

    B-string Gold Supporting Member

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    Distortion always sounds louder than an undistorted one. Look to get your overdriven sound in your preamp. The signal from the preamp should not be strong enough to overdrive your existing power amp though.
     
  17. J03YW

    J03YW

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    do you think it could bring my 25 watt amp up to the same loudness as a 250 watt at around 12 o'clock master volume? i want to have my bg250 do clean lows and have a frankensteined tube preamped crate solid state for highs, but it's like 25 or 50 watts at most and i really want it to be stronger.
     
  18. B-string

    B-string Gold Supporting Member

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    Include a crossover so the little amp only sees about 500Hz and above and it might stand a chance. In near field anyway. The further you get the weaker it will be. 50 watts from a guitar (our ears hear better there) will shred your ears, 1/2 mile away the 100 watt bass will be heard well over the guitar.
     
  19. JimmyM

    JimmyM Supporting Member

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    A power amp is what it is, and while you can eke a little bit of performance out of a tube power amp sometimes, don't expect miracles. OTOH, if all you need it for is highs and upper mids, 25w is likely going to work with a "250w" amp like the BG250. Hell, my main gigging rig is only 25w!
     
  20. J03YW

    J03YW

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    awesome, can't wait to dirty it up
     
  21. shackled

    shackled

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    Hey, thanks for that link! I've been looking for something like it.
     

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