Pics of My Home Brew Tube Bass Preamp

Discussion in 'Amps and Cabs [BG]' started by lneal, Apr 16, 2007.

  1. lneal


    Apr 12, 2002
    Lee County, Alabama
    Here are a few bad pics of an all tube bass preamp that I designed and hand built myself called "Magnum". I have been reluctant to post anything much about it before now because I didn't feel it was "ready" until recently. Yes, I use it on every gig now and it has proven itself reliable. It has 6 audio tubes and 1 rectifier tube, is mostly transformer coupled (except for the tone section), input to output and weighs over 23 pounds! The "Gain" control is a 5 position sealed switch that selects taps on an attenuator transformer to control the input gain instead of the usual potentiometer. The input and output are push-pull and it has a transformer coupled DI output. The tone section is 3 band, tube driven by 6CG7 tubes and adds just enough grit to give it balls and can also be bypassed. The sound? Clean and natural with stunning clarity with the tone bypassed. Switch in the Tone section and it adds smooth, natural lows and highs and if I crank the Mid it can get as nasty as I want, but never peaky like those SS op amp things. The schematic will be forthcoming and one day I'll get the web site up with full details. I posted this to prove that you can have exactly what you want, no compromises, but you pretty much have to do it yourself.....:cool:

    The 1st pic is the front panel; the 2nd shows the audio tubes, in order: 6SN7GT (Input), 6CG7 (DI Output), 6CG7 (Mid), 6CG7 (Low/High), 6SN7GT (Buffer/Driver), 5691 (Output)

    Attached Files:

  2. lneal


    Apr 12, 2002
    Lee County, Alabama
    First pic is the whole thing from the top and the second shows the vintage Triad A65J output tranny for the Stage out as well as the 5Y3GT rectifier tube. You can also see in the upper left from top the B+ tranny, Filament tranny and the filter chokes at the bottom. The 2 black capacitors are for the DC filament supply.

    Attached Files:

  3. That is awesome. I love how all your knobs go to 11. This one goes one louder.
  4. fdeck

    fdeck Supporting Member Commercial User

    Mar 20, 2004
    Madison WI
    HPF Technology LLC
  5. Fat.Mike


    Dec 15, 2006
    Tulsa, Ok
    10 is just NOT enough. Long live the Tap! Awesome work!
  6. Awesome.... great JOB!!!! espesh the '11' Must be extra special tones & extra loud with that! ;-)
  7. Bard2dbone


    Aug 4, 2002
    Arlington TX
    NIce. So what do you use as your power amp?
  8. msquared


    Sep 19, 2004
    Kansas City
    And how could this thread go without mentioning the color? It's like, how much more black could this be? And the answer is none. None more black.
  9. jokerjkny


    Jan 19, 2002
    NY / NJ / PHL

    to "11"... :cool:
  10. Passinwind

    Passinwind I know nothing. Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    Beauty! How about some sound clips?

    Where did you get the rack case BTW?

    I'll be posting some pics of my new DIY tube line driver in the next week or two, hopefully. All the parts should be in by later this week.
  11. svtb15

    svtb15 Inactive

    Mar 22, 2004
    Austin,TX - McKinney,TX - NY,NY, - Nashville,TN
    I play it all. Whatever works for the gig. Q+
    that looks like a high end piece of studio gear... if that does not sound Tubey.. nothing will...
    very nice..
  12. Trevorus


    Oct 18, 2002
    Urbana, IL
    What's with the somewhat out of the ordinary tube compliment?
  13. okabass


    Mar 19, 2005
    Oh, yeah. Huh.

    Those Lundahl, Sowter and Hammond irons costs at least 20 times more than a "normal" modern IC-bass pre.

    Never seen that kind of bass pre. Great.

    However, two answeres.

    You are using polypropylen Solen caps. Why the big blue electrolyte? Why all tube bases are not ceramic?

    Triad xformer? I have about 20 JS (Jörgen Schou, DK) line irons. Interested?
  14. getz76


    Apr 3, 2005
    Hoboken, NJ
    That's pretty hot. I'd buy it without even listening to it (mostly due to the "11").

  15. markjazzbassist

    markjazzbassist Supporting Member

    Apr 19, 2005
    Shaker Heights, OH
    looks cool. how much?:smug:
  16. seanm

    seanm I'd kill for a Nobel Peace Prize! Supporting Member

    Feb 19, 2004
    Ottawa, Canada
    Looks nice!

    I noticed an XLR on the back, does it have a tube DI?
  17. seanm

    seanm I'd kill for a Nobel Peace Prize! Supporting Member

    Feb 19, 2004
    Ottawa, Canada
    Could you post a link here when you do? I, for one, don't want to miss it.
  18. WOW!!! For a preamp, that really looks "beefy." Looks like you didn't shortchange the transformers. :eek:

    <Couldn't really think of another word than beefy.>

    Nice work! :)
  19. lneal


    Apr 12, 2002
    Lee County, Alabama
    Thanks for the compliments, guys. I'm mighty proud of it.
    To answer some questions:
    I use a QSC 1700 power amp and yes I have drawn up plans for an all tube transformer coupled power amp.

    As far as the look, I was going for that 1950's laboratory gear look, stark and badass.

    The out of ordinary tube lineup comes from my dislike of the ubiquitous, non-linear 12A_7 junk, I wanted the input and output sections to be clean and clear, not distorted and colored, letting the tone section provide the warmth and goodness.

    The electrolytics are for the B+ supply only and the Solens are in the signal path. There are also a few NOS Siemens plastic caps in there.

    The DI gets a feed from the input stage off the Lundahl and is a totem-pole cathode follower driving a Sowter plate to line tranny.

    The rack case is from Hammond.

    I'm going to work and won't be able to reply anymore til tonight.
  20. Cool, very cool! Congratulations!