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Anatomy of a preamp (four of 'em, actually)

Discussion in 'Amps and Cabs [BG]' started by tombowlus, Mar 30, 2005.


  1. tombowlus

    tombowlus If it sounds good, it is good Gold Supporting Member

    Apr 3, 2003
    North central Ohio
    Editor-in-Chief, Bass Gear Magazine
    Well, based upon all of the recent preamp threads, and specifically relating to some talking about comparing the construction of various units, I thought I would take this opportunity to take a peek inside my preamps and share what I found. It was a sunny day here in Ohio, and I like to let them out for some fresh air anyway!

    [Check the link below to a stopgap fix. Sorry for the inconvenience.]

    Enjoy!

    Tom.

    P.S.
    One thing I did note is that the 680 is one heavy mo-fo! I have heads that weigh less! Nice construction, for sure.
     
  2. IvanMike

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

    Nov 10, 2002
    Middletown CT, USA
    gee, i bet those all look cool, but they "can't be found"

    i'll have to post the innards of my demeter sometime - almost nuthin in there, but done well.

    i have the 2nd generation of the 1.5 u demeter, i hear the original generation had "that look what i built in my garage look" on the inside, but this one is a work of art.
     
  3. tombowlus

    tombowlus If it sounds good, it is good Gold Supporting Member

    Apr 3, 2003
    North central Ohio
    Editor-in-Chief, Bass Gear Magazine
  4. Joe P

    Joe P

    Jul 15, 2004
    Milwaukee, WI
    Coooool!

    It looks like the DB680 and F-1X are the only two that have the pots and switches WIRED-over to a board??

    Am I seeing wrong, or do the others have the pots themselves connected directly to circuit boards?

    ~~~~~~~~~~~
    Even though 'every one knows' they're worth it, I have to admit that seeing this somehow makes it harder to whip-out $900 for an F-1x... You could almost run that thing on-board the bass (with a little cable that provided the three or four voltages for it to operate with). You could surely get the whole thing into a Hofner. Coool.

    Joe
     
  5. lsimy

    lsimy Supporting Member

    Apr 18, 2003
    Virginia, USA
    Cool thread Tom !! Interesting !!

    Dig the orange drops in the F1X as well as the simplicity of the Fender-style circuit. Dig it !! You could plug anything into that pre.

    The Ag's are beasts and the Nav looks complex.

    Thanks again!!
     
  6. SirPoonga

    SirPoonga

    Jan 18, 2005
    Cool.

    I've been looking at making my own head. These pics have given me layout ideas.

    Yep, some of those pots are directly on the board. Takes a good pcb designer to figure that out.
     
  7. tombowlus

    tombowlus If it sounds good, it is good Gold Supporting Member

    Apr 3, 2003
    North central Ohio
    Editor-in-Chief, Bass Gear Magazine
    The direct links (to larger photos) are still causing me fits, but the shared photo album, above, seems to work just find.

    Thank you for your patience!

    Tom.
     
  8. jokerjkny

    jokerjkny

    Jan 19, 2002
    NY / NJ / PA
    very cool, tom!

    i havent had a chance to pry open my alembic pre, but WOW, that is a thing of pure, simplified tube beauty. :bassist:

    btw, for anyone else about to do the same, pleez remember to keep the pics small like tom's, and not to show too much detail like cap values, and what not. :ninja:
     
  9. Pickebass

    Pickebass Supporting Member

    Jul 12, 2004
    San Antonio, TX
    :meh: interesting.... Based on what you see, do you see anything that a new preamp buyer should be concerned in regards to their purchase?

    primarily in regards to reliability/durability? As the pictures show some are more fragile than others, and some circuit board designs may cause headaches depending on how it is used....

    Just curious...
     
  10. tombowlus

    tombowlus If it sounds good, it is good Gold Supporting Member

    Apr 3, 2003
    North central Ohio
    Editor-in-Chief, Bass Gear Magazine
    Actually, quite the opposite. What I saw made me feel very good about all four of them. Each one is very well made, and nice and neat. The DB 680, though, takes the cake for the most over the top, top dawg quality.

    But I feel very confident saying that any of them would serve you well, and are well constructed.

    Tom.
     
  11. BillyB_from_LZ

    BillyB_from_LZ Supporting Member

    Sep 7, 2000
    Chicago
    Aren't the photos of the DB659 and F1-X backwards? The knobs are reversed and the marking on the Aggie's transformer is written backwards....or is it just really, really late and I should be in bed...

    BTW, thanks for posting those photos...I love that kind of thing.
     
  12. tombowlus

    tombowlus If it sounds good, it is good Gold Supporting Member

    Apr 3, 2003
    North central Ohio
    Editor-in-Chief, Bass Gear Magazine
    You are corret! I have attempted to correct the problem (though SBC Yahoo! seems intent on making this as difficult as possible!).

    Tom.
     
  13. Tedintheshed

    Tedintheshed Banned

    Oct 8, 2004
    Columbus, Ohio
    Tom,

    I'll be cleaning the pots on my Demeter HBP-1 this weekend- want me to send some pics along to you?

    Ted
     
  14. tombowlus

    tombowlus If it sounds good, it is good Gold Supporting Member

    Apr 3, 2003
    North central Ohio
    Editor-in-Chief, Bass Gear Magazine
    That'd be great! I'll post them right alongside. Actually, I am working on finding some more web space to host some pictures in a more user friendly fashion!

    Thanks, Tom.
     
  15. dood

    dood

    Dec 9, 2004
    sitting down,facingforward..UK
    Endorsements: Shuker Guitars, Dingwall Designer Guitars, D'Addario, Planet Waves, Barefaced Bass
    Has anyone got an SVP-pro they can post? I'm gonna do mine soon, but I can't help thinking that something has been 'fiddled' with in it. Looks like it has been customised somehow... :meh:

    I'd like to compare it with mine.
     
  16. IvanMike

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

    Nov 10, 2002
    Middletown CT, USA

    i hear ya, i get the same impression from the inside of my demeter vtbp-201

    but it just goes to show ya, some of the best sounding units have almost nothing to them. not saying you think this way, but i do get a kick out of players who want a "transparent" preamp that is as close to a "bare wire sound" as possible, then they get mad that there's almost nothing inside it. :p
     
  17. dood

    dood

    Dec 9, 2004
    sitting down,facingforward..UK
    Endorsements: Shuker Guitars, Dingwall Designer Guitars, D'Addario, Planet Waves, Barefaced Bass
    OK, as per above, here is the inside of my SVP.

    Can anyone tell me if the inside is what should be expected?

    In the first link, I have circled the area that the other two links are homing in on. The images are rather large, so sorry if that is annoying.. (hence why I haven't pasted them directly on the board!!!)

    Full image, a bit blurred..

    First close up

    Second close up

    My main concern, on the images there is R16 & R17, yop right hand corner.. whats going on here? has this been customised or is this how the Pre left the factory?? and the Electrolytics down in the Left hand corner, what is going on there!! what an abortion!!

    This AMpeg is a black faced year 2000 model.
     
  18. Funky Doctor

    Funky Doctor

    Aug 28, 2003
    Australia
    Funny you should mention that... Back when I could be bothered, I found a picture of the insides of one (actually, it was an F-2B). I looked and remembered what each component value was (with a little help from the fender amp field guide). Being a common, simple topology, I whipped it up in no time. Sounded great. I didn't bother putting it in a rack unit, in fact, I didn't really use it for more than just a little bit of experimenting. It is probably still laying around somewhere.
     
  19. Joelc73

    Joelc73 Supporting Member

    Nov 13, 2000
    New York
    Tom,

    This is a very cool thread. I posted some pictures a few weeks back on my site of the innards of a DB680 with a few other angles. I posted the Demeter VTHF300M at the same time. You can find them here:

    http://thegrooveshoppe.com/Aguilar/DB680.html
     
  20. tombowlus

    tombowlus If it sounds good, it is good Gold Supporting Member

    Apr 3, 2003
    North central Ohio
    Editor-in-Chief, Bass Gear Magazine
    I added a shot of the inside of the DB 359. This shot was taken by the seller to help me figure out where to put the tubes when I get it (he packaged them seperately, which is nice).

    Preamp photos