Carl Thompson mods

Discussion in 'Luthier's Corner' started by Zentner, Jan 5, 2017.

  1. Hello everyone,

    I've done the unthinkable and made mods to one of my favorite instruments.

    I got the idea from a NY jazz musician, Gene Perla who made a similar mod to his bass - a removable low C extension. My build includes no permanent mods to the bass to uphold Mr. Thompson's original intention for the instrument. It clamps through the tuning peg hole, and all components (save the string tree and gotoh tuner) were made by yours truly.

    The build includes a replacement 3 string nut, a nut for the extension, the capo, rear disc, some brass work, and the extension itself. Woods used include Honduan mahogany, Desert Ironwood veneers, and a Mun Ebony fingerboard. Black Ebony was used for the capo, and the string tree (as made by THG knobs) is flamed Koa. I also built a pickup cover which uses the existing screw holes for the pickup ring of the Schaller pickup, which also fits neatly under the desert ironwood cover.

    Enough talk, here's the bass. I'm happy to answer any design questions you've got. Everything was done with hand tools (dremel primarily) a bandsaw, and a lathe for the thru headstock dowel.

  2. madbass6

    madbass6 Inactive

    Jan 13, 2009
    I do not give consent to use any of my photos ! please respect that. thank you.
    Well Got to give you credit for having your Balls in place!
    awsome idea (in theory)
    but damm dude,
    We're talking about a monster gorgeous master piece of a Bass !
    I mean you're messing with a CARL THOMPSON Bass!! Hey at the end of the day it's your Bass , your choice! Enjoy!!
  3. Will_White


    Jul 1, 2011
    Salem, OR
    It's just like a C extension on an upright (which are often worth more then a Carl Thompson), he hasn't really hurt anything no extra holes no wood carved away.
    salcott, funkbass187 and tbrannon like this.
  4. bassbombs84


    Dec 26, 2008
    Seriously? Get your head together man!
  5. Beej


    Feb 10, 2007
    Vancouver Island
    Looks great! Well done... :)
    Max Allstadt likes this.
  6. rufus.K


    Oct 18, 2015
    Wow! The ingenuity and work involved are fantastic. Well done!
    salcott likes this.
  7. I-Am-The-Slime


    Jan 8, 2010
    SW VA
    looks great, nice work
    salcott likes this.
  8. madbass6

    madbass6 Inactive

    Jan 13, 2009
    I do not give consent to use any of my photos ! please respect that. thank you.
    salcott likes this.
  9. madbass6

    madbass6 Inactive

    Jan 13, 2009
    I do not give consent to use any of my photos ! please respect that. thank you.
    Maybe so, but still we're talking about a CARL THOMPSON Bass! Not a Squire here not to mention a gorgeous master piece of a bass! (Before the mod)
    again, his bass, his choice !
    I mean in my opinion (Personally)
    I would of experimented with a much lower end Bass first like a Squire/Ibanez/ PV etc.
    Defenetly Not with a
    CARL THOMPSON/Smith/fodera etc.

    wish is why I give him credit for having his Balls in place!
    Hey at the end of the day if the guy is happy with it that's what really matters..
    Last edited: Jan 6, 2017
  10. Beej


    Feb 10, 2007
    Vancouver Island
    I don't get it @madbass6 ?

    He has not altered the bass in any way, just added an extension - plus he did it in such a way as it looks like Carl built it himself. No balls required... :)
    salcott, funkbass187 and Scoops like this.
  11. Will_White


    Jul 1, 2011
    Salem, OR
    I was talking about the Upright costing more than a Carl Thompson, not the C extension costing more than a CT
  12. madbass6

    madbass6 Inactive

    Jan 13, 2009
    I do not give consent to use any of my photos ! please respect that. thank you.
    Yeah I got it..,
    Wish is why I edited my original reply. Thanks .
  13. madbass6

    madbass6 Inactive

    Jan 13, 2009
    I do not give consent to use any of my photos ! please respect that. thank you.
    Experimenting with any $5,000 + Bass defenetly requires balls in place!
    But you do have a Valid point If he didn't altered with it in any way! (?)
    Hey I'm just stating my humble opinion. again if he's happy with it at the end of the day it's what really matterrs.
    Beej likes this.
  14. J Posega

    J Posega Cat Dad and Dingwall Enthusiast Supporting Member

    Jul 16, 2005
    Los Angeles, CA
    I don't really get it. It doesn't look very playable. It looks well built, but not at all fun to play any of the notes between C and E.
  15. GuilhermeBMotta


    Jan 2, 2017
    Oh wow! Just like those double basses with low C extension. I have to say I've never seen this on electric, I was kind of expecting something like a whammy bar by the title. That's awesome. I would love to see how it works on video
  16. Keith Guitars

    Keith Guitars Supporting Member Commercial User

    Aug 25, 2004
    Woodstock, NY
    Builder: Martin Keith Guitars
    Really cool! Well done.
    Fits the spirit and aesthetic of the original, and in a completely reversible way.
    This is a great little project.
  17. Thanks for your replies everyone. The extension is completely playable above the E, though the technique must be altered to accommodate the additional length. This is to be expected, as the technique in fingering a C extension on an upright bass includes extended reach when not using a mechanical extension. That said, it's fairly comfortable in part because of the way Carl's basses balance and where the twelfth fret sits in relation to the body.

    Making the extension completely removable and unobtrusive to the original design of the instrument was very important. There are no additional holes drilled, no original parts modified from the bass, and everything can be put back to stock in about 10 minutes. I also had the strings made by Octave4Plus, and had additional standard E strings made, so the bass can play balanced with either the low C extension installed or not.

    As for the sound; the C is very deep (as you might expect for 42.75" scale), thick, and has a piano-like quality that only an extended scale can produce. When the capo is in use, the E sounds as a fingered note does; a bit less volume than an open string, so it functions as intended. The action on the bass is very low across all strings, although slightly higher for the C. Action at the 12th position is 3/64 on the G, 6/64 for the C.

    All in all I'm happy with the result. It functions better than expected, and beyond the obvious changes in technique when playing beyond the E, there is no change in playability. I wouldn't have considered this project had it not been possible to achieve without permanently modifying the instrument. Carl is a genius, I mean no disrespect to his work.

    Here are some pictures of Gene Perla's extension. I owe most of my inspiration to him, but there are some differences between our basses. Gene's is a more permanent mod if I'm not mistaken - it attaches on the top side of the headstock, but I'm not sure if it screws in at the nut as well? Either way, without the few pictures I've found on the web of his bass, I wouldn't have even thought of attempting it.


    Attached Files:

    Last edited: Jan 9, 2017
  18. S.O.T.G. Rich

    S.O.T.G. Rich Gold Supporting Member

    Nov 14, 2014
    Corpus Christi Texas
    Well executed mod for sure. It's not something I would do because in my own experience of modding basses (done quite a bit of it) I've reached a point where I'd rather just pay to have a builder create a bass that met the specs I want. It was always cool but something always went wrong or didn't function properly. As bullet proof as Carl's basses are I would still be concerned about the new geometry affecting an instrument of its age. After a couple of years all instruments settle into their own. Either way man it is bad ass that you love your bass. If you would rather have a bass built to spec lemme know and I'll pay to build you one in trade for that classic :)
  19. Really interesting. There's another thread talking about extensions at the moment too. I have mixed feeling about them, but your workmanship is second to none. Well done. :)