doublebass C-extensions

For a few years I've opted not to make capos for C-extensions, as those made by Rob Anzelotti in Germany are of excellent quality, light weight, pleasing appearance and good durability. No need to make one-off capos when Rob's are doing the job so nicely. His capos and various other equally well thought out and finely executed products (such as a very tidy offset endpin with good adjustability) can be found at Here's a bunch of extensions I've made, not an exhaustive gallery, just those I've remembered to photograph.

First extension for 2018. All one piece of ebony, on a big German bass from the mid-1800's. side view of extension close

The one below was carved in late spring 2018 for a bass made by Canadian luthier Peter Mach in the late 1980's, now used by a VSO bassist. The body is carved from padauk wood which is somewhat lighter weight than ebony (and less threatened) while providing exceptional stability through seasonal changes and very good toughness. The cap is a closed-grained ebony from East Africa (ethically sourced and certified). One of Rob Anzelotti's capos holds down the E, and I've bevelled the bottom (thumb) face parallel to the string face such that a guitar capo may be used as a sliding stop. One of Rob's brass wheels turns the string around at the top - he uses a very low friction plastic sleeve in these to keep them tuning smoothly. A length of paracord casing covers the string to guide it around the scroll, such that the C string resides on the normal E tuner; no change in habits for the player this way, and no holes drilled in the scroll. A steel piece is screwed and epoxied into the extension around Eb to fix it there and string tension holds the carefully fitted padauk against the scroll at the other end.

front of C-extension
side of C-extension
side of C-extension

This is a simpler version. Single capo at the E. The bassist liked the extensions seen at Kansas City Strings, especially the deep curve for the thumb. I made this very comfortable for noting C# and D, and made a similar neck-like area lower down for playing D and D#.

capo side of C-extension
hand side of C-extension, capos open
hand side of C-extension, capos closed

The nut end is reinforced underneath with an inlaid, dovetailed piece of brass, which is threaded to be bolted to the stainless steel capo mount. A single allen bolt into the base of the pegbox holds this steel part in place. Another bolt attaches the top end to the scroll, in a minimally disruptive fashion. A rubberised cork gasket material lines the juncture. The string path with a figure-eight loop around the pulley turned out to have too much friction on the string sides, so I later modified this one to run through the length of the ebony, as shown in the second image:

front of extension side of extension after string path changed

treble side of C-extension

And the last one for this season is a hybrid of the two previous extensions. This player has used a single-capo extension for about 15 years and has wanted a 4-capo model for his ancient Italian bass for years... since seeing one I made for a Vancouver Symphony member's 7/8th-size French bass in 1998.

His older extension was somewhat sculpted, with a very round/deep thumb area just below the scroll, and he wanted this again. The blank was a considerable volume of ebony, but the cutouts for scroll, thumb hollow, and the tapered end closer to the nut can all be used as bass nuts and saddles, not wasted.

This one is very comfortable to use, with a rounded surface in the E to D position as well, and lots of room there for the thumb. The capos grab the string automatically; no pre-pressing of the string is needed (something I had to The string routing was dictated by the previous luthier's choice to go through the scroll, so a wheel embedded above the scroll was necessary. The finish on the aluminum capo rail is baked enamel.

face of C-extension detail of wheel, upper extension

capos on rail

hand side of extension

It seems that my ambivalence towards C-extension design and building had some influence... as it took until 2008 before I was again asked to make one. Actually the first extension in this year was a partial re-design of one of those above, the single capo model shown as second on this page. It seems the path I chose for the string was not adequately low in friction, some binding happened in use, and a string was broken eventually. So I did some serious frowning and then came up with a rather radically different path for the string - drilling a hole from the top end almost to above the E tuning shaft and setting a wheel there for the string to pass over. This was very difficult to drill, as the hole was over 10 inches long and in a rather narrow piece of ebony, but it worked. The resulting path was very free for tuning and surprisingly easy to re-string, considering how long the string end is hidden inside the ebony. And as a nice bonus the string is nowhere exposed until it comes out inside the pegbox, freeing the thumb area entirely and un-cluttering the look of the scroll a bit.

Two new extensions were made in 2008, both for clients who had extensions made in 2005, but of course on different basses. The first of these was a finely carved Pollmann bass being passed from a father to a son. The second was put onto a German bass bought in Poland the previous winter, to be used in the opera. In the first case ebony capos were requested. As ebony is much more prone to splitting in short lengths than many other woods I extended these back to include 'tails' which may be used in lifting them off the string. This almost doubles the capo length and makes them much stronger. I also used large-headed bolts to hold them in place, further bracing the delicate ebony. Also incorporated into this design was the long string hole as described above, using a second pulley hidden inside the lower part near the D capo.

bass side of extension, capos open oblique view of extension, capos open

front of extension, capos open front of extension, capos closed treble side of extension, capos closed

And this is the last for 2008. A bit different, or a lot, depending on one's perspective, as there is no tunability here. The fingerboard on the bass was pleasing to the player, and to be fair it was nicely dressed and the neck plus fingerboard thickness felt good, but the very thin top end of the board made for a special challenge in fitting an extension. With four capos. After much thinking, it seemed the only practical approach was to use a sheet of stainless steel running through all four capos, cut out between to leave platforms for each. This was inlaid into a long groove in the underside of the ebony and up into the backwards-curving portion of the thumb rest area. What resulted was very solid in feel, though plainly without the versatility of the aluminum rail type. Still, a satisfying solution.

bass side of extension, capos open oblique view of extension, capos open front of extension, capos open

front of extension, capos closed treble side of extension, capos closed

From August of 2009, a two capo extension fitted to a bass by Peter Chandler. Owing to minimal clearance above the scroll edge, the ebony was left quite wide which leaves a strong portion beside the scroll. This offers an advantage in terms of thumb placement; I was able to carve a long hollow from scroll to nut which gives a secure anchor for the thumb, and leaves better access to the pegs for string changes.

front, capos open

front, capos closed

bass side

treble side

closer view of thumb rail