Introduction: DIY Bass Uke

Picture of DIY Bass Uke
Being and enthusiast of DIY musical instruments, I have postposed this instructable until having a day off.

What is a Bass Uke?
Merely a copy of the bestseller Kala UBASS, which is a short scale bass guitar in the body of an ukulele. The main component of this special bass is the string material. The strings are based in the silicon strings used by the Ashbory, later evolved to polyurethane strings when Kala launched their Kala UBASS; and Aquila has its own version of these strings called Thundergut.
The idea came to me after seeing a 3/4 classical guitar at a local shop. After comparing side by side with a Kala UBASS, I discovered to my surprise that the scale length (distance between the frets) was the same, so I had a donor to begin my DIY Bass Uke.

Note than this instrument is not a real ukelele, neither the UBASS. When Kala introduced the UBASS, they used an uke body shape because they are a ukulele brand, thus only for marketing reasons.

- 3/4 classical or steel string guitar
- Aquila Thundergut set of strings
- Bass guitar tuners

- Screwdrivers
- Electric drill and wood drill-bits
- Small rat file

Step 1: Select a Good Donor Instrument

Picture of Select a Good Donor Instrument

I found a cheap guitar at 35EUR which had the same scale length of the Kala UBASS, so it was the perfect donor guitar.

Other guitars may work, but the thing is that you must go for a guitar with a suitable string length for the polyurethane strings, or it will not work.

The proper string length is around 560 mm.

Step 2: Assembling the Tuners

Picture of Assembling the Tuners

First you have to remove the old tuners.

Then I just realized that it would be better if the outer strings were looped from the outside, so there is better string alignment.

At the beginning I though I would cover the holes, put a face veneer or something like that, etc. But later decided that this should be a DIY approach, and would be better to leave a rude look. 

Take care when assembling the bass guitar tuners, because with minor rotations, you can be able to fix them with three or four screws.

Also notice that the two tuners for the first and fourth strings are reversed and offset (because there was not enough space).

Step 3: Measuring

Picture of Measuring

Begin by measuring the nut and bridge saddle length, which in my guitar was 45 and 70 mm.

Then, you have to measure the strings diameter. The Aquila Thundergut strings are 2,5mm, 3mm, 4mm and 5mm.

I decided to leave 5 mm from the outside of each string to the nut and saddle.

2,5+3+4+5 = 14,5 mm is the space taken by the strings

14,5+5+5 = 24,5 mm, is the total space needed for the strings and free space at each end.

At the nut, the string spacing should be = (45 - 24,5) / 3 = 6,83 mm

At the bridge saddle the string spacing should be = (70 - 24,5) / 3 = 15,16 mm

Why to make all these numbers?
Because we want to have the same free space between each of the strings. If we don´t consider the string diameter, then the centerline of the strings would be equally spaced, but the third and fourth would be closer that the first and second.

Make a template in a piece of paper with all the measures and tape it to the fretboard right next to the nut, and do the same at the brigde. Prior to fixing the bridge template mark the centerline of the place where the strings are tied.

Test with a real string if the templates are right, and if the alignment is ok with the fretboard. Remember that it´s better to check three times before cutting.

Step 4: Make the Holes at the Bridge

Picture of Make the Holes at the Bridge

I used a battery hand drill with a 1mm drill-bit to make all the bridge holes. Then I enlarged the holes with a drill-bit which was 0,5mm wider that the strings. If you don´t have so many drill-bits, you can just make 5 mm holes for the four strings.

After making the holes, it was obvious that the string angle was not very good so I had to file a ramp.

Also discovered that under these innocent pearl dots, a fixing screw was hiden ;)

CAUTION: I used a black marker to paint the hole inside, and was not cautious to wait until the ink dried, so I ended with a tinted string. Wait a few minutes before inserting the strings.

Step 5: Insert the Strings

Picture of Insert the Strings

The strings go from the inside to the outside. In the Kala UBASS there is a cover at the back to be able to insert the strings from the inside, but I preferred to make it the other way and make my own knot with a washer just to ensure a better contact.

The slots at the bass tuners are not wide enough for the 5mm string so I had to file it a little bit. After some fight, the string was inside the tuner slot with enough pressure that ensures it will not slip or go out.

For the first string, I was able to make a double knot.

And voilá, you can see the four strings attached, seeing how the two outside strings are rolled from the outside and the other two by the inside.

NOTE: The black dirty marks on the fourth string are the result of not waiting the ink to dry before inserting the string in the bridge.

Step 6: How It Sounds?

At this moment I just finished the assembly, and I´m waiting the strings to settle and stabilize the tuning.

In a few days I will post a video comparing the original Kala UBASS and my DIY Bass Uke.

Thanks and hope you are able to make your own version.

You can follow me on my Ukulele Facebook Page and see my other uke things on my Ukelele website in spanish


Kowalc (author)2016-08-19

I have successfully made one of these 'micro-basses' with this type of strings (of which there are now several brands) using a new, cheaply bought 5/16 classical guitar as the donor instrument. My searching found that this instrument size was perfect for the strings recommended scale length, in this case the scale is 550mm or just under 22". The wider classical neck is perfect for the fat strings, the original tuners I even used by carefully drilling out the barrels. Undersaddle pickup and pre-amp equalizer all sourced cheaply online means the entire project including donor instrument (new) was $133.00 New Zealand. So much fun to play. Been using it through large and small amps with huge satisfaction for over a year. Next project is the same idea, cheap online cello, 1/2 size is ideal for correct scale length, modified to be a micro-double-bass. The width of the neck at the nut will need some attention perhaps but this will yield a fretless bass with crowned fingerboard, lovely body and all up about double the cost (hope to keep it under 300.00 NZ) of the classical instrument hack. There is a fine instrument/maker luthier here in New Zealand who scratch makes a similar thing out of beautiful woods, calls it a 1/4 bass and it sells for about 2000 NZ dollars. If it fails to please I will reconvert to cello and sell it off, or will I? small house, many instruments, Ha!

Kowalc (author)Kowalc2016-08-31

Cello to bass conversion. Naively thought I was onto something newish but of course found useful info on utube and a website belonging to a creative muso named Dennis Havlena. First option I will try is, this is for a 1/2 cello, modifying nut/bridge/tailpiece to accept Fender light guage flatwounds for electric bass, all recommended by Dennis and easier than option two, my first idea, which was to fit the compound rubber type 'micro-bass' strings. There are utube vids of both ideas and In either case the volume of the body is twice or more that of the 5/16 classical micro-bass so I expect better acoustic volume, especially with the fat strings. Bit of fun, still expect to electrify and plug in.

barefoot77 (author)2016-04-10

I have a small guitar with a aprox. 22.5 inch scale length. I am considering converting it to a UBass type instrument. Would Aquila thundergut or Ashbory strings stretch sufficiently for this length which would range from 27 to 29 inches?

Kowalc (author)barefoot772016-08-19

New to this forum, don't know if anyone else replied but the scale length seems spot on to me if I'm right in thinking that the 27/79" refers to the total length of string needed for that instrument with the scale mentioned that should be ok as the strings come long enough unless that small guitar has a tailpiece at the bottom end which could need longer strings than if they just went to a glued-on-top bridge. I have just measured some new strings I have received (D'Addario NYLTECH EJ88UB for ubasses) and their total supplied length is just over 805mm/31" so that could do. My cello-micro-bass project will use the same strings but with the very high bridge and tailpiece I will have to develop a method to add wire tails to the strings to lengthen. Hopefully a lightbulb moment will occur as there are a few design challenges.

barefoot77 (author)Kowalc2016-08-25

Thanks, I ended up moving the bridge so the scale(nut to saddle) was 21 inches and converted it to fretless. All is well and happy with the result. AQUILLA nylagut strings work the best. I have tried other and they break, especially the D and G strings.

So what are you building? What is a cello/bass. Will you bow it or pluck it, regarding extending the strings, maybe you could extend the tailpiece. Still anchor it over the end edge but extend it somehow to meet the strings, part way towards the bridge etc??

TalisF (author)2016-04-11

Hi, I am thinking about doing this with a small kids electric guitar. I have a few questions.

Would the Ubass strings fit into the bridge of a bass guitar?

Would the Ubass strings even work with an electric guitar? I imagine hey do since there are many electric Ubasses

Is there anything else I should be careful of?


Sociocivilizado (author)2016-04-03

Hi! I was looking for something like this!

I was wondering whether it would sound louder with a 3/4 steel guitar!

I'd like to try and make it soon!

Finn Bjerke (author)2015-04-08

SirCooksalot (author)2014-12-19

hey, where do you get a 20" scale length guitar? I'm wanting to build a ubass and can't find anything that short, even the 3/4 length acoustics are longer. Thanks for any help you can offer!

olivergon (author)SirCooksalot2014-12-21

The guitar is a classic guitar but 3/4.
THe scale length has not to be exactly the same, but approximately.

alan.rolemberg (author)2014-12-09

Here`s my version. I used a 20' scale length guitar. Thanks for the tips. I have only a problem with the "E String". Its rumbling too much when you play with punch. I will try to file the ramp like you did, or change the strings. I will also put a piezo pickup. I tested with a normal piezo for guitars and could see it works with these strings.

ivebeentotheyear3000 (author)2014-10-13

would it be possible to do using steel or nylon bass strings instead?

No, because they are made for longer scale length instruments

qwerty155 (author)2014-04-18

Hi. Great project! I'm looking forward to getting down to it.

One potentially stupid question... Where you've attached the strings on the bridge: have you drilled holes through the body, fed the strings through and the attached the washer so that it's on the inside of the guitar body? Is that right?

olivergon (author)qwerty1552014-04-19

Yes, thats right!
The original UBASS has the same method for ataching the strings, but it has a lid at the back so you can access the holes from the inside of the instrument.

SphericDirection (author)2014-04-11

Groovy instructible mate. I have 3/4 guitar which I was given, it's just sitting around with a broken machine head and a very slightly warped bridge (don't ask how it happened, it was like that before I got it) it's pretty useless as a guitar now, but produces a surprisingly deep tone quite nicely. This might be just the solution for it, I'd love a mini bass I can travel with.

jdlomr (author)2014-03-17

Would this conversion work on a full size guitar?? Cause I got a classical guitar laying around with a lot of bass boom but it's 66cm which misses the ubass mark by around 10cm. Will that affect it?

olivergon (author)jdlomr2014-03-18

The problem with a standard classic guitar is the string length which is far too long for the polyurethane strings.
That is the reason for using a 3/4 guitar, having the right fretboard scale.

ragtimelil (author)2014-02-27

I butchered the bridge, but otherwise it wasn't as hard as I thought. I'm waiting for the strings to settle so I can actually play it! Thanks for the instructions!

smorrise made it! (author)2014-02-04

I just finished my own thanks to your guidance. Sounds pretty good. I used a 1/2 size classical guitar. I did install a cheap $15 pickup w/tuner. I cut off the under saddle pickup and soldered on a piezo disc and stuck it to the soundboard inside.

jaymethunt (author)2013-08-18

So, I've been waiting for your video to post comparing the two... I'm looking to do this project so I can play with a soprano and a tenor uke duo and make it a trio.

What were your final thoughts on this?

olivergon (author)jaymethunt2013-08-19

Well, you must consider that this is a bass sounding instrument, not a ukulele at all except for the size. If you want to play professionally I would suggest you to use a UBASS because you will need amplification. If you consider all the work and parts, it would be easier to get a second hand UBASS for the same price and you will end up with a more quality instrument.

kylerahtjen (author)2013-07-09

How does the finished product sound? And do you know the exact length of the strings?

olivergon (author)kylerahtjen2013-07-10

I don´t hace the strings to measure them, but they are commercial strings from Aquila so if your buy them , you should not have any problem.

olivergon (author)kylerahtjen2013-07-10

It sounds like a UBASS, which is similar to an upright bass when plugged in to an amp, but just louder.

marco tellez (author)2013-07-03

hi and thank you so much! I have a little question :)
the exact length scale must be 56cm? because I have searched at the local stores and the lenght of the 3/4 guitar around here is 58cm, is there any problem with that?
thanks :D

TheUkulelePanda (author)2013-07-03

Yeah, I've got some pahoehoe strings, and I've got some bass tuners but as soon as the string wraps round once or twice, it risks flying off. Broken one tuner already because I tried to widen it with some pliers, fun fun fun

mkreidler (author)2013-06-21

How loud is this? The U Bass is usually sold as an acoustic electric, would adding an acoustic guitar sound hole pickup work on this?

olivergon (author)mkreidler2013-07-03

Yes, adding a piezo or surface mounting pickup could work, but not an acoustic sound hole pickup since these are intended for steel strings. The UBASS strings are plastic so a magnetic pickup could not make any sound from them.

TheUkulelePanda (author)2013-07-02

I'm making my own out of a 1/2 size guitar, only problem I'm finding is the tuning pegs.

The tuning pegs I used were standar electric bass guitar, but I had to make the string hole wider since the UBASS strings have a bigger diameter.

BigBadgers2001 (author)2012-12-31

Now that is groovy. I cant wait to hear how it sounds. Great instructable chum.

I would love to hear it, it looks great!

Shreddi (author)2013-05-11

Do you need guitar with truss rod to deal with stress of bass strings? I don't think some nylon string guitars have them. Just wondering, thanks much for this.

olivergon (author)Shreddi2013-05-12

There is no need for a truss rod since these polyurethane strings are very low tension.

dchall8 (author)2012-12-31

Is there an advantage of playing a bass ukelele over a bass guitar? I'm not much of a musician but I can play patterns with my electric bass. I played the 32-note bluegrass/gospel background pattern (which amounts to about half the bluegrass music ever written) 3 nights a week for 6 months or so, and I can keep up with the basic, 4-beat country dance music. Just wondering if the bass uke plays the same pattern in different keys?

olivergon (author)dchall82013-01-01

The main advantage is the size of these bass ukes, which make them easy to transport. On the other hand, the sound is more like a double bass than like the electric bass.

dchall8 (author)olivergon2013-01-01

Do the uke frets match the bass frets? Could I simply tune it in the bass guitar keys? I'd love to have an acoustic bass guitar.

olivergon (author)dchall82013-01-02

The normal ukulele scale length depends of the size: soprano, concert, tenor and baritone. Neither of them has the UBASS scale length.
The problem with the guitar is that the strings are not able to sound an octave lower. For the bass sound you need special strings that are very thick, so you can´t put them straight away in a guitar. If you read the step by step, you might see all the changes that have to be done to a guitar to become an acoustic short-scale bass guitar, or now-a-days called bass uke.

About This Instructable




Bio: I have a practical point of view for problem solving, and having an engineering education might be the cause. I love to tinker around with ... More »
More by olivergon:Easy Leds With ArduinoSTAMP CARVING + UKELELEKazoo DIY with paper roll
Add instructable to: