Double Bass Advice needed on pickups for EUB build

[Big B.]

Thanks for everyone's comments. Its been a while since I posted in this thread but I have been getting work done on the bass. With this being a prototype I have been working on it in my spare time and solving problems as I go.

I'm at the point of designing the bridge and pickup choice will influence that greatly. First I'll bring you up to date on the bass and hopefully you guys can add your experience to the mix. Everything is still in progress so forgive the rough edges here and there.

The bass is neck through body construction with radiused alder body wings. The top and back are covered with Madrone burl veneer. The pegbox has already been routed out but my pics are on my phone which is currently dead so they'll have to wait. :scowl:

Front view:

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Rear view:

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The neck, other than the added width for the sixth string, is carved to match the profile of my 5 string Solano DB.

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The radius wings were glued on in a barrel stave style glue up and then sanded to the radius. Here is a pic of the radius. Pencil lines are drawn on the seams to show the original glue lines.

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When the center block was profiled for the neck, I cut the angle of the body back away from the neck as much as possile so as you get further from the end of the neck, the fingerboard is further and further off the body allowing for more bridge clearance. The tapering thickness of the fingerboard adds to the neck angle as well. All said and done, I expect about 4 inches clearance between the body and top of the fingerboard.

And now to the pickups and bridge, and this is where your advice comes in. I see one of two options and I hope you guys can offer some input. Keep in mind this bass is designed with arco use in mind as well so that definitely needs to be considered with pickup choices.

1: A narrow, full width bridge ala NS Design. Essentially a bridge saddle with a narrow groove routed into the body and a piezo strip underneath the brige.

2: A more traditionally carved bridge, though clearly shorter, with 2 radiused feet and an arch cut between. This bridge could either use a wing slot pickup or piezo film under the foot.

As far as sound goes, I have a great DB so making this bass sound like a real DB is not an issue. I really want a cool sound of its own. Something between the mwaah of a great fretless bass guitar and the thump of a DB. Bassically, I dont need it to sound a certain way, I just need it to sound GOOD.

Thoughts? Considerations? General hatred of my plan?

Feel free to throw your ideas out there. Woodwork is my specialty. Electronics... not so much. Thanks for following along.

 

[MARCOvdBoogert]

Looks great!
I would definitely go for piezo disks under the bridge with an acoustic preamp. Cheap as chips and sounds great, warm, woody and acoustic!

 

[DoubleMIDI]

+1

Piezos under the bridge feet sound good (specially with bowing), but the signal may be a bit weak.
You can try to stack a few disks connected in serial to get a stringer signal, but the output impedance will rise that way, so you need a preamp with 5 to 10 MOhms input impedance.

 

[Big B.]

Thanks for the replies. I'm leaning strongly towards using piezo cable ala an acoustic guitar's undersaddle tranducer. I've ordered the piezo cable already but I may still try the piezo film under the feet as well. Any thoughts on sound differences between the film and the cable?

 

[kozmikyak]

I have a facsimile of the NS Design pickup system in my 7-string Ergo cello.

Two small piezo discs, one underneath each bridge foot. Potentially padded with a bit of leather or neoprene washer, though it does dull the sound somewhat.

If both piezos are oriented the same way, and you connect both red wires and both black wires to the terminals of the jack, you get the "pizz" sound. Much closer to a fretless bass guitar.

If, however, you flip one of the piezo discs upside down, and connect both red wires and both black wires to the terminals of the jack, you get the "arco" sound. Good bow sound and pizz more like an upright--thumpy, lots of attack, less sustain.

You might ask, why not just leave them both "right-side up" and connect a red/black pair to one jack terminal and another red/black pair to the other jack terminal? Because whenever I try this I get horrible ground noise. But I'm not at _all_ careful about shielding. I find it easier to physically flip one of these upside down, than to worry about the extra care in shielding.

I actually went one fancier than this, and use _two_ simultaneous sets of pickups. Each "pair" is one disc under the left foot, and one disc under the right foot. The arco pair is out of phase and is the "top" layer of the sandwich. The pizz pair is in phase and is the "bottom" layer of the sandwich. Shielding between the halves of the sandwich. I wire the brass shield wires of both pairs to the shield of a stereo jack, and wire the red pair from each sandwich half to tip and ring, respectively. Then I can A/B switch between them at will, using an external box and my foot, instead of trying to scramble to flip a switch with the same hand that's trying to grab a bow on the fly.

Works quite well for me. Another alternative are those plastic piezoelectric tabs. The same general principles apply, but warning: soldering to them is an exercise in frustration, as you end up melting the plastic. Conductive epoxy works better with those.

I use Baggs GigPro preamps, one for each "half" of the sandwich, and velcro them to the back of the instrument. I use an insert cable (TRS male to dual TS male) to connect the instrument to the two preamps. These preamps are a good balance of functionality; they have high-pass filtering, bass, treble, gain, volume, and phase controls in a very small package, and are relatively inexpensive.

Have fun whatever you decide to do.

 

[DoubleMIDI]

Don't forget how much pressure is on the bridge by the strings. It might destroy the piezo cable. If you put the cable directly under the string the slipping of the string over the bridge may damage the cable too.

Better get a pickup ready-made, you will have a lot of trouble making your own and need a lot of time until you are satisfied with the result.
A Shadow SH-965NFX would be nice, not too expensive and has an impedance buffer built-in. (You might want to get the smaller one for violoncello if you have smaller bridge feet.)

 

[Big B.]

Don't forget how much pressure is on the bridge by the strings. It might destroy the piezo cable. If you put the cable directly under the string the slipping of the string over the bridge may damage the cable too.

Better get a pickup ready-made, you will have a lot of trouble making your own and need a lot of time until you are satisfied with the result.
A Shadow SH-965NFX would be nice, not too expensive and has an impedance buffer built-in. (You might want to get the smaller one for violoncello if you have smaller bridge feet.)

I appreciate your concern but time is something I have plenty of and I can buy the parts to make ten pickups for the price of any decent commercial pickup. Though I dont build many EUB's I do build a lot of bass guitars and piezo applications are something I've been interested in for a while so it's worth it to me to put in the time and make it work. The wiring of the piezo cable itself is relatively simple and the trial and error of placement is just a natural part of any prototype process. Still, your suggestions are appreciated.

My phone is working again so I will post a few pics later showing the bridge and how it will relate to the body/strings. Being a six string with low neck angle my bridge is about 6 1/2" wide and 3 1/2" inches tall. I didn't care for the look or long term stability of this bridge only being supported by two feet so I am going with a full width bridge along the lines of the NS Design bridges but with a more traditional cut. The bottom of the bridge will be 3/8" wide and will sit in a 3/8" wide slot that will house the pickup and keep the bridge in the proper placement. Essentially just a large saddle style pickup as you would find on an acoustic guitar.

 

[DoubleMIDI]

Piezo cable is used in the Stagg EUB, but the bridge foot can only press partly on it because it lays in a slot and only the top of it makes contact to the bridge.

I forgot that there was a piezo cable in there last time I wrote. So you might get a useable result with the piezo wire.
But keep the high impedance preamp as close as possible to the piezos. Any cable from the piezo to the high impedance input is sensitive to tapping and vibration, so keep it short.

BTW, a 6-string instrument would be difficult to bow, it is hard enough on a 5-string. You can make the bridge a bit rounder than on an acoustic double bass, but then the fingerboard curvature needs to fit the bridge curvature which seems to be rather low, even for a 4-string double bass. So, you might get problems with a bow, I think.