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Double Bass Trouble Shooting my new EUB Build

Nate74

Nate74

Mar 3, 2007
789
78
DFW
#1
I just finished (sort of) my first EUB build. I used a K&K Big Twin and FDeck's preamp. Everything else was pretty much my own design.

Plays well enough at this point, but the sound isn't right. I get plenty of string noise and the pickups even seem to pick up the sound of me touching the bridge, but there's very little sound generated by actually plucking the strings.

My initial thought is I didn't wire the preamp correctly. I'll be checking that out today. My second thought is that maybe I damaged the transducers somehow... but this being my first experience with a piezo pickup, I really don't know.

Any input would be great!

I'll of course provide any additioanl information I can as needed.

thanks in advance!
 
#3
Good point.

Here are some shots.

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Hope this helps.

Some new info: I'm playing through a little 100-watt 12" Combo amp (Aggy) and when I turn the volume up to about 50% and turn the Bass EQ knob all the way up, it sounds... OK. Of course at this setting, one of my jazz basses would shatter windows. I also had to turn the Treble EQ all the way down to avoid the shrill 5k plus noise.
 
#5
Interesting to know Rvl. Thanks.

I'm actually sort of hoping it's an issue with the bridge that can be remedied by designing a lower mass version.

I fear the Big Twin wouldn't work in an under bridge configuration but I did just order some elements from Mouser that might work, especially with some cork above/below them.

It'll be interesting to hear what some others have to say.
 
#6
UPDATE: I decided to try an underbridge setup (thanks Rvl) so I took the two probes off the side of the bridge, loosened the strings, and put one under each of the two ends, roughly under the two adjustment screws.

I only tightened the D string up into tune and the volume and balance increase was quite noticable and in the 'good' direction.

So in the am, I'm going to try some cork and see if I can get a decent sound.

If that gets me close the sound I want, I may have to think about a different bridge design since the current setup won't be that stable with the probes under the the bridge... I don't think.
 
#7
Other important point: the input impedance of the amp.
I strongly advise you use a buffering preamp to connect the pickup to before it goes to the amp, unless you know the amp has at least 1 megohm.
I often use a simple K&K preamp 97, and it's great.
A loaded piezo pickup (too low input impedance) looses all the fundamental and sound thin and shrill, which seems to be your case.

The "under the feet" is a good idea too.
You may want to make small cavities under the bridge's base, and slide the Big twin elements there. (just the metallic part. don't squeeze the piezo element itself!)
 
#8
Thanks for the input guys!

The little Fdeck buffer seems to be doing it's job well enough and now with the elements under the bridge, I'm getting loads of fundemental signal as well as some nice harmonics. Plenty for my little 3 band eq to get some really nice tones. Plenty of signal strength too.

I may experiement with some cork and as you suggest Francois, some small cavities to house them.

But for the time being, I'm really enjoying playing it!

Again, thanks to you all for the input!

Now to figure out what drum hardware I'll need to hold it ;)
 
#9
Nate,

I dealt with these exact same problems when I built my EUB several years ago. We have very similar designs and I'm also using the Big Twin with a buffer. I spent days experimenting with probably twenty different mounting methods materials. Based on my experience your on the right track. The big twin does not perform well stuck on the side of the bridge as you found out already. After moving the elements under the bridge I experimented with mounting materials from cork to rubber to fiber gasketing. After all this experimentation I came to the conclusion that nothing sounded better than having the elements mounted directly under the bridge feet with no other buffer material.

The key to getting good sound in this manner is making sure that the two surfaces between which the piezo's are pinned are both perfectly flat and perfectly parallel. Even slight imperfections or variations in pressure can be very detrimental to the sound. I was also very surprised to find that even the way in which the pickup leads were arranged and secured could affect the sound if there was pressure on them or if they were touching other parts of the bridge. Piezo's can be very finicky, but if you spend a few hours experimenting with all the variables you should be able to find a good sound with your bridge.
 
#10
Nice looking bass!
Nate74 said:
I may have to think about a different bridge design since the current setup won't be that stable with the probes under the the bridge...
Click to expand...
My Paulin bass has a similar bridge, which I don't think has enough 'flex' to activate a 'stick-on' piezo. However I get a big solid sound with piezos under the bridge. I make my own pickups by wrapping a piezo film in copper shielding with conductive adhesive. Here's how: Link Removed

After a few weeks, the bridge started to slide off them and destroy the pickup, so, as Francois has suggested, I worked with the bass maker (Bill Paulin) to cut some hidden recesses under the bridge feet so there could be no lateral movement.
When I was originally experimentingt with these pickups, I found that the slightest movement of bridge angle or position made a big difference to the volume. A thin sliver of cork gasket material under the pickups has solved that problem, and possibly made it all a bit louder by allowing more flex in the piezo.
 

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