Double Bass First EUB build

[DoubleMIDI]

For the PreAmp/Buffer look at the FDeck quick 'n' dirty and HPF-Pre and probably also his BBBB preamps. He explains a lot and has very good designs (much better than most built-in commercial preamps). Look at the input impedance data for your preamp in the technical data. If it is not mentioned it migh be suboptimal (means you might be lucky or not).
The black-chip with lots of legs can be any kind of OpAmp, with J-FET input or not. You need to look at the type identifier on it and search for a datasheet and read it. THere you will find the input impedance.
Also the half cylinder (rather side cut cylinder or metal hat) has to be searched for the type identifier and the datasheet until you know what kind of component it is. If it is a J-FET this will be shown on the first page of the datasheet.

You can always buy some piezo and experiment with them. The mechanical fitting is the more difficult task and sound will suffer more from doing this wrong (and there are many ways to do it wrong) than from a mismatching input impedance (or the mismatch must be really bad).

If you think you know what you do and why you want to do it this way go ahead and build your instrument. Pickups bridges and even a fingerboard could be replaced, but the overall mechanical structure needs to be correct in the first place.
Don't use bass guitar tuning machines, use double bass tuners, strings have more room for winding strings and the strings will get less damage than from bass guitar tuners (even the better ones).

 

[hoytbasses]

Don't use bass guitar tuning machines, use double bass tuners, strings have more room for winding strings and the strings will get less damage than from bass guitar tuners (even the better ones).

I have built 16 Electric upright basses which are out there in circulation. I agree with you DoubleMIDI about bass guitar tuners that have 3/8"(10mm) posts. However, all of my basses use Hipshot "fender style' tuners with 1/2" shafts (13mm?) . My headstock design is a bit smaller than a regular URB and those tuners fit the design very nicely. To date I have had no issues with those tuners, and some of my EUB's are over 10 years old.

I have to say, Mr Goldfish, I admire your pluckiness and you are definitely wise beyond your years... I look forward to seeing your project progress.

KFH

 

[josiah goldfish]

I have built 16 Electric upright basses which are out there in circulation. I agree with you DoubleMIDI about bass guitar tuners that have 3/8"(10mm) posts. However, all of my basses use Hipshot "fender style' tuners with 1/2" shafts (13mm?) . My headstock design is a bit smaller than a regular URB and those tuners fit the design very nicely. To date I have had no issues with those tuners, and some of my EUB's are over 10 years old.

I have to say, Mr Goldfish, I admire your pluckiness and you are definitely wise beyond your years... I look forward to seeing your project progress.

KFH

Haha thanks!
I've found a piezo preamp on eBay (£5) and I'm going to order it just to see if it works. It's only a fiver right? (btw, it has a jfet)
As for the tuning keys, I'd already decided to get DB ones as I'm going to buy the neck anyway (so it will have a DB pegbox etc).
I haven't had any chance to do much recently but I hope to get back to work next week. My goal is to have a bridge cut out and a face glued by the end of next week

 

[josiah goldfish]

Question: will it work?
Info: It's listed as an electro-acoustic guitar preamp, so I'd assume it's designed for piezos. It's got a volume pot and 3 sliders (bass, middle, treble). There's loads of different components, and I'm a novice at electronics so I'll describe them:

1) a capacitor (one of the cylinder-ones)
2) 2 integrated circuits (i think, they're little black boxes with 4 legs a side) both saying 062 H028G JRC
3) 2 littler black boxes with a leg a side. One says WTE GS1G.
4) 9 tiny silver boxes with a small cream-ish block in the middle.
5) 16 tiny silver boxes with a small black box with letters/numbers printed on them. EG a few say '103'
External parts:
6) a volume pot
7) 3 sliders
8) a 9V battery snap
9) a jack plug wrapped in a black plastic box and black rubber.

So, will it work? I'll post pics later, I'm just hoping it works seeing as i just bought it! (don't judge me, it was going for £5 so i bought it before anyone else could)
Thanks

Joe

Here's some pics. Sorry for the appalling quality, my iphone camera sucks. You'd think that something so advanced would at least have a decent camera.

 

[DoubleMIDI]

The 062 is probably a TL062 wich is a JFET-OpAmp.
I have one in my active DI-Box with a 1 MOhms input resistor. I read the data sheet and know that I can replace it with a higher resistance (10 MOhms) if I feel the need to do so. In an DI box this resistor is in parallel with the amp input resistor, so it might be a good idea to exchange the DI box input resistor for a larger value than the amp input resistor (at least twice the value of the amp resistor, better some more but not more than 22 MegOhms).
Your preamp should do the job. There might be some better OpAmps out (read the FDeck hints on OpAmps), but with some more noise than optimal the TL062 will do the job.
At least, you can use it until you feel the need of something better (and you may be happy staying with it).
I leaned a lot from FDeck's designs (thanks!), you might want to look at his designs and notes too.

 

[josiah goldfish]

The 062 is probably a TL062 wich is a JFET-OpAmp.
I have one in my active DI-Box with a 1 MOhms input resistor. I read the data sheet and know that I can replace it with a higher resistance (10 MOhms) if I feel the need to do so. In an DI box this resistor is in parallel with the amp input resistor, so it might be a good idea to exchange the DI box input resistor for a larger value than the amp input resistor (at least twice the value of the amp resistor, better some more but not more than 22 MegOhms).
Your preamp should do the job. There might be some better OpAmps out (read the FDeck hints on OpAmps), but with some more noise than optimal the TL062 will do the job.
At least, you can use it until you feel the need of something better (and you may be happy staying with it).
I leaned a lot from FDeck's designs (thanks!), you might want to look at his designs and notes too.

Thanks! Also, there's two solder blobs with the labels 'in' and 'grd' (assuming it's input and ground) do I solder the piezo in here? Which wire goes in which hole?
Also, I just finished doing the bridge (I didn't have access to a bandsaw or a router so couldn't do anything else) and it came out pretty well! Will post pics later
Btw, the jack input has a black box and it's wrapped in rubber. Does that mean that if I unplug the jack lead it'll cut power to the battery? Or do I need to get a new socket?