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Double Bass Homebuilt EUB build thread

In parallel with all of the woodwork going on, I get to figure out how to connect all of this together into a working pickup system.

6x piezo preamp
1x condenser microphone preamp
Jacks for all the above
Trim pots
Power connections
And somewhere around here I have a battery box or two...

Pick is for scale reference.
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So I have been burning up my Google-fu, and the best idea I have for the electronics (because I am using someone else's preamp) is to build a passive mixer network on the outputs of the preamps, using a 10k trim pot and a 10k resistor. The output of the mixer will go into the P1 Input of the blend knob on the Kaish bass setup (3 band eq) where the direct output of the condenser microphone preamp will go into P2 input on the blend pot.

I plan on testing this before soldering everything up,but does anyone see any immediate problems?
 
So I have been burning up my Google-fu, and the best idea I have for the electronics (because I am using someone else's preamp) is to build a passive mixer network on the outputs of the preamps, using a 10k trim pot and a 10k resistor. The output of the mixer will go into the P1 Input of the blend knob on the Kaish bass setup (3 band eq) where the direct output of the condenser microphone preamp will go into P2 input on the blend pot.

I plan on testing this before soldering everything up,but does anyone see any immediate problems?

In general I would recommend an active mixer. A summing amplifier requires a virtual ground to be able to mix a bunch of separate things without having them interfere with each other. Without it, the level of one input will also be affected by the levels of all the other inputs. The simplest way to make a virtual ground is with an op-amp inverting amplifier:

op-amp-sum-mix.gif


That "-" input on the left hand op-amp (triangle) where R1, R2 and R3 connect will be 0V in normal operation which is why it is called a virtual ground. Because it is at 0 volts signal coming through, for example, R1 won't affect signal coming from R2 or R3.

Of course, you can also try a passive version and see if you are happy with it. Depending on your requirements it may meet your needs.
 
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Ran out of clamps again. Got a bit ambitious with tonight's glue up.
That said, this is the last major gluing operation. I have the front top on this side, and then the front end on the other side. Then the 2 arc pieces on the front.

My thoughts on approaching the arcs on the front is since I have ripped the side pieces in 1" strips, I will do the same with the top pieces and working from the center out fill in the arcs...

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So close I can see it...
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I did some fooling around last night just to see how it feels with the body on it, and seated in a regular chair, that curve is where your off hand knee wants to go, and the body feels very natural to me. It's deep enough that the you're not reaching for the neck, nor is it too close to you. Keep in mind that I am not a schooled player, but it feels very natural to me.

I am reaching the point where I am getting super excited to string this thing up and start making noise with it!
 
Spent the afternoon puzzle piecing the front. Got one side done and glued. I'll do the final fitting with the glued piece. This is quite a bit more difficult than I expected (and I expected it to be quite difficult). Lots of tape and fitting and sanding and more fitting... pretty happy with the grain matching across the pieces though.

We'll see how it winds up tomorrow...
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Honestly, I think I am rapidly reaching the intersection between my ambition and skill...
I typically blow through that intersection at about 90mph... (red light or no)... get in an accident... get busted... and have to go to traffic school to learn how to do it right. :confused:
Great way to learn stuff. o_O;)
 
Found a few minutes this afternoon to set the front piece in place. I think it's going to work just fine.

Used tape to hold it in place while the first epoxy was set, then added epoxy to the gaps and clamped the one end that didn't want to lay correctly. I am optimistic that this will look pretty good once I clean it up.

20211014_141557.jpg
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Ok, It's time again to say thank you to all of the readers of this build thread. I know it's taken longer than I expected initially, but despite all of the delays, I am still plugging away at it, and posting things here (and the feedback I am getting) is helping me stay on task and I am optimistic that I can see the light (or the tunes) at the end of the tunnel.

I strung it up last night to see how the bass sounds with the body mostly built, and the 'reverberation chamber'(TM) works as I hoped it would. I am very much looking forward to placing a microphone inside it. I have also learned that roundwounds will be largely incompatible with this bass between the finger squeaks and the other string noises which get unduly amplified by the acoustic portion of the bass. I am looking forward to getting the finish work done, so I can string it up with some flatwounds. Acoustically it seems to have a pretty warm tone rather than a deep bloomy one, as one would expect from an instrument mostly made from maple. I am very much looking forward to getting the electronics done to see how that affects the tone.

On the to do list:
Finish the last piece of woodworking
Finish wiring up and testing the electronics
Finish sanding the bass
Apply finish to the bass

There's a couple of collaborative steps in there, I am working with a local luthier to help make the nut, and I have another buddy who is going to help me dye the maple to help the figure pop.

My concern with the finish for the bass, is that it's already getting into the part of the year where highs are in the 60s and that drops off pretty quickly over the next few weeks. (Occasionally we get snow this time of year) I currently work in my garage which is not climate controlled, and I don't have a workspace that is climate controlled to do the work in.
 
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Ok, It's time again to say thank you to all of the readers of this build thread.
Of course! Without fail, every 100 posts.
'reverberation chamber'(TM)
:roflmao:
I have also learned that roundwounds will be largely incompatible with this bass between the finger squeaks and the other string noises which get unduly amplified by the acoustic portion of the bass.
There's an additional argument against roundwound strings: they will wear out your beautiful purpleheart fingerboard.
 
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