Tuesday, June 3, 2014

LeSpork Bass Prototype - Spinning Wheel

Would you mind a reflecting sign
Just let it shine within your mind
And show you the colors that are real

A few weeks ago, I found a great deal on eBay on a late 80's Kramer bass body with the following description:
This is a late 80's Kramer body, in rough shape, but genuine. I bought the guitar project mainly for the neck, (which I'm keeping). The body is plywood, which was used a lot back then, and somebody decided to paint it white... with a brush, and house paint! Lol.... Does come with the original pickup and wiring harness. I know it's genuine Kramer because of the tighter neck bolt pattern, (and I have the neck). Only comes with what's pictured. It's not pretty, but maybe somebody can use it.
The paint is horrible, what looks like cracks are only the streaks in paint. The body is actually in fair, and usable condition.
Thanks for looking!

That's just what I needed to get back to my LeSpork Bass prototype.  I made a bid, and thanks to eBay member 8486randy, the Kramer body was at my doorstep within a few days!

Buying a body has definitely changed the scope and nature of the project.  It's not exactly a prototype anymore, although it will take some thought and effort to modify the Kramer body neck pocket to accept the Aria Pro neck and end up with the right scale length.

Of course, I can "suggest" the LeSpork shape my making a custom pickguard...

Ok, so this project has become more about making things fit and some finish techniques.  Maybe Frankenbass would be a more appropriate name for this build.

BUT, it is also an opportunity to do some electronics modifications!  Comparing the Kramer body I bought with the picture of a Kramer bass above, I noticed a slight difference: mine has a third control hole.  At first, I thought it might have housed a switch for an on-board preamp, since Kramer did offer some models with active EMG pickups.  A little more internet research revealed the hole closest to the bridge was used for an output jack on some entry-level models.  Although, like on a Gibson ES-335, I'd say it's not an ideal location, it is manageable.

That's all well and good, but this body also has a hole at the side, drilled into the control cavity, where one would  install an output jack.

Liking the side location for the output jack better than having the jack next to the control knobs, I decided to find a use for the third control hole.  So, what can you do with a three control holes for a single-pickup guitar?

Like the use of colors and textures in a painting, tonal color is part of what makes each piece of music unique.  And though each of us may find some tones more appealing than others, we can all agree that we prefer some variety of tonal color in listening to music.  With electrified musical instruments, we can use the electronics to enhance the inherent tonal quality of the materials used to make an instrument, as well as to modify and add some variety to that inherent tonal quality.  With that in mind, I decided to use a G&L-type two-band passive filter tone control circuit.  As my friend Bruce put it:
The standard “tone” control is nothing more than a high-pass filter…selectively dumping low frequencies (as determined by the 3-dB point) to ground.  This seems to be what you have labeled below as the “treble” control.

The “bass” control seems to be a low-pass filter…blocking high frequencies as you decrease the resistance...
So, the LeSpork Bass will have this circuit, allowing for separate treble and bass tone filters in front of the volume control.

Despite having an engineering degree, I'm not much of an electrical engineer.  Opinions about which values of caps and pots produce great tone vary widely, as sound is a subjective topic.  One aspect we all agree on with a basic low-pass filter is that, as you substitute caps of higher value, you lose more and more highs as you lower the pot.  From experience, I do know that the type and values of the capacitors and potentiometers in a circuit will have effects on the tone.  Not wanting to leave the quality aspect up to chance, I'll be using Sprague Orange Drop capacitors and CTS linear taper pots.  I'll try combinations of common values of audio filter control caps and pots in the circuit, starting with a 0.0022, 0.0033 and 0.0047 uF caps tied to a 1 meg-ohm pot in the bass leg, and a 0.022, 0.033 and 0.047 uF caps tied to a 500 k-ohm treble pot in the treble leg , until I find a tonal range I like.  I'll have some time waiting for the delivery of electronic parts to arrive, so I'll get to work on modifying the Kramer neck pocket to accommodate that Aria neck, and mounting a Fender bridge to end up with a 34-inch scale length.

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