Wednesday, May 12, 2010

Guitar Electronics Mod


 I have been playing guitar since my sophomore year in high school.  That would be 2002, which makes it 8 years since I started playing.  That's a little ridiculous to think about.  At least it's not ten.  Then I would feel old.

A few years ago I bought an EC-100QM Ltd guitar, ESP guitars' second brand.  I love it.  The playing action on it is great.  The frets are pretty high, and I find it easy to play.  Of course, I want to mess with it.

I've already done a similar mod on my first guitar, a Dean Playmate.  Not a high quality instrument, but good enough to start with.  That involved my accidentally drilling through the guitar with an auger bit and filling the hole with bondo.  My goal is to not do that this time.

Reasons for the Mod 
  1.  There are separate volume controls for each pickup on the guitar (humbuckers btw).  They are wired in the configuration shown in figure 1.  Although I do like the flexibility of the wiring scheme, there are at least 3 problems.  a) There is no single volume control knob when in the middle position.  This makes it hard to adjust the volume easily and/or reproducibly.  b) There is no single control to blend between pickups.  That's what we really want here.  There's no reason to have separate knobs, though it is better than simply shorting them together with no control over blend.  c) When blending, the circuit presents a continuously varying impedance to the pickups.  Turning one pickup down low changes the sound of the other pickup due to the decreased load.  Having one pickup turned all the way up and the other turned all the way down shorts the desired pickup to ground and results in silence.  
  2.  I would like to check out the capabilities of humbuckers wired in series, parallel, and coil cut configurations.  The current wiring scheme does not allow for this.
  3. The stock pickups in the guitar are very very very muddy and unpleasant.  I want to replace them with a pair of Seymour Duncan SH-55 Seth Lover pickups that are clean and beautiful.  These are pretty expensive at about $100 a piece.  So that will be the second phase of the project.  It's reasonably easy to modify stock pickups to pull out the leads for each coil.  And if you mess up a little bit, there are so many coils on there, you can afford to lose one or two.  I've done this on my last guitar with success.
  4.  As always, the challenge, and the chance to leverage my electrical knowledge to make something more usable.  Not to mention that I want to get more knowledgeable about analog.  (most of my study was digitally based).

Goals of the Mod 
  1.  1 knob that always controls volume.
  2. Preserve the neck, blend, bridge option with a single knob to control blending between pickups (preferably with a center detent!)
  3. 1 switch for switching between series, parallel, and coil cut for both pickups. 
  4. 1 switch for switching between neck, blend, and bridge for output.  
  5. Provide a more stable impedance to the pickups.  Or at least don't let the impedance fall below 500K.   
  6. No new holes/ routing in the guitar.  Minimal deepening of original routed area, and only if absolutely necessary.  
 To Be Continued...

You know, I'm thinking that one way to keep these posts from being too long is to split them up.  I will describe the project in the first post, and then do background, theory, and implementation in separate posts.  Maybe that will be a good thing.   

Thanks for reading,

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