Piezo in an Electromatic Center Block Jr...

Discussion in 'The Pickup Place' started by GlenP, May 24, 2021.

  1. GlenP

    GlenP Country Gent

    Jul 23, 2019
    WA
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    I found a good spot near the edge between the jack and the center block where the battery door can sit fairly flat on the contoured back. I marked out where I would drill the holes and cut the access hole, and just have to sit back and think about it for a bit before I dig into this one. The jr. depth is just enough to fit this battery box.
     
  2. GlenP

    GlenP Country Gent

    Jul 23, 2019
    WA
    I don't know why, but cutting into the back for the battery box has me kind of nervous. I will double check my clearances for everything before drilling holes around the perimeter. I have an electric scroller saw, but will probably connect the dots by hand with a key-hole saw blade. I plan to under cut the hole slightly and use a sanding block to get it to the final size. I also need to expand the jack hole a bit to allow the stereo switched jack to be pulled through.
     
  3. GlenP

    GlenP Country Gent

    Jul 23, 2019
    WA
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    A few drilled holes, a few passes with a keyhole saw, and now I have a rough cut slightly small rectangle. I will finish this up and bring it to size with a sanding stick and medium grit. So far going to plan.
     
    Last edited: Sep 17, 2021
  4. GlenP

    GlenP Country Gent

    Jul 23, 2019
    WA
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    Not too clean edges, but no major chip outs and the frame hides the edges pretty well. I am just going to take a breather before I drill the mounting screws and breathe a big sigh of relief. It sits about as flat as you can on the arched back in that location. And I think I can access the door pretty well while holding the guitar in typical sitting down playing position. These wires can reach out the jack hole along with the preamp’s prewired battery plug that will get re-wired together.
     
    Last edited: Sep 17, 2021
  5. GlenP

    GlenP Country Gent

    Jul 23, 2019
    WA
    I guess I am ready to start installing the harness and finish up wiring the pickups: the piezo to the preamp, and the mags into the blend pot. Then the battery box and the bridge grounding wire. Finally seeing the light at the end of the tunnel.
     
  6. GlenP

    GlenP Country Gent

    Jul 23, 2019
    WA
    Just trying to visualize everything here in preparation for pulling everything into place and making those final connections. Pickup leads are not soldered yet.

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  7. GlenP

    GlenP Country Gent

    Jul 23, 2019
    WA
    The piezo summing board is mounted on foam tape to the bottom of the bridge cavity, plenty of room there. The main piezo signal lead and ground have enough reach to get to the piezo preamp board.

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    Henry likes this.
  8. GlenP

    GlenP Country Gent

    Jul 23, 2019
    WA
    Piezo signal wire and ground hooked up to the preamp board. I added some heat shrink insulation so that portion of the exposed ground shield won’t short anything on the other nearby pots.

    Don’t ask me how I got that preamp installed. When I practiced it had no wires, the cables made for a lot less clearance. The battery access hole helped move things around and get the jack in place, and then rotate the preamp/pot about 180-deg so that the trim pot is facing the open jack hole, and the stereo/mono pop up switch is lined up with its hole.

    remaining wiring is the neck and bridge pickups to the blend pot, the bridge ground wire, and the battery box wires to replace the 9V receptacle. Starting to look like a guitar again.


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  9. GlenP

    GlenP Country Gent

    Jul 23, 2019
    WA
    Last edited: Sep 23, 2021
  10. GlenP

    GlenP Country Gent

    Jul 23, 2019
    WA
    I just realized that the mini toggle shaft is about the same dia as the threaded shaft on the stock 3 position switch was, so potentially I could cut threads on it and reuse the original switch tip. I will have to see if I can find a die cutter to match the thread. I can always try it out on the original chrome mini DPDT switch to see if it works before trying it on the gold mini toggle that I already wired and installed on the guitar.
     
  11. GlenP

    GlenP Country Gent

    Jul 23, 2019
    WA
    D27A4EFD-3500-4A5B-B8DA-2AA24D416952.jpeg Neck pick up installed and wired to blend pot
     
  12. GlenP

    GlenP Country Gent

    Jul 23, 2019
    WA
    Bridge pick up installed and ground wire connected to blend pot. Done! Ready to string this baby up. The push button has a white and black tip, I kind of like the black tip better. B69C5747-53B2-4E0B-A29E-DCB666943452.jpeg 587321BF-8AA8-40A1-9ED1-60F9E06E9BF6.jpeg

    blend pot knob is pointing up with all the others at their max value, when blend pot is at middle detent for the “both” neck&brige position. Turning “down” goes to neck, turning “up” goes to bridge.
     
    Last edited: Sep 23, 2021
  13. GlenP

    GlenP Country Gent

    Jul 23, 2019
    WA
    As a result of my careful planning, I can pull out the jack and access the internal phase switch and trim pot on the CTRL-X preamp. FA17691C-A139-4709-A806-BFB6A772C499.jpeg

    (@thunder58 football jack plate temporarily removed for clarity.)
     
    Last edited: Sep 24, 2021
  14. LivingMyDream

    LivingMyDream Friend of Fred

    Glen, I've been extra busy since I bought a horse about 6 weeks ago, so I have been catching up on your progress. I can't wait to hear how you love the piezo blended with the mag pickups. IMHO, it is truly an amazing sound.
     
    GlenP likes this.
  15. GlenP

    GlenP Country Gent

    Jul 23, 2019
    WA
    I have already started doing that on my acoustics, blending the built-in piezo with a sound hole humbucker, humbucker into my amp and piezo straight into the PA, and the amp is also mic'ed :) . So much for Keep It Simple, but I have fun with it.

    It will be a little bit longer before I get this Gretsch fully operational, I just found a short in the wiring splice I did to the battery box which powers the piezo preamp, D'oh! I think I might have melted the insulation when melting the heat-shrink and will have to cut that part out and splice it again, plenty of cable there still. The mags work fine with the new blend pot at least.

    It has been fun planning this out and sharing my story along the way here, it has kind of helped me think things through.

    A Centerblock jr, is really a bit too small for something like this, it really helps to plan out the harness, not just for the placement in the guitar, ie the "pickguard" layout, but also in the single-file line train that you will have to put everything in when you install it one part at a time through one of the pickup routs, that may require some extra wiring, especially for that pre-amp board that can only go in one way, but then I needed to rotate it 180-deg once it got into position to face the jack. This was much more challenging than doing my home-built Tele wiring.
     
    Last edited: Sep 24, 2021
  16. GlenP

    GlenP Country Gent

    Jul 23, 2019
    WA
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    Restrung the guitar and was surprised that the intonation was about right. I had measured the saddle placement from the original bridge and adjusted the piezo saddles to match on the new bridge. Also, I installed a String Spoiler from Vibramate, because, well, more gold!

    I still plan to put the pickguard back on, but kind of like it without, so I won’t be in a hurry to do that just yet.
     
    Last edited: Sep 25, 2021
  17. GlenP

    GlenP Country Gent

    Jul 23, 2019
    WA
    Seems to be working fine, the piezo output was way hotter, but I was able to reach the trim pot and make an adjustment to balance the level with the mags. Although most of the time I will be splitting the signals in stereo mode and adjusting gain/volume externally via the corresponding amp/PA anyway. The piezo adds some of that clarity and percussive attack, although the BT filtertrons aleady have lots of clarity to begin with, you know?

    Installing the CTRL-X pot/pre-amp board was the most difficult part in this size guitar. I would not recommend doing that unless you have plenty of extra wiring length. A better idea would be to cut open a control access panel on the back and install a plate. Hard to do that on a contoured semi-hollow center block since there is not a flat spot on the back of the guitar where you could put one. Would have been much easier to install a passive piezo pickup with a simple Vol pot only, wire it straight to a separate jack, or the ring of a stereo jack and then use some external pedal pre-amp/DI. That would avoid the battery, mag/pie switch, and internal pre-amp board, much easier to just do the mixing/blending outside of the guitar with separate mag/pie outputs rather than install all that extra stuff in a centerblock jr.
     
    Last edited: Sep 25, 2021
  18. GlenP

    GlenP Country Gent

    Jul 23, 2019
    WA
    Playing around with it a bit, just with both pickups into two channels on my amp, I really like it. Pretty much exactly like what I was expecting and the piezo sounds great by itself or blended with the magnetic pickups.

    Another new thing with this mod, is the blend pot for the neck and bridge magnetics, that is kind of neat too. From center, you can slightly emphasize either pick up before gradually rolling into the full neck or full bridge position. Probably can achieve the same sounds with the individual Vol pots that were removed, but just a new way of getting there. I like how I wired it going from neck to bridge as you rotate in the same direction as turning up a vol pot. It is kind of intuitive and makes sense that way. Same great sounds, just a new way of dialing them in. And a bit of a punchy clarity added in with the piezo, pretty happy with it overall.

    I am kind of glad the shop I initially took this in to do the mod for me came back with a really high estimate of doing the work, that gave me the impetus to take this on myself and clear out my workbench for this over-the-summer project. I have a little more pride in the guitar in having done this mod myself, sweat equity, you know? I only got burned once, when I was changing from right hand to left hand, and my left choked up on the grip a bit too high and a finger touched the hot part of the iron for a bit, man that hurt, it left a very tiny blister. It would not have taken that long, I guess I started acquiring parts back in May, but I only had some spare weekends occasionally to work on this, and I spent a lot of time just trying to understand the wiring diagrams they make for Gibson and Fender and trying to Gretch-ify that. Once I got into it, I just took my time and only did small portions at once. It could be done much faster by someone with more experience than me.
     
  19. GlenP

    GlenP Country Gent

    Jul 23, 2019
    WA
    Initial impressions with the new strings, still stretching out a bit, but staying in tune pretty well now. Since I measured the saddle locations from the stock saddle and placed the piezo saddles in the same locations, the intonation was actually pretty much spot on. Since the neck had been unstring for a while not sure if I need to let it get acclimated to the tension again, but it seems like I can get decent action at the 12th fret with the bridge height of the TOM where I want it, but the D and G strings buzz a tiny bit on the first fret, so I think I might need to get a new nut re-cut. I will give it time for the neck to settle back into where it wants to be first. There is plenty of graphite powder in the nut slots, but I did not add anything to the new piezeo saddles, they seem to slide pretty smoothly when using the Bigsby. The Bricks BiggsFix I just installed might be helping with that too.

    Overall, I really like the sound of the piezo pickup all by itself, and kind of a nice wet/dry mix with the piezo and mags blended into two different amp channels, or into a separate amp and a PA, with a bit of stereo chorus on the clean piezo signal in the PA. Was a fun project, and the more I play with it, the more I like it. Not exactly a NGD, but kind of feels like a new guitar. The Kingfisher rides again!

    Thanks for listening!
     
  20. LivingMyDream

    LivingMyDream Friend of Fred

    Sorry GlenP, but I've missed your last few posts. COVID bit my grandson, and then it went right through the house. It was a week or so of feeling lousy, but we're all better now.

    It was nice catching up on your progress, and I'm glad you're enjoying the finished project! My PRS piezo is still my first reach, just because the sound is so cool. :)
     
    GlenP likes this.
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