michaelmx - Posted - 01/29/2014:  20:01:49

This is a little long, but I hope that it is interesting or useful to some.  I was playing my biscuit reso one day when I wondered how it would sound with a little more sustain on the top strings.  Then I wondered if electrifying it might increase the sustain a bit, which of course lead me to think of the National Hot Plate.  Since I imagine that I could buy a pretty nice electric guitar complete for that price, I began to wonder if I couldn't build a Home Brew Hot Plate for about half-price.  I checked my various stashes and found I had all the electronics on hand:  Pickup, pots, tone cap, switch, jack and knobs.  Not wanting to cut into the original cover plate, I went ahead and ordered a replacement cover plate from Stew-Mac.  There are other suppliers out there, but I liked the looks of that one and so I went with it. 

A photo below shows all the parts that I rounded up.  I did not use all of them.  Once I had all the parts assembled, I went to work chopping up the cover plate.  I cut a slot for the pickup and drilled holes for the other components.  The mounting holes on the cover plate didn't line up with the ones on the guitar and I didn't want to redrill the guitar, so I egged out the mounting holes in the cover plate.  The next photo shows a dry run test fit for the modified cover plate.  The pickup is a humbucker with a coil tap from GFS.  The switch above the control knobs chooses between single-coil and humbucker.  Again, lots of pups out there to choose from.  I have had good luck with GFS and I had this one at hand.  The next photo shows everything wired up.  I retaped the pickup wire so the sieve holes are not blocked.  I could have been more careful in my work; I scratched up the front of the cover plate a bit, so I painted a little design to try and improve the looks a bit.  The last two photos show the finished job.  

When I first started on this, I didn't realize that Republic Guitars offers a product similar to the National one called the Electro Plate.  Inspired by these two products, I decided to call my creation the Combination Plate because it offers a combination of two pickup types. 

Right now, I'm up to the playing and testing stage and, frankly, I'm a little disappointed in the results.  Acoustic, there is no change in sound of course.  Plugged in, this sounds very much like an electric guitar with very little of the 'cone sound' coming through.  I'm also getting some feedback similar to what you get with a soundhole pup in a flattop.  I still have the acoustic phosphor-bronze strings on it and the volume across the string is uneven.  I think that one or more string trials may be in order and perhaps a change of amp as well.  However, overall, I think that the actual project, so far, has been successful. 

Possible Parts For The Combination Plate	Modified Cover Plate	First Test Fit For Combination Plate	Combination Plate Wired
Close-up Finished Combination Plate	Overall Finished Combination Plate

Brad Bechtel - Posted - 01/30/2014:  08:05:04

You really need to use nickel wound strings to get the pickup to respond properly.  I'm not surprised that an electric guitar pickup attached to the cover plate makes it sound like an electric guitar.  There's a reason why piezo style pickups are generally attached to the cone or bridge - although not perfect, they give more of the resonator sound.

Good for you for experimenting!  Keep it up and you'll find something that works for you.