Lap Steel & Hot Rails Humbucker

[Tom Geldner]

I bought a cheap Rogue lap steel to goof around on and decided I wanted a beefier sound out of it than the stock single coil pickup. Also thought it would be fun to try the "spin-a-split" style wiring where the second pot changes from single coil to double coil instead of being a tone control. I used to have a Peavey T-60 guitar and it had that sort of wiring which I found really useful.

My amp and foot pedals are better for tone control anyway so no big deal losing the tone knob.

Anyway, I thought I'd share my (so far) successful mod steps in case anyone wanted to try the same thing.

1. Bought a cheap Chinese "hot rails" style pickup off eBay for $6 including shipping. Looks like this:



2. The pickup bars are curved to a fretboard radius. Filed them down flatter.

3. Get an appropriate wiring diagram for spin-a-split with a single humbucker pickup. I used this one:

http://www.seymourduncan.com/support/wi ... 1h_1v_1sas

4. The wire colors are totally different from standard pickups like Seymour Duncan. So I had to figure out what color was doing what. The seller was no help and ignored my email for a wiring diagram. The pickup comes preset for a standard humbucker install but I needed more detail to do the spin-a-split. While I could make a good educated guess as to what was what based on the wires coming off the back, it's always good to have confirmation. Sooooooo, I found an awesome video on YouTube showing you how to figure out what's what on a humbucker using a voltmeter and a compass. Highly recommended watching!

https://www.youtube.com/watch?v=7UfxQBhqen8

5. Realized that my brain was getting twisted up trying to figure out the colors so I had an adult beverage. That helped. Following the instructions above, the colors on the Chinese pickup are:

Black (-) - South Start (GREEN -)
Red (+) - South End (RED +)
Yellow (+) - North Start (BLACK +)
White (-) - North End (WHITE -)
Bare - Ground (GROUND)

The Seymour Duncan reference colors are in parentheses.

The cheapo pickup came pre-wired as Red/White (series), Black/Bare (ground) and Yellow (hot).

6. De-soldered stuff that wasn't needed (capacitor, wire running between pots), took off old P/U and then checked to see what the ohmage on the pots was. Hmmmm, usually single coils are 250K but these are 500K. OK well that works because most humbuckers use 500K pots. But it's clearly a non-standard choice for a production single coil guitar.

7. Installed new pickup and soldered everything according the Seymour Duncan diagram.

8. Reassembled everything, installed one string for testing and OMFG IT WORKED FIRST TIME!

The only thing is the ramp from single coil to double is too fast. Which means my next mod on this will either be to install a switch for single/double coil and turn the spinner back into a tone control or replace the pot with a different taper. Or probably just live with it and spend the money saved on a couple of beers.

Anyway, the sound is definitely more robust and I had fun doing this project. Next step is trying out a new set of SIT semi-flatwound strings. Next after that is really learning how to play C6 lap steel.

[David Mason]

There are a couple of ways to change the chutzpah of a pickup/pot/cap assembly. You can lower a pot's K value by bridging a resistor across the outside lugs, as in this:
http://www.projectguitar.com/tut/potm.htm

And because capacitors are additive when wired in PARALLEL, you can always start with a low value cap, and add another in beside it if needed. If I'm not wiring something entirely predictable - a new untried pickup for example - I start with a little cap like .015uF and just leave room to grow... and after I started measuring ALL pots before use, I quit even buying so-called "250K" pots. Even with respectable brands from reliable sellers, I found them skirting the 20% tolerance, and always on the low side. I can "fix" a 500K pot to around 300 with a 750K resistor, so, I do.

[Tom Geldner]

Thanks for the suggestion. What affect would it have on the spin-a-split pot which would seem more affected by the taper than actual pot value?