SX Series/parallel pickup switch mod

bassbenj · #1 10-07-2009, 12:12 AM

What with all the SX threads going on I sort of got inspired. I mentioned here my favorite mod a couple of times. And that is changing the vol/vol/tone setup on the SX to a volume/ pickup switch/ tone arrangement.

I hate the vol/vol thing so common in passive basses. I love to change tone on the fly and the vol/vol setup drives me nuts. What I like are sort of pre-programed settings you can just switch in without have to fine tune knobs. PLUS I love the series pickup wiring as a great P-bass like option.

So my solution was to put a rotary switch in the second volume position. It selects: Neck pickup only/both pickups in series/ both pickups in parallel/ bridge pickup only. It takes a bit of thought to figure out the wiring but it's not that complex. Note that there are three sections to the rotary switch even though it is possible to get away with only using two. The reason is that trial and error showed me that the 3 pole circuit had less noise and switching clicks.

Anyway, I got busy and for all you SX lovers I've drawn out the wiring diagram for my mod. And I'd note that I've put the same mode on my Fender V even though it had vol/pan. Love that switch selectable pickup wiring. Probably it's my G&L that got me into this where it has lots of switches for tone including the single coil option I installed...but that is a story for another thread and day.

Below is the diagram of my SX mod:

Note: If I recall correctly I think I bought the switch at Radio Shack. But since they aren't very reliable at keeping parts in stock, I can't say if you'll find one there. Good luck!

savit260 · #2 10-07-2009, 06:26 AM

I had a Jerry Jones with that same 4 way rotary wiring scheme. Worked well.

**line6man** · #3 10-07-2009, 07:20 AM

I'm curious though, you're not putting in a 250K resistor across the outer lugs of the volume pot to simulate the effect of the other volume pot you removed?

**Bryan R. Tyler** · #4 10-07-2009, 09:08 AM

Moved to Pickups and Electronics

bassbenj · #5 10-07-2009, 01:30 PM

Quote:

Originally Posted by line6man

I'm curious though, you're not putting in a 250K resistor across the outer lugs of the volume pot to simulate the effect of the other volume pot you removed?

No. In fact I've changed the way the volume is wired as well. The original (and common) circuit puts the pickup to the slider. This presents a changing impedance to the pickup as you change volume. That at least has the potential of changing tone with volume changes due to the changing load. So I put the pickup to the end and took output from the center. There still is a slight changing load (from 250k to the 50k or so of the amp) but at least it doesn't go zero like it was.

You certainly could put a 250k to simulate the old circuit, and use the original volume wiring, but I liked the new wiring better. But once you plug in the amp the 50-100k swamps the 250k pretty much.

Since the thread is now moved to pickups and electronics, I'll add that in using this circuit on my Fender Deluxe V, I added a load resistor to ground across the output line of the switch. The reason is that the Fender Active electronics had a 1 meg input which left the pickups essentially open circuited except for the volume control. Originally they were wired into a pan pot that provided a reasonably low load to them. So in that case the resistor was added to preserve the original pan pot load and tone resulting from that load as you suggest.

Also let me add that in the Fender case I got quieter results by changing the switch wiring so it was the neck pickup rather than the Bridge pickup that "floated" in the series position. Why this is I have no idea. And Oh, by the way, on the Fender you have to go under the floating pickup and cut a ground wire which ties the output "lo" side to shield ground.

That's about it.