[Bass of the Week] Modified Steinberger Spirit XZ-25

This week’s BotW is our first featured Steinberger. Generally speaking, it is not easy to mod one of these due to very limited space because of the smaller size and unique design. But the owner was up to the challenge up getting some good upgrades into it, and did so successfully.

Fraser Thomson (owner and modder of the bass) writes:

I bought this Steinberger XZ-25 Spirit bass (left-handed) brand-new back in 2004 or so. It’s one of the Korean-made Steinbergers, costing me $300-400 or so at the time.

Despite the lowish cost, the instrument itself is actually pretty well-made, but the out-of-the box pickups and electronics were pretty dull-sounding (as you should expect on a $400 instrument).

This thing was begging for an upgrade, since the mechanical elements of the bass seemed ready to go a lot further than the stock electronics could take it. So I decided to mod this bass with Bartolini innards.

I bought a Bartolini 5.2AP Preamp, 9V battery box, and Bartolini M45CBC-B and M45CBC-T pickups from Best Bass Gear and set to work.

There wasn’t much room for the battery box on the Steinberger, because its body is small to begin with and because much of the body near its edges is contoured, leaving very little flush surface space to mount the box. The best spot I found for the battery box was on the back of the bass, right in between the two pickups. This is a pretty dangerous spot to rout out a big hole, since a 0.25” error either way would put me right into the pickup cavities, routed on the opposite side of the bass.

Adding to the challenge was the fact that measuring precise positions on both the front and back of the instrument is really tough, since there’s so easy reference plane from which to measure positions of things on both the front and the back of the bass.

I rigged up a little system of 3 different reference planes, and measured my battery box position about 10 times from each plane to be reasonably sure I wasn’t going to drill into the routed pickup cavity. I put down vinyl tape to protect the surface of the bass, and carpenter’s tape to draw lines to position the routing template. I attached the acrylic battery box template I bought from Best Bass Gear to the bass with double-sided tape; lining it up was easy thanks to the centerlines etched on the template!

The rest was pretty easy… routing job itself was done in 10 minutes or so. The old Spirit pickups that came with the bass were the spring-positioned drop-in types that are suspended from a metal mounting ring that is screwed into the surface of the bass.

Since the Bartolini soapbars screw right into the body of the bass, I chose a soapbar size that was bigger than the original pickups, but not too big for this small bass with very little real estate. That way, enlarging the cavity to fit the new pickups would rout away the screw holes left in the surface from the old pickup mounting rings, but not cut into the electronics cavity on the back of the instrument.

The 4”x1.5” Bartolini soapbar size was just about perfect; I used my router and the EMG40 template from Best Bass Gear to enlarge the pickup cavities to accommodate the Barts; a much easier job than routing the battery box since I already had 2 cavities to use for aligning the template.

At this point, I hit the first real snag of the project: the pickup cavities had been countersunk to accommodate the spring-loaded height adjustment bolts for the old pickups…right where the Bartolinis were supposed to screw into the body.

There was no way I would be able to screw the Barts in because even if the screws were long enough, the screws would break through the back of the instrument after only a few threads were engaged because the body was so thin.

Looking around online, I settled on the idea of using Minwax high-performance wood filler to fill in the countersinks, because it claimed to be able to hold screws as strongly as wood can. This ended up working well. I filled ‘em in, routed the cavity flush again, and then used satin black model paint to paint the cavity.

Just as it came time to start on the electronics, I decided to make a design change. The wiring diagram(s) that came with the Bartolini pickups made it clear that I could further broaden the tonal range of the Steinberger. I decided to add 2 on-on-on toggle switches, configuring each pickup for series/single-coil/parallel wiring on each switch.

I wired the single-coil position to select the bridge coil on the bridge pickup, and the neck coil on the neck pickup…the so-called ‘outer single coil’ configuration.

According to Bartolini, this “gives a ‘Tele’-like sound for guitars and a ‘J’-like sound for basses”. There was almost no room at all in the electronics compartment for 2 new switches. I ended up having to put them just south of the bridge pickup… not really where I had in mind but it actually worked out pretty well.

I had already drilled 2 new holes for the new pots that I had now with the 5.2AP Preamp, so I drilled 2 more to accommodate the switches. I put them close enough together so that I could easily throw both switches at once, yet far enough apart that I can still easily switch them individually.

Soldering the pickup wires to the switches was pretty fiddly, but worked out well. I don’t think anything else could possibly fit in the electronics cavity on the bass. I got the thing all soldered together and buttoned up, put on some new strings, and… well, “wow” starts to get towards the difference the Bartolini preamp and pickups made.

Now there is an incredible range of tone available from this bass…from muffled, thuddy tones to distinct, aggressive/percussive funky tones, and everything in between. I had originally thought my next project might be to convert this bass to fretless, but I’m so happy with its funk/slap tone that I think I’m going to pass on that. I made a few mistakes here and there, but all in all the thing torned out great.

I would highly recommend Bartolini products, and Best Bass Gear had everything I needed to make this mod a reality. Thanks a lot!

Modding a Steinberger is rarely an easy task, but this one ended up working out great. Well done, Fraser!

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