Korg CX-3 Improvements

The Korg CX-3 is a modeling synthesizer -- essentially, a specialized, pre-programmed computer -- and so is not really open to "hot rod" modifications to improve the sound. Sorry, but what you see is what you get. You can do some things outside the instrument, and in the programming menus, that will improve the playability, however.

The feel of the vibrato select (V-C) knob on the CX-3 is extremely light -- much easier to turn than the monstrous 6P6T switch on a Hammond B-3. I find that it's easy to overshoot the desired setting on the gig. The following modification will change the feel significantly, it won't affect the warranty on the organ, and it costs less than $2, even if you have none of the parts laying around!

1. Remove the knob; it just pulls off with finger pressure, although it takes a little bit of a tug the first time out. Turn the knob over, and you'll see that it's hollow, with a tube sticking up through the bottom to attach it to the rotary switch.

2. You'll need a flat rubber plumbing washer about 3/4" (19 mm) in diameter x 1/16" (1.6 mm) thick, with a hole about 1/4" (6.4 mm) in diameter. (The hole should be just a little smaller than the tube area of the knob.) Luckily, this seems to be a common plumbing part: If you can't find one individually, then buy one of those plumbing repair kits with the assortment of different washers; there should be at least one in the kit. The color of the washer doesn't matter -- it's smaller than the knob, so it doesn't show -- but the washer should be a little bit glossy on the surface, rather than having a completely matte finish. (You'll see why in a minute.)

3. You need something behind the washer to shim it up until only about 1/64" (0.4 mm) of the center shaft is exposed. I used a rubber foot of the proper height -- 9/32" (7.1 mm). I don't have the part number, but the one I used is grey colored, and available in a 4-pack at True Value hardware stores in the US. The foot has a center depression (for the screw head) of about the same diameter as the knob, and I used an X-Acto knife to carve out the rest of the center to make the foot into a short, fat rubber tube. The actual shim or shims used is not very important, but the height is. Also, while I could have used a plastic or metal shim, I think the slight give of the rubber foot is important to the overall feel of the final result.

4. Put the rubber foot into the bottom of the knob, with the wider side facing the bottom (it's tapered slightly). Then gently force the plumbing washer over the tube part of the knob. If everything works out right, the tube part should show through the washer, protruding by the 1/64" amount.
   

5. Press the knob assembly back on the switch shaft, taking care to line up the flat parts of the two pieces. Push the knob on all the way down, but don't press so hard that you crack the PC board! The knob should now resist movements, but the detent at each position should still be felt. If you cannot feel the detent, then the knob is too far down on the shaft. This is also the reason for using a semi-gloss washer; softer washers stick too much, and remove the feel of the detents.

I think this small change makes a big difference in the usability of the V-C knob on the gig.

If you're connecting the CX-3 to a real Leslie, I've found that the Preamp setting, which is arguably the "correct" selection for this setup, is not the idea setting, tone-wise. Here's what I came up with, through experimentation.

NOTE: These settings were determined using a well-maintained Leslie 251 speaker, with an ART Dual MP tube preamp set for a moderate amount of overdrive, sent to a hi-fi class MOSFET power amp. With other gear, your results may vary.

If you're trying to simulate a Leslie 122 or 147, the stock settings for the EQ and Leslie parameters are not quite right. Here's what I came up with, through experimentation, compared to recordings of various Hammond B-3's.

NOTE: These settings were determined by comparing a well-maintained Leslie 251 speaker to the CX-3, driven directly into a Mackie 1402 stereo mixer, with and without the use of an ART Dual MP tube preamp set for a moderate amount of overdrive. With other gear, or at higher distortion settings, your results may vary. Speaker selection and room acoustics may also affect the final settings.

NOTE: These are not the original settings that I posted in 4/2001. I found, over time, that I preferred a different setup.

** The EQ frequencies and style (LPF, HPF, etc.) of the CX-3 are not fully suitable to provide the tonal characteristics of the Leslie Speaker cabinet. Additional EQ at the board is necessary.

If you're looking for the sound that Goldy MacJohn had on the early Steppenwolf albums, a Leslie 122 or 147 is not the correct model. It's been suggested that he disabled the crossover and horn of a 122, and just used the lower speaker for all the sound. Judging by the tone and speed changes, however, I'm more inclined to think he used one or more Leslie 125's, usually at or near full-tilt.

When trying to simulate a Leslie 125 or 825, with its single 12" speaker, the simulator settings have to be changed. The same is true of simulating Fender® Vibratone® and Leslie 16/18 speakers. The following settings seem to get pretty close.

NOTE: The CX-3 does not have a single-rotor algorithm, and setting the balance to 0:100 is too bassy, so the two-rotor style must be fooled into sounding like a single rotor. This is not completely possible, as there is no way to synchronize the two "rotors" to the same phase, except by pure chance. Therefore, the sound of this simulation will tend to slightly improve and deteriorate during performance, as the simulated rotors line up or disperse.