GumiElectronic

I’ve received a number of e-mails from DIYers with good questions about my CR-8000 mods. I’ve compiled and answered them below:

What are the differences between the Gumi mods and the AS mods?
There are too many differences to list here, so the easiest thing to do is cross reference my mods with the AS mods. It should be easy to spot which AS mods I used, the associated component values I changed, and the mods I developed myself.

How do I install the individual outs on the CR-8000?
This territory has been pretty well covered by other DIYers. I think Estecho provides the best tutorial on installing individual outs. But you can also look at how others have installed individual outs on the TR-606. The process is nearly identical between the two machines. Learn more here.

Is the CR-8000 velocity sensitive? I’m not hearing the full voice when triggering the CR externally. What’s wrong?
Yes, several of the voices on the CR-8000 respond to velocity (or more accurately, voltage), which is one of the greatest advantages of adding external triggers. You can pull a very wide range of sounds out of the CR via velocity programming alone. However, you have to use a MIDI to trigger converter capable of producing trigger voltages that vary with MIDI velocity. So far the only kit I’ve found that does this well is the Elby MIDI2SDS(X). So, if you’ve wired external triggers to the CR and you’re not hearing the full voice (for example, when triggering the Snare Drum you don’t hear the noise source or it just sounds like a Tom), it’s likely that you’re not giving it the voltage required to trigger the noise source. Try sending a MIDI velocity of 127. If that doesn’t work, your MIDI to trigger unit might not be producing the necessary voltages. Check your device’s documentation and cross reference that info with the CR-8000 Service Manual for troubleshooting.

How do I get Hi-Hat Tune, BPF, and Decay?
These mods are listed under CYM in the list of Gumi mods. They effect the Cymbal and both Hi-Hats.

How do I wire the pots when using them to replace the stock CR-8000 resistors?
In most cases I just wired two pins on the pots (the wiper and either other pin depending on the direction of adjustment needed).  Some pots use all three pins (such as those that replace the VR trimmers on the PCB).  I didn’t ground all of the pots together, though it might a good idea to do so or connect the third (unused) pin to the wiper.

Should I use linear or logarithmic pots?
This is sometimes a matter of preference. I use linear pots throughout the entire mod, but you should experiment with using logarithmic pots to see if you like their behavior better.

What kind of switches do you use for the NORM and CUT toggles?
I use SPDT toggles switches.

What do the NORM and CUT switches do?
The NORM switches allow you to toggle in and out of the factory setting. For example, the NORM switches for the Cowbell Tune toggle between the original resistors and the new pot. This way, you can retain the original Cowbell sound, which might be difficult to recreate using only the two Tune pots. It also gives you more dynamic control over the voice mods when performing live.

The CUT switches are used to toggle individual voice boosts, oscillators, and/or noise sources on and off. For example, the NOISE CUT for the Toms removes the noise source, which really makes the Toms bang without that crappy wet cardboard sound. As with the NORM switches, the CUTs also give you more dynamic control over the voice mods when performing live.

The CYM Master Tune (R228) looks like a bad idea. What gives?
Okay, so this one might be more of a “bend” than a “mod.” I know it doesn’t add up and the behavior of this mod is a bit funky, but try it before ruling it out! You can get some cool effects, especially when using the pot with the NORM switch.