Introduction to the GK QuadBox, 1-input, 4 output Roland Guitar Synth Signal Distributor:
Dual Roland US-20s and/or GKP-4 Clone with Expansion Options:
The GK QuadBox is the essential tool that Roland guitar synth players have been searching for: a combination of the Roland US-20 unit switcher, with the long discontinued Roland GKP-4. The QuadBox combines the features of these two units together, allowing one guitar to play up to four Roland guitar synthesizers at the same time.
The GK QuadBox starts with the basic design of the GKP-4 and adds individually buffered GK Synth Volume outputs. This enables the output (GK Synth Volume) of each synth to be turned on and off, just like with the Roland US-20.
GK S1/S2 Switching:
|Click to enlarge.
The Roland US-20 allows either Synth A or Synth B to receive GK S1/S2 commands from the guitar controller, but not both at the same time. While the original GKP-4 used micro-switches to turn GK S1/S2 commands on or off.
The GK QuadBox takes a different approach: by default, GK S1/S2 commands from the guitar are sent to all four outputs simultaneusly. But the GK QuadBox has individual 1/4" TRS input jacks to allow access to the GK S1/S2 control signals for each synth.
In the style of the Roland GKP-4, if you want to disable GK S1/S2 commands to an individual synth, just plug a dummy TRS jack or TRS cable to interrupt the GK command from the guitar. This accomplishes the same duty as the micro-switches in the GKP-4.
But the GK QuadBox goes further, giving the player options not available with either the US-20 or GKP-4. By plugging in a Roland FS-6, or similar, foot switch, you can generate new, independent GK S1/S2 commands for each attached synth. Any simple on/off foot switch will work. And the GK QuadBox circuit includes internal capacitors to prevent switch bounce as well.
GK Synth Volume
There are even more options for GK Synth Volume commands. For the advanced user with DIY, do-it-yourself ambitions. the QuadBox provides access to the GK Synth Volume signal at two points: before and after the control voltage buffer amplifiers.
Before the buffer amplifier, you can select from either the GK Synth Volume signal from the guitar, or the onboard, regulated +5 volt supply. This 5 volt supply can be used to set any synth to maximum volume. This is same design used in the GKP-4.
After the buffer amplifier, there are four more jumpers in place that allow the user to individually reroute the GK Synth Volume signal. This is designed so that a basic 10K control pot, or a Roland EV-5, can be inserted to control the volume of each synth individually.
So you can mix and match volume control from the guitar, or volume control from a EV-5 pedal or additional control pot.Links to more information: