Roland US-2 Unit Switcher
Features and Specifications:
Control: Foot Switch - A, Foot Switch - B
Indicators: Channel - A On-Off, Channel B - On-off
Input:24-pin connector (guitar)
Output: 24-in connectors (2)
Dimensions: 200 mm (W) 70 mm (H) 120 mm (D)
Accessories:24-Pin Cable C-24E (1 meter) and Dummy Plug (1)
Weight: 1 kg
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Roland US-2 with GR-300 and GR-100 |
Introduction to the Roland US-2 Unit Switcher:
The US-2 is the single most requested item people search for. Almost every day I receive requests for a US-2, or I am asked to build a compatible unit. While the technology in the US-2 is not difficult to duplicate, the parts are. This unit uses two of the male, 24-pin connectors, with two panel mount shells. The only known source for these connectors are actual vintage Roland guitars. So you would have to sacrifice two vintage Roland guitars, or perhaps two LPK-1 kits, plus a GR-300 or GR-100 , to compile all the necessary hardware to build a US-2.
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Roland US-2 with GR-33B and GR-77B. Thanks to Pablo Leocata for the photo! |
For those of you unfamiliar with the US-2, you plug a vintage Roland guitar synth controller, like a G-202, G-303, G-808, G-808, or a bass unit like the G-88 or G-77 into the female 24-pin input connector. Plug the channel A and B outputs into a vintage synth, and you now can play either synth A, synth B, or both. The US-2 receives its power from synth A. However, you can plug a bus converter, like a BX-13 into the synth B output, enabling you to play a 24-pin and 13-pin synth at the same time.
If you are familiar with how the GR-300, GR-33B or GR-100 look when they are working, well, you get the same light show! The front panel LEDs flash just like they do on the synths, until you push down on the footswitch and engage an output. Then the respective LED lights solid.
Volume Levels with the US-2:
I noticed one day that my GR-300 seem slightly lower in volume when I was using the US-2. I wondered if distributing the strings signals was lowering the output. I did some tests with my oscilloscope and the individual string levels seemed to be identical. Then I decided to check the voltage of control line nine, or synthesizer volume. Sure enough, the switching system in the US-2 slightly reduces the over all master synthesizer volume.
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| Measuring control line nine, synthesizer volume, with a guitar plugged in to a US-2, and the US-2 output A connected to a GR-300. The voltage reads 10.77 volts. | Measuring control line nine, synthesizer volume, with a guitar connected directly to a GR-300. The voltage reads 11.90 volts. |
For my tests I used a G-505 plugged into a US-2, then I plugged a GR-300 into Synth Output A, and a GR-700 into Synth Output B. I used a multimeter to measure the synthesizer volume voltage directly at the 24-pin connector inside the GR-300. The voltage was 10.77 volts with the US-2. However, when I removed the US-2 from the circuit, and plugged the G-505 directly into the GR-300, the voltage went up to 11.90 volts, or about ten percent higher.
Links to more information: 1982 Roland Product Brochure - Japanese - Featuring the G-303 and G-808.
More information on using the US-2 with vintage synths on the 24-pin cable pin output page.
Schematics - Repairs - Service Bulletins:
The US-2 service manual recommends replacing the original TC4069UBP (4069 chip) to a HD14584B (14584B) chip. This is to help control flip-flop mistrigger due to variation in the foot switch contacts. In addition to replacing the chip, select resistor values are increased, and resistors are added to the US-2.
Download the US-2 Service Manual Schematics.
14585B Hex Schmitt Trigger replacement chip available at Mouser.com.
Roland US-2 Turbo:
The US-2 Turbo is a modified Roland US-2, designed to be used with the RC-1324-VR, 13 to 24 pin guitar synth converter, or used with the 24-to-25 pin conversion kit.
The rare, 24-pin connectors have been replaced by common, DB 25-pin connectors. This allows the US-2 Turbo to be used with commonly available 25-pin cables, in place of the ultra rare, very expensive proprietary Roland 24-pin cables.
The DB 25-pin format follows the same pin outs as the Roland 24-pin format, so pin #1 is +15 volts, pin #2 is - 15 volts, etc.
Re-wiring the US-2 Turbo with 25 pin connectors provided access to the circuitry inside the US-2. This gave me the opportunity to address one of the biggest shortfalls of the original US-2: the lack of independent controls for each synth. For example, if you were playing a GR-300 and GR-100, the filter and resonance controls on the guitar affected each synth equally. There was no way to have different control settings for each synth, which really limited what a multi synth vintage system was capable of. The US-2 Turbo has three additional 1/4" control input jacks on the side. By plugging a standard Roland EV-5 pedal into these inputs, you enable independent control over filter, resonance and LFO for synthesizer B. These controls only effect synthesizer B, and do not effect synthesizer A.
In the video, I use the RC-1324-VR to convert the modern, 13-pin output from a Parker PM-10 guitar (GK-2A internal electronics) to the vintage Roland format. The US-2 Turbo splits that output to two vintage synths: a Roland GR-300, and a Roland GM-70.
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Click on image to enlarge |
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US-3X - Roland US-2 Alternative
In 2011 I made a one-off unit called the US-3X. The US-3X provided the inspiration for the Roland US-2 Turbo, but the US-3X still uses the original 24-pin connectors.
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Click on image to enlarge |
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WATCH NOW! YouTube Video Playlist |
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GR-100, GR-300, US-2, G-505 and G-202 Magazine Advertising:
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This advertisement originally appeared in the February 1982 issue of International Musician and Recording World magazine! |
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