2024-02-03
#music #electronics

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RBUS-ADAT User Manual

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-This version of the manual is for revision 1 of the board. -Copyright Chris Xiong 2024. Copying of this hardware and its design as well as this documentation is permitted -under the terms of CERN-OHL-P v2. - - -

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1 Preface

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If you are reading this, chances are you have become an unfortunate test subject of the RBUS-ADAT conversion -board (or have the nerves to think about becoming one). Well, here is (almost) everything you will want to know -about the board. If you want to learn about some less useful information about this thing, consider checking out -the devlog, which can be found by following the link to the project homepage listed under “Useful -links”. -

As this manual is written as if it’s a blog post, which is prone to being very rambly, I’ll try to keep the rambling -low, at least make an attempt to do so. -

Pictures in this manual are renders (computer-generated) and are for illustration purposes only. -

This product is neither affiliated with or endorsed by Roland Corporation. Roland does not approve -connecting unofficial accessories to proprietary Roland interfaces. -

Visit chrisoft.org/rbusif for any future updates to this manual and the hardware. - -

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2 NO WARRANTY

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THIS BOARD IS HOMEBREW AND EXPERIMENTAL HARDWARE. THERE IS NO WARRANTY FOR THIS -HARDWARE, INCLUDING ITS DESIGN AND THE FINISHED PRODUCT, TO THE EXTENT PERMITTED BY -APPLICABLE LAW. THE DESIGNER SHALL NOT BE HELD LIABLE FOR ANY DAMAGE CAUSED BY USING -THIS HARDWARE, UNLESS REQUIRED BY APPLICABLE LAW. -

For the full legalese text on warranty and liability, please refer to the license text. -

If this board fried your equipment, don’t try to extract anything from me. That’s what this section is trying to -say. - -

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3 Open hardware

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This board is open hardware licensed under the CERN Open Hardware Licence Version 2 - Permissive -license. Feel free to make as many of this board as you wish and sell them, as long as your follow the -terms. -

Contributions welcome and will be appreciated. If you have any suggestions to improve the board, -please feel free to contact the author. The author’s contact information can be found on the project -homepage. - -

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4 Safety notice

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There’s no enclosure for this board. As a result there would be exposed conductors on both sides of the board. -You’re advised to take measures to prevent them from shorting out. You may try any combination of the -following: -

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Placing the board on an non-conductive surface. -
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There are two M2 mounting holes in the board. Using two M2 screws and nuts, install a plastic sheet - (or cardboard even) under and / or over the board. - - -
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Don’t use the board at all. Don’t even think about it.

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Again, if you fried your equipment while using this board, it’s all your fault. I mean not really – I would still -want to know what happened. But it’s all your fault. - - - -

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5 Intended usage and applicable devices

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RBUS-ADAT is designed for use with the Roland XV-5080. It converts the 8 digital outputs exposed by XV-5080’s -R-BUS port to a standard ADAT lightpipe stream which can be recorded with any audio interface with an ADAT -input. -

The ADAT output from this converter is 20-bit and has the same sampling rate as the input supplied from the -R-BUS port. -

This converter cannot: -

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Convert ADAT back to R-BUS input. i.e. you can’t record an ADAT stream on a V-Studio through - R-BUS with this converter. -
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Serve as a clock source for the connected R-BUS device. You should always select “internal” as the - clock source for the connected R-BUS device. -
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Expose the MIDI interface on the R-BUS port.

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The converter is designed and tested with the XV-5080. In addition, the only audio interface that -has been verified to work is Focusrite Scarlett 18i8 3rd gen. I don’t have the resources to test other -devices. -

The converter has not been tested against VM- or VS- devices that feature RMDB 2 / R-BUS ports -or MV-8××× fitted with the MV8-OP1 expansion but may still work as a unidirectional converter -as intended. If you decide to try this converter with these devices, reporting the results would be -appreciated. -

The converter is not compatible with devices with the older RMDB port. - -

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6 What’s on the board

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R-BUS DB-25 Connector. See “Choosing a suitable cable” for what you should and shouldn’t plug - into this connector. -
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Power indicator. Illuminates if the board is receiving power. - - -
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ADAT Lightpipe output. Connect to a device capable of recording ADAT data stream with a - TOSLINK cable. -
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Pure hecking magic.

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7 Quick start

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Using a suitable cable (see the following chapter), connect the R-BUS DB-25 connector on the board - to the R-BUS port on your Roland device. -
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Connect the ADAT output on the board to the ADAT input of your recording equipment with a - TOSLINK optical fiber cable. -
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Turn on the Roland device, then turn on your recording equipment.

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8 Choosing a suitable cable

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DO NOT USE ROLAND’S OFFICIAL R-BUS CABLE!!! -

Please use a straight through DB-25 male-to-male (pins on both ends) cable to connect the R-BUS port on your -device to the port on the converter. These cables connect pin 1 to pin 1, pin 2 to pin 2, pin 3 to pin 3 -etc. These cables are usually sold as “DB-25 RS-232 serial cable”. Do NOT use any of the following -cables: -

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Roland’s official R-BUS / RMDB 2 cable -
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Parallel port cable -
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SCSI cable -
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LPT port Printer cable -
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Null modem cable

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These cables all use the same DB-25 connector but are wired differently. Using the wrong cable may damage the -converter and / or your device. -

Note that many RS-232 serial cables designed for relatively newer computers use the DE-9 connector. You’ll -need the older style with DB-25 connectors (which conveniently have 25 pins). -

DO NOT USE ROLAND’S OFFICIAL R-BUS CABLE!!! - -

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9 Notes

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Digital recording made from Scarlett 18i8 of the converted ADAT stream seem to have the full 24-bit - resolution. However this might be due to interpolation done by the audio interface or the operating - system. I do not have proper equipment to verify the bit depth of the output data stream. As such, - only 20 bits out output resolution is guaranteed. -
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The optical output port is a tight fit. You have to insert the plug all the way in until you hear a click.

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10 Specifications

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Signal processing	24-bit internal, 20-bit output

Sampling rate	44.1 kHz, 48 kHz

Connectors	R-BUS (Input only): DB-25 Digital output: ADAT Lightpipe (JIS F05 connector)

Chipset	coolaudio V1401 (Alesis AL1401 equiv.)

Rated current	<8 mA

Rated power	<0.04 W

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11 Appendices

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11.1 Build instructions

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This is intended for people who didn’t end up with a pre-assembled board. If you already have a fully assembled -board, you may ignore this section. -

If you have a kit, you may skip to step 3. - -

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11.1.1 PCB production

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I assume if you have chosen to take this route, you know what you are doing. - - -

You’ll find Gerber files in the out directory of the project repository that you can upload to your favorite PCB -production service provider. Or alternatively if you want to tweak the board you can open up the KiCad project -files, which are also found in the project repository. -

Many PCB manufacturers will add a board identifier to each PCB they make and allow customization of where -this identifier will be placed. The front side silkscreen text “Production ID” is reserved for this purpose. Please refer -to the ordering instructions of your PCB manufacturer for the details. Usually this will involve changing -the text to something specific to that manufacturer and selecting an option before submitting your -order. - -

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11.1.2 Bill of materials

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Designator	Part	Qty

C1	16V 100μF electrolytic	1

C2, C3, C4	50V 0.1μF ceramic	3

CN1	Cliff FCR684208T	1

D1	1N4002	1

D2	Red GaAsP / GaP LED 3mm ^a	1

J1	Adam Tech DB25-SL-25 ^b	1

R1	1/4W 1kΩ	1

R2	1/4W 2.2kΩ	1

U1	SN74LS04N	1

U2	coolaudio V1401	1

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11.1.3 Assembling

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Again, I assume if you are assembling the board yourself, you possess the appropriate set of skills. It’s now time for -them to shine. Most components are through hole so it should be easy. If it’s not already obvious, solder the only -SMD chip first. - -

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11.1.4 Testing

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If you have a 5V power source, it is suggested to test your assembled board first. Supply 5V between the anode of -the D1 and the metal shell of the DB-25 connector (GND). Check if anything pops. - -

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11.2 Useful links

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R-BUS project homepage: https://chrisoft.org/rbusif -
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Project repository for this board: https://cgit.chrisoft.org/rbus-adat.git -
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Online version of this manual:
https://chrisoft.org/blog/post/rbus-adat-m.html (html version)
https://filestorage.chrisoft.org/blog/data/rbus_adat_m.pdf (pdf version)

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11.3 Schematic

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11.4 Circuit board

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Front side

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Back side

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^a5mm used in prototypes

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^bOr any right angle DB-25 receptacle with 8.1mm backset spacing

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Chrisoft

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