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BX-13-MICRO 24-to-13 Pin Bus Converter

Features and Specifications:

  • NEW Internal Voltage-Controlled Amplifier design, brings GR-300/GR-700 functionality to BX-13-MICRO
  • All-new circuit design for clean, latency-free analog signal processing to convert 24-pin signals to 13-pin format
  • Tested with Vintage Roland and Ibanez Guitar and Bass Guitar Synthesizer Controllers
  • Vintage GK Mode Switch Automatically Converts to Modern GK Switch
  • Backed by Two-Year Parts and Labor Warranty
  • Size: 120 (W) mm x 103 (H) mm x 31 mm
  • Weight: 10 oz.
  • Ordering Information
  • Download BX-13 Micro Schematic

Introduction to the BX-13-MICRO:

The ground breaking GS-500 guitar did not have a 1/4" output on the guitar.
The ground breaking GS-500 guitar did not have a 1/4" output on the guitar.

For about ten years, Roland Corporation and other manufacturers produced a range of unique, very high quality 24-pin guitar synthesizer controllers. At the transition from the 24-pin format to the 13-pin format, Roland released the rare BC-13, a 24-pin to 13-pin bus converter specifically design to allow 24-pin guitars to play the newly released Roland GR-50 guitar synthesizer.

Since the brief appearance of the BC-13 in late 1989, Roland has continued to developed the 13-pin synthesizer format, with the current GR-55 containing a multiple guitar synthesis technologies, both analog/physical modeling synthesis and pitch-to-MIDI PCM synthesis.

The BX-13 series of bus converters are designed to update the original Roland BC-13. To appreciate what is new about the BX-13-MICRO, you have to look back at the Roland GR/GS-500, the original 1977 Roland guitar synth system.

Roland G-808 Side View
Later Roland guitars have a second passive signal path and 1/4" output for the guitar signal

Surprisingly, the GS-500 guitar did not have a standard 1/4” output. The guitar signal tapped directly off the humbucker pickup, and control voltages generated in the guitar operated voltage controlled amplifiers in the GR-500. These VCAs controlled the guitar level, plus the solo mono synth, polyensemble, and bass section.

Later Roland added a separate passive signal path for a 1/4” output on their guitars, but again the signal sent down the 24-pin cable is tapped right off the humbucker, so the guitar signal arriving at the synth is always on maximum.

The original Roland BC-13 required two cables for full volume control.
The original Roland BC-13 required two cables for full volume control.

Roland changed direction when they developed the new 13-pin format in the early nineties, taping the guitar signal AFTER the passive volume control. The original Roland BC-13 bus converter, using the maximum guitar signal, offered no way to directly control the guitar volume when connecting vintage 24-pin guitars to the new Roland 13-pin guitar synthesizers, like the GR-50.

Roland engineers tried to work around this problem by requiring guitar players to run two cables from the vintage controller: the Roland C-24 cable, plus a standard 1/4" guitar cable. This gave the guitar player more control, enabling the use of the master volume as the guitar’s volume control, but was an awkward solution at best.

More recently the BX-13 series of clone converters has included a dedicated volume knob, or EV-5 pedal input, to add control over the guitar volume level without necessitating using a second cable.

With the VG-99 this is not such a bid deal, since no factory patches access the normal guitar sound. But the Roland GR-55 has several factory patches that use the normal guitar output, and part of the appeal of the powerful GR-55 is its ability to simultaneously process up to four sound sources, including the normal guitar output!

New Internal Voltage Controlled Amplifier:


The BX-13-MICRO takes this problem head-on with most logical solution: including a voltage-controlled amplifier inside the BX-13, doing the same job as the voltage controlled amplifiers found inside a GR-500, GR-300 or GR-700. And here is an added plus: no loss of tone as you turn the guitar volume down!

Check out the BX-13-MICRO with the GR-55 factory patch 30-1. With the foot pedal in the back (up) position, you can hear the guitar output alone. While moving the Master Volume knob on the guitar, check out the guitar tone: the advanced VCA design does not roll off tone like a passive volume control!

You get the full range of tone at any volume. With an entirely redesigned circuit, the BX-13-MICRO is smallest and easiest to operate 24-to-13 pin converter ever built. There are no levels to adjust, no additional cables, just clean, analog signal processing with no latency.

Designed for the Roland GR-55 Player:

Roland GR-55 with BX-13-MICRO

The BX-13-MICRO was specifically designed and tested with the Roland GR-55 in mind. The powerful GR-55 has the ability to process up to four sounds at the same time: two PCM synth tones, COSM modeled guitar, and the normal guitar output. Check out factory patches 30-1, 30-2 or 30-3 to hear the great tones made by blending vintage pickups with modern synth sounds. Operation is simple: Filter cutoff, or CV#1, generates GK Volume commands, and the guitar’s GR Mode switch now sends GK S1 and S2 commands. And with the new VCA circuit, the Master Volume knob on the guitar controls the volume of the normal guitar sound in the GR-55.

In the GK setup menu of a Roland GR-55/VG-99, select GK-2A for the pickup type. You will notice that a vintage guitar with the BX-13-MICRO, has a much stronger and more robust output than a modern GK-3 pickup. While the GR-55 defaults to inputs settings of 65, using the BX-13-MICRO, you can set levels as low as 20 or even 10.

And the BX-13-MICRO works great with vintage Roland basses as well. Just boot up the GR-55 into Bass mode, and you are ready to go. Be sure to select GK-2B, and set the GK Pickup Position to 4STR-3.

Vintage Versus Modern GK-3 Pickup Technology:

Vintage Vs Modern Pickup

Compare a typical vintage pickup to the GK-3 pickup. The vintage pickup may have as much as 10 times the coil windings, and a much higher impedance. A stronger source signal at the guitar means better signal-to-noise ratio, less cross talk between strings, and lower gain settings in the Roland synthesizer.

Unfortunately these larger more powerful pickups went away when Roland stopping building their own guitars in partnership with Fujigen Gakki, one of the greatest Japanese guitar builders. In addition to building guitars with Roland, Fujigen is also responsible for the highly valued Japanese Fender guitars, and prime vintage Ibanez guitars as well.

But the good news is this: if you love vintage guitar synth controllers, like the G-303 or the radical G-707, the BX-13-MICRO just made it easier than ever to connect these premium quality guitars with the latest in cutting edge guitar technology.

Praise for the BX-13 Series:

Everything works great and it tracks well!

I just want to really thank you. I have had these 2 Roland (strat-style) controllers and a GR-300 for years and all I’ve ever wanted to do was go 13-pin with them and control a MIDI guitar synth with them (I have a lot of sound modules not to mention computer programs). I knew there had to be a way..... I just never wanted to do it bad enough to slap a GK-2 on one of my other guitars.

You've helped me to realize a dream.....and it works great too!

Sincerely - D. MacManus

But I just wanted to say the BX-13-VX ROCKS! I originally purchased it from you two years ago when I was planning on using it with a VG-99. But the VG-99 library of sounds fell short of my expectations, so it was not until I obtained a GR-55 that I really got the chance to put the BX-13-VX to good use. With the G-303 guitar and the GR-55, the BX-13-VX works like a champ!

Thanks and happy new year,

David Kasle

VG-99/GR-55 Settings - Guitar (GK):

1) Go to your GK System settings (System/GK) and set pickup type to GK-2A, scale type to LP for a G-303 or G-808, and ST for the Roland G-202, G-505 G-707, or Ibanez IMG2010. GK Phase, Pickup Direction and S1/S2 position are all Normal.

2) Sensitivity Settings: I designed the BX-13-VC to work with the GK sensitivity settings at "10." That is, "10" on a range of "0" to "100". This is so the VG-99/GR-55 does not have to add additional gain for a solid response. However, this setting of "10" also depends on two other factors: the settings of the internal trimmers in the vintage guitar, and how hard you play. The setting of "10", gives you some room to reduce gain if needed. Adjust the internal trimmers in the vintage guitar to match your playing style. Also, check the pickup height of your vintage guitar pickup.

With proper settings, you should find the vintage Roland guitar is actually quieter than any GK-3 guitar. I have yet to find a GK-3 guitar than can match the signal-to-noise ratio of a vintage Roland guitar. The principle is a bit like the acclaimed EMG pickups. EMG pickups boost the output level of the pickup at the source, the pickup. This makes for a stronger signal sent through the cable. The vintage Roland guitar has output circuitry that works at about twice the level of a newer GK-2A/GK-3 pickup. If you reduce the GK settings in the 13-pin synth to around "10," the 13-pin synth is adding much less gain (noise) at the synthesizer.

VG-99/GR-55 Settings - Bass Guitar (GK):

1) Go to your GK System settings (System/GK) and set pickup type to GK-2B, scale type to LONG JB/PB for a G-33, G-77 and G-88. GK Phase, Pickup Direction and S1/S2 position are all Normal. GK PU POS is set to 4STR-3.

Links to more information:


Click on any image for larger view.

Videos: Demo

Video: Build Your Own BX-13

Frequently Asked Questions:

  • Does the BX-13-MICRO add any latency or delay?

  • No. None of my processors add any delay at all. Like the GR-300 and GR-100, they are purely analog processors that do not suffer from the inevitable latency introduced by digital systems. Many players notice that their guitar synths actually play better, since the gain stages have been especially designed to deliver the best possible signal to the guitar synthesizer.

  • Will the BX-13-MICRO work with ANY Vintage Roland Guitar Controller or Guitar Synth?

  • YES! I have tested this with the Roland G-202, G-303, G-505, G-707, and G-808 guitar electronics and the Ibanez IMG2010. The BX-13-VC is also designed to work well with the Roland GK-1, and other third party controllers built by Gibson, Steinberger and others. The BX-13-VC has also been tested with the Roland GI-20 and VG-88, VG-99 and Roland VB-99.

  • Does this unit require any power?

  • No. The BX-13-MICRO gets its power from the connection to the guitar synthesizer. This is the same approach Roland used for the BC-13, US-20 and GKP-4.

  • Is there anything like a "reverse" BC-13 or BX-13-MICRO? I want to use a modern, 13-pin guitar synth controller to control a vintage, 24-pin synth.

  • YES! The RC-1324-VR Bus Converter translates modern, 13-pin signals into 24-pin signals, and provides all the necessary control voltages plus hex fuzz.

  • Where do you get the connectors? I thought they were discontinued by Roland a long time ago.

  • YES! Roland discontinued the connectors from active production about twenty years ago. So the 24 pin connectors are virtually impossible to find. I bought as many of these connectors as I could from Roland a while back. I also routinely contact Roland service centers from around the world, in search of the elusive 24-pin connectors. Depending on availability, I also use connectors refurbished vintage guitars and synths. Either way, there is no new supply of these connectors, so all the processors I build have a very, very limited production run.