Roland MKS-50 (1987)

A rackmount Alpha Juno with a genuine analog voice and a very digital menu system, all in one rack space.

Overview

The MKS-50 is the rack half of Roland's Alpha Juno line. It has the same analog DCO architecture as the keyboard versions, squeezed into a 1U module for studios that had already run out of desk space. The service documentation carries a "JAN. 1987" date stamp, which is as close as the surviving paperwork gets to a birth certificate. A buyer gets a single rack space of six-voice analog synthesis with 128 patch memories and 16 chord memories. The chord memories are a late-'80s idea: store a whole chord and trigger it from one key. Recording Engineer (March 1987, p.109) covered it in the new-products column as a module for MIDI users. That is what it was - a way to add an analog voice to a MIDI rig without buying another keyboard.

The architecture is DCO-based rather than VCO. The tuning is stable in a way that vintage VCO polysynths are not, and the service manual's calibration procedure shows why. Each of the six modules has its own trimmer (VR1A through the rest), and the factory expected a tech to sit there with a scope and match them by hand. The DCO section lists a tuning range of ±50 cents, LFO modulation of ±400 cents, envelope modulation of ±3200 cents, and a bender range of ±1200 cents. The aftertouch figure sits at ±400 cents. You can push this synth well past subtlety if you want to.

The filter is where the MKS-50 earns its keep. It's a -24dB/octave lowpass with a cutoff sweep of 8Hz to 33kHz, envelope modulation of ±12 octaves, LFO modulation of ±6 octaves, and aftertouch opening it up by +6 octaves. Key follow is adjustable from 0 to 100%. The envelope-modulation range is the headline. Twelve octaves of sweep is enough to make the filter act like a percussion instrument if you set the envelope short, and the 4ms-to-30s envelope times on all four stages cover the other end of the spectrum. The LFO runs from 0.03Hz to 60Hz with a delay time up to 30 seconds. That is a long delay for a synth of this era, and it makes slow filter swells usable.

Output is listed at -3dBm on the audio jacks, with the headphone output spec'd for 8-150 ohm stereo loads. Power consumption is 16W, or 12W for the Japan-market version. The unit weighs 3.5kg / 7 lb. The dimensions in the manual are partly garbled in the surviving scan. The height reads as 44mm, and the depth and height figures appear as 16 inches deep by 1-3/4 inches high, which is a 1U rack footprint. Treat the depth figure with some caution, given the OCR state of the source.

Recording Engineer (March 1987, p.109) noted the patch and chord memory counts in its launch writeup. What the spec sheet doesn't tell you, and what the service documentation makes clear, is how much of the MKS-50's operation lives behind a menu. The panel has 18 switches wired into a 3-by-8 matrix through a gate array, and the front panel is a small LCD with a handful of buttons. Editing happens through parameter pages, not through a knob per function. That is the defining experience of owning one, and it's the thing to decide about before you buy.

The RAM initialization procedure is worth knowing, because it can turn a dead-looking MKS-50 back into a working one. The unit runs on a backup battery, and when that battery dies, the user program goes with it. Roland's own documentation says initialization should be performed when RAM or the backup battery has been replaced, when RAM contents have been erased, or when the MIDI mode is being changed between poly and mono. The procedure loads the tune/MIDI function, 16 chord memories, 64 tones for the A group, and 128 patches for the A/B groups from ROM into RAM. It also copies the A-group tone names over to the A-group patch names. There are two entry points. Holding number buttons 4 and 8 at power-on initializes in poly mode, and holding 3 and 7 initializes in mono mode. Both briefly display "FACTORY PRESET." If a used MKS-50 has a blank or scrambled display, this is the first thing to try. It costs nothing and fixes a surprising number of "broken" units.

The same documentation gives a RAM check that doesn't erase anything. Power off, hold PATCH A-B and DATA TRANSFER together, and power on. The display reports either "RAM CHECK OK!!" or "RAM wr/rd ERR!!". It's a two-second diagnostic worth running before you hand over money. There's also a full test mode, entered by holding TUNE/MIDI and PATCH A-B at power-on. It puts the unit into an adjustment and inspection state where several switches change function. That's useful for your own calibration, and an easy way to confuse yourself if you're not expecting it.

On the MIDI side, the MKS-50 speaks the usual Roland system-exclusive dialect. The manual documents bulk dump, individual parameter, and file request operations. The format type field is shared across the JU-1, JU-2, HS-10, HS-80, and MKS-50, and the MKS-50 adds a group number and patch data on top. Patch or chord memory data is valid only for the MKS-50 in that format family. That means sysex files from the keyboard Alpha Junos are not simply interchangeable with the module, so expect to deal with that when moving patches between an Alpha Juno and an MKS-50.

The MKS-50 shows up in studio gear lists of the period as a working module rather than a curiosity. EQ Magazine (June 1991, p.22) lists one in Axel Kroell's rack at European American Recording, alongside a Super Jupiter, an Oberheim Matrix 6R, and a Moog.

The MKS-50 shares its voice architecture with the Alpha Juno keyboards, and the rack format is the reason to want one. It's the same sound in less space. The tradeoff is that you give up the keyboard's direct controls for a menu-driven front panel. Prices and current market conditions are not documented in the available sources, so no figure is offered here. The practical concerns are the backup battery, the menu-based editing, and the sysex compatibility caveat above. The six-voice polyphony and 128-patch memory are modest by later standards but normal for 1987.

The DCOs don't drift, and the filter has more modulation range than most players will ever use. The calibration procedure in the service manual suggests Roland expected these to be maintained rather than discarded. The menu system is the price of admission.