Oberheim Matrix 6R: The Analogue Rack Synth Perth Owners Need to Know

If you’ve just picked up an Oberheim Matrix 6R — or you’re thinking about it — you’re looking at one of the most underrated analogue rack synthesizers ever made. Not the flashiest piece of gear from the mid-1980s, not the most famous, but quietly one of the most capable. It sat in professional studios worldwide, doing serious work on serious records, while the Yamaha DX7 got all the press.

We recently completed a service on an Oberheim Matrix 6R here in Perth, and it’s a good reminder of why these units are worth saving. So let’s dig into what it actually is, why it sounds the way it does, and what you need to know if you own one.

AST Repair Perth offers specialist synthesizer repair in Perth for vintage and modern keyboards and synths. See our synthesizer repair page for more detail on what we take on.

From the OB-X to the Matrix: How Oberheim Got Here

To understand the Matrix 6R, you need a quick look at where Oberheim came from.

Tom Oberheim started with the SEM — Synthesizer Expander Module — in 1974. A keyboardless module designed to expand other synths, the SEM’s legacy was in what happened when you stacked them: the Two Voice and Four Voice systems of 1975–76, the first widely available polyphonic synthesizers. From there came the OB-X in 1979, Oberheim’s first fully integrated polysynth and a direct competitor to the Sequential Circuits Prophet-5.

The OB-Xa followed in 1980 — the first Oberheim with the iconic blue pinstripe-on-black look — introducing Curtis CEM chips to reduce manufacturing costs while keeping the sound warm and analogue. The OB-8 arrived in 1983, adding MIDI, expanded modulation, and bi-timbral operation.

Then the Yamaha DX7 hit the market and changed everything. FM synthesis was cheaper, more stable, and more versatile on paper. Oberheim’s response wasn’t to go digital — it was to go deeper. The Matrix series was born: first the ambitious Matrix 12 and its sibling the Xpander, then the more accessible Matrix 6 in 1985 and the rackmount Matrix 6R in 1986.

What the Matrix series introduced over the OB line wasn’t a new filter or a new oscillator. It was Matrix Modulation — a fully software-defined virtual patching system that gave musicians patch-cable flexibility without the cables. That was new for an affordable polysynth, and it’s still the reason people seek these units out today.

Matrix 6 vs Matrix 6R — What’s the Difference?

The Matrix 6R is the Matrix 6 without the 61-key keyboard, packaged into a 3U rackmount chassis.

The voice architecture is identical — same CEM3396 chips, same filter, same modulation engine, same sound. For producers and studio engineers who already had a MIDI controller or keyboard in their rack, the 6R made complete sense. You got the full Oberheim sound in a compact format, at a slightly lower price point (around USD $1,000 at launch, versus $1,295 for the keyboard version).

There is one subtle but interesting difference between the 6R and the later Matrix 1000 — the budget preset-only module that followed in 1987. In the 6R, each of the six voice oscillators is paired with its own individual crystal. The tiny variations between those crystals mean the oscillators drift very slightly relative to each other over time, creating a natural, organic chorusing in the sound. The Matrix 1000 “fixed” this with a single shared crystal — and many users consider that a step backwards. That gentle drift is part of what makes the 6R sound alive.

The Technology Inside — CEM3396 and Matrix Modulation

The heart of the Matrix 6R is the CEM3396 — a remarkable integrated circuit from Curtis Electromusic Specialties that packs an enormous amount of analogue circuitry into a single chip.

Each of the six voices gets its own CEM3396. Inside that chip: two DCOs, a 24dB/octave resonant low-pass filter capable of self-oscillation, and two VCAs. Six chips, six voices, all working in parallel. It’s an elegant and efficient design that kept manufacturing costs down without sacrificing the analogue signal path.

The Waveforms — Saw, Pulse and Triangle (No Sine, by Design)

Each voice runs two DCOs, and the waveform palette is deliberately classic:

• DCO 1 offers sawtooth and pulse (with pulse-width modulation)

• DCO 2 offers sawtooth, pulse (with PWM), and triangle — the triangle is exclusive to the second oscillator

You won’t find a sine wave, and that’s not an oversight. Subtractive synthesis works by filtering harmonic content away from a complex source. A sine wave is harmonically pure — it’s just the fundamental frequency, with nothing above it. There’s nothing for the filter to work with. The Matrix 6R’s waveforms are chosen precisely because they’re harmonically rich:

• The sawtooth carries every harmonic — fundamental, odd and even — making it the brightest and fattest starting point, ideal for brass, strings, and leads

• The triangle (DCO 2 only) is the softest of the three — odd harmonics only, decaying fast — sitting closer to a sine in character without being one. It softens the overall voice when blended with DCO 1

• The pulse wave carries odd harmonics, and with PWM driven by an LFO, it produces that classic thickening, detuned pad movement that defined a lot of 1980s production

Run any combination of these through the CEM3396’s 24dB low-pass filter and the famous Oberheim warmth emerges. The filter does the heavy lifting — but it needs harmonic raw material to shape. That’s the logic of the whole design.

Matrix Modulation — Where the Real Power Lives

The raw waveforms are simple. What makes the Matrix 6R so deep is what happens downstream in the modulation architecture.

The Matrix Modulation system gives you up to 10 active modulation routings per patch, drawing from a pool of 20 sources and 32 destinations. You can route any source to virtually any parameter: LFO to pulse width, filter envelope to oscillator pitch, velocity to filter cutoff, aftertouch to LFO depth — or combinations that would require a wall of patch cables on a modular system. All of it is programmable in software, recalled instantly with a patch change.

This is where the Matrix 6R earns its name. Those simple saw and pulse waves stop sounding simple very quickly once the modulation matrix gets involved.

What the Interface Is Actually Like

One thing to know upfront: there are no knobs. The Matrix 6R uses membrane buttons and a single data slider to navigate 99 voice parameters. It was designed for studio use — set your patch, play — not for live tweaking.

The front panel also hides one of the most common new-owner confusions: the Matrix 6R has two audio outputs, but in normal single-patch mode, only the left output carries sound. The right output only activates in split/bi-timbral mode, where the synth is divided into two independent zones. This trips up a lot of new owners who assume the right channel is broken. It almost certainly isn’t — check your mode settings first.

For deep programming, a MIDI editor (software like Ctrlr, or a hardware controller like the Stereoping) is near-essential. The front panel alone is workable but slow.

Who Used the Matrix 6R? A Studio Pedigree Worth Knowing

The Matrix 6/6R didn’t make the cover of many magazines, but it appeared on an impressive list of records.

Enya used the Matrix 6R specifically on Watermark (1988) — the album that produced “Orinoco Flow” and introduced her to audiences worldwide. It sat alongside a Roland D-50, Juno-60, and Yamaha TX802 in a studio setup that became one of the most distinctive sounds of the late 1980s.

Philip Glass used the Matrix series for his minimalist compositions. Tangerine Dream relied on it for their evolving, textural work. In electronic music, Orbital, Future Sound of London, The Shamen, and Apollo 440 all used it. In deep house, Larry Heard — one of the originators of the Chicago sound — had it in his setup. More recently, Tame Impala, Lorn, and Com Truise have all worked with the Matrix 6.

OMD, Sparks, and composer Mel Wesson — whose film and TV scoring work spans decades — are also confirmed users.

The common thread: the Matrix 6R was a trusted studio rack workhorse. Not the frontline showpiece synth, but the one doing serious harmonic and textural work in the background of productions that hold up decades later.

In Perth, this kind of instrument increasingly turns up in home studios, collector setups, and live rigs — where its age means it usually needs servicing and maintaining for continued performance and reliability. Its not uncommon for owners to of vintage pro audio equipment to over look the maintenance of 30+ year old equipment - avoid expensive repairs, by having your equipment serviced, calibrated and maintained, by a technical workshop who who has a grounding and understanding of how they work, and what is required to ensure long lasting performance.

Frequently Asked Questions About the Oberheim Matrix 6R

What is the difference between the Oberheim Matrix 6 and Matrix 6R?

The Matrix 6R is the rackmount version of the Matrix 6 — the same six-voice analogue engine, the same CEM3396 chips, and the same Matrix Modulation system, but without the 61-key keyboard. It occupies 3U of rack space and is otherwise sonically identical to the keyboard version.

Why does only one output on my Matrix 6R produce sound?

This is normal behaviour. In standard single-patch mode, the Matrix 6R outputs through the left channel only. The right output only carries audio when the unit is operating in split or bi-timbral mode, with voices allocated across two zones. If your right output is silent in normal use, your unit is working correctly.

Is the Oberheim Matrix 6R worth repairing?

Yes, in most cases. Professionally serviced units sell for significantly more than unserviced examples, the parts and documentation are available, and the Matrix 6R has a well-established repair community. The instrument produces sounds that remain in demand — from lush analogue pads to complex modulated textures — and age-related faults are generally fixable.

Can you get an Oberheim Matrix 6R repaired in Perth?

Yes. AST Repair Perth provides synthesizer repair in Perth for vintage and modern keyboards and synths. We work on instruments of all eras — from assessment of the overall health, and what areas need maintaining due to age, to diagnosis and repair of faults. Get in touch to discuss your unit and book it in.

Get Your Matrix 6R Repaired or Serviced in Perth

If your Matrix 6R has come back from storage, arrived from an interstate purchase, or simply hasn’t been looked at in years — it’s worth having it properly assessed before you commit it to regular use.

At AST Repair Perth, we specialise in vintage synthesizer repair in Perth — covering keyboards, synths, and pro audio equipment of all eras.

Vintage synthesizer repair and keyboard repair in Perth is a specialist discipline — it’s not the same as general electronics work, and experience with the specific quirks of these instruments matters. Perth has limited options for this kind of work, and we’ve built our reputation on doing it properly, from baseline industry experience and training.

Book in your synthesizer repair with AST Repair Perth

Call us to discuss your instrument and book it in. We’re open by appointment only, there is no provision for walk in inquiries.

AST Repair Perth — synthesizer repair, keyboard repair, amplifier, turntable and pro audio repair. Perth, Western Australia.