Yamaha CK88: Yes, I played one

Posted on May 15, 2023 by pj

I always hesitate calling one of these posts a “review,” especially when the actual trial is serendipitous. Had to stop at Whole Foods and decided to drop into Guitar Center just to see what they had on the floor. Lo and behold, a Yamaha CK88!

It was a nice surprise, but I didn’t have the usual lead sheets that I use when testing. So, it came down to random plunking and noodling.

First, I’m going to lay out most of the good news. For instruments in the $1,000USD (61 key) to $1,500 (88 key) range, the CK sounds damned good. The user interface (UI) is intuitively direct and had only one “What the?” moment.

I played and listened to the CK88 through its built-in speakers. The built-in speakers are a bit unusual for Yamaha stage/synth instruments, but not so for its digital pianos and arranger keyboards. The CK88 has sufficient volume for practice and maybe enough for an acoustic-level rehearsal. Thus, I put the CK’s speakers in the “courtesy speaker” category. Being 2x6W, 12cm by 6cm ovals, they are not unlike the courtesy speakers on the Case CT-S1000V (or S500) — just OK. They are not boxy, something I don’t tolerate under any circumstance.

I started out with acoustic piano because, err, it was the 88 GHS keybed in front of me. I found both the main acoustic piano (CFX) and Rhodes (78Rd) to be satisfying. I would prefer to play the Rhodes on the GHS rather than the CFX. I don’t know if it’s because I’ve been playing the Petrof grand occasionally, but the GHS just did provide the same enjoyment. On again, off again, I’ve been thinking about a digital piano for home and the GHS action ain’t it. The GHS seems to bottom out, for lack of a better description. Forget organ swipes on the 88, too, unless your hands are made of leather.

Practical tips department. The piano sounded muffled when I first started playing. The last customer pulled all of the EQ sliders to -12dB, thank you. Reset, always reset.

Next, I jumped into the acoustic, non-keyboard sounds. The CKs are like a “greatest AWM2 hits” from MODX/Montage. The brass voices are pleasant enough and would be useable in a band setting. The voices range from Jerry Bruckheimer to mellow, more musical horns. The only voice that threw me is “Sweet Trumpet” which is suitable only for mariachi covers.

The saxes are typical AWM2 saxes — emergency use only. I’m spoiled by Super Articulation sax. The oboe is a bit too bright for my taste. The clarinet and bassoon are not bad. The flutes are cool. Strings are varied and useable. I can’t be too harsh because the CK beats the up-scale, expensive YC61 for orchestral voices and, notably, pipe organ.

Venturing into synth brass, pads and leads, we’re back to greatest hits territory. You’ll probably find something close enough for rock’n’roll among the lot. There’s no point in getting too OCD on a machine with limited editing and few real-time parameters to tweeze. CK has what I would call “Yamaha Quick Edit” which apply offsets to the actual voice parameters. Want deep editing? Look to MODX/Montage.

Now to the organs. The CK cops the pipe organs from Genos™ — excellent choice. Maybe it was the EQ or sumptin’, but the VOX (V) didn’t pierce my ears and the Farfisa (F) didn’t have that Sam The Sham rasp. Oddly, I give Reface YC the edge as far as combo organs are concerned.

As to the main event — Hammond B-3 — the CK is much more than Reface YC in a tuxedo. The drawbars are nice and smooth, offering the right amount of resistance. The drawbar throw is a little short (a la Reface) when compared to Yamaha’s clonewheels. The CK drawbars slide and don’t have the Reface drawbar detents.

To my ears, the CK and Reface YC basic drawbar sound is the same — pretty clean and artifact (e.g., leakage) free. The rotary speaker sim and effects chain are what make the difference. Obviously, the CK is richer in that regard. You get so much more for the money with CK (full-size keyboard, better effects chain, acoustic piano, EP, decent acoustic/electronic instruments, A/D input, audio playback, etc.), why would anyone bother with Reface anymore, unless they absolutely must have the portability?

I like the CK vibrato/chorus implementation and UI more than Reface, too. All of the organ controls are more Hammond-like even if they are a bit small.

I developed a preference for the CK Rotary 2 sim over Rotary 1. I wish I knew which rotary speaker algorithms Yamaha chose for CK as I would like to recreate the CK sound on MODX. The CK horn/rotor turn a bit too fast and, unfortunately, the speeds cannot be changed.

The only “What the?” moment had to do with the DRIVE buttons and what they apply to the internal signal. If I were giving the CK a serious spin, I would study the effects chain and controls before sitting down in the driver’s seat.

So, there it is. The CKs offer great value for the money, no doubt about it. I personally would go with the 61-key model (CK61) since I play mainly organ/synth. The GHS isn’t for me and suggests that I should “go large” if I ever follow through and buy a digital piano for home. Having MODX, I don’t feel like I’m missing out although I need to make better use of MODX sliders for real-time drawbar control.

Other reviews and comments about digital pianos:

Review: Roland Micro Cube GX for keyboard

Posted on September 4, 2020 by pj

You’ll find plenty of rave on-line reviews for the Roland Micro Cube GX — the go-to battery-powered practice amp for guitar.You won’t find a review covering the Micro Cube GX as a portable keyboard practice amp — until now.

Here’s a quick rundown (from the Roland site):

Compact guitar amp with a 5 inch (12cm) custom-designed speaker
3 Watt rated output power
Eight COSM amp tones, including the ultra-heavy EXTREME amp
Eight DSP effects, including HEAVY OCTAVE and dedicated DELAY/REVERB with spring emulation
MEMORY function for saving favorite amp and effects settings
i-CUBE LINK jack provides audio interfacing with Apple’s iPhone, iPad, and iPod touch
Free CUBE JAM app for iOS
Chromatic tuner built in
Runs on battery power (6xAA) or supplied AC adapter; carrying strap included
6 pounds (2.7kg)

I haven’t tried the Roland CUBE JAM application yet, so I’ll be concentrating on the amplifier itself. The included 3.5mm cable is the usual 4 conductor affair although it’s rather short. Roland also includes the AC adapter.

I’ve been searching for a good portable, battery-powered keyboard rig for quite some time. On the keyboard side, the line-up includes Yamaha Reface YC, Yamaha SHS-500 Sonogenic and Korg MicroKorg XL+. Although the YC and Sonogenic have built-in speakers, their sound quality is decidedly inadequate and poor quality. The MicroKorg XL+ doesn’t have built-in speakers. All three keyboards have mini-keys and are battery-powered.

To this point, I’ve been using a JBL Charge 2 Bluetooth speaker.The JBL has solid bass, but its output volume is easily overwhelmed during living room jams. It’s been a good side-kick, but I found myself wanting.

Roland Micro Cube GX and Yamaha SHS-500 Sonogenic

So, the latest addition is the Roland Micro Cube GX. Without comments from fellow keyboard players, buying the GX was a risk. Guitar amps are notoriously voiced for electric (or acoustic) guitar tone. Like the GX, you’ll typically find amp and cabinet simulators that help a guitar player chase their “tone.” The GX, however, includes a “MIC” amp type in addition to the usual 3.5mm stereo AUX input. Fortunately, my intuition was correct and the “MIC” setting does not add too much coloration.

Of course, there is some compromise in sound quality. The amp puts out 3W max through a 5 inch speaker (no coaxial or separate tweeter). Needless to say, you don’t hear much high frequency “air.” The GX cabinet does have a forward-facing bass port, producing acceptable bass even with B-3 organ. No, you will not go full Keith Emerson or Jon Lord with this set-up. 🙂 I first tested the GX with Yamaha MODX and found the B-3 to be acceptable.

Volume-wise, yes, you can get loud — too loud for your bedroom or ear-health. Bass heavy sounds can get buzzy. For clean acoustic instruments, I recommend the “MIC” amp setting. The reverb is pleasant enough and adds depth to my normally dry live patches. The delay is a nice alternative to the reverb ranging from reverb-like echo to explicit (non-tempo synch’ed) repeats.

I find the Sonogenic/Micro Cube GX combination to be the most fun. The SHS-500 has DSP effects, but they are rather tentative, as if Yamaha is afraid to offend anyone. That’s where the GX makes a good companion for the Sonogenic. Feel free to dial in the Jazz Chorus amp with the jazz guitar patch or a British stack with electric guitar. Or, try any of the modulation effects on the Sonogenic’s electric piano. Working with the GX is a far more intuitive and rewarding experience than the built-in Sonogenic DSP effects. You can cover Steely Dan EP to Clapton with this rig!

I have to call out the Heavy Octave and Spring reverb effects. You’ll find them at the right-most position of the modulation (EFX) and delay/reverb knobs, respectively. You can think of them as “going up to eleven.” The spring reverb is decent and you can throw the Heavy Octave onto just about anything to thicken up the sound.

Overall build quality is good. The Micro Cube GX feels solid. A metal grill protects the speaker. The knobs have a pleasant resistance and don’t feel cheap. The only not-so-robust feature is the battery compartment and its cover. As long as you avoid heavy abuse, you should be OK.

For the money, $160USD, it’s a decent sounding, inexpensive package. Given the physical cabinet, output power and speaker size, one should adjust expectations. However, if you’re a keyboardist and need a light, portable, battery-powered amp, the Roland Micro Cube GX is worth a try.

Back In The Day

Posted on February 25, 2020 by pj

A Keyboard Corner member asked what people did for keyboard amplification before PA. Man, that question really kicked off some memories.

Back in the day (1966), I played a Farfisa Mini Compact Deluxe through an Ampeg SB-12 bass amp. It was all I could afford. Mom and Dad lent me the money and I mopped floors at the local donut shop to pay them back. The shop had a wooden floor that was impregnated with grease. I still can’t face donuts to this day. 🙂

While packing for the house move, I found an original Farfisa brochure from the 60s era.

The Portaflex was pretty cool with its flip top. The amp was mounted to a covered board which acted as a base for the head and, when flipped over, it became the cabinet cover. The clamps held the base/cover board in place and did double-duty as the speaker connections to the cabinet.

The SB-12 had a 12″ Jensen speaker powered by a 25 Watt tube amp. It weighed 47 pounds — the first of a long line of heavy schleps.

Being the 1960s, of course, that wasn’t enough. Since I started playing with electronics and DIY at an early age, I tried my hand at an extension cabinet. I somehow came into a 15″ JBL speaker with a small tear in the cone. Impedance be damned, I just hooked it up in parallel with the Jensen via the clamps. Before building a cabinet, I would carry the JBL around in a suitcase which doubled as a “cabinet.” (!) The tear in the cone lent more bad-itude. [Why fizzy digital distortion doesn’t cut the mustard.]

In the R&B band, the guitars and vocals went through matching Ampeg guitar amps (probably Gemini’s). Only the top local bands could really afford PA for vocals (typically Fenders). Nobody put instruments through PA. The bass player had a Guild ThunderBass amp with that funky head. The bass player was quite good and laid down decent grooves. Can’t remember too much about the psychedelic band…

My failed experiments at extension and PA speaker cabs wound up as end-of-gig props. When we saw The Who trash their gear, we thought “What the heck!” I’d pull one of the legs off of the Farf and ram it through one of the prop cabinets.

My dream rig would have been a Vox Continental through a Fender Twin Reverb or Fender Super Reverb. I copped the Fender tilt-back idea and built a tilt-back stand for the SB-12. That got the speaker pointing up toward my ears.

Both the Connie and the Fenders were out of my financial reach. It took me three years to pay back my folks. By then, I had to sell the whole rig in order to make the college tuition nut. Given the rigors of college math, physics and computer science, it was the end of playing for quite a while. I can’t believe how much a vintage SB-12 fetches on the market these days!

The Farfisa Mini Compact Deluxe left me with no delusions about 1960s electronics. I tried tuning the F# oscillator and bunged the tuning coil. That was an unnecessary repair expense. That’s why I’m happy as a clam to play the Yamaha Reface YC today. The YC does a good job nailing the Farfisa and Vox.

A few other memories stick out like playing music fairs on stage/demo gear with the psychedelic band. One stage was incredibly small and I had a horn driver literally right in my ear. We played Doors, Steppenwolf, Vanilla Fudge, etc. at phenomenally loud volume, attracting every biker within earshot. They loved us. I think I still suffer hearing loss from those jobs.

Before signing off, I want to plug “Classic Keys: Keyboard Sounds That Launched Rock Music” by Alan Lenhoff and David Robertson. I received a copy yesterday and gave it a quick browse. The photography is excellent and the example gear is in tip-top shape. The book is long on history — less on playing technique and artistis, so some may be disappointed. Discount and used copies are coming onto the market and you may be able to save a few bucks if you can’t pony up the full $60USD. Recommended.

Yamaha Reface YC on the go

Posted on September 28, 2017 by pj

Trumpet?

No, Yamaha Reface YC!

I finally had enough time ‘shedding with the Yamaha Reface YC to have the confidence to take the YC to rehearsal with me. [Click images to enlarge.]

I need to write a long review, but here’s a few quick thoughts.

The Reface YC makes a good, lightweight rehearsal rig. Usually, I need strings, horns and a few woodwinds in addition to organ to cover our repertoire of liturgical music. However, I dialed in 608400000 for most of the non-organ church tunes and covered things reasonably well. Slow rotary or clean were enough. For the gospel tunes, I threw in a little 1′ and 2′ to brighten the sound. Nothin’ major.

One advantage of the mini-keys is the ability to kick the SPEED switch while holding a bass note. It took some ‘shedding to get used to the narrow width of the mini-keys. Even though I had enough range for most tunes, three octaves ain’t enough. I really wish the YC had four octaves. Think Harry Connick Jr. rocking a Reface CP on Fallon: “There’s not a lot of room. But, I’m havin’ fun.”

The YC drew favorable comments from both the MD and our pianist. (Thanks John, Margie and Steve — bless you.) The small, light rig got a few envious looks as folks carried out their guitars. (Envy is a deadly sin.)

That’s a JBL Charge 2 portable speaker in the bag. I shut off the YC’s internal speakers and play it through the Charge 2. Its passive radiators do a pretty decent job of bass reproduction. I’ve been kicking simple bass lines with my left hand and the JBL Charge 2 is just enough for our (mostly) acoustic rehearsals. Surprisingly, no break-up with full organ chords either.

The whole deal is battery powered. If I had enough shed time before our annual outdoor service, I might have played the Reface YC instead of schlepping the MOX6.

More thoughts after the Genos™ craziness settles down. In the meantime, if you want to know what’s inside of a Reface YC and CP, check out my blog post about Reface YC and CP internal design. Shucks, find out what’s inside of a Reface DX and CS, too.

Inside Reface YC and CP

Posted on September 6, 2017 by pj

Like the Yamaha Reface DX and CS, the Reface YC and CP are brother and sister.

The Reface DX and CS use the Yamaha proprietary SSP2 integrated circuit (IC) for sound synthesis. A few minor hardware differences and the front panel aside, the main difference between DX and CS is software. The YC and CP designs are analogous although the tone generation method and hardware are different.

Sample playback and memory bandwidth

Many people focus on the computational aspects of tone generation and wave memory size, not realizing that memory bandwidth is just as important, if not critical, for sample playback. Waveform samples need to flow from wave memory to the tone generation apparatus whether tone generation is performed on a CPU or a proprietary tone generator IC like Yamaha’s previous generation SWP51L and the now current SWP70.

Sustainable polyphony depends on memory bandwidth. If available bandwidth is low, then polyphony is low. Raise bandwidth and you can raise polyphony, too, provided adequate computational resources (e.g., tone generation channels or CPU cycles) are available.

Several factors affect memory bandwidth.

The most obvious factor is the raw speed of the memory technology. Fast memory means high bandwidth.
Next is the kind of memory communication channel: shared or dedicated. If waveform samples and CPU code reside in the same physical memory component, then bandwidth must be shared between the CPU and the tone generator, lowering tone generation bandwidth and polyphony. Bandwidth is higher when the CPU and tone generator each have their own memory channel and component. Concurrency wins!
Bandwidth sometimes depends on the read access mode or pattern of the memory component. Concerns here include random vs. sequential access, word vs. paged, etc. This subject is a little too deep for this short note.
Finally, bandwidth depends on the bus organization: serial or parallel. Parallel buses move each bit in a word on a dedicated wire. Serial buses move moves sequentially on one or a few wires. Parallel is fast; serial is slower.

Of course, there are further factors and choices like the necessity for read-write access, non-volatile data storage, and so forth.

The instrument designer faces the challenge of supplying sufficient memory bandwidth, tone generation channels and polyphony at a particular price point. Polyphony and price point are market-driven requirements. Memory bandwidth and tone generation resources are technological. The designer must work within both kinds of requirements and constraints.

Internet discussions tend to dwell on memory speed and component cost alone, neglecting system-level design costs like board complexity, wiring and testing. A simple rule of thumb is, “More IC pins and wires means higher system cost.” Serial communication decreases pins and wires, but it compromises bandwidth. Shared buses also decrease the number of pins and wires, again, penalizing bandwidth. One expects to find serial communication and/or shared buses in low price products, while higher price products can reap the benefits of dedicated, parallel communication.

I must note that commodity bulk flash memory uses a serialized memory bus, but it does so by sequential paged reads and data caching. The SWP70 is compatible with commodity flash and uses a dedicated RAM cache to achieve high sample bandwidth. This scheme is cheaper than the SWP51L with its parallel dedicated wave bus.

Processor primer

Yamaha have several different processors at their disposal for main CPU, tone generation and effect processing (DSP) chores:

SWLxx: SWL processors, like the SWL01U, have integrated CPU, tone generation and DSP resources in the same IC. CPU instructions, data and waveform samples travel on the same shared bus. SWL processors are typically designed into value (i.e., entry-level) products. SWLs are also low power and ready for battery operation.
SWXxx: SWX processors have integrated CPU, tone generation and DSP resources on the same IC. CPU, tone generation and DSP each have a dedicated memory channel. SWX processors often appear in mid-range products.
SWPxx: SWP processors have a large number of tone generation and DSP elements, and no main CPU. The SWPs must be controlled by a separate main CPU.
SSP2: The SSP2 has an integrated CPU and DSP elements. The SSP2 is not used in AWM2 applications, appearing instead in computationally intensive synthesis engines (Reface CS and DX), vocal harmony processors, and digital mixers.

The SWL, SWX and SSP2 series processors are true “system on a chip (SOC)” designs with analog-to-digital conversion, bit-serial data (UART), USB, SPI and other interfaces. The CPU core is usually a variant of the Renesas SH architecture family. Architectural commonality facilitates code reuse across products. Yamaha have damned good engineers.

There are two different types of SWX processor: SWX02/SWX03 and the SWX08. The 02/03 variants appear in lower priced mid-range products. Examples include the MOX6 (SWX02), PSR-S650 (SWX02) and Piaggero NP-32 (SWX03). The SWX08 appear in the upper mid-range: PSR-S770, Reface YC and Reface CP.

Sometimes an SWX processor is used as the main computer controlling an SWP. For example, the SWX02 is the main computer in the MOX6/MOX8, controlling an SWP51L. Similarly, the SWX08 is the main computer in the PSR-S750, controlling an SWP51L. In both cases, the SWP51L handles all tone generation duties. Yamaha increases fabrication volume when it uses an SWX in this way.

At this point, semiconductor folks might ask if Yamaha fuses off TG or DSP deficient SWX08s and assigns them to main computer duty only. This strategy cuts waste as it deploys SWX08s with perfectly good CPUs and faulty, fused off TG and/or DSP circuitry. This is standard practice throughout the industry, so please don’t freak out.

Reface YC and Reface CP

The Yamaha Reface YC and the CP share the same digital logic board design. The main large-scale integrated (LSI) components are:

IC CPU (SWX08)   Yamaha R8A02042BG         SH-2A CPU core
Work SDRAM       Winbond W9812G6JH-6       8M x 16-bit word, 166MHz
DSP SDRAM        Winbond W9864G6KH-6       4M x 16-bit word, 166MHz
Program/Wave YC  Cypress S29GL256S90TFI020 16M x 16-bit word NOR flash
DAC              Asaki Kasei AK4396VF-E2   192kHz, 24-bit stereo DAC
Panel scan CPU   MB9AF141LAPMC1            ARM Cortex-M3 (32-bit core)
ADC              TI PCM1803ADBR            96kHz, 24-bit stereo ADC

The same ARM Cortex-M3 (32-bit core) processor is used in the Reface CS and Reface DX for panel and keyboard scan. Potentiometers and so forth are sensed by the ARM’s 12-bit analog to digital converter (ADC). Key scanning is performed through GPIO lines. (I don’t see any way to expand beyond 37 keys, unfortunately.)

The SWX08 is the main control computer. It handles the 5-pin MIDI interface and the USB interface. The ARM communicates with the SWX08 over a serial link (UART). Integral tone generation and DSP elements synthesize digital audio and effects.

The AK4396VF-E2 digital to analog converter (DAC) is also used in the PSR-S770 and PSR-S970 arranger workstations (among other Yamaha products.) The Montage employs the AK4393VM-E2 DAC by way of comparison. Digital audio for the internal speakers is converted by the Yamaha YDA176 digital amplifier.

The PCM1803ADBR ADC sends serial digital audio (24-bit I2S format) to the SWX08 where it is mixed with the synthesized tones.

DSP processors on the SWX08 have their own dedicated 16-bit data channel to DSP SDRAM (i.e., working memory for effects). The wave memory (NOR flash ROM) has a dedicated 16-bit parallel channel for samples. Wave memory is labelled “E:64MB / O:32MB”. Presumably, this means that the CP needs 64MBytes for electric piano waveforms and the YC needs 32MBytes for organ waveforms. I wonder if Yamaha substitute a larger, pin-compatible flash ROM in the Reface CP? I don’t have the Reface CP service manual in order to resolve this conjecture.

Summary

So, there you have it. Yamaha wisely designed the CS and DX as a pair and designed the CP and YC as a pair. I’m sure that shared board designs reduced their manufacturing costs.

Reface sales seem to be coming to an end. Nearly all Reface models have sold through in North America. Yamaha has either decided to cancel the Reface after the first production run or they will launch Reface 2.0, perhaps with full-size keyboards. They could easily design the guts of the YC and/or CP into the Piaggero NP-12 chassis. That would make for one killer, battery-powered stage machine!

Inside Reface DX and Reface CS

Posted on August 1, 2016 by pj

With so much to do and learn, it’s been a long while since I’ve taken a peek below the hood of an electronic musical instrument.

Yamaha caught the world by surprise with its Reface series of portable keyboards. So far, there are four models in the series: Reface YC (organ), Reface CP (electric piano), Reface CS (analog modeling synthesizer), and Reface DX (4-op FM synthesizer).

Before I get to the DX and CS, here’s a few thoughts about the YC and CP. According to Yamaha specifications, the Reface YC tone generation engine is “AWM (Organ Flutes)”. This suggests to me that the YC uses a standard AWM tone generation integrated circuit (IC) like the SWP70. Hammond-like “Organ Flutes” have been part of the mid- and upper-tier arranger workstations like Tyros for a very long time. Thus, I suspect that the YC implementation is an updated implementation of the arranger technology.

The Reface CP tone generation engine is specified as “SCM + AWM2”. SCM or “Spectral Component Modeling” is the modeling technique first employed in the flagship CP-1 stage piano. SCM and AWM2 are also used in the CP-4 and CP-40 models. The CP-1 uses three tried-and-true SWP51L tone generation ICs: master, slave and effects. The master and slave generate the base piano tones and the two ICs share the same WAVE ROM. Total WAVE ROM size is 1024Mbits or 128MBytes (organized as 16-bit words) which is a ridiculously small amount of memory for a top quality piano. Such is the power of SCM!

The CP-1’s samples are stored in two Lapis Semiconductor MR26V51252R devices (32M by 16-bit words each). The processor is a Yamaha SWX02 (SH-2A CPU core operating at 135.4752MHz). There’s not much to the CP-1 user interface, so a relatively light-weight, low-cost processor is enough for the job. The SWP51Ls handle all of the heavy computation.

Thus, the Reface YC and Reface CP are relatively uninteresting from a technologist’s point of view. The YC and CP use proven technology from other Yamaha products. That leaves the Reface CS and Reface DX.

Although the CS and DX implement two different tone generation techniques — analog physical modeling vs. frequency modulation (FM) — they are fraternal twins at the hardware level. They share much of the same base hardware design with a few variations to handle their unique user interface requirements.

The CS and DX both use a Fujitsu MB9AF141LAPMC1 processor to handle key and panel scanning. Here’s a quick summary of its characteristics:

    CPU                 Cortex-M3
    CPU Frequency       40MHz

    On-chip flash memory   Main area   64KBytes
    On-chip flash memory   Work area   32KBytes
    On-chip SRAM           SRAM0        8KBytes
    On-chip SRAM           SRAM1        8KBytes

    Peripheral interfaces:
        DMAC            8 channel
        Serial I/F      8 channel
        Base timer      8 channel
        Dual timer      1
        Realtime clock  1
        Watch counter   1
        12-bit A/D      12 channel

This processor is a good choice for embedded control applications where low power and low cost are important. To my knowledge, this is the first product line using an ARM embedded microcontroller.

The Reface CS and Reface DX both use the proprietary Yamaha SSP2 (uPD800500F1-011-KN9-A) for tone generation. The SSP2 is Yamaha’s designated hitter for DSP tasks and is incorporated into many products. The SSP2 has an SH-2A CPU core operating at an internal clock speed of 135.4752MHz. The SSP2 has its own ADC, GPIO, UART, USB and serial audio interfaces. The SSP2 UART handles 5-pin MIDI communications. The SSP2 USB interface handles external USB communications.

The SSP2 has two memory interfaces:

DSP RAM: Connecting to 8MBytes of DSP SDRAM.
CPU bus: Connecting to 8MBytes of program ROM and 16MBytes of SDRAM.

Memory sizes and devices are the same in both products.

The AUX IN and audio out hardware design is also the same across the two products:

PCM1803ADBR ADC: AUX IN analog-to-digital converstion
AK4396: Digital-to-analog conversion for OUTPUT L/R and PHONES OUT
YDA176 D-Amp: DAC and amplification for internal speakers

This shouldn’t be any surprise. All of the Reface series products ahare the same external jack, power and key switch boards.

Digital audio is transfered serially between the SSP2, the ADC, the DAC and the digital amplifier. The SSP2 generates the master clock (MCLK) and bit clock (BCLK) to synchronize data transfers. MCLK and BCLK are derived from the SSP2 clock, in case you’re wondering about those odd-looking CPU clock frequencies. MCLK is 256*fs and BCLK is 64*fs, where fs is the sampling frequency, 44.1KHz. MCLK operates the AK4396’s digital interpolation filter and delta signal modulator. Data format is I2S and is probably 24-bit as it is in workstation products.

Aside from the other front panel controls, the Reface DX has two major additions: Capacitive sensors for the front panel touch strips and the LCD panel display. The printed circuit board positions for the LCD interface are not populated (i.e., no mount) in the Reface CS as it has no LCD display.

There you have it — two more examples of solid and conservative Yamaha hardware design.

Now, you may find the SSP2 to be incredibly boring. It is, however, a good choice for a low-cost, compact product. The Reface CS and DX need a metal shield over the SSP2, perhaps to control RF emissions, perhaps to radiate heat, or maybe both purposes together. Low power is a vital concern throughout the Reface series due to battery power concerns.

I’m a little hesitant to draw any inferences about future products. The Yamaha Montage supports 128 note, 8 operator FM polyphony. The Reface DX provides a relatively meager 8 note, 4 operator FM polyphony. Thus, there must be considerable hardware resources at work in the Montage. Well-worth the price, one hopes! And speaking of hopes, many people would like an analog modeling extension to the Montage. That would depend, of course, on the availability of spare computational horsepower.

Reface YC and DX teardowns

Posted on December 16, 2015 by pj

Markus Fuller posted two Yamaha Reface teardowns (YC and DX) to Youtube:

In case you’re not familiar with the term “teardown,” think of a teardown as a casual tour through the insides of a keyboard.

Both Reface keyboards have an ARM FM3 handing the user interface panel. The switch to ARM is major news. In the past, Yamaha used Renesas H8 or SH4 microcontrollers for interface applications. They apparently have decided to ride the embedded cost curve and that curve leads to ARM, the current leader in low-power, high function embedded microcontrollers.

I wonder if Yamaha will adopt ARM in their entry-level keyboards? This would be a smart move. Yamaha currently use their own SWL01 processor in battery-powered entry-level products. Now that Yamaha have sold off their integrated circuit fabrication plant, they are free to move to off-the-shelf parts when it makes sense. ARM is the choice for battery-powered embedded devices. Further, the ARM-resident, XG-capable sound engine in Yamaha Mobile Music Sequencer has a better spec than the entry-level ‘boards. (MMS reference)

Both Reface keyboards have a large metal plate over one or more integrated circuits. This is the honey pot. 🙂 I understand Markus’s reluctance to remove the heat sink. This is, however, where the digital signal processing (DSP) is being performed. Apparently, Yamaha had a minor power dissipation problem and resolved it using a simple heat sink (no fan). Heat is an important product design problem; x86 fans take note. (More on x86 and instrument design.)

Here are some notes about the integrated circuits in the Reface YC:

Winbond W9864G6KH-6 SDRAM  (64Mbits)
    4Mx16 bits = 1M words x 4 banks x 16 bits (8MBytes equivalent)
    166MHz/CL3
    Parallel interface
    Burst-oriented accesses

Winbond W9812G6JH-6 SDRAM (128Mbits)
    8Mx16 bits = 2M words x 4 banks x 16 bits (16MBytes equivalent)
    Parallel interface
    166MHz/CL3
    Burst-oriented accesses

AKM AK4396VF (Asahi Kasei Microdevices Corporation)
    Digital-to-analog converter (DAC)
    24-bit 192KHz 128x oversampling
    I2S data interface
    Integrated digital filter

Texas Instruments / Burr Brown PCM1803A
    Stereo analog-to-digital converter
    24-bit, 64x or 128x oversampling
    I2S data interface

The circuits are all pretty typical for a Yamaha design. Not enough information here to indicate whether the SWP70 tone generator is in use or not. Yamaha have used W9864G6KH as DSP SDRAM in past designs.

I’m glad that Markus posts his teardowns. I like it when he zooms in and identifies the integrated circuits. One very small quibble with the YC teardown — I believe the “A” stands for “Acetone.”

While you’re here, catch my Reface CP snap review.

Sand, software and sound

Electronics and computing for the fun of it

Tag Archives: Reface YC