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. 🙂
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.
Ampeg SB-12 bass amplifier
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.
After analyzing the Yamaha SHS-500 Sonogenic from every possible angle (even the service manual!), I finally got one. On-line retailers are currently flooded with post-Christmas returns and bargains can be had. And so it was.
First, I must compliment Sweetwater for their prompt service and excellent packing. The SHS-500 was double-boxed. (The inner box was Yamaha’s original packing carton.) The unit is in excellent condition, matching Sweetwater’s assessment of its condition. Even though the inner carton has a big “DEMO” sticker on it, the Sonogenic is “like new.” Money saved and well-spent.
Since the Sonogenic was a demo, the initial settings are probably not factory. Thus, your out-of-the-box experience may be a little different than mine. I loaded the battery compartment with six AA batteries and turned it on.
Yamaha SHS-500 Sonogenic in fire-engine red
The internal speaker is not going to impress anyone. Sound quality is at roughly the same level as Reface and I never warmed to that. I’ll be playing the Sonogenic through either headphones, my trusty, portable JBL Charge 2 or a powered monitor. Sonogenic has a master EQ and it’s important to set it appropriately. My unit was set to “Line Out” and the sound through the speaker was weak. Changing to the “Speaker” EQ setting was much better. Be sure to change back to “Line Out” when connecting to an external powered monitor. (Or “Boost,” or “Mild”.)
The SHS-500 is quite solid in the hands — much better build quality than the new PSS series or the SHS-300. Key feel is comparable to Reface. After playing the Sonogenic, the PSS keys have a cheaper feel. Yes, you get what you pay for. The SHS-500 is like a Reface keytar.
Natch, the first thing was quick tour of the sounds. Every panel voice has a DSP effect. (See the table below for default assignments.) Sound quality is on-par with good PSR E-series voices and in a few cases, S-series. The SHS-500 is not a Genos. 🙂 However, the SHS-500 is better than PSS by far.
SHS-500 Bank Bank Voice MSB LSB PC# Default effect ----------------- ---- ---- --- -------------- Saw Lead 1 104 20 91 LPF Saw Lead 2 0 104 82 Flanger Quack Lead 0 112 85 DSP Chrs Bright Decay 104 21 85 Phaser Square Lead 0 112 81 Phaser Under Heim 104 51 88 DSP Chrs Analogon 104 52 82 Flanger Synth Brass 0 113 64 DSP Chrs Electric Piano 104 28 5 Phaser DX Electric Piano 0 112 6 DSP Chrs Electric Guitar 104 3 31 Dist.2 Jazz Guitar 104 0 27 DSP Chrs Acoustic Guitar 0 117 26 LPF Electric Bass 104 6 34 LPF Slap Bass 0 112 37 DSP Chrs Synth Bass 0 112 39 Phaser DX Bass 0 118 40 LPF Piano 0 112 2 DSP Chrs Piano & Strings 104 39 1 DSP Chrs Piano & Pad 104 40 1 DSP Chrs Air Choir 0 112 55 LPF Strings 0 116 49 DSP Chrs Brass 0 117 63 DSP Chrs Trumpet 0 115 57 HPF Flute 0 115 74 LPF Alto Sax 104 2 66 LPF Tenor Sax 104 3 67 LPF Harmonica 0 112 23 Tremolo House Kit 127 0 65 LPF Power Kit 127 0 88 LPF
The House Kit has the same program selection numbers as the House Kit in the PSR-E463 and PSR-EW410. These instruments and the SHS-500 are the only ones with this “House Kit.” Go figure.
My favorite voices are the Electric Piano, Jazz Guitar, Electric Bass, Synth Bass, Piano & Pad, Strings, Flute, Tenor Sax and Harmonica. Electric Piano with the Tremolo DSP effect is nice. Can’t wait to try these out with my backing tracks. Here’s a few more snap opinions.
I’ve never been that excited by the PSR synth voices although Quack Lead, Under Heim and Analogon can be fun. Drop Quack Lead down an octave or two for an alternative synth bass.
The electric guitar is OK and the DSP distortion effect is welcome versus a static sampled overdriven guitar. However, the DSP effect is not up to the PSR S-series, Genos or MODX, that’s for sure. It’s an early Yamaha algorithm.
The main piano is bright — think “house.” The piano in the layered voices is warmer.
The tenor sax needs to be played stylistically. The low end gets into baritone territory — a plus.
The harmonica is decent enough to go a little Jon Batiste or Stevie with the thing.
A few of the voices (e.g., flute, tenor sax) have vibrato sampled in. If you’re a PSR-type person, you’ll recognize these as “Sweet!”
The LPF is a bit of a let-down. One can hear changes due to cut-off, but a certain dynamic aspect is missing.
The DSP effects sound a little over-done. It’s easy enough to strip the effect off by dialing it out with the Effect Control knob. One might get tired of doing this after every voice change, which is why I want to experiment with MIDI Designer as a graphical front end for the Sonogenic.
In addition to the default DSP effect, the Sonogenic sets the octave which is appropriate (in some sound designer’s view) for the instrument. Change the voice and you change the octave, too. Depending upon the scenario, this could be a drag. There isn’t a way to go directly to a voice; you need to spin the Select knob and step through the voices — another motivation for a MIDI Designer front-end.
Jack positions all seem well thought out. The USB and MIDI DIN connector are hidden behind a rubbery cover. The MIDI DIN connector is the same as the Reface connector and takes the same breakout adapter to produce 5-pin IN and OUT.
The audio Line Out is mono. (Yes, mono, according to the Service Manual.) The headphone output is stereo. If you need stereo, give the headphone output a try. Dunno if the waveforms or effects are stereo, but the stereo signals are sent to the headphone jack. (The DAC is an AK4430ET, BTW.)
The SHS-500 includes a PA-130 power adapter. I have a PA-150 plugged in at all times and it works just fine with the SHS. The PA-150 supplies the same voltage and has a higher amp rating. All good.
Overall, the Sonogenic SHS-500 is worth the (reduced) price. Will I take it to rehearsals? Heck, yeah! It’s a shame that Yamaha left at least one organ patch out of the voice set. There is enough here for those weeks when organ is not in the church gig spotlight. Almost wish the SHS-500 and Reface YC were combined into the same ax…
There’s been an extended discussion in the YamahaSynth.com Montage Forum about the ability to add Virtual Analog (VA) synthesis to the current Montage and MODX platforms. It’s been a good discussion and it encouraged me to jot down a few musings about the hardware support for AWM2 and FM-X.
In case you don’t visit YamahaSynth.com, I reposted my musings here and added a diagram or two.
Before saying anything, I have to emphasize “Speculatively speaking.” With as much invested in AWM2/FM-X and their implementation in silicon, Yamaha have not published about the internal design. This whole discussion — including my own comments — would be on much sounder footing (no pun intended) if the micro-architecture were published. Yamaha are tight-lipped so “Hah!” to us all. 😀
BTW, we’re lucky that we can speculate at all since Korg, Nord, etc. have largely buttoned up their service manuals.
I’m skeptical
I’m skeptical about adding VA through an update given the current platform because of limitations in the current synthesis pipeline.
Yamaha regard their expertise in large scale integration as a strategically important asset. (Please see their annual financial reports.) The SWP70 is a major investment in the future. It’s a generational step and a design with a long expected life time. A long life is needed in order to recoup Yamaha’s investment. Thus, we haven’t seen all of its potential capabilities as yet.
At some point, the current hardware platforms (Montage and MODX) will limit the features which can be delivered solely through software. That will necessitate a new hardware model in each product line. Speculatively speaking, I’m not sure if the SWP70 is capable of CS-like VA synthesis. The Reface CS (and DX) employ a Yamaha SSP2 (SH-2 CPU core) for synthesis. The mere presence of an SSP2 in the Montage is not significant for VA because it clearly supports UR-like digital audio in the existing design.
Of course, business decisions will take precedence eventually. We all love the free updates and improvements in our instruments. (I certainly do!) Like cellphones, tablets and other high-end electronics which enjoy periodic updates, we will need to buy a new upgraded platform in order to fuel the future. Nobody rides for free forever.
My mental model
I suspect that we nerds (and I mean that as a compliment!) have different architectural models in mind as to the SWP70 internals. One model is the “standard DSP” model — a pipelined single instruction, single data (SISD) CPU. Naturally, there may be enhancements for vector processing instructions and so forth.
An example of such a generic model is the Yamaha SSP2, which consists of an SH-2 DSP core and several effect DSP processors. The SSP2 is the heart of Reface CS with an internal clock of 135.4752MHz (a multiple of 44,100Hz, BTW). Another example would be the DSP56362 in early Nord/Korg modeling keyboards. The Reface CS manages 8 voices of polyphony (using the word “voice” loosely) with the effects handled by the SSP2 effect DSP processors. (The effect DSP processors are mini, small core, reprogrammable processors.)
The architectural model which I think is used in the SWP70 is a SIMD architecture more akin to a GPU. The Montage/MODX DSP RAM and wave work RAM memory clock is 95.9616.MHz, also a multiple of 44,100Hz. The SWP70 pumps out a finished sample every 2,176 memory clock ticks. The internal clock is probably a small multiple (maybe two) of the memory clock. Everything needs to run in a modest power envelope without a heat sink, etc., so it’s not possible to run at GHz rates.
After writing this, I realized that the AWM2/FM-X synthesis core may not have an instruction stream at all. It might be a block of 1 to N dedicated pipelines where each pipeline is, roughly speaking, an AWM voice element.
I image a block of tone generation (TG) cores dedicated to AWM2/FM-X. Part of that “dedication” is a pipeline specifically tailored and tuned to AWM2/FM-X. (I believe this design IP (the basic core design) is re-used in other AWM2 products.) Yamaha are in the AWM2/FM-X business so it makes sense to design hardware specific to these tasks. It’s no simple feat to produce 128 channels of tone generation with low latency and no burps and hiccups.
I don’t know how much flexibility is built into the so-called “oscillator” part of a TG core pipeline. Could Yamaha write a new SIMD program for VA using the existing TG core design? I don’t know and hence, my doubt.
That said, since Yamaha haven’t published a darned thing and my job easier (Hah!), I could be totally wrong. Yamaha are smart engineers, especially at the hardware level.
The choices made for Reface may or may not be revealing. Reface YC/CP use the SWX08 for AWM2/SCM synthesis. The SWX08 — in my imagination — use a similar AWM2 TG core assist. Reface DX/CS use SSP2 and its SH-2 core. Was something missing in the SWX08 TG core which was available later in the advanced SWP70 cores? Did SWP70 become VA capable as well?
Example: Yamaha YMW820
The closest I’ve ever gotten to understanding Yamaha’s approach to AWM2 is by studying the datasheet and MIDI spec for the YMW820 (NSX-1). Admittedly, the YMW820 is a low-end device implementing a large subset of the XG voice architecture with only chorus, reverb and a single variation effect.
YMW820 (NSX-1) block diagram
The YMW820 has a control CPU (dual issue, 32-bit RISC), mixer hardware, DSP for effects, and a “wavetable synthesis core” (Yamaha’s exact terminology). Both the synthesis core and DSP are controlled by the CPU.
The wavetable synthesis core supports 64 channels (polyphony). The YMW820 has a 2MByte wavetable ROM which presumably contains the General MIDI waveforms. It also has a 3 MByte wave RAM which can be loaded with eVocaloid waveforms or Real Acoustic Sound (Articulation Element Modeling).
The 64 channel synthesis core is drawn as a distinct hardware subsystem from the effects DSP. Each channel is what we consider an element: pitch generator, oscillator, digitally controlled filter (DCF), envelope generator (EG), LFO. I suspect that other AWM2-based products have similar wavetable synthesis cores, including the SWP70. [Click image below to enlarge.]
YMW820 (NSX-1) synthesis core and effect DSPs
Of course, the SWP70 synthesis core is the ultimate in the entire AWM2 family. It also has many effect DSPs for system and insertion effects.
Bottom line, Yamaha exploit massive parallelism for AWM2 synthesis where each channel is a wavetable synthesis element. A true DSP processor like the SSP2 is better suited for VA synthesis which is why the SSP2 is deployed in the Reface CS, not an AWM2-oriented SWX processor. (The SWX has an embedded wavetable synthesis core, too.) I believe that Yamaha will need to add another SSP2 (or some such) to the Montage in order to implement VA. There’s a reason why it’s called a “Standard Wave Processor” — it is hardware specifically designed for AMW2, FM-X, AEM, and SCM synthesis. It isn’t a general purpose programmable DSP. Maybe VA can be warped to the existing pipeline(s), maybe not.
BTW, the new VCM MINI FILTER and MINI BOOSTER are DSP effects. The effect DSPs are programmable — the AWM2 channel filters likely are not.
Big DSP vs. little effect DSPs
I tend to think of the internals as a tone generation front end followed by a flock of small DSP units in the mixer/effects back-end. This seems to be the canonical Yamaha pipeline. In Montage/MODX, some of the small DSPs are routed as insert effects and some as system/master effects. (The effect routing in Genos, BTW, is different and probably different in the high-end digital pianos.) I suspect that the data flow is predominantly (solely?) front to back.
I don’t really know if the small effect DSPs are general purpose or not.They are probably small simple cores because an SWP has at least 15 and real estate is limited. (Lower capacity parts like the SWXs and SWLs have far fewer small DSP cores.) A small core may not have much throughput and the front-to-back dataflow might prevent feeding data from the DSP cores back to the filters, etc. in the front-end.
There is also the issue of getting note and controller data to the effect DSPs in the back end. Note and controller data are delivered on the E-bus directly from the key, knob, slider, etc. scanning processor(s) to the tone generation core. Does all E-bus data get back to the small DSP cores? Certain some data gets through as knobs, sliders, etc. can tweak effect parameters in real-time.
Overall, even as a consumer, I would be happier with a dedicated SSP2 for VA. The VA SSP2 would inject its digital output stream into the existing mixer/DSP infrastructure. [The SSP2 vocal harmony processing does something like this in Tyros5.] The VA SSP2 gets its own DSP RAM and NOR flash for program, and the processing is totally out of the way of FM-X and AWM2. It would be possible to implement different VA algorithms without making compromises. Yamaha could periodically offer new engines as updates/upgrades.
If you’re an ARM aficionado, you might be thinking “big.LITTLE”. It’s a similar concept. Engineers need to make best use of limited real estate. Yamaha need lots of little DSPs for insertion effects. The SSP2 itself is organized as a big SH-2 DSP core and several little effect DSPs (plus a digital mixer). The mix of channel strip and guitar effects is limited.
Down memory lane
The discussion took me down memory lane to the venerable AN-200 and PLG150-AN. Both products use Yamaha’s AN (Analog Physical Modeling) daughter card. I love the old AN-200 and keep one handy. It is a pretty decent approximation of a five voice Prophet 5.
The daughter card contains two Yamaha LSI components:
YSS-236-F: An enormous 160 pin QFP for analog synthesis
YSS-233-F: A merely huge 128 pin QFP for mixing and effects
The 236 is also known as the “VOP3” and the 233 is known as the “MDSP”. The MDSP is deployed in the PLG150-DX daughter card, again in the mixing and effects role. The An1x, by the way, has two of each, implementing ten voice polyphony.
Some sites ascribe synthesis to the Hitachi H8/3002 on the daughter card. This is wrong. The H8/3002 is the microcontroller that issues commands and maintains digital communication with the mothership. The VOP3 does synthesis.
The VOP3 moonlights as the vocal harmony processor in early arranger keyboards like the PSR-9000. The VOP3 is the predecessor to the SSP and SSP2. The SSP and SSP2 subsume the mixing and effect DSP roles of the MDSP. Such is the march of large scale integration (LSI) fabrication technology.
Given this history, I’m not surprised that Yamaha chose the SSP2 for Reface CS.
I like surprises
Watch, Yamaha will come up with something completely different. 😀 Maybe an SWP71. There were different spins of the SWP50 family, so why not? 🙂 From the marketing point of view, demand for VA is sufficiently high that they may require everyone to buy a new platform anyway. Perceived value means “mo’ money.”
I’m currently holed up in a hotel outside Everett, WA — 3,000 miles west of our old home. Fortunately, our former house sold quickly and we found a new house in just two weeks of intensive search. We’re still waiting to move to the new house and nearly everything is in storage. Probably a month to go before we will get our stuff and to try to get back to normal.
Our grandson is a hyperactive package of joy. It’s a real kick to be here as he learns so much every day. I started reading “Child Language” by Mathew Saxton, an easy read that I can recommend already. He is well into the “vocabulary spurt.” [Most grandparents don’t see their grandchildren as science experiments.]
“Nearly everything is in storage” means that I did bring along a few items for amusement…
So, OK, what is my desert island synthesizer? Ta-da, it’s the Yamaha MODX. It’s my regular gig instrument and I need to keep my chops up in order to audition for a new church group. Before moving, I built 30+ Performances for pop, rock, jazz and funk, expecting to play a few favorites over backing tracks. I can’t live on church music alone!
I shipped the MODX ahead, not wanting to check it with the airline. For that, I packed the Yamaha Reface YC, my rehearsal machine. The YC fits into the enormous suitcase which also holds my clothes. The clothes and gig bag held the YC rather securely and like the MODX, it got here just fine.
I guess that makes two desert island synths. 🙂
Blog posts will remain rather sparse in the near term, I’m afraid. We need to plan for delivery, complete the deal and get the job done. Yamaha just announced three new portable toys: the PSS-E30, PSS-F30 and PSS-A50. Might be good for amusement?
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.
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!
