Comparisons of synthesizer models



Index:

* Synths organized by Class

A table listing hardware attributes

A table listing comparing features (under construction)

A philosophical note on why I believe Analog synths have made a comeback against digital in general.

2006 POLL from the synth DIY group about which synths are best in various categories.

Discussion of Terms used when we talk about synthesizer features. (eg. polyphony, vco)

A discussion of how keyboards interface with ciruitry in synthesizers.

How memory is commonly implemented in analog machines.



Notes on synth architecture and abbreviations used in describing features-

      You will see terms like DCO, VCO, VCF etc. strewn about these pages. The 'V' usually stands for "voltage". THe 'C' usually stands for "controlled". 'O' is usually "oscillator" and 'F' is "filter", except in the case of "LFO" which means "low frequency oscillator"; a circuit often used to stimulate a vibrato or tremelo effect. Or occasionally "LF" or "HF" for low and high frequency. Also occasionally you may see LPF or HPF for low and high pass filter. 'D' usually denotes "digital". This...is where things get confusing. :-)
     Well, in one way they do. Because when manufacturers say "digitally controlled" they might mean several things.



I propose this. That we reference

VCO = Any synth that uses entirely analog oscillators.

VDO = Voltage controlled digital oscillator like the DS-1. **

DCO = The common digitally controlled saw core scheme like most early 80's polysynths.

VDCO= The siel DK600 etc. Analog ocillator source that is of course controllable by analog signals like bender directly/smoothly and 'suffer's from some drift which can add that dimension of warmth to 2 oscillator + units.

DGO = Anything that generates waveforms digitally. Which can include PWM, Fixed Pulse (anyone use this?) or NCO /wavetable synths. NCO = Specifically anything that generates signal from numeric lookup tables and/or mathematical calucations that form numberic values in interaction with user inputs etc. I don't use this terminology for purely digital synths because nothing is really oscillating except the mathematic representations :-). However synthesizers like the Kawai K3 generated signals from numeric values fed through a DAC to produce analog simulated oscillations at least. :-)

I'm open to suggestions. I also thought maybe VCDO on the DS-1 type scheme. And let me know if I left out anything of significance. Contact Sound on Sound has a good article on these machines though and they deserve a special mention as they are sort of the first hybrids which combine additive synthesis (through the ability to select or mix footages from the divide down network) with often fairly elaborate subtractive.
     "Subtractive" synths start with a harmonic laden waveform like a square or sawtooth or pulse or noise usually. A filter is then used to selectively alter the harmonic content according to time (using an envelope) after the key is hit, velocity, lfo or other mod sources....or just the basic setting of the 'cutoff frequency' control! This architecture was basically the standard overall until digital synths appeared, save a few strange ones.

     Additive synthesis involves taking less harmonically laden sounds in general, and adding them together often with distinct envelopes and other modulations. The RMI Harmonic Synthesizer is the first of this type I know. Kurzweil and Kawai followed using digital technology about a decade later! But these renditions of the additive architecture were focused more around creating a sound by adding the harmonics you want at the time you want it. The Kawai K5 for instance had the ability in each patch to stack two 63 harmonic sets alongside or in linear order up to 126...and to assign each one to one of the 4 busses available for each half. Each buss had a 6 segment envelope and various modulations. Then the 'signal' went on to a digital filter on each half and a final "DDA" as they called it. A 7 segment envelope. Anyway that's only a small part of what the machine would do.
     Many machines had the ability to perform frequency modulation (Octave Cat for instance or modulars) long before the Yamaha synths appeared which were called "FM synthesizers". This is because their ability to do so was still more of a 'side show' to their overall design. The Cat is primarily still a subtractive synth architecture as it lacks dynamic control of the FM abilities it has save the player turning knobs. Machines may include other sound altering elements like this or ring modulation. But when the digital technologies came of age, programmers were now able to design machines that would emulate properties of nature that would be vastly complex and expensive to build with analog circuits.
     Yamaha's efforts created a totally new sound that sold like mad. Other manufacturers tried to follow with their own ideas. Casio with 'phase distortion'. Kawai and Kurzweil with their harmonic synths and so on. With software, there are no bounds basically. This may be a good thing in some ways...it may be bad in others. I find that the human spirit benefits most from contemplating real natural 'struggles'. In software, there is no such thing. Only the modelling thereof at best. Hearing actual work being done by electrons in a vast array of analog circuits though...there is nothing quite like it. -Bob





Below see Synths organized by architecture and features!

***Note that there are 'gray areas'. For instance the Siel boards use SSM2031 analog HF oscillators to drive a divide down network chips. Whereas most other DCO synths actually use digital clock based processing to originate the waveforms which may be pulsed to an op amp as pre ROland JX8P/JX10/MKS70, or 8253 Programmable timers maybe be used as per Kawai SX, Roland JX3P etc.*** Also read FAQ on how memory is commonly implemented in analog machines.

Monophonic single oscillator simple subtractive-
ARP Axxe, JEN SX-1000, JEN SX-2000, KORG 770, Moog Micromoog, Roland SH-3a, Roland SH-09, Siel Mono, Teisco/Kawai Synthesizer 100-F, Yamaha CS-5, Yamaha CS-10

Monophonic single oscillator subtractive with significant other features-
Octave Kitten, Roland SH-1, Roland SH-101

Monophonic single oscillator subtractive with digital control from presets-
ARP Pro-Soloist(DGX), ARP Explorer, Conn Electric Band, Elka Soloist 505, Korg M500 micro preset, Moog MinitMoog, Moog Satellite, Roland SH-1000, Roland S-2000, Yamaha SY-1, Yamaha SY-2

Monophonic dual oscillator simple subtractive-
Moog Prodigy, Moog Multimoog, Moog Rogue, Moog Taurus II, Roland SH-2, Yamaha CS-15

Monophonic dual oscillator subtractive with significant other features-
ARP Solus, Crumar DS series, Crumar Spirit, KORG MiniKorg700s, Moog MG-1, Moog Liberation, Oberheim 2-voice, Roland SH-5, SCI Pro One, Yamaha CS-15D, Korg Sigma (last two have presets and various controls), Yamaha CS-30 (around 80 knobs, 2VCF, 3ADSR)

Duophonic subtractive-
ARP Odyssey, Korg MaxiKorg 800DV, Moog Sonic 6, Octave Cat, Roland SH-7, Yamaha CS-40M

Monophonic dual oscillator with memory-
Moog Source, Oberheim OB-1, OSC Oscar, Roland ProMars MRS-2, Teisco/Kawai Synthesizer 110-F, Yamaha CS-20M

Monophonic three or four oscillator subtractive-
Moog Minimoog(3 vco wide range), Korg Mono/Poly (4 vco narrow range, but poly mode though only one SSM2044 VCF) Murom Aelita (3VCO driving divide down network, 1 LFO)

5-voice or less polyphonic subtractive-
Oberheim 4-Voice, Oberheim OBX(a)(4voice) Roland JP-4, SCI Prophet 5, Yamaha CS-50

6-voice polyphonic subtractive, one VCO/voice-
Akai AX-60, Akai AX-73, Korg PolySix, SCI Six-Trak, SCI MAX, SCI Multi-Trak

6-voice polyphonic subtractive, two VCO/voice-
Fender Chroma Polaris, Oberheim OBX(a)(6voice),Roland JP-6,SCI Prophet 600

6-voice polyphonic subtractive, three VCO/voice-
Moog Memorymoog

8-voice polyphonic subtractive, one VCO/voice-
SCI Split 8/Pro-8, Yamaha CS-60

8-voice or more polyphonic subtractive, two VCO/voice-
Elka Synthex, Oberheim OBX(a)(8voice), Oberheim OB-8, Oberheim Matrix 12, Rhodes Chroma(or 16voice 1 osc/voice),Roland JP-8, Roland MKS-80, SCI Prophet T8, Yamaha CS-80

6-voice polyphonic subtractive, one DCO/voice-
Roland Juno-6, Roland Juno-60, Roland Juno-106

6-voice polyphonic subtractive, two DCO/voice-
Crumar Bit One, Crumar Bit 01, Crumar Bit 99, Cheetah MS-6, Elka EK-22, Roland JX-3P/MKS-30, Roland JX-8P, Korg Poly 61(M), Oberheim Matrix 6, Siel DK-600/Opera 6,

8-voice polyphonic subtractive, one DCO/voice-
Kawai SX-210

8-voice polyphonic subtractive, two DCO/voice-
Akai AX-80, Kawai SX-240

Polyphonic DCO paraphonic VCF.-
Korg Poly800(II), Siel DK-70, Siel DK-80 (two DK-70's using only 6voice per chip instead of 8)

Bi-Timbral polyphonic subtractive analog with various DCO designs-
Roland JX-10, Roland MKS-70

Digital divider oscillators, Full Paraphonic analog-
Arp Solina String Ensemble, ARP Quartet, ARP Omni (1/2), Crumar Orchestrator, Crumar Performer, Korg Delta, Moog Opus 3, Roland RS-09, SCI Prelude, Siel Orchestrator (1/2), Yamaha SK series(combo synths; some containing 7 vc polysynth or monosynths)

Digital divider oscillators from VCO's, Full Polyphonic analog-
Korg Lambda, Korg PSS series, Moog Polymoog synth, Moog Polymoog keyboard

Digital divider oscillators, paraphonic analog with mono section-
Crumar DS-2,Crumar Composer, SCI Fugue, Yamaha SK30, SK50D

Divide down oscillator, polysynth hardware /combo synths-
Crumar Stratus (organ and 6 voice para-poly scheme), Crumar Trilogy (adds string section to Stratus)

Digital synths with analog filters (hybrids)-
Ensoniq ESQ-1, Ensoniq SQ-1, Ensoniq SQ-80, Kawai K3, Korg DW-6000, Korg DW-8000

Digital physical modelling; FM-
Yamaha DX series, Yamaha SY-22, Yamaha SY-55, Yamaha SY-77, Yamaha SY-99, Yamaha YS-200, Yamaha DSR-2000, Yamaha DS-55

Digital physical modelling; Additive-
Kawai K5, Kawai K5000, Kurzweil K150

Digital physical modelling; Phase distortion and vintage misc.-
Casio CZ series, Korg DS-8, Korg 01 series, Peavey DPM series, Roland JD-800

Digital physical modelling; Acoustic-
Korg Prophecy, Yamaha VL-1

Digital physical modelling; Analog-
Access Virus series, Clavia Nord Series, E-mu Vintage Keys, E-MuMorpheus, Ensoniq Halo, Korg MicroKorg, Korg MS-2000, Oberheim OB-12, Roland JP-8000, Roland J* series, Yamaha CS-1x, CS-2x, Yamaha CS-6x

Digital physical modelling;Established instruments (Hammond, Wurlitzer and Rhodes EP, Clavinet Clavinet)-
Clavia Nord Electro, E-mu B-3, Hammond XB-2, Korg CX-3, Voce V series

Digital sampling synth, with Analog filters-
E-mu Emulator series, Ensoniq Mirage, Korg DSS-1, Korg DSM-1, SCI Prophet 2000, SCI Prophet 3000

Digital sampling synth-
Casio SK-1, Ensoniq ASR series, Ensoniq EPS(16(+)), Fairlight CMI, Kurzweil K250, Roland S-series

Wavetable synth-
Ensoniq SD-1, Ensoniq Fizmo, Ensoniq VFX(SD), Korg Wavestation series, PPG Wave, SCI Prophet VS, Waldorf Microwave

Miscellaneous ROM sample based synths of interest-
Alesis QS series, E-mu Proteus series, Ensoniq TS series, Kawai k1 series, Kawai K4, Kawai XD-5, Korg M1, Kurzweil K1000 series, Roland/Rhodes MK-60/80, Roland D series, Roland JD series, Yamaha SY-85

Advanced workstation synths-
Ensoniq MR series, Korg Karma, Korg M3, Korg Triton series, Korg Oasys, Kurzweil K2xxx series, Roland Fantom, Yamaha Motif series
















Table showing architectural class, and essential component type if analog


Model Architecture(s) Oscillator(s) Envelope(s) Filter(s> Amplifiers Effect(s)
Akai AX80 subtractive Digital Digital CEM3372 Discrete NA
Akai AX60/73 subtractive CEM3394 Digital CEM3394 LM13600/CEM3394 MN3009
ARP Odyssey, Axxe, Pro-soloist subtractive Discrete Discrete Discrete Discrete n/a
ARP Omni/ Omni 2 Subtractive/String LC VCO, MK50240 TOS and Dividers Discrete Discrete Discrete MN3002
Crumar Multiman and early Performer subtractive/String TOS/Divider Discrete Discrete Discrete TCA350Y/Z
Crumar Performer subtractive/String TOS/Divider Discrete SSM2040 Discrete TCA350Z
Crumar DS-1/2 subtractive/String(2) DCO Discrete Discrete Discrete n/a
Crumar Spirit subtractive uA726 Discrete Discrete Discrete n/a
Crumar Stratus, Trilogy subtractive/String TOS/Dividers CEM3310 CEM3320 CEM3330, SSM2020 TCA350Z
Crumar Composer subtractive/String TOS/Dividers CEM3310 CEM3320 CEM3330 TDA1022
Crumar Bit One, 99, 01 subtractive/String DCO Digital CEM3328 LM13700 n/a
Kawai 100F/110F subtractive uA726 discrete discrete discrete n/a
Kawai 100P subtractive uA726 discrete discrete discrete MN3009
Kawai SX-210/SX-240 subtractive digital digital SSM2044 BA6110 OTA's MN3009 BBD
Kawai K3 subtractive digital digital SSM2044 BA6110 OTA's MN3009+MN3011 BBD
Korg 700/700S/800DV subtractive discrete discrete TS201012 module discrete n/a
Korg MS/PS series subtractive discrete discrete Korg 35 discrete n/a
Korg Sigma subtractive discrete discrete Korg 35 discrete n/a
Korg Delta subtractive/String discrete VCO/M50241TOS discrete LM13700 discrete 2-MN3004
Korg Lamda subtractive/String discrete VCO/M50241TOS discrete discrete discrete MN3010
Korg Trident subtractive uA726 SSM2056 SSM2044 discrete 3-MN3004/2-NE571
Korg Mono/Poly subtractive SSM2033 SSM2056 SSM2044 discrete MN3004
Korg Polysix subtractive discrete SSM2056 SSM2044 discrete MN3004
Korg Poly-61 subtractive digital SSM2056 LM13700 discrete NA
Korg Poly800 subtractive DCO Digital 1-NJM2069 NJM2069 MN3209/NE570
Korg Poly800 II subtractive DCO Digital 1-NJM2069 NJM2069 Digital
Korg DW6000/DW8000 DSS-1/DSM-1 subtractive Digital Digital NJM2069 NJM2069 Digital
Moog Minimoog subtractive uA726 Discrete Discrete Discrete NA
Moog Polymoog subtractive uA726/MK50240 Discrete Discrete CA3080 NA
Moog Memorymoog subtractive CEM3340 CEM3310 CEM3320 CEM3360 NA
Oberheim OB1 subtractive discrete discrete 4xCA3080 CA3080
Oberheim OBX subtractive discrete CEM3310 2xCA3080 CA3080
Oberheim OBXa/OB8 subtractive CEM3340 CEM3310 CEM3320 CEM3360 R5106 or 5107
Oberheim Matrix 6 subtractive digital digital CEM3396 CEM3396 R5106 or 5107 delay
Oberheim Matrix 12/xpander subtractive cem3374 digital CEM3372 CEM3372/
Roland SH-1000/2000 subtractive Discrete Discrete Discrete Discrete NA
Roland SH-3a subtractive Discrete Discrete Discrete CA3080 NA
Roland SH-5/7 subtractive uA726 Discrete Discrete CA3080 LM1496 r.m.
Roland SH-1/2? subtractive uA726 Discrete CA3080 CA3080 NA
Roland JP4 (Jupiter-4) subtractive Discrete pulsed capacitors IR3109 BA662 MN3004/MN3101 BBD
Roland SH-101 subtractive CEM3340 Discrete IR3109 BA662 NA
Roland JP8 (Jupiter-8) subtractive discrete IR3R01 IR3109 BA662 n/a
Roland Juno-6/60 subtractive digital IR3R01 IR3109 BA662 MN3009/MN3101 BBD
Roland JP6/MKS80(early) subtractive CEM3340 Digital IR3109 CEM3360, BA662 n/a
Roland JX3P subtractive digital digital IR3109 Transistor MN3009/MN3101 BBD
Roland MKS-30 subtractive digital digital IR3109 (in module) BA662 (in module) MN3009/MN3101 BBD
Roland Juno-106 subtractive digital digital IR3109 (in module) BA662 (in module) MN3009/MN3101 BBD
Roland MKS80 (later) subtractive IR3R03 digital IR3R05 CEM3360, BA662 MN3009/MN3101 BBD
Roland JX8P/JX10/MKS70 subtractive digital digital IR3R05 M5241 MN3009/MN3101 BBD
Roland Alpha Juno 1/2 subtractive digital digital IR3R05 M5241 MN3009
Siel DK600 (Opera 6) subtractive SSM2031 VCO Custom Divider IC's Disc. WSC SSM2056 SSM2044 SSM2024 n/a
Siel DK70 DK80 subtractive SSM2031 VCO Custom Divider/WSC IC's Digital SSM2045 SSM2045 n/a
Yamaha SY-1/2 subtractive Discrete Discrete Disc. Module CA3080 n/a
Yamaha CS series subtractive IG00153 VCO
IG00158 WSC
IG00159 IG00156 IG00151 n/a
Yamaha SK series subtractive Custom IC's IG00159 IG00156 IG00151 and IG02600 MN3009









Table showing feature comparison of Analog Synthesizers and some digitals


(see KEY below)
Synth Model Architecture Keys/Vel/AT? Editing i/f Controllers Interface(s) Poly MT Memory osc/note #LFO/range/types/rout's Filter(s) Amplifier(s) Envelope(s) effects
Akai AX80 subtr. Poly 61u/Yes/No dial/(2) Pitch/Mod Wh. MIDI 8 1 32 pre
64 usr
2 DCO 4/Mid/4/3 CEM3372 Analog 3-Digital xmod
Akai AX60 subtr. Poly 61u/No/No Sliders Pitch/Mod Wh. MIDI 6 1 64 usr 1 CEM3394 2/Mid/4/4 CEM3394 CEM3394 2-Digital Chorus
Akai AX73
+VX90
subtr. Poly 73u/Yes/No cursor/(1) Pitch/Mod Wh. MIDI 6 1 100 usr 1 CEM3394 1D/Mid/4/3 CEM3394 CEM3394 2-Digital Chorus
ARP 2600 subtr. Solo 49u/No/No Sliders PW/ Patch 1 1 none 3 VCO 4/Hi/4/5 Analog Analog 2-Analog Port., Reverb
ARP Odyssey subtr. solo 37u/No/No Sliders PW or PPC pad CV/gate 2 1 none 2 VCO 1/Mid/3/3 Analog Analog 2-Analog Port.
ARP Pro-Soloist subtr. solo 37u/No/M Sliders AT none 1 1 30 pre 1 VCO 1/Mid/2?/3 Analog Analog Analog Port.
ARP Solina SE subtr./String 49u/No/No Sliders None CV/gate 16p1 1 6 pre 1 dd 1/Mid/1/2 Analog Analog Analog bbd phaser
ARP Explorer subtr. Solo 37u/No/No Sliders bender none 1 1 8waves/noise 1 VCO 1d/Mid/1/2 Analog Analog Analog Port.
ARP Omni1/2 subtr./String 49u/No/No Sliders None CV/gate 49p1 1 none 1 dd 1/Mid/1/2 Analog Analog Analog 3-bbd phaser
ARP Axxe subtr. Solo 37u/No/No Sliders Exp. Pitch knob CV/gate 1 1 none 1 VCO 1/Mid/3/3 Analog Analog Analog Port.
ARP Quartet See Siel Orchestra
ARP Quadra subtr. Mixed 61u/No/20ct Sliders none CV/gate and ASI 1 1 16 semi 2 VCO + dd 1/Mid/2/2 Analog Analog Analog Phaser,S+H, Port.
ARP Solus subtr. solo 37u/No/No Sliders exp. pitch knob CV/gate/trig 1 1 none 2 VCO 1/Mid/1/3 Analog Analog Analog Port.
Crumar Multiman string/subtr 49u/No/No Sliders pedals none 49p1 1 none 1 dd 1/Mid/1/1 Moog Analog Analog 3-bbd Ens.
Crumar Orchestrator String/subtr 49u/no/no sliders(1) pedals none 49p1 1 none 1 dd 1/Mid/1/1 moog Analog Analog 3-bbd Ens.
Crumar PerformerA/B String/Subtract 49u/No/No Sliders None Gate 49p1 1 none 1 dd 1/mid/1/2 moog/SSM2040 Analog disc./SSM2050 3-bbd Ens.
Crumar DS1 Subtr. solo 49u/no/no Knob/slide Bend lev. gate i/o 1 1 None 2DCO 1/Hi/4/4 Analog Analog Analog Glide
Crumar DS2 Subtr. Solo +ddpoly 49u/no/no knobs/slides pitch lev. gate i/o 49p1/1 1 None 1 dd+2DCO 2D/Hi/5/4 Analog Analog Analog Glide
Crumar Spirit Subtr. Solo 37u/no/no knobs/sliders Bend/2xMod gate/CV 1 1 None 2 vco 2/Hi/8?/5 Analog Analog Analog Ringmod/arp.
Crumar Stratus Subtr.
add dd
49u/no/no knobs +
sliders
Joystick +
TM i/f (Steiner)
none 49p6 +
dd
1 none 2 dd 1/Mid/2/3 CEM3320 CEM3330 CEM3310 none
Crumar Trilogy Subtr. +
add/String
49u/no/no knobs(1) joystick +
TM i/f (Steiner)
none 49p6 +
dd
1 8-(int.
trimmers)
2 dd 1d/Mid/2/3 CEM3320 CEM3330 +
1-SSM2020
CEM3310 3-BBD Ens.
Crumar Composer String/Subt. 49/no/no Knobs/Slides(1) breath, 2-wheel, finger vibrato none 1+49p1 split 14 pres. 3 dd 1/Mid/1/1 CEM3320 CEM3330 CEM3310 3-bbd Ens.+
bbd rotary
Crumar Bit One A/B Subtr. Poly 61u/yes/No buttons (1) Pitch + Mod MIDI + Tape 6 1 63 2 DCO 2DM/Mid/3/4 SSM2044/CEM3328 Analog Digital None
Crumar Bit01/ 99 Subtr. Poly 61u/yes/AT? Buttons (1) Pitch + Mod MIDI + Tape 6 split 75 + 24split 2DCO 2/Mid/3/4 CEM3328 LM13700 Digital None
Elka Soloist 505 Subtr. Solo 49u/no/no Sliders (1) Pedal none 1 1 presets 1 VCO ?/?/?/? analog Analog Analog none
Elka Synthex Subtr. Poly 61u/no/no Knobs/slides joystick + Pedals Seq. + Tape 8 1 40pr. 40user 2 DCO 2/Mid/4/4 CEM3320 Analog digital 4-BBD chorus + Seq.
Elka EK-22 Subtr. Poly 61w/yes/yes data slider(1) bend/mod trig. MIDI 6 2 64pr 32User 2 DCO 1d/?/4/4 ? Analog Analog Digital bbd Chorus
Fender/Rhodes Chroma Subtractive 64w/yes/opt data slide(2) pitch + Mod lever Chroma + Tape 16/8 2 50 1 /2 hyb. 2DM/Mid/16/4 CEM3350 CEM3360 4-hybrid none
Fender Chroma Polaris Subtractive 61w/yes/no sliders PB/MW/PP Chroma, MIDI, Tape 6 8 132 2 CEM3374 1/Mid/2/3 CEM3372 Analog Hybrid seq.
Kawai S100P Subtr. Solo 37u/no/M Sliders BS, VP none 1 1 32pre 1 VCO 1/?/?/? analog Analog 2-preset Analog port./Gliss, reverb, flanger
Kawai SX-400 Subtr. 49u/no/M Knobs + Sliders PB CV/Gate 4 1 8pre, 8usr 1 VCO 2/?/3+1/3 Analog (Moog type) Analog Analog Port. + Ensemble
Kawai SX-210 Subtr. 61u/no/no Knob (2) PB tape 8 1 32 1 DCO 1/1mid/3/3 SSM2044 Analog 2-Digital Ensemble
Kawai SX-240 Subtr. 61u/no/no Knob (2) PB tape, MIDI 8 1 48 +
8 seq
2 DCO 1/mid/3/3 SSM2044 2-Analog digital Chorus
Korg 700 subtractive 37u/no/no Sliders none none 1 1 none 1 VCO 1/Mid/1/1 Korg 35 Analog Analog bbd chorus + Repeat
SCI Prophet 5 Subtr. Poly 61u/no/no Knobs PB/MW tape 5 1 40-120 2-SSM2030 or CEM3340 1/Mid/3/3 SSM2040 or CEM3320 SSM2020 or CA3280 SSM2050 or CEM3310 polymod
SCI Prelude SEE Siel Orch 2
SCI Pro-One Subtr. Solo 37u/no/no Knobs PB/MW CV/gate 1 1 none 2-CEM3340 1/Mid/3/3 CEM3320 Analog Analog Seq/Arp, Porta
SCI Prophet 600 Subtr. Poly 61u/no/no Knobs PB/MW MIDI 6 1 100 2-CEM3340 1/Lo/2/3 CEM3372 CA3280 Digital polymod, Glide, seq/arp
SCI Prophet T8 Subtr. Poly 76h/yes/no Dial/(1) PB/MW MIDI 2x4 2 100 2-CEM3340 1/Lo/3/3 CEM3374 CEM3360 Digital polymod, Glide, seq
SCI Six-Trak Subtr. Poly 49u/no/no Dial/(1) PB/MW MIDI 6 6 100 1-CEM3394 1/Mid/2/3 CEM3394 CEM3394 3-Digital polymod, Port., seq/arp
SCI Multi-trak Subtr. Poly 49u/yes/no Dial/(1) PB/MW MIDI 6 6 100 1-CEM3394 1/Mid/2/3 CEM3394 CEM3394 3-Digital polymod, Port. seq/arp
SCI Split-8 Subtr. Poly 49u/no/no Dial/(1) PB/MW MIDI 8 2 100 1-CEM3394 1/Mid/3/3 CEM3394 CEM3394 2-Digital polymod, Port.
Yamaha SY-1/2 Subtr. Mono 37u/No/M Knob/Slides None None 1 1 none 1 VCO 1/Mid/1/1 Analog Analog Analog none
Yamaha CS50 subtr. Poly 49u/no/M Knobs + Sliders none none 4 1 13 pre 1-IG00153 1/mid/1/3 8-IG00156 IG00151 IG00159 Ring Mod, Port./Gliss
Yamaha CS80 Subtr. 61h/yes/P knobs + Sliders RC/Ex.M none 8 1 28 pre +
4 alt. sliders
2-IG00153 1/mid/5/3 4-IG00156 IG00151 4-IG00159 Ring Mod, Port./Gliss
Yamaha CS60 Subtr. 61u/no/M knobs + Sliders RC CV/Gate 8 1 12 pre +
1 alt. sliders
1-IG00153 1/mid/5/3 2-IG00156 IG00151 2-IG00159 Ring Mod, Port./Gliss
Yamaha CS10 Subtr. 37u/no/no knobs + Sliders PB CV/Gate 1 1 none 1-IG00153 1/Hi/2/3 1-IG00156 IG00151 2-IG00159 Port.
Yamaha CS30 Subtr. 44u/no/no knobs + Sliders PB CV/Gate +ext. trig 1 1 none 2-IG00153 1+ext./Hi/5/3 2-IG00156 IG00151 3-IG00159 Port., Step seq.
Yamaha CS5 Subtr. 37u/no/no knobs + Sliders PB ext. Trig 1 1 none 1-IG00153 1/Hi/3/3 1-IG00156 IG00151 1-IG00159 Port.
Yamaha CS15 Subtr. 37u/no/no knobs + Sliders PB ext. Trig 1 1 none 2-IG00153 1/Hi/3/3 2-IG00156 2-IG00151 2-IG00159 Port.
Yamaha CS15D Subtr. 2 chan. w/pan 37u/no/no knobs + Sliders PB/MW CV/ Trig 1 1 29 pre + manual 2-IG00153 1/Hi/3/3 1-IG00156 IG00151 2-IG00159 Port.
Yamaha CS20M Subtr. 37u/no/no knobs + Sliders PB/MW CV/ Trig 1 1 8 usr* 2-IG00153 1/Hi/5/4 1-IG00156 IG00151 2-IG00159 Port./Gliss
Yamaha CS40M Subtr. duo 44u/no/no knobs + Sliders PB/MW CV/ Trig 2 1 10 usr* 2-IG00153 1/Hi/5/4 1-IG00156 IG00151 2-IG00159 Port./Gliss + Ring Mod.
Yamaha DX7 6-op FM 61u/yes/Yes 1 Data Slider or inc-dec keys/(2) PW/MW/VP/DS/BC MIDI/Tape 16 1 32 patch 6 1/hi/7/? 0 4-Digital 4-Digital Port.
Yamaha DX21 4-op FM 61u/No/No 1 Data Slider or inc-dec keys/(2) PW/MW/VP/DS/BC MIDI/Tape 8/4 2 128 patch / 16 perf. 4 1/hi/4/? 0 6-Digital 6-Digital Port.+ Chorus
Synth Model Architecture Keys/Vel/AT? Editing i/f (1) Controllers Interface(s) Poly MT Memory osc/note #LFO/range/types/rout's Filter(s) Amplifier(s) Envelope(s) effects


KEY TO FEATURE TABLE:


Architecture is a general note about the primary design type. "Additive" would indicate the machine primarily synthesizes a sound by adding components like harmonics. "Subtractive" indicates it starts with an already complex waveform like square or sawtooth and uses dynamic filtration to contour the harmonic content.

Key number followed by 'u' means unweighted. 'w' means weighted. 'h' means hammer action simulation. Velo refers to Velocity sensetivity in a keyboard and AT is 'aftertouch' with M=Mono and P=Poly

Editing interfaces with dial or cursor keys: type 1= parameter picked from num pad type 2= parameter picked from dedicated or semi-dedicated button, type 3= paramter picked from switch matrix type 4= cursor through menus.

Controllers includes anything that is already on the panel dedicated for rapid access to various key parameters for expression during performance. Bender mechanisms (PB), Mod wheel (MW), Ribbon Controller (RC), and Bend Slider (BS, appropriate name if you've ever used one) Pedal input (PP=programmable pedal, VP=Volume pedal, FP=Filter control pedal), breath controller (BC), Damper/Sustain switch (DS), Programmable/multi-function switch (PS), External Modulation (ExM)

Interfaces include things for carrying data to and from the machine including tape, MIDI, Chroma i/f and others

Polyphony may be simply a number which indicates the number of notes that can simultaneously be sounded, or a code of this form. px = Paraphonic with x facilities. eg. many oscillators share 'x' eg/filter circuits in some part of synth. String synths commonly have AR envelopes for each note, but often there is just one synth filter/eg. ALSO 'dd' is 'divide down'. Meaning there is a full poly section spawned from one oscillator using a top octave synth chip and divider chips to create all frequencies with stable relationships to one another.

MT= Multi-timbrality. IE. How many different sounds can the synth play at once. None of the pre-MIDI synths had this feature unless you include things like Oberheim x-Voice synths whose SEM modules could each be programmed to a sound but there was no way of organizing them to sound on a 'channel' basis, but rather like Korg Mono/Poly they just appear in order of the sequence of notes you are playing. So while interesting this isn't called multi-timbral on the table.

Memory uses the abbreivation of 'pre' for preset. The Crumar Trilogy for example has presents that actually can be manipulated by trimmers inside the box. The CS-20M, CS40M, JP-4 and others have 'snapshot' memory. usr* is used to denote this. Once you save you can't recall and edit it. You have to write down what you did basically to have an actual record of it. Whereas Prophet 5 and most after that had memory saves that allowed recall/edit sessions. The CS60 and CS80 provide simply another set of sliders or 4 of them in the case of the cs80 in miniature! Yamaha YC45D actually also uses this 'trick' to have what they called 'memory'.

Osc/note is just the number of oscillators that can be layered together in one key press (min/max. Eg. Kawai SX210 has ability to have 1, 2, 4 or 8 osc. stacks but in normal poly mode just 1 oscillator per note so 1/8 is it's entry) Again 'dd' means divide down where there is typically just one actual source oscillator that drives a top octave synth chip that outputs a high frequency of each of the 12 notes and then go through series of dividers to create the lower octaves. So it 'appears' there is an oscillator for each note but in reality there is only one oscillator from which various generated frequences can be accessed simultaneously. ie. each note may be comprised of several 'footages' or octaves, and in some units there are even harmonics from the fifth for instance that may be layered in as well.

#LFO/range/types/rout's - How many total LFO's on board? ('d' next to number indicates minimally featured delay in some way. Big 'D' means it gradually comes in smooth AND delay time can be set. "m" means you can modulate the LFO with velocity or other aspects other than panel controllers. NExt we ask What is their relative 'range'. Eg. Prophet 600 has a very narrow range without the Teensy upgrade or other mod. So 'lo' is it's entry. 'mid' is common and 'hi' on ones that delve into the audio range above 20hz like JP4 etc. "Types" refers to how many waveforms are available. Often if one LFO is dedicated to pwm it will only have triangle wave available for that lfo. However it may have 4 different waveforms for pitch, Filter and/or VCA. The 'rout' is short for routings. Again how many total things can LFO's be routed to without regard to whether all or just some of the LFO's can be routed to particular things. Eg. Siel DK600 uses LFO 1/2 to modulate the two oscillators while LFO 3 can be routed to either of the osc's PWM and/or Filter. To avoid confusing we will only count TYPES of routings. Eg. if there are 2 oscillators that each have an individual lfo then that's only one routing because it is assumed that if there is an LFO that can be assigned to one osc. then the other will also have a routing. eg. again Siel DK600 has 3 actual LFO's. Hi range. Two types (Square and Triangle). And three routings (pitch, pwm, vcf) though there are only controls to vary two sets of parameters there is still added warmth from having two independent ones on pitch.

Filters may be noted as Moog meaning the ladder filter Bob Moog designed which finds it's way into many products, or as 'Analog' meaning some other design using discrete transistors, resistors, capacitors, diodes and op amps. Otherwise the specific chip may be noted that is the core element of the design. A number before the type or chip indicates the number of filters PER VOICE or PER CHANNEL eg. CS15D.

Envelopes are listed with a number before the type or chip used which indicates the number of facilities per voice.

Effects may be digital in which case there are probably several configurations. Or BBD which is a hybrid device that passes analog voltages along with a digital clock setting the rate at which the voltages are passed from stage to stage. So if it says 4-BBD that means there are four different BBD based fx. Eg. Polysix which has Ensemble, Phaser, Chorus would say 3-BBD. Poly800 meanwhile there are two versions I/II. It will say 1-BBD/Digital because version 1 has a bbd chorus effect and version 2 has a digital effect with more options.







Why is Analog making a comeback?


     When the DX7 came to town, it appeared to be all over. Yamaha getting a slightly later start into the Analog game became determined to lead the pack in this new direction and utterly abandoned their attempts to market analog designs. Roland was a major player and robust enough to where they didn't have to have to lead the industry all the time. They had established a name early on with the SH series synths which heartily competed sonically with the American machines. And that momentum kept people looking at what they would do next for many years to come. And so about the time the DX came out so did the Juno-106 which took a simple to program great sounding series and added the MIDI interface and many people just had to take their music into that realm with Roland, so they sold 70,000 units or so even in the face of a landslide towards the Yamaha products. While these products had digital oscillator sections, they still involved analog vcf/vca modules and vca chips adding a lot of expense and setup hassle to the productions. Where the new Yamaha machines were pretty much assembled and shipped.
      Even as Roland began coming out with professional digital products including the S series samplers in 1986 and the D50 in 1987, they were still doing well in analog product sales with the JX series and alpha Junos. The market hadn't dried up completely yet but Roland dominated what was left of it pretty much. But all of these even had digital oscillator control.
     Korg had followed on the heels and developed a pattern which would make them dominant in the market eventually. They let someone else do the ground breaking, and then they set forth to make it better and cheaper. The PolySix had been a huge success and instead of trying to do something bigger and better, they saw where things were going and released a synth that would probably use up some of the parts they had left over, (the Poly61 with DCO's but analog EG's and OTA based filters) and again sold quite a few though not a raving success. But it was their venture into the MIDI world and it gave them a chance to evaluate where they wanted to take things next.
     Then the Poly800 came out with a price tag and sound quality that turned it into a good success. The DSS-1 probably didn't make them much money but it did look big and bad and kept them in the spotlight with another great sounding synth and a sampler until the M1 was ready. Korg never made another synthesizer with major analog components after the DSM-1, and the DS8 which came out about the same time was again an attempt to build something similar/cheaper to what others had been doing in the digital market. The M1 was the ultimate example though, taking the best of the Kurzweil K250 in the eyes of the typical working musician and hobbyist. Leaving behind the seldom used by the typical user sampling interface, keeping the great sampled sounds in ROM, and creating an easy to use sequencer interface in a light weight yet decent feeling package (DX7 keyboard movement). Result: One of the best sellers of all time.
      Meanwhile Sequential's direction was to continue making synths with analog vco's until the Prophet VS which was a consuming project that forged the way for a new approach to synthesis, but cost them I'm sure as they only sold 3000 of them. Their Prophet 2000 sampler was somewhat popular, but Ensoniq had come out of nowhere and snagged the pole position in the econo-sampling market with the Mirage. So SCI wound up with some better products perhaps but the pricing/popularity point ARP had already gone by the way due to bad management and Moog had the SL-8 on the table but when they saw the DX7 knew there was no way they could compete. They had poured their efforts into a direction that would result in small volume sales.
     Crumar had been popular overseas and developed the first DCO synth, but they continued into the mid 80's reaping the dwindling harvest of analog hybrid sales and never really produced a significant digital intrument and eventually called it quits in '87. Siel and Elka both continued on the similar path with compromised partly analog instruments that followed trends in that area, and continued also to try to scavenge what was left of that market. Siel had began by making synths that used divider network chips with one analog VCO behind it and a full analog synth on the other side (DK600), which maintained the warmth but got rid of the expensive dedicated analog oscillators. And they began to harvest the market that was seeking a different analog sound at budget prices. Then after some variations they made some with far fewer analog components (DK70, DK80) and then some cheap digital products. They had gained enough attention to where apparently Roland thought it best for business to buy them out and shut down the factory.
     In general though those who didn't begin to design innovative digital products by 1985 ceased to do business shortly thereafter. Except for Korg, because Korg made it their business to shadow the technology and they found a great following with people who were willing to wait a couple years maybe but get something that would do the job for cheaper. So by 1987 there wasn't really an analog product that was getting any significant amount of sales and hence no advertising was devoted to these products. In the public eye that can make something very unhip, so analog synths began to be sold for very cheap prices as people tried to get money for the latest digital.
     So goes the consumer market. Anyway the first digitals all had something in common. They emulated physical processes or, actually sampled physical sounds then performed physical processes on them largely. For instance the DX7 was an "FM" synth. A natural process emulated digitally. The K150 and K5 allowed construction of harmonic arrays as we see vibrations stimulating overtones in nature. Etc. Basically doing it digitally lost some quality but the hearer could still catch the essence of a real process and they could tweak it in a way that would have been extraordinarily expensive to set up...had it not been for digital processing! However..there was a down side. With so many options and so many WRONG (in terms of the way things really interact in nature) ways you could set things up for a sound, it is easy to get lost making utterly silly sounds with these units. This inspired me to write the K5 'macro' software which allowed you to construct presets that were useful and call them up as needed so as to be able to construct a 'skeleton patch' which one could then go in and tweak to perfection. Rather than getting distracted and totally losing the idea you had as you explore all the absurd possibilities. (Though that's still fun sometimes and you do stumble onto something interesting occasionally that way...)
     Down along the path software people began to put processes more and more distanced from nature at the fingertips of the synth programmer. While it might SEEM on the surface that having a synth that can do arbitrarily bizarre things is good, many really learned quite another lesson. Perhaps a lesson analogous to what old Solomon spoke of in Ecclesiastes. He tried everything. But it kind of left him..empty! A 'chasing after the wind' and that sort of thing.
     Human beings need meaning. Connectedness. Their souls long to be in touch with something firm. Not necessarily predictable to them. But something that rather..grows with them. A great musician is like this with his/her audience. Awesome live shows aren't just a pre-planned thing that starts at time "A" and shuts off with "thank you and goodnight" at point "B". Rather awesome live shows are where the musicians are in touch with the audience and they convey something together. Something that causes each person to grow together somehow.
     Even my beloved K5m...I find sounds that are way bizarre and unreachable by other synths, but they leave me flat and cold because the processes are completely distanced from nature. They are rather arbitrary and in that way they don't connect. A sound that connects is one that has surprising qualities that lend themself to the song they are being used in (or often, inspire I find. Sometimes in creating a sound a song will emerge just from playing the sound the first time) and work together with it somehow to make the concepts all the more real to the listener.
     A friend of mine, Paul Rose, let me listen to an old 80's group called 'Negativelyland'. The first cut is a farsical message to radio station managers, explaining how they've developed this new technology which will produce a 'hit song' that is ready for release in the current market. Then they play the 'designer song' which amounts to a bunch of crazy samples of cartoon noises and annoying music hewn together with a guy finally yelling "just a minute" over and over and "I can't hear a thing" as they flow into the 'is there any escape, from noise" theme. Very funny piece.
     But also quite relevant in terms of the direction things had taken in 1987 when that was released. Many great digital instruments have been made; most of them affording us the ability to carry nice sounding piano's around without a moving crew and the like. However...sometimes too much creative headroom...into the space of being arbitrary ....can actually be a distraction to productive creativity! I know many musicians who just spend too much time fiddling and not enough actually creating music that anyone wants to listen too. There are so many sounds available for download. But where does a person stop and actually learn to play an instrument well?
     In the wake of all this, many people began to remember...something real. Analog circuitry. Subtle deep intricasies that lend themselves to making...MUSIC! Well music that lends itself to communication. Hearing natural processes unfold, rather than hearing a software engineer's idea of what sounds like it could be a natural process if like wormholes were real and the whole studio got caught in one. :-) Real..bonafide..natural processes. Like any other musical instrument that was created prior to the idea that we could write software that would be able to let us design our own instruments in an arbitrary fashion. And up many of the prices started to go again. There are still some little known gems out there that can be found at a super bargain price. But don't expect to find a Matrix 12, CS-80, Synthex, Chroma, Minimoog, Prophet 5/10 or Jupiter 8 for a few hundred dollars anywhere anytime soon again. :-)
     It's interesting to think about..creation. And how the best things come when we explore it and work within it's boundaries instead of just arbitrarily saying "hmm wonder what would happen if I totally twisted that aspect of nature?" There's nothing like the real thing. Never was, never will be. -Bob
















The Synth Poll!

(Note: The number in parenthesis before a synth indicates the number who voted for it)

1) Best Analog synth (barring all thoughts of not having roadies to haul it, techs to keep it running, etc.)
    (2)Yamaha CS-80, Jupiter-8, Fenix, ARP 2600, Alesis Andromeda A6

2) Best Monophonic analog ("" "" )
    (3)MiniMoog, MiniMoog Voyager, EMS VCS3, Sequential Pro-One

3) Best practical poly analog
    Sequential Prophet 5 ( Rev. 3.3 w/ MIDI ), Roland Jupiter-8, Roland Jupiter-6, (3)Alesis Andromeda A6

4) Best practical mono or duo analog
    Sequential Pro One, (2)MiniMoog voyager, Roland SH-101, MultiMoog

5) Best full polyphonic
    (3)Korg PS-3200/3300

6) Best practical full polyphonic
    Korg PE-2000 Polyphonic Ensemble Orchestra, Korg PS-3200, Korg Lambda

7) Best paraphonic
    Roland 505, Crumar Trilogy (hey..it's semi-paraphonic with 6 shared filter/eg's) or Korg Delta

8) Best preset mono
    (2)Korg Sigma, Roland SH-1000

9) Best bang/buck monophonic
    Moog Prodigy, Sequential Pro-One, Moog Voyager, Waldorf Pulse, Yamaha CS-20M

10) Best bang/buck polyphonic
    Sequential Prophet VS, Sequential Prophet 600, (2)Alesis Andromeda A6, Akai AX80

11) Best bang/buck full polyphonic
    ARP/Solina String Ensemble (Technically partially paraphonic with one filter but poly decay eg.), Korg Lambda

12) Best bang/buck paraphonic
    is there any? (ha...ha. Only answer others gave) I'd say the Korg Delta! Or possibly Poly 800.

13) Best classic modular synthesizer
    Roland System 700

14) Best currently available modular synthesizer
    Serge Modular

15) Best bang/buck modular synthesizer
    Synthesizers.com

Honorary Mentions: Some people didn't apparently understand some of the questions. So I thought it good to mention that the Rhodes chroma did get nominated as best 'full polyphony' though it's max 16 voice poly, and also Alesis Andromeda in that category. Roland VP330 got a vote for best paraphonic. It's a vocoder and may have some paraphonic aspects. I'm not sure. That question was more aimed at the ARP omni and that type of synth which has paraphonic sharing of the filter but is full poly in terms of notes via divide down osc. Also Moog Voyager got an entry for best preset mono. However it's a programmable oriented mono not a preset oriented. This term usually refers to things like Sigma which have more preset aspects than parameters. Though it's close on sigma :-).



THanks to Steven Parsick, Mike Kent, 'jk', Guido, Alex Prescott, and...me.




























Keyboards and how they interface to synthesizer circuitry -by Bob Weigel



     There are two primary types of keyboard circuit employed in synthesizers. Well, not counting those where each note is wired to an individual keying circuit. This is common in electronic organs where sometimes the 'circuit' is simply a switch that connects some tone or mixture of tones to a mixing buss. It is also used in fully polyphonic/paraphonic synthesizers though. Each note in those cases, is often wired to some diode/resistor/capacitor circuitry that allows for each note to have a discrete attack and or release time. Well the time is usually global but I mean the timing circuit starts for each note when it's engaged. Machines like the Korg Lambda have complete independence in both attack and sustain while many others compromise and leave off one or the other so that a decay or attack is interrupted when another key is struck.

Meanwhile Monophonic synthesizers like the minimoog use a resistor ladder. If you put precision resistors in series and put a precision voltage reference across them, then at each joint between resistors a voltage will reside that is of course proportional to the location in the chain. in cases where there are an even number of resistors for instance, if you have a 5V source across the chain, then half way between will be 2.5V within the precision afforded by the resistors.
      A control voltage for a VCO may therefore be achieved in this sort of way. When a key is pressed then a contact shorts one of the connections between resistances to the control voltage buss and the change is detected and a sample and hold cell is opened to read the voltage. The voltage can then be stored when the key is released so that the oscillator does not drift in pitch during a release envelope for example.
     If multiple keys are held, then in this sort of arrangement the pitch will vary strangely. For example what happens if you hold the second highest and lowest notes? This would create a wire that touches between the first and last resistance and hence the contacted buss would be at about half the reference voltage! ie. it would play a note from the middle of the keyboard.
     To overcome this an op amp bias supply is used. In this circuit the whole ladder is placed in the feedback loop of the amplifier. When a key is pressed it taps the voltage ratio between the ends of course and that goes to the input of a buffer amp which then feeds the sample and hold circuit. But when multiple keys are pressed the reduction in impedence results in a rapid adjustment of the output of the amplifier to correct it so that the highest or lowest note being hit is represented in the CV. The easiest circuit to study I think is the moog satellite.

      Polyphonic synthesizers demand a different method since there must be multiple keys whose positions are recorded simultaneously. For this task digital methods are much easier. The Yamaha SK20 diagram shows a fairly easy to see example of a key scan circuit. Here a processor has lines wired to each octave of notes. That is to say all the switches have a common let in that octave. Octave 3 for instance. The other side of each switch in that octave goes to the anode of a diode. And the cathode of each diode ties to another line that is common to all of it's note value. (Eg. "Dflat"). And these lines go to another pin on the processor.
     In this way a processor can be programmed to continuously be cycling through a routine of raising the voltage on one of the octaves at a time. And as it holds that line high it then checks the status of each of the note value lines. If it reads that one is high then it now knows which note of which octave is being held at that moment in time. Were it not for the diodes of course, then the situation could occur where you are holding, say, an F# in the 5th octave. But not the C#. You are holding an F# also in the 2nd octave and also a C# there. Without the diodes, the F# bus going high would feed back through the F# of 2nd octaves' key switch to the C#'s closed switch and would raise also the C# buss. THe processor upon scanning would discover the high C# buss and would assume that the 5th octave's C# was being held. Or it would have no way to tell that it wasn't being held at that point I should say. Hence the diodes.
     Once the CPU has captured this information it is then able to store it and circuitry is able to act on the information. Since processors usually run 100's of thousands or millions of instructions per second, it is quite impossible to sense any delay in the sensing process. That summarizes the typical key scanning method employed in most digital and analogy polysynths.





Memory implementation in analog synths. -by Bob Weigel


(Note: You may prefer to watch the video on this topic on my sounddoctorin youtube channel!)
     In units with panel controls, Variable resistors give a span of voltages as they are turned, and this voltage is attached to the input of an analog multiplexer. (this is a chip that has often 8, 10, or 16 lines; one of which at a time can be addressed to attach to a common line. So obviously the 8 channel mux has 3 address lines since there are 8 possibile combinations of address line highs and lows.)
     Ok so the CPU walks through the address possibilities AND further "selects" are used often to decide which chip is going to be accessed out of an array of them if we need more than 8 knobs to be read for instance. So anyway it walks through all the knobs and as it does it also calls forth the data previously stored in association with that knob from RAM. For machines which allow knob editing of previously stored data, there is a 'patch buffer' which is volatile memory often that stores a temporary copy of the data being worked on. Anyway, this data is latched for a DAC to convert it to an analog voltage. This voltage is fed to the pin of a comparator and the other leg of the comparator reads the knob's voltage that is currently being read. The output is always high or low on the comparator and so say they really are the same data..ie...nothing has changed in the voltage being fed from the knob's potentiometer. The CPU begins stepping the RAM data up until the comparator flops the other way! In the case where the data was supposed to be the same...this should be within ....whatever the resolution uncertainty is decided to be for the conversion process. And the software that runs the cpu is written such that if the comparator flops the other way within x number of increments, the data is considered the same and no change is made. The old data is refetched and written back, lest we walk around and create a perceived movement that wasn't actually there I suppose.
     And if a knob is actually moved (or you get a dirty/broken pot and it thinks it has moved...) then the cpu recognizes that the resolution limit has been exceeded and it assumes movement has occurred and allows the new data to remain stored in the patch buffer until a write command is issued in which case it will overwrite the old SRAM data.
     MEANWHILE..how does this information actually get to the analog circuitry? Usually the DAC output. Thus when you move the knob it takes the comparator acting as an ADC in conjunction with the CPU in order to bump the data up, and modify the DAC output to correlate with what the knobs are saying. This information simultaneously drives the comparator input AND is fed to another series of 4051 common inputs. As a chip is selected and the appropriate address is fed, the appropriate chip opens it's 'gate' and allows the analog voltage to flow onto a small sample and hold cell's capacitor. Then when the gate closes as the next function is being dealt with, the JFET or MOSFET input op amp buffers that voltage so that the capacitor is not quickly drained. And it's that output voltage of the op amp which actually drives the analog circuitry that is performing the analog synthesis function.