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Hello, everyone! I'm aware that the CTK-1000 (1993 or so) manual is hard to find online, so I'm sharing a PDF copy here for those who didn't have it and may find it useful. I still don't have the keyboard, sadly, but I was able to get this digital copy through someone who has it. I reckon that some of its features aren't super clear, so I'm sure that having the manual helps. Enjoy! https://mega.nz/#!rpwWjSza!1TKyDG-ctUmj3SP0-WFoLl0IKqJDZViytiE352iXHcU

On eBay I saw a rare workstation keyboard Casio CTK-711EX, which looks like an even bulkier variant of the mythical CTK-1000 with additional LCD display, 232 ToneBank, 110 rhythms and 3.5'' diskette drive. May it be that this one was "the real thing" while CTK-1000 was only a cut down household variant? (See here for my info and hardware analysis of CTK-1000.) Here is a YouTube clip about the CTK-711EX: My CTK-1000 panel PCB contains a strange adapter like when the hardware was originally designed for something else. Perhaps it was the LCD based CTK-711EX. This would namely explain why the fairly complex sequencer and synth in CTK-1000 was made but not means of data storage. By the way, I found out the mysterious meaning of "IXA Sound Source". It's "Integrated Cross-Sound Architecture" (thanks Synrise for info), which IMO sounds more like an advertisement name without technical meaning and therefore likely soon was dropped by Casio. I just found the CTK-711EX service manual from 1998, and the main ICs do strongly differ (see CTK-1000 hardware analysis). Thus it is likely more the case design than technical similarity.

I finally got my hands on a Casio CTK-1000. It is unfortunately excessively bulky (like a 1970th Antonelli; at least the speakers are not bad). The synthesized IXA presets respond nicely to velocity and not only turn brighter and louder, but partly into metallic and resonant distorted timbres (physical modelling?). Picked strings, organs and synth pads are very nice. It can sound like a warm analogue synth and is well suited for new age music. In any preset sound 3 synth parameters {wave, attack, release} can be edited and saved as user preset. Their values can be 1..9, where 0 is the default. The behaviour of 'wave' depends on the preset sound. What sucks is that many brass, string and ensemble timbres are only loop samples with sampled vibrato, which of course changes speed with the note pitch until the next (well audible) split zone is reached; this rather reminds to 1990th Bontempi GM home keyboards or Potex sound toys than a serious synth. Despite many DSP effects, there are no vibrato or tremolo settings; instead many voices contain an annoying delayed vibrato that can not be disabled. Obnoxious is also that there seems to be no easy way to play in the chord section chords without rhythm or accompaniment. (May be you can program this as a "style", but thats not what a keyboard should do.) There is no key split mode except as part of some "split" preset sounds. The entire thing somehow feels like an ill designed cross between MA-130 kiddy keyboard and a very serious workstation. Absolutely insane is that despite complex multi-track sequencer with even editable styles and synth user presets there are no means at all for backup, so the only way not to loose them is to have fresh D-cells inserted and keep the AC adapter connected while changing batteries. (Why is there not even SysEx dump!? An SRAM upgrade module like those for SK-series could fix this.) The manual even warns to disable auto-power-off (hold 'tone' button and switch power on) during programming to avoid data loss. Interesting is that at least through midi (haven't tried) the sound engine is multi-timbrale and there is a "local off" mode that may permit to route the keyboard input through a PC to circumvent some design flaws (e.g. key split). Despite superficial similarities to the Casio VA-10 (both from 1993), the ICs are much bigger and have nothing common. main ICs: CPU= "NEC D939GD 010, 9315BA 006" (160 pin SMD, PCB label "UPD939GD-00X, NM-110", 20 MHz? crystal clocked)key velocity IC= "Casio HG52E35P, CDHG256, 3C33, Japan" (64 pin SDIL)ROM= "NEC D23C16000BCZ 065, 9314E7003, Japan" (42 pin DIL, 2MB)SRAM= "NEC D43256AC-12L, 9310AD019, Japan" (28 pin DIL, 256KB)DRAM= "Sanyo LC33832PL-70, 3DD0, Japan" (28 pin DIL, 256KB pseudo-static, PCB label HM65256BSP)DAC= "NEC D6376CX, 92498H003, Japan" (16 pin DIL)panel CPU= "NEC D78CP14CW, 9246PX701, Japan" (64 pin SDIL, 12 MHz crystal clocked)power amp= "LA 4620, 2J1" (23 pin SIL)IC= "F MB3771, 311F40" (8 pin DIL, PCB label "MB3771P")2x IC= "Mitsubishi 5216A 2607R" (8 pin DIL)transistor array= "LB1216, 3N9" (16 pin DIL)transistor array= "LB1233, 1H8" (16 pin DIL)optoisolator= "NJL 51270,2Y" (6 pin DIL)3x hybrid= "B9HC0118, 101Kx8" (9 pin SIL)The 16 bit ROM (I dumped it) is 2MB large and contains plenty of samples and curves, as well as plenty of strange wavy ramps; possibly IXA employs the mysterious "triangular wave modulation" (https://www.google.com/patents/US5164530). With ROM removed, the panel LEDs and display ("00") look normal, but nothing responds and no sound. The CPU "NEC D939GD 010" (160 pin SMD, 20MHz) seems to be successor of the MT-540 CPU ("NEC D938GD 005", 120 pin SMD, 2.17248MHz), but unlike the latter it interfaces velocity sensitive keys and parts of the control panel through 2 external large ICs and uses most of its 160 pins to access SRAM, DRAM and 2MB ROM simultaneously (no shared bus) to increase throughput per clock cycle. Despite high complexity it fortunately does not run hot and so neither shortens its own lifespan not that of the batteries. Strange is that parts of the control panel are handled by a fairly large CPU "NEC D78CP14CW" (64 pin SDIL) on a daughterboard with ribbon cable wired to empty IC holes on the panel PCB. This hints that Casio had planned a different user interface (perhaps a professional synth?). Many D78CP14CW pins are unused; most do nothing but some output matrix signals. Possibly an LCD was planned but no software written for it. Annoying is that you e.g. can not see the effect settings and so have to tweak sound by ear and count button presses (MT-750 did the same). Also the menu structure is quite restrictive; e.g. various mode changes stop rhythm. Perhaps the panel CPU was added to save computing time in the main CPU, which has more sound glitches and irregularities than MT-540. E.g. effect buttons cause strange transient pop noises, the sample split zones are much more audible (i.e. lack interpolation) and the awesome algorithmic program loops synthesis sounds are gone. (I.e. the 'sound effect' preset consists here only of a bunch of very plain behaving loop samples.) Knowing that MT-540 was a high grade variant of the softsynth-on-a-chip (Casio SA-series), I guess that Casio threw a lot of goodies out of their algorithm to save computing time for the IXA synthesis, effect section and higher polyphony. The only special behaving preset is 'synth-lead 2', which stays always monophonic with portamento, which hints that there are many hidden synthesis parameters. The effect section DSP may be in fact hardware (seen in Casio patents) and likely uses the DRAM. So it might be possible to install a microcontroller between CPU and RAM to edit further parameters or at least backup its content on persistent memory. It also may be that the strange D78CP14CW can be replaced with a programmable microcontroller to unleash hidden synth capabilities of this thing. Somewhat similar like CTK-1000 is the much smaller Casio VA-10 "Voice Arranger", which also has a DSP effect section and can route microphone input through it. But the ICs are different: CPU= "NEC D911GF 003, 9243AA005, Japan" (120 pin SMD)DSP?= "OKI M6583-04, 2432202, Japan" (60 pin SMD)DRAM= "Toshiba TC51832APL-85, 9236HAK, Japan" (28 pin DIL, 32KB pseudo-static)op-amp= "XRAI5218, 245 214A" (8 pin DIL, PCB label "M5218APR")power amp= "Motorola AN8056, 2'D6" (28 pin DIL)3x hybrid= "B9HC0118, 101Kx8, 2N" (9 pin SIL, PCB label "CNB8X101K")hybrid= "B9XC0118, 101Kx7, 20" (8 pin SIL)Although the main voice preset sounds resemble much Casio SA series keyboards, the main ICs strongly differ from all other small Casio keyboards. The double sided PCB is fairly complex with 3 large digital ICs and plenty of discrete components. The CPU "D911GF" is such exotic, that not even Google finds its name. As expected, also the "OKI M6583" has no datasheet, but plenty of Mitsubishi ICs with "M6583..." (different pin count) are audio delay DSP for reverb and echo effects in things like karaoke machines, so technical relations would be very plausible.