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circuit bending detailsPCB layoutWhen the CT-410V is opened (keys facing down, all views at solder side), there are beside various smaller ones 2 large PCBs. The lower one is the main PCB ('M485-MAIM (D)'); from left to right it is divided into the following areas:
accompaniment CPU D930GThe NEC D930G is one of the most interesting squarewave accompaniment chips ever made by Casio, because although it features only 12 rhythms, it has for each of them 4 chord, 4 bass and 4 arpeggio variants and features wonderful dark and sonorously droning multipulse squarewave bass and chord tones with different pulse patterns. All tones have separate output lines (those partly need external envelope capacitors) and it features also separate trigger outputs for analogue drums. The 80 pin SMD chip has own keyboard matrix input lines for control switches and accompaniment section keys, and it apparently also can act as a keyboard matrix decoder to communicate (through a serial port?) with an external main voice soundchip (the NEC D931C in the case of the Casio CT-410V ), while in other instruments (e.g. my Casio MT-45) this feature is not used. Most key matrix pins are at the top, and 2 at the left side of the chip package. The sound output and drum trigger lines are at the bottom side. Bass and arpeggio employ a capacitor envelope for their release phase.Apparently a direct predecessor of this hardware class was the accompaniment CPU D910G and main voice soundchip D990G, those were used in the Casio MT-60. keyboard matrix
All unknown function names and in/ out numbers in this chart were chosen by me. The input lines are active- low, i.e. react on GND, thus any functions are triggered by a switch in series to a diode from one 'in' to one 'out' pin.
The main voice sounds are generated by the D931C soundchip. Unlike various older Casio instruments, during trilled notes it does not occupy one new sound channel per repeated note, but re- uses only 1 sound channel per pressed key. This helps to save polyphony, but also makes the sound more boring because it prevents the typical phasing and volume increase effect known from older polyphonic Casios. I am still not sure why the main voice polyphony is reduced from 8 to 4 notes when chord/ bass or accompaniment are active, despite as well the accompaniment CPU as the main voice soundchip contain their own sets of totally independent tone generators. I can only imagine that by a design flaw the keyboard matrix decoder in the accompaniment CPU contains too little memory to handle more than 8 simultaneously held down keys, which makes it cut down the polyphony.
The CT-410V has a fixed diode at in7->out4, while the MT-45 has at this location the 'chord memory' switch and apparently the diode instead at in8->out9. Thus with the CT-410V solder a switch in series to the diode at in7->out4 and add a fixed diode at in8->out9.
My Casio MT-45 has arpeggio, and an MT-65/ MT-68 includes even 4 selectable variations of them. I really love this rhythmical chinking accompaniment effect, which IMO is one of the most typical and interesting style elements of classic electronic keyboards, thus it is a pity that with later Casio and Yamaha keyboards it was omitted because manufacturers apparently considered it out of fashion.
filter and chorus input jacksTo send an external signal to filter + chorus, connect a cinch jack through a 100nF cap in series to a 1 kOhm resistor with the rightmost pin of a black resistor array module in the middle of the PCB, which seems to act as DAC for the main voice soundchip D931C. This modifies the external sound by everything that actually modifies the main voice (including its muffling capacitors).To send a signal only through the filter (in any mode), connect a cinch jack through a 100nF cap in series to a 2.2 kOhm resistor with the strange looking divided solder pad below the filter resonance preset trimmer pot at the left side of the main PCB. This solder pad is round and consists of 2 semi- circular halves with a small bridge in the middle; likely it was intended as a cuttable jumper for test purposes. The external signal this way will be sent always through the filter, no matter if the filter processes internal signals at the moment. Oblivion modding guide 2019. (So far nothing is currently triggering the filter envelope, the 'sustain level' and 'cut off' controls must be set high enough to get the external signal audible.) These jacks can be likely also used as separate outputs. main voice volume controlParticularly when using the filter, it is annoying that no independent volume control for the main voice exists. To add one, cut the trace from pin 1, 2 at the op- amp '4558-2' in the middle of the main PCB. Connect the the op-amp side with the right pin of a 22 kOhm log potentiometer, and its wiper output with the other trace end. Connect the left pin of the pot through a 10µF capacitor with GND. (This volume control works not when the main voice runs through the filter - apparently the filter gets the signal from another line that bypasses the timbre muffling capacitors.)
timbre change & distortionThe main voice sounds of the CT-410V consist of 2 mixed multipulse squarewave tones with different pulse patterns and different digital volume envelopes. (Also the reverb is technically only an envelope modification.) The waveforms are outputted through a resistor array DAC(?) and are post- processed by 4 low pass filtering capacitors those are controlled through a '4066' analogue switch IC. These filter caps have the values {4.7nF, 33nF, 5.6nF, 470pF} and are located to the left of the NEC D931C soundchip. The 4066 is DC controlled by the soundchip, and can be also easily controlled by external switches to modify the timbres. (This timbre filter circuit is part of the main voice sound generator and has nothing to do with the additional cut- off/ resonance synthesizer filter of the CT-410V).I soldered a 4 channel alternating switch into the control lines to the 4066 to make the 4066 inputs (pin 5, 6, 12,13) switchable between their original soundchip outputs and 4 external controls. Instead of 4 simple switches I connected here the wipers of 4 10 kOhm potentiometers to permit analogue control over these inputs (use shielded cables against hum). The 4066 in this instrument switches its load fully 'off' at voltages below about 2.8V and fully 'on' at about 2.87V, thus the pots need about 2.8V at the left and 2.87V at the right end. To generate these voltages, I built 2 voltage dividers those each consist of [a chain made from a 330 Ohm resistor, a 100 Ohm trimmer and a 220 Ohm resistor in series] from GND to +5V. The trimmer wiper of the 1st voltage divider is connected with the 'left' pins of the 4 pots, and the trimmer wiper of the 2nd with the 'right' pins. The trimmers have to be adjusted until the potentiometers block all sounds when fully turned left, and let it pass undistorted when turned a bit less than fully right. The filter capacitor #1 seems to be a pop noise protection or the like, because when its pot is turned fully close (left), the main voice sound is muted, independant from the other pot settings. Cap #2 and #3 simply modify the timbre. With these pots are in an intermediate position (between left and right) the sounds turn gradually quieter and distorts in interesting ways. Cap #4 also changes the timbre, but it behaves special, because when its pot is in an intermediate position, there is much static, humming, and depending on the other pot settings the amp even tends to toot loudly by self- oscillation. There is also a popping noise while pot 4 is turned (unless the sound is muted with pot 1).
note: When the main voice is routed through the synth filter, these pots do nothing since the main voice apparently bypasses the normal timbre filter caps for this. remove dullnessIn comparison to a Casio MT-60 or MT-45, the CT-410V sounds quite dull. One reason for this are the big speakers with poor trebles, but the main reason is a totally useless and permanently active 1nF capacitor near the main voice filter caps in the middle of the main PCB. This annoying cap makes all sounds dull, which e.g. makes the characteristic harpsichord attack click almost inaudible. It is therefore strictly recommended to disconnect this muffler.extended tempo rangeUnlike with older Casios, the maximum rhythm tempo of the CT-410V is a little slow. A 10nF capacitor at the right upper end of the main PCB controls the tempo oscillator. Replace it with 1.7nF to speed up the tempo a lot. (The still functioning minimum value may vary among instrument specimen, since with a slightly smaller cap my CT-410V stopped the rhythm entirely.) Due to this also rises the minimum tempo a little high, connect the open end of the tempo potentiometer with a 680 kOhm resistor in series with a trimmer pot (e.g. 300 kOhm) against GND. Adjust the trimmer in a way that the rhythm barely stops (arpeggio can make a continuous tone here) when the tempo pot is moved to minimum. This will provide you the maximum possible tempo range. (With full tempo arpeggio sounds great.)filter resonance improvementThe synthesizer filter of the CT-410V sounds a little boring because it refuses high resonance values. Despite there is a resonance preset trimmer at the left lower half of the main PCB, high settings of it eat much bass. Even worse, instead of gently tweeting near the cut- off frequency, at high resonance settings the filter op- amp tends to run amok and suddenly squeak without warning terribly loud (about 10 times of the rest) like a police whistle at a far higher frequency than the cut- off value. To make the filter behave nicely, solder at the white wire of the grey shielded cable from the resonance pot (upper left main PCB area) a 56nF capacitor in series to a 6.8 kOhm trimmer pot (as adjustable resistor) against GND. By alternatingly tweaking the resonance preset and the new trimmer, you can now adjust the filter to friendly tweet around the cut- off frequency at low volume without blasting away your ears. The filter can this way even safely howl in self- oscillation by its automatic envelope at maximum resonance and sustain level without squeaking unbearable loud, and it will stop as soon sustain level or the envelope drops below the necessary value. This permits also nice 'acid house' sound effects, although the timbre is a bit different from a TB303. (Unfortunately there is no sequencer, thus you can only send the accompaniment through the filter.)Attention: Someone e-mailed me that this mod does not work with Casio MT-400V due to different hardware. I am not sure if both keyboards are indeed technically different or if there is even an error in my description. This is what he wrote: A couple of notes. On the 400v there's the resonance pot, right next to it is the cutoff pot. By tweaking these two it's possible to get the filter sounding pretty good. Also the wiring's different so I couldn't get the mod to work without having a drastic drop in volume on the filter output. bass circuitThe bass output of the D930G employs a very similar envelope capacitor circuit like the arpeggio. It consists of an 1µF electrolytic capacitor (for decay duration) from pin 11 to GND and a 82 kOhm resistor from pin 11 to pin 5. There is a diode from pin 5 through a 22 kOhm resistor to pin 80. The sound is outputted through a 1µF electrolytic capacitor from pin 5.Interesting is that the Casio MT-45 produces a much softer, duller and more pressureful bass which timbre resembles a triangular wave or Roland TB303 (without resonance), while the CT-410V bass is a more sonorous droning squarewave tone. The MT-45 has instead of the 1µF envelope cap a 0.47µF one, and behind the 1µF output cap follows a 220 kOhm resistor against GND, a 120 kOhm resistor against +5V and a 47 kOhm resistor to the amplifier, but I doubt that this causes the difference. The CT-410V has after the 1µF output cap a black cable that leads to one input of the bass volume potentiometer, and its wiper (?) output is connected with a 22nF muffling cap against GND (located 3cm below the bass volume pot cable near the corner at the top of the middle of the main PCB) and resistors lead the signal to the amplifier. Bridging the muffling cap with a bigger one makes the bass indeed duller, but in spite of this it won't really sound as smooth and pressureful as the MT-45; a too big additional cap here only reduces the bass volume too much. I guess that the MT-45 circuitry has a much higher inner resistance and thus doesn't damp the bass as much as the bass volume pot stuff of the CT-410V does. (When I experimented with adding the bass potentiometer to the Testron I discovered similar behaviour.) Increasing the envelope cap value makes the bass decay slower (and thus sound less dry), but this also doesn't imitate the MT-45 bass sound. (The MT-45 has even a smaller instead of a larger cap, but this is likely rather caused by the higher inner resistance of the rest of its circuit, because it doesn't seem to fade the bass silent much faster. Certainly potentiometers can be added here to make the envelope and muffling capacitor values adjustable etc., but I didn't modify this.) Possibly the CT-410V has even intentionally a less dull bass with more overtones to sound stronger when processed by the synth filter. Which bass sounds 'better' is a matter of situation or personal taste and there is no objective answer for this. Crossover 19.0.1.32209 for macos free. 2020-8-28 CrossOver 19 是一款可以让您可以在 Mac系统上运行 Windows 应用,不必重启系统,不必使用虚拟机。通过 CrossOver, 您可以直接在mac电脑上直接运行exe程序,与您的 Mac 和 Windows 系统功能无缝集成。CrossOver 19 支持 10.15 64位系统。. stereo chorus modificationThe stereo chorus is a separate unit that can post- process the main voice. It was intended to approximates a rotary speaker effect by panning a pitch shifted version of the signal left and right, that is mixed with the original signal, but in fact it resembles much rather the hemi- sync signal of a mind machine, and thus can be greatly used for meditation music, because the chorus speed is stepless adjustable by a slider. The stereo chorus circuit is located at the right side of the amplifier PCB; it contains 3 small ICs (each 8 pins, from top to bottom: 'MN3209', 'MN3102', '4558DD-1') and various discrete stuff with 2 (?) transistors. I am still not sure how the pitch shifting functions, but the entire thing seems to be analogue.
analogue drumsThe percussion sounds are fully analogue and have trimmers for decay time adjustment, thus they can be certainly modified in a lot of ways. Because they are triggered by pulses on individual output lines of the D930G, it would be certainly possible to modify the preset rhythms a lot by muting individual drums or even connecting them through a switch matrix in different orders (the 'Super Drums' rhythm variation slide switch feature of certain old Casios does possibly the same). (I didn't modify this.) Different Casio keyboards with the D930G also can be equipped with varying percussion; my MT-45 has e.g. some drums (2 toms) less than the CT-410V.pitchbendThis instrument has already a built-in tuning potentiometer, thus here certainly easily one or more pitchbend pots could be added. (I didn't add one yet.) But be warned that the clock oscillator is AC controlled, thus do not connect simple sensor contacts here, because they would flood your nervous system with maladjusting and potentially cancer causing high frequency crap.shitshotBy re- plugging the power supply plug, the main voice sound envelopes change a lot. Most of these shitshot sounds distort much during polyphonic play. While sustain and vibrato behaves as usual, the operation of the added 'envelope' switches always reset to a default sound. Also selecting another sound clears these sounds (as expected), thus I conclude that much like with Yamaha FM keyboards, the D931C soundchip is programmed with synthesis parameters a single time by the main CPU D930G when a sound is selected, and it keeps these parameters in internal registers until a new sound or envelope is selected (or a shitshot messes them up). |
Re: [music-dsp] patents (the softsynth was patented 1997)To: music-dsp from shoko calarts edu Regarding digital musical instrument patents, around 1981 when I began modifying the Casio M10, I met a chap who was the agent here for Allen digital organs. These were serious 'pipe organ' like things for churches, full of Rockwell LSI chips with round metal chip covers, black plastic packages with quad inline staggered leads. He assured me that Allen had licensed a patent, by one Ralph Deutsch (if I remember correctly, and I haven't thought of it for 18 years or so) which was for a musical instrument which worked by storing a digital representation of a waveform in its memory. He showed me the patents - I may still have copies somewhere. He was intrigued by the Casios - the first production digital keyboards. He was convinced they used a curious form of synthesis, the name of Walsh Functions - some mathematical abstraction of little obvious importance - because he was sure that Casio would not want to be caught out on Allen's worldwide patents. The Casio M10 chip and its siblings in the MT-30, MT31, CT-201 (the very first Casio - 4 octaves, full size, two chips with different waveforms) work by generating complex 16 step waves (I assume this from what I know about a later chip I describe below), eight notes at a time. The waves are made of two component waveforms and there is crude envelope control over each. The sum of the 8 waves appears as a 14 bit binary number at a sampling rate of about 500 kHz. This means nice, crisp, non-aliased high tones! The DAC was inverters driving a R-2R resistor array for 12 bits and a few resistors for the least significant 2 bits. There was no sample and hold - just an op-amp - so timing anomalies in the bits from the chip and the inverter slew rates caused spikes when the wave went from 10000x to 01111x. The waveforms were pretty crude and of course made of stair-steps. The signal went through a switchable analogue LPF - but my mods bypass that. I even made a super-low glitch tweaked dual 14 bit DAC mod board for the CT-202, using the standard Casio R-2R network and some extra resistors, trimpots and judiciously clocked HC174 latches so the rising and falling edges were symmetrical. Later, in 1982, Casio produced a similar sounding MT-65 and its full-size equivalent. The sound chip in this is a 42 pin custom LSI which has its note playing and waveforms loaded into it by an external CPU and software. Around then, I figured out the protocol for talking to the chip and wrote a C program (BDS-C for Z80 CPM) to write waveform data to the chip via the parallel port of a Big Board I. The reason I mention the Casio is that the chip (the NEC D931) did not actually receive, or apparently store, waveforms. It received and stored *increments* - and used these steps to generate the waveform. If your increments did not add up to 0 then all sorts of trouble occurred! Let me look into my archives . . In less than a minute I found the patent! US Patent Office 2 June 1970 Patent 3,515,792There is no mention in the prior art of computer software generation of music - though I guess no-one had used a computer to make an *organ*. Using increments (albeit simple +/- 1, +/- 2 +/- 4 +/- 8) was probably harder than simply storing the waveform, and led to less flexibility than a stored waveform - but I figure that Casio did it so they didn't have to worry about the Allen patent. So the dull force of patent law made a popular instrument more awkward, or at least more idiosyncratic. I just found my doco file for the chip in the MT-65 - the D931. All the guff is there on how to talk to it. I have C-code as well - and 8 D931 chips, seven unused. I was able to load novel waveforms into the D931 in my MT-65 it and then play it from the MT-65's CPU via its keyboard, or the MIDI interface I added. I also made up a second D931 on an external board with an independent clock source so I could have two waveforms and detuning. A web search for: 'Ralph Deutsch' and patentleads to: http://www.allenorgan.com/book/jbook.htmwhere there are two blank pages, entitled: Honoring the Intellectual Property of Othersamongst a lot of other similarly empty pages referring to patent litigation. The author is Allen Organ founder Jerome Markowitz, who died in 1991. He had been dabbling in electronic organ patents since the 1930s. I have some patents of his here, from 1973, on internal plumbing inside digital organs. - Robin dupswapdrop -- the music-dsp mailing list and website: subscription info, FAQ, source code archive, list archive, book reviews, dsp links http://shoko.calarts.edu/musicdsp/ |
removal of these screws voids warranty.. |
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