The older Casiotone keyboards with analogue circuitry can generally be modified to accept external clock signals for synchronising their rhythms to other equipment - but there are a few caveats:
1. there are various Casiotone 'families' based on different chipsets and implementations. This means there's no standard way to do this across all models and even models that share the same CPU might be programmed differently. For example, with an external clock signal, the CT-310 and the MT-65 sync at the same tempo while the MT-86 plays at half their speed.
2. the mod outlined below might not deliver a rock solid sync - the resultant system can be prone to glitches unless buffered in some way, so making adjustments to tempo on the fly or switching other gear on and off, can cause things to go awry.
3. there are various sync signal formats in use, (12 , 24 or 48 ppqn being common), however, these do not apply to the Casiotones. With the mod below, they require multiplying the external clock signal to achieve a 1:1 sync with the external system.
Regarding 2 & 3 above, my workarounds include using buffered multiples for a more clean/robust signal based on this Ray Wilson/Music from Outer Space project and stepping up the clock with an Arduino clock multiplier by sinneb.
So with the above in mind, here are some details on the modification of a Casiotone CT-310.
I used a switched 3.5mm mono jack mounted to the case for patching the external clock in so that when a cable is plugged in, it disconnects the CT310's internal clock.
Note: the schematics here come from the MT-65, MT-68, MT-100, CT-405 service manual - the CT-310 is of the same family. Thus you could likely perform this mod on any of these and no doubt others. In addition, the same principles should apply to other families of Casitone, so investigating the circuitry around the CPU and tracing where the Tempo adjustment enters things, should reveal suitable patch points. I found a PDF of the service manual online.
(click images to enlarge)
1. Here's the CPU pinout table - pin 43 is what we are interested in.
Also of interest here are the drum trigger pins 13-23 (as well as bass and arpeggio envelope outputs). Hopefully we can return to those another day.
2. From the schematic we can locate pin 43 and examine the related circuitry. I patched the signal in just after the 150 ohm resistor (it's actually a 160 ohm on the CT-310). It's possible to patch at several points and achieve the same results but this resistor is located at the edge of the PCB and therefore provides convenient access.
3. Here's the CT-310 with the back off - note the shaded area to the right
1. there are various Casiotone 'families' based on different chipsets and implementations. This means there's no standard way to do this across all models and even models that share the same CPU might be programmed differently. For example, with an external clock signal, the CT-310 and the MT-65 sync at the same tempo while the MT-86 plays at half their speed.
2. the mod outlined below might not deliver a rock solid sync - the resultant system can be prone to glitches unless buffered in some way, so making adjustments to tempo on the fly or switching other gear on and off, can cause things to go awry.
3. there are various sync signal formats in use, (12 , 24 or 48 ppqn being common), however, these do not apply to the Casiotones. With the mod below, they require multiplying the external clock signal to achieve a 1:1 sync with the external system.
Regarding 2 & 3 above, my workarounds include using buffered multiples for a more clean/robust signal based on this Ray Wilson/Music from Outer Space project and stepping up the clock with an Arduino clock multiplier by sinneb.
So with the above in mind, here are some details on the modification of a Casiotone CT-310.
I used a switched 3.5mm mono jack mounted to the case for patching the external clock in so that when a cable is plugged in, it disconnects the CT310's internal clock.
Note: the schematics here come from the MT-65, MT-68, MT-100, CT-405 service manual - the CT-310 is of the same family. Thus you could likely perform this mod on any of these and no doubt others. In addition, the same principles should apply to other families of Casitone, so investigating the circuitry around the CPU and tracing where the Tempo adjustment enters things, should reveal suitable patch points. I found a PDF of the service manual online.
(click images to enlarge)
1. Here's the CPU pinout table - pin 43 is what we are interested in.
Also of interest here are the drum trigger pins 13-23 (as well as bass and arpeggio envelope outputs). Hopefully we can return to those another day.
2. From the schematic we can locate pin 43 and examine the related circuitry. I patched the signal in just after the 150 ohm resistor (it's actually a 160 ohm on the CT-310). It's possible to patch at several points and achieve the same results but this resistor is located at the edge of the PCB and therefore provides convenient access.
3. Here's the CT-310 with the back off - note the shaded area to the right
4. Here's that shaded area enlarged and rotated 90° anti-clockwise, showing the patch points. A ground connection can be easily made using the mounting screw to the left.
5. With the above PCB flipped over, this is what you'll find.
Step by step
1. de-solder one end of resistor closest to the ‘E’ labelling on the PCB & lift the free end clear from the PCB
2. attach a length of wire to the freed end & heatshrink it (green in the photo above)
3. solder length of wire to the PCB where resistor was previously connected - this wire is for the external clock signal (yellow in the photo above)
4. run these two wires to a switched jack mounted somewhere convenient
on the case
5. run a ground wire from the switched jack to the PCB (blue in the photo above)
Final Thoughts
It's quite possible there are other, better ways to do this. I poked around with a multi-meter and cautiously experimented with patching clock signals at different points on the circuit before settling on the above. The signals I use never exceed 5v so it might be worth taking care if you are playing with anything larger.
I should get round to making some updated videos of this, along with the other Casiotones I've treated but in the meantime you can see it in action in the following videos (note: there are a few timing glitches since this was before I was using the buffered multiples)
...and this nonsense
Questions, thoughts, recommendations? Please share.
This is great! Really helpful to have such detail on the CT-310... you've got me inspired to tinker with mine. Looking at the drum triggers, would it be possible to have manual triggers for each drum sound? to set up some sort of drum pad using the CT-310 default sounds?
ReplyDeleteLooking forward to any more tinkering if you have to do with this keyboard :)
Thanks. Individual drum triggers is on my 'to do' list - along with a million other projects but it should be possible. I recall doing some preliminary investigation probing around the circuit but I don't remember any specific details. Usually, the most complex part is getting the white noise to trigger correctly for the snare as this sound is combines two separate sounds. But, it might be fairly simple on the CT-310 compared to other casiotone families? I'd need to investigate again.
ReplyDeleteAnother point here is that the circuits generating the drum sounds (and maybe other accompaniments?) only become active when the start button is pressed. Therefore, you need to disable the clock signal so that the system 'stalls', otherwise the preset rhythms will play. With my mod above, you can simply insert a plug into the socket to achieve this - there's no need to run an external signal in. With the start button pressed the internal system believes it's good to go and the drum circuits are activated and waiting to be triggered - pressing stop then mutes them. This behaviour appears to be common for all such keyboards.
Anyway, I've modded my Korg SAS-20 for external triggering of each drum sound - a recent video is on my Youtube channel: https://youtu.be/rHqMvMqj6U8
I'm sure the same approach is possible with the casiotones.
Hello and thank you for a great article on the ct310!
ReplyDeleteI have a question concerning the clock souĊce signal to be utilised on the ct310 ext sync mod.
Can I use the 'trigger out' signal from my roland tr606 as sync signal?
Eric from Norway
Hi Eric. Thanks for kind words.
DeleteI'm almost certain the TR606 trigger out would work. I've used triggers from old Boss drum machines and I believe it's more or less identical in terms of signal voltage levels (5v) and duration. However, the tempo will not match - you'll need a way to multiply the TR606 signal otherwise the Casio will be super slow. I now use one of these: https://www.audiowerkstatt.de/en/trigger2midi2trigger-v2
It incorporates a clock multiplier that can be used for analog signals independently of its MIDI conversion functions. It's more reliable than the arduino clock multiplier I was using at first.
I forget how many times I need to multiply the external signal for the Casio to run at the same tempo as the source, but it needs a considerably faster clock rate.
Are you thinking of using the LT or HT trigger out? or the DinSync out? I know the DinSync is 24 ppnq and you may need to multiply that by 4 for the Casio to tempo match.
Anyway, if you have any questions, I can try to help.
Hi, and thanks for the reply. By the way, I totally love Cuckoo Bollox. I'll play it next time I'm drunk with good friends.
DeleteHooking my ct310 to the din of my tr606 would be great. I'll message you as soon as I`ve acquired the multiplier. Again, thanks. Eric