Korg PA4X without aftertouch

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mattf
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Korg PA4X without aftertouch

Post by mattf » Fri Sep 04, 2020 7:48 am

I recently bought an used pa4x and it's my first Korg keyboard and my first with aftertouch. Problem is, I am unable to hear the after touch doing anything.

I factory restarted it and upgrade to 3.1, the factory reset again and choose the big band brass 1 as in one of the demo videos on YouTube, but applying more pressure to the keys after they are playing does not have the same effect as the joystick up(modulation) or any effect at all.

The after touch is not off under global settings, I tried different modes there as well and none seem to do nothing (different curves). It is enabled under sound eddit -> keyboard assembly as well! The keys don't seem broken at all, the keyboard was "new".

I dissembled it today and tested the ends of the cable of the aftertouch strip and it is there, clean and working. The resistance varies when I apply pressure over the keys.

I started printing the midi events send by the keyboard on my pc and I noticed something suspicious. The control 11 (0xB in hexadecimal) keeps sending the value 127. I didn't find nothing that triggers that controller. 1 and 2 were the y+ and y-, 7 was the channel volume and 16 the ribbon controller. What is 11? Is it the aftertouch? I didn't find a korg midi implementation/specification that showed what controller the after touch is supposed to take. Can anyone share this info?

Another hypothesis is that this is somehow disabled in some hidden menu. Does this keyboard have that secret maintenance mod triggered by holding some keys while powering up? Like the mz x500 has with power up + intro + tone (or something like that, now I forgot ).

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Re: Korg PA4X without aftertouch

Post by Ashe37 » Fri Sep 04, 2020 10:09 am

does it have an aftertouch calibration routine?

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Tidda
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Re: Korg PA4X without aftertouch

Post by Tidda » Fri Sep 04, 2020 8:43 pm

CC#11 is expression (volume) usually controlled by a pedal. Not sure why it keeps sending a value, it should only change when the pedal is moved. That is when the pedal is assigned to CC#11 of course. Anyway, nothing to do with aftertouch.

Aftertouch is not one of the CC#, it is a channel voice message of it's own.
It is 0xD0 (for MIDI channel 1, 0xD1 for channel 2, etc.) followed by a value between 0 and 127.

See also https://www.midi.org/specifications-old ... di-message

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Re: Korg PA4X without aftertouch

Post by mattf » Sun Sep 06, 2020 2:38 am

I did calibrate it already many times. I got it working badly now. The resistance on both ends of the strip seems to vary from infinity to 130 ohms when pressure is applied but I will have to test it again more properly to be sure. When calibrating it seems to want the triggering pressure to be applied over a key, but if I simply don't apply any pressure it still requires some high pressure to trigger the effect.

On the calibration screen it shows a value varying from about 300 up to 500 when maximum pressure is reached. Those values are different for different weights I tried.

The way I got it now by watching the midi messages the after touch varies from 0-20 (when it should be 0-127), the strip's fault for being worn out I think. The keyboard has an option of changing the aftertouch curve which causes this range to change to 80-100, 50-90.... And other ranges that don't start from 0 which is bad since it doesn't reset the aftertouch once it is applied the first time. I made a test shorting the connector of the AT strip on the PCB it attaches to and I got the value 0 for aftertouch message.

These strips aren't sold separately, only the keybed which is too expensive. By the way I found this: https://www.aliexpress.com/item/33031549373.html. I am thinking on using two of these as parallel resistors. Do you guys think it would work?

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