yamaha kx 88 with midibox kb

[Hermes]

Hi

its been a while since i last posted here...i have an old kx88 MIDI controller 88note kbd. While the feel of the keys is better than anything else

[TK.]

Hi,

do you have a schematic for this keyboard?

Best Regards, Thorsten.

[Hermes]

Hi,

do you have a schematic for this keyboard?

Best Regards, Thorsten.

Hi Thorsten and i feel good to be back in the forum again!! Sorry for the unfinished first post ... I accidentally hit the post button and then i did not have time to edit, because an emergency came up... :)

I do have the service manual for the keyboard and I could pm it to you if required, but I think that there is no schemnatic for the KX88 keybed... nevertheless here is the short story of what I would like to do...

THe KX 88 is an old MIDI controller 88note kbd (no sounds) which has been praised by many many users as maybe the best feeling piano action keyborad ever manufactured. While the feel of the keys isindeed better than anything else i ve tried regarding piano action, the velocity range of the kx88 is only 15-127 (measured in midi ox and other monitors). No matter how lightly you press a key, the lower vel value is laways 15. Stangely, in the midi specs chart of the kx88 manual it is stated that the velocity range is 0-127! I have tested all keys and itsthe same with all of them, so I think this is not a mechanical issue, but more like a software limitation (0other users experience same issues). I really wanted to achieve the missing 1-14 vel values, so I saw 3 possible options 1) contact yamaha to solve the problem, with a EPROM update,2) alter the firmware myslf, 3) remidify the kbd myslf. 1) Contacting Yamaha did not solve anything, as the kx88 is old (1984) and no one there seemed to know what it was (!!!), 2) is not really an option as my programming skills aRE super primitive plus i do not think there is a source code availabe (THough I could copy the ROM, as I have a chip programmer, I can read the ROM in midiox :)). So this leaves option 3 using your platform for the midibox KB.

The thing is, to my understanding , the KX88 does not use the make-break switch approach, as it does not have rubber switches, but it uses all metal switches DX7 style like shown here http://www.syntaur.com/images/3120-Lg.jpg, so i do not know if these switches work in the same way like make break ones.... In these switches there are two metal stops and a middle metal spring that initially is in contact with the upper metal stop. When a key is pressed it touches the middle spring which then travels a short distancfe and gets in contact with the lower stop (I hope i make sense). i believe that the velocity is measured by the time it takes the middle spring to trael from upper stop to lower stop, so in this case only one switch is pressed?.

So is the midification possible, and will i be able to achieve 0-127 vel values?

I ll try to find a schematic for the keybd and i can send you a pdf of the service manual , if you wish.

Thank you in advance

[Hawkeye]

Hi,

couldn´t you just scale 15-127 to 0-127 with an in-between LPC1769? I doubt you would hear the difference and it might save some work instead of doing a full remidification :)

Many greets,

Peter

[TK.]

Yes, under these circumstances I also recommend you to convert the MIDI notes instead of replacing the (perfectly working) keyboard scan hardware!

The converter could either be MBHP_CORE or MBHP_CORE_LPC17 based, it doesn't really matter - actually even the PIC is too powerful just for this conversion job ;-)

Best Regards, Thorsten.