Percussion on "A" drawbar set

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Registriert: 5. Mai 2017, 11:02

Re: Percussion on "A" drawbar set

Beitragvon Drawbi » 3. Jun 2017, 13:17

Hello Michael,

yes, I think the HX3 can support four sets of drawbars.
not via midi.

Have a look on the MAG-Organs website:
I think this baby has a HX3 engine build in and has four sets of drawbars.

At the Keyboardpartner Github respository you will find the schematic for the drawbar sets: ... ematic.pdf

I think (I think means = I do not know) the technology behind it is working this way: There are two sets of drawbars and an A/B switch where you can choose which set of drawbar is active. This A/B switch sends also an information to the HX3 sound engine to cancel the percussion depending on the selected drawbar set. There are three CD4053 ICs. They switch between the two sets of drawbars. These two sets of drawbars control the volume of the different footages by a control voltage on the slider. This control voltage is switched by the CD4053. When you switch from A to B the HX3 Sound Engine is told "Enable the percussion and adjust the footage to the new volume levels!"

Midi controlling works a little bit different: When you start the HX3 Remote application and choose the "Midi Custom CC" tab, you can see the controllers and the assigned controller numbers. There is only one set of drawbars for each manual. Each footage has one controller number assigned. Midi controllers do not send permanent information. The Information is only sent, when you activate the controller by pressing a button or sliding a slider. The informtion flows only in one direction; from the controller to the HX3 expander. You can not manage two sets of drawbars with one controller. The problem is: When you set drawbar set A to 888888888 and set B to 111111111 the silders on your midi controller keep in the "111111111" position when you switch back to set A. If you move a slider from "1" to "2" position the will send the information of position "2". The setting aof drawbar set A was "888888888", so the value of this slider will jump from 8 to 2 and not to 7...

There are two ways to solve this problem: Keyboardpartner updates his software / firmware and implements a second sets of drawbars in the CC map where you can assign different CC numbers. Two switches with different CC controller numbers to switch between the drawbar sets A and B for UM and LM are also needed. The second way is to build a midi controller that will do the same job the Kexboardpartner hardware does: To send all values of all necessary controllers when you switch between the two drawbar sets.

I started building a controller which is working that way, but it will take some time for me to finish this project.

Yeah, HX3 is a great sounding Hammond clone and the idea behind it is brilliant, the developer a genius! But VIA MIDI is is not playable like a Hammond at all (at the moment). I'm also a little bit disappointed about that. A Midi Implementation Chart in the User Manual is missing, so I did not know that fact before buying the Expander.

Perhaps this feature will be integrated during the next updates... Hope so. Or I will sell it and keep my VB3.
13 Heimorgeln, 1 Sakralorgel und diverse andere Kleinteile

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Registriert: 19. Jan 2015, 13:18

Re: Percussion on "A" drawbar set

Beitragvon PortlandMike » 3. Jun 2017, 13:55

Thanks, Drawbi! I was starting to come to the same conclusion – that the expander won't work that way. I also realized that the custom MIDI CC only accepts CC's on channel 1, as far as I can tell, so I can't use it with the Keyb Legend Live. I might consider selling both and buying a Mag organ... we'll see. I seem only to learn after making expensive mistakes!

Edit: I am going to to see if I can use MIDI processing/ perhaps the Midi Solutions Event Processor Plus to achieve the desired effect (maybe having the A# preset and other presets besides B also send a "program change" message, to remove it from the "live" setting... hopefully the timing will work so that the drawbar information also affects that same "common preset" that the program change brings up. If not, perhaps I can orchestrate a delay, or have it resend the drawbar information.

Beiträge: 18
Registriert: 5. Mai 2017, 11:02

Re: Percussion on "A" drawbar set

Beitragvon Drawbi » 17. Jul 2017, 10:53

Hello Michael,

it is possible to play a HX3 expander like a "real B3" via MIDI, but you have to build a special controller. Here is my result; the B3-Controller-Cheap-Trick-Prototype:

You need:
Four sets of drawbars (from my box of odds and sods)
Doepfer USB64 (I had to buy this...)
A few switches for vibrato and percussion
A 6 position rotary switch for vibrato setting
Two 2-poles switches (for A/B drawbar switching and cancelling percussion)
Some ICs with analog switches (I use CD4066)
Cables and resistors
A custom MIDI-CC set


The Doepfer USB will generate the controller messages depending on the setting of the drawbars and different switches. I use controller number 72 and up. Avoid using CC#7 and CC#11 (see HX3 Expander manual). The inputs of the Doepfer USB64 are connected to the different switches and drawbars.

The vibrato setting is realized by a six position rotary switch with 6 different resistors and a ground resistor (adjustable voltage divider) to obtain different output voltages. The controller in the CC set is set to "Vibrato Knob".


To switch between the drawbar sets A and B I use some CMOS analog switches (4066). The are cheap and work well. The outputs of two switches are connected together. Input of switch "A" is e.g. connected to drawbar 16' from set A and the input of switch "B" is connected to drawbar 16' from set B. The 2-poles switch is connected to the control lines of these two groups of switches for set A and B. The control line of drawbar set B is pulled up by a 10k resistor and the switch will ground this line when switched to set A. The other way around the control line of set A is pulled down by a 10k resistor and the 2-poles switch will pull it up to 5 Volts when switched to set A. The output voltage of these CMOS analog switches will change every time when set A or B is choosen and the controller will send the corresponding midi control messages. The 2-poles switch will also disconnect the 5 Volts line to the percussion switch when set A is active; so percussion is disabled in this case.

Preset switching can by done by my organ, a doepfer CTM64 or by using multiplexer ICs instead of the CD4066 and a hard wired resistor matrix (a little bit like the original thing ;-))

13 Heimorgeln, 1 Sakralorgel und diverse andere Kleinteile

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