Voxa Harmonia · ModSystem
Building an organ console, converting an existing manual or looking for electronics for your stop controls? ModSystem brings together controller and connection boards designed for specific tasks. Explore the options for key sensing, stop inputs, expression pedals and LED feedback, then visit Voxa Harmonia to discuss the modules your project needs.
Digital Hall switches, reed contacts and analogue Hall sensors produce different signals. Choosing a manual board starts with the keyboard mechanism and the function you need. This makes sensor requirements and wiring arrangements explicit before the console electronics are assembled.
Reading a stop switch and driving its indicator are related tasks with different electrical requirements. The range includes an integrated stop and LED board as well as a separate USB-MIDI LED controller. Select the approach according to the layout, channel count and feedback behaviour required.
The central controller, input boards and matrix connection boards have distinct roles. Document the manuals, pedalboard, stop banks and power supplies in one plan. That provides a useful basis for selecting components, checking connections and discussing a project quotation.
01 / MODSYSTEM
Ten modules cover central control, key sensing, stop inputs and matrix connections. Compare their technical descriptions to identify the functions your project needs. Manual 64 Velocity is a variant still in development.
10 / 10 Modules shown
Central control
The central ModSystem controller built around a Raspberry Pi Pico. It connects manuals, a pedalboard and the stop module, with separate driver-bus connections.
LED control
A dedicated USB-MIDI controller for daisy-chained LED Driver 64 boards. It converts computer MIDI messages into LED-driver control signals.
Please note LED power is supplied separately through the driver boards’ 5 V power connectors.
LED driving
A driver board for 64 individual LED channels, using four TLC5925 constant-current ICs. BUS_IN and CHAIN_OUT allow daisy-chaining to further boards.
Keyboard – digital Hall
A manual board for 64 individual digital Hall sensors. Magnetic key sensing provides contactless on/off states to the central controller.
Please note External Hall switches are placed at the keys. This version senses on/off states.
Keyboard – switch matrix
A manual board that reads an 8×8 switch matrix for reed-switch or other suitable contact keyboards. The matrix accepts 64 switching points.
Keyboard – analogue Hall
A board sampling 64 analogue Hall inputs to track key movement. Central-controller firmware can derive key velocity from the 12-bit ADC’s raw samples.
Please note Velocity operation requires calibration and suitable controller firmware. Firmware implementation and physical prototype measurements are still in development.
Stops and expression
A module for stop switches and four analogue expression controls. It forwards switch-matrix and pedal signals to the central controller.
Stops, LEDs and expression
A board combining three 8×8 stop banks, LED feedback and four expression inputs. A single module handles switch scanning and illuminated stop indication.
Please note The 5 V LED supply and the 3.3 V logic bus use separate power networks.
LED-matrix connections
An 8×8 row–column connection board for an LED matrix. IDC connectors provide organised wiring for 64 matrix positions.
Switch matrix
A Col-to-Row matrix board organising 64 switching points. Individual 1N4148W diodes provide isolation within the switch network.
02 / Selection guide
Start with what the console must do and how it is built. These four areas help you list the signals involved and identify relevant modules. Before settling on an assembly, review its connections, power requirements and firmware functions together.
For contactless on/off key sensing, consider the digital Hall inputs of Manual 64 Hall. Manual 64 Reed scans an 8×8 switch matrix for reed contacts or other suitable keyboard contacts. Manual 64 Velocity is intended to sample analogue Hall sensors and track key movement; velocity firmware implementation and physical prototype measurements remain in development. Treat this variant as a development option. Alongside the number of keys, record the sensor type, its position and the available wiring space.
Stop Expression 128 is a starting point when you need stop-switch inputs and analogue pedal inputs. If the same assembly also needs illuminated stop feedback, Stop LED Expression 192 combines three 8×8 stop banks with LED-matrix drivers. Both modules provide four analogue expression inputs. When choosing between them, describe the stop-bank layout, pedal electrical characteristics and intended indication as well as the number of switches. This helps establish the actual input and feedback requirements.
For a separate LED control path, Control Module LED converts USB-MIDI messages into control signals for LED Driver 64. Each driver handles 64 individual LED channels; up to 3–4 modules can be daisy-chained to build a 192–256-channel LED system, with firmware configured for the module count. The LEDs need a separate 5 V supply. For a row-and-column LED arrangement, the 8×8 Scan Matrix LED connection board may be relevant alongside a suitable external matrix driver. Individual LED channels and an LED matrix require different wiring arrangements.
Control Module Driver is the central connection point for manuals, the pedalboard and the stop module. It provides five manual ports, one pedalboard port and dedicated module connections. The diode version of 8×8 Scan Matrix organises 64 switch positions with individual isolation diodes and requires a suitable matrix input. For a complete console, map the signal paths and module connections first, then discuss the power supplies and desired MIDI mapping. Connector size alone does not establish electrical compatibility.
03 / MODSYSTEM
Keys, stop switches and expression pedals reach the central controller through their corresponding input modules. LED feedback has a separate driver path. This is a functional overview; wiring and power distribution must be planned for the selected modules.
System overview diagrams. Confirm the exact wiring and power requirements for your selected modules before installation.
04 / Questions
An organ console brings several types of signal together: the switching states of keys and stops, analogue pedal positions and visual feedback from the computer. Each calls for a different input or driver. ModSystem helps you choose electronics by function, whether you are planning a DIY MIDI organ or an electronic conversion of an existing console. The sensors, wiring and controller firmware need to be considered together. A clear description of those connections is more useful than choosing a board by its channel count alone.
List the number of keys in each manual and pedalboard, the sensor types, stop switches, expression pedals and LEDs. That establishes which input and driver functions you need. Prepare the intended MIDI mapping for your virtual organ software too, so the hardware and software requirements can be discussed together.
Manual 64 Hall accepts on/off signals from individual digital Hall sensors. Manual 64 Reed reads switch positions arranged in an 8×8 matrix. Choose according to the sensors already fitted or planned for the keyboard. Their signal wiring and input arrangements differ, so they should not be treated as interchangeable connections.
The digital Hall version senses on/off states. The analogue Hall-based Manual 64 Velocity is intended to sample key movement. Velocity operation needs suitable controller firmware and calibration; firmware implementation and physical prototype measurements are still in development. It should therefore not be specified as a finished velocity solution.
Discuss the exact organ software and controller firmware versions during planning, along with MIDI message types, channel assignments and stop-feedback mapping. Those details are needed to assess the proposed configuration. This overview does not establish general compatibility or compatibility with every software version.
Document the existing key sensors, switches and wiring first. The relevant connections can then be assessed against the module requirements. A description of the console, connector information and photographs will help. The relationship between mechanical components, sensors and electronics needs to be reviewed for the individual project.
Stop LED Expression 192 combines stop-switch scanning, LED-matrix driving and four expression inputs. For a separate LED system, consider Control Module LED with LED Driver 64. Select the arrangement according to the physical layout and number of indicators, and agree how the software should return feedback.
Use the contact option on the Voxa Harmonia main website to describe your project and the modules you are considering. The required configuration, functions still in development and ordering terms can be clarified directly. The checklist below helps prepare an enquiry even if you do not yet have a complete circuit or wiring plan.
The organ components presented here are electronic boards: central controllers, manual input boards for key sensors, stop and expression modules, LED drivers and matrix connection boards. Discuss the keyboard, sensors, mechanical parts and power supply separately when planning the build. Selecting a module does not by itself constitute an order for a complete, ready-to-install console.
05 / VOXA HARMONIA
You do not need a finished circuit diagram to start an enquiry. A clear project description helps identify the components you already have and the functions that still need electronics. Contact Voxa Harmonia through the main website to discuss your requirements.
Quotations and order arrangements are handled on the Voxa Harmonia website.
