Goblin – MIDI Mod

There are two variants, depending on the effects device to be modified

• Goblin-SPST: For effects devices with up to five SPST- or, tap tempo switches, connections for external switches, expression inputs and potentiometers of digital pedals.
• Goblin-3PDT: For effect devices that have one or more 3PDT switches and optionally an additional SPST switch or external switch connection.

Goblin-SPST

The Goblin-SPST in its new 2.0 version is the most powerful and versatile MIDI modification for effects devices. It inherites the functions from the first version, like bypass, MIDI synced tap tempo and control over external switch connections. But it comes with a brand new and unique Control Voltage function, that gives the Goblin-SPST-2.0 the ability to control expression inputs and even potentiometers of digital pedals. It’s also the first Goblin that brings user presets to the table.

Bypass/Tap Tempo Switches

The SPST variant uses existing SPST soft switches and their control electronics (which can be e.g. a microcontroller and relay) and takes over the control, triggered by the foot switch, or MIDI. It does not matter whether the switches are independent of one another or what function they perform.

The original switches are retained during installation. The Goblin is wired between the switches and the effects device. Effects devices with SPST switches and relay switching often do not remember the switching status after powering down (e.g. Earthquaker Devices). The Goblin also fixes this problem and remembers the switching status after turning off.

External Switch Connections

Following the example of the Garbage Collector the Goblin can control external switch connections (e.g. Strymon Favorite Switch, external Tap Tempo etc.) like below. The Goblin can control two lines of an external switch connection at each port. These lines then can be switched, pulsed and also synchronized with MIDI clock, or used like before from the outside.

Expression/CV

The Goblin-SPST-2.0 has some new and exciting features. It can take control of an expression port using one of its four CV (Control Voltage) ports. But how does that work? Expression inputs are just control voltage inputs with an external potentiometer. The effects device provides a voltage which is divided down by the potentiometer inside the expression pedal and therefore works as an voltage divider.

The Goblin-SPST-2.0 provides the control voltage directly, rather than using a üotentiometer. There is a connection for a reference voltage, to handle expression ports that doesn’t use 5V as reference.

Similar to the wiring of external switch connections, the signals are tapped at the socket. The Goblin-SPST works with nearly all expression inputs, but is limited to +5V, which is the unofficial standard for expression inputs.

Potentiometers of Digital Effects Devices

This is the real game changer, though. The Goblin-SPST-2.0 can use its CV ports together with an ADC (Analog/Digital Converter) to make a potentiometer not only controllable with MIDI, but it retains its original function.

Here’s how it works. Digital effects devices use potentiometers to set parameters. But unlike analog effects they don’use the potentiometers to manipulate the audio signal directly, they use it to generate a control voltage. This control voltage is then read by the ADC of the DSP or micrcontroller and is used to set various parameters, like volume or delay time. It’s the same principle as an expression port, but the potentiometer isn’t connected from the outside, it’s integrated.

So, the wiring of these potentiometers is always the same. One leg goes to a reference voltage and one to GND. The middle leg, or wiper, then gives a control voltage depending on the position of the potentiometer. The Goblin is now put between the wiper of the potentiometer and the control voltage connection of the effects device. The Goblin either reads the control voltage at the wiper and forwards it to the effects device, or sets the control voltage depending on MIDI commands.

User Presets

The Goblin-SPST-2.0 is able to easily save all parameters of the Goblin to a non-volatile memory. Just send the according MIDI command to get into presets save mode, set up the pedal how you like it and send a PC command. The current configuration is saved to that PC command.

Goblin-3PDT

The 3PDT variant of the Goblin has up to two relays as a replacement for true bypass 3PDT switches. In addition, either a tap-tempo switch or an external switch input can be controlled.

During installation, the original 3PDT switches are removed and replaced with SPST soft switches. The socket for external effects can still be used normally, or it can be switched from inside via MIDI.

The Goblin-3PDT is either available as dual or as single relay version. The single relay version can control an additional external switch or SPST switch like the Goblin-SPST and is used for the Electro Harmonix POG2 MIDI mod.

A special feature of the Goblin-3PDT is that its cable connections are laid out in a 2.54mm grid. This way, neat wiring with flat ribbon cables is possible. It is also possible to attach the Goblin-3PDT to other electronics using pin header connectors. That way effects device manufacturers in small series can easily integrate relay bypass and MIDI into their effects.

Installation

Screws

Using two screw holes with screws and spacers available separately in the shop, the Goblin can be mounted on the base plate. With an installation height of only around 15 mm sometimes the Goblin fits under the switch.

Switches

Additional SPST switches are required for the Goblin-3PDT. These have to be Normally Open and can of course also be ordered in the shop.

Mounting Brackets

There are 3D printed mounting brackets available. At the moment there is a mounting bracket for the Goblin-SPST that fits Electro Harmonix pedals like the Pitch Fork. There is also a mounting bracket specifically made for the Universal Audio Astra, Starlight and Golden MIDI mod. Finally there is a mounting bracket for the EHX POG2 MIDI mod. The Goblin is attached with screws and the bracket is attached to the enclosure with the foot switches. No need for drilling. The mounting brackets are included in the bundles.

Special Versions for Popular Pedals

There are pre-configured Goblins available for purchase for some popular pedals. It brings MIDI to Universal Audio pedals and the EHX POG2 and Pitch Fork. They all have special software and come with mounting brackets. For all of these are particular installation guides available.

Universal Audio Starlight MIDI Mod, Astra MIDI mod and Golden MIDI mod are only supported with a special software, so make sure to order the right one. Universal Audio Lion MIDI mod, Ruby MIDI mod, Woodrow MIDI mod and Dream MIDI mod are possible with a standard Goblin-SPST. Bypass and preset is supported.

Media

Instructions

If you have trouble with the installation, there is an addition to the installation manual that explains in depth the roles, measurements and the configuration.