TUBBUTEC TRS Bridge 4×4 TRS Midi Router User Guide
- June 13, 2024
- Tubbutec
Table of Contents
TRS Bridge
User Guide
Features
- 4x TRS MIDI inputs, 4x TRS MIDI outputs
- Can route, split and merge MIDI streams
- Independent MIDI flow settings for notes/CC (red), clock (blue) and sysex (yellow)
- Easy to use user interface, quickly change routes, color coded routes and events.
- MIDI event monitor with color coding for various message types
- Save and recall up to 8 routing settings
- Automatically accepts both TRS A and TRS B at the inputs
- Outputs individually selectable between TRS A and TRS B
- Convert between TRS A and TRS B
- Save detach: Will send note off messages if a connection is detached
- Auto-restarter Will send re-sync new clock connections automatically
- Sysex Buffer: Buffers Sysex messages if necessary in order to merge them
- Adjustable LED brightness
- Full galvanic separation of inputs – no ground loops.
Introduction
TRS Bridge is a midi router, merger and splitter with four TRS-style inputs
and four TRS outputs.
MIDI messages received at the inputs can be forwarded to one or multiple MIDI
outputs.
Similarly each of the outputs can receive MIDI messages from one or multiple
inputs.
TRS Bridge can set these routes in a simple modes for all types of MIDI
messages, but it is also possible to route different kinds of messages
differently:
Note and controller data
These are all the midi messages that can be merged without any issues. If two
devices send midi at the same time, data will be interleaved and sent to the
receiving device.
Clock Data
Clock data can not be merged, only one midi clock stream can be used at a
time. When changing the routing, TRS Bridge makes sure that each output only
receives clock from a single input.
Sysex data
Sysex data is even trickier to handle than clock data, because sysex messages
can have an arbitrary length. if multiple sysex streams are received
simultaneously, USB bridge A buffers the data and will forward it to the
receiver as soon as possible. This way sysex messages are merged as well.
User interface
TRS-Bridge features four MIDI inputs at the top, and four MIDI outputs at the bottom. Each of the channels has a multicolor LED and a button associated with them. In this manual we will use terminology such as “input 4 LED” or “output 2 button”.
Color coding
TRS-Bridge uses color coding to show different kinds of MIDI messages, being
able to see colors is however not nessesary to use TRS-Bridge.
Note/CC: Notes, MIDI CC, Pitch Bend, as well as other kinds of MIDI messages
that do not fall in the following categories are shown in RED.
Clock: MIDI Clock, Start, Stop, Continue and ‘transport’ messages are shown in
BLUE.
Sysex: Sysex Messages are shown in YELLOW.
If multiple kinds of messages are displayed, the colors are mixed in a mostly
additive
manner:
Notes + Clock (RED + BLUE) = PURPLE
Notes + Sysex (RED + YELLOW) = ORANGE
Clock + Sysex (BLUE + YELLOW) = GREEN
Notes + Clock + Sysex = WHITE
Status page
After turning on TRS-Bridge, it starts up with the status page. The status
page shows the activity of the MIDI inputs and outputs. If there is no
activity, the LEDs glow dimmly.
Activity on the inputs and outputs is indicated according to the color coding
mentioned above.
An example:
If a note or MIDI CC message is received, the respective input will light up
in red. Outputs that send this message will light up simultaneously. The same
is true for clock and sysex messages.
A special case are clock signals. Additionally to the activity, the clock LEDs
are also pulsing with the clock tempo and indicating a quarter-note downbeat.
An example of a status page:
Input 1 receives note or CC messages
Input 3 receives clock messages
Output 2 sends clock and note messages
Output 3 sends clock messages
Output 4 sends note messages|
---|---
Simple routing
There are two ways to connect inputs and outputs.
- • Input side of view: Connect an input to one or multiple outputs
- Output side of view: Connect an output to one or multiple inputs
Both methods can result in the same routing and both methods are supported by
TRSBridge
The Simple routing method can be used to quickly connect inputs and outputs
without having to think about the various kinds of MIDI messages.
Connect an input to outputs
From the status page press one of the input buttons.
The input will blink in white.
The output LEDs show the connections between this input and the outputs.
Press the output buttons to turn connections between the selected input and
this output on or off.
You can also select a different input by pressing another input button.
To exit the simple routing page and go back to the status page, press the
selected (blinking) input again.
Connect an output to inputs
From the status page press one of the output buttons.
The selected output will blink in white.
The input LEDs show the connections between this output and the inputs.
Press the input buttons to turn connections between the selected input and
this output on or off. Note: Since only only one clock can be received by an
output, TRS-bridge will automatically remove previous clock routings when a
new connection is made. You will see previously white connections (All message
types routed) turn orange (Only Note and Sysex messages routed).
You can also select a different output by pressing another output button.
To exit the simple routing page and go back to the status page, press the
active (blinking) output again.
Simple routing, input side of view.
Input 1 is selected and blinking
Outputs 1 and 2 are connected to input 1| 
| Simple routing,
output side of view.
Output 3 is selected and blinking
inputs 1, 3 and 4 are connected to output 3
However, only the clock from intput 1 is routed to output 3.
From inputs 3 and 4 clock is not received| 
---|---|---|---
Advanced routing
With advanced routing you can route the various message types (Notes/CC, Clock
and Sysex) independently.
Routing notes / CC
From the status page press inputs 1 & 2 simultaneously. Inputs 1 & 2 will
blink in red indicating that you can now select channels for Note routing.
You can select either an input channel or an output channel and continue
routing the same way as in Simple Routing.
Routing clock
From the status page press inputs 2 & 3 simultaneously. Inputs 2 & 3 will
blink in blue indicating that you can now select channels for Clock routing.
You can select either an input channel or an output channel and continue
routing the same way as in Simple Routing. You will notice that only one input
can be selected for each output.
Routing sysex
From the status page press inputs 3 & 4 simultaneously. Inputs 3 & 4 will
blink in yellow indicating that you can now select channels for Sysex routing.
You can select either an input channel or an output channel and continue
routing the same way as in Simple Routing.
An example of Note Routing
After pressing inputs 1 & 2, note routing mode is selected.
This is indicated by inputs 1 & 2 blinking in red.| 
| After selecting an input,
Note routing mode is active
input 1 is connected to outputs 1 & 2| 
---|---|---|---
TRS A/B select
There are two kinds of MIDI TRS pinouts: TRS A and B.
TRS Bridge automatically accepts both types at the inputs. The outputs can be
individually switched between Type A and Type B. This means TRS Bridge can
also be used to convert one type into another and works well to connect gear
of any type.
To change the TRS type of an output, press output buttons 3 & 4
simultaneously.
The four outputs will light up in either red or blue:
- Red: Output is TRS type A
- Blue: output is TRS type B
To change the TRS type of an output press its button.
To exit the TRS type menu, press output buttons 3 & 4 simultaneously again.
The TRS type setting is saved and will be available after power down.
Outputs 1,2 and 4 are configured as TRS-A,
Output 3 is configured as TRS-B| 
---|---
Change LED brightness
To change the LED brightness, press output buttons 1 & 3 simultaneously.
Output buttons 1 & 3 will blink in yellow indicating the LED brightness menu.
Press any of the 8 buttons to change the LED brightness in 8 steps.
When finished, press output buttons 1 & 3 again.
The LED bridghness setting is saved and will be available after power down.
Save and load routings
Up to 8 different routings can be saved and recalled.
After changing routes, you need to save manually if you want the settings to
be preserved.
When powering up TRS Bridge, the last saved or loaded configuration will be
loaded.
Save routings
To save the current routing setting, press output buttons 1 & 2
simultaneously.
Outputs 1 & 2 will light up in white indicating that routing settings can now
be saved. Press any of the 8 buttons to save the current routing in one of 8
slots.
TRS Bridge will automatically return to the Status Page after saving.
To cancel saving, press buttons 1 & 2 simultaneously again.
Load routings
To load one of the 8 saved routings, press output buttons 2 & 3
simultaneously.
Outputs 1 & 2 will light up in white indicating that routing settings can now
be loaded.
Press any of the 8 buttons to load a previously saved setting from this slot.
TRS Bridge will automatically return to the Status Page after loading.
To cancel loading, press buttons 2 & 3 simultaneously again.
Save detach
Normally, deactivating a connection to an output might result in hanging
notes, as no NoteOff midi signals are sent anymore.
TRS bridge memorizes which notes are sent to an output. When disconnecting an
output in the router, TRS-Bridge sends Note-Off messages for all currently
active notes.
As a result the problem with hanging notes is elliminated.
Auto restarter
Establishing a new clock connection while your incoming MIDI clock is already
running will normally result in an out of phase clock. This is because the
receiving MIDI device did not receive a Midi-Start message. Or maybe it did
receive a Start message at an earlier time, but the clock is now out of sync.
To mitigate this, TRS-Bridge automatically detects such a situation and re-
syncs the output clock:
When a new clock connection is made, TRS-Bridge waits until the end of the
current bar, then sends a Midi-Stop and Midi-Start message to restart the MIDI
device. Clock routing then continues normally.
While waiting for the current bar to finish, no clock messages are sent. This
is to make sure the clock is always in sync and avoids issues with multiple
clock domains.
Galvanic input separation
MIDI works with a current loop and without a ground connection between
devices.
This avoids issues with ground loops for example.
MIDI devices therefore do not have ground connected on the input connectors.
This is often problematic with TRS jacks, due to their sleeve being connected
to the (conducting) front panel. This would result in a ground connection
between multiple MIDI devices.
TRS-Bridge uses custom insulators to make sure there is no ground connection
and to achieve full galvanic separation between the inputs.
Firmware updates
Firmware can be updated via midi sysex
For the newest firmware follow the link on https://tubbutec.de/trs-
bridge/
Specifications
3U Eurorack format
6HP wide
25mm total height, Depth behind panel: 21mm (including power connector)
Weight: 63g
Latency:
- End of received message to start of output message: 30µS
- Clock latency edge to edge 250µS (220µS clock message length + 30µS latency)
Electrical:
- Galvanically isolated MIDI inputs
- 5V midi outputs
- Supply: 12V
- Current draw: 50mA – 150mA (depending on LED brightness)
Tubbutec GmbH
https://tubbutec.de
This work is licensed under a Creative Commons
Attribution-NonCommercial 4.0
International License.
Documents / Resources
|
TUBBUTEC TRS Bridge 4×4 TRS Midi
Router
[pdf] User Guide
TRS Bridge 4 4 TRS Midi Router, 4 4 TRS Midi Router, Midi Router, Router
---|---