Microdesignum MIDI Agente Relay Loop 4L2R1D

The Microdesignum MIDI Agente Relay Loop 4L2R1D is a MIDI-controlled looper and amp channel switcher in an aluminum box: it switches four mono effect loops and two amplifier channels, and it is driven entirely by MIDI from a foot controller rather than by its own footswitches¹². It belongs to the wider MIDI Agente Relay Loop family, which Microdesignum describes as a programmable switcher of guitar effects and channels on a guitar amp, responding to incoming Program Change, Control Change or Note On messages³.

For a player, the point of a unit like this is that one MIDI program change from a controller can bring a whole pedalboard state and an amp channel change alive at once: loops 1 to 4 engage or bypass effects, and Switch A and Switch B replace the amp's own footswitch. The signal path is mono, the unit has one display, and it is currently listed by the maker as temporarily unavailable².

Four loops in two sections, or one serial chain

The looper contains two sections, I and II, each with two loops, and the two sections can work fully independently in parallel¹. Each loop has a Send and Ret pair (Send 1/Ret 1 through Send 4/Ret 4) wired with mono 6.3 mm Jack patch cables¹. When a loop is on, its front-panel LED lights, the signal goes out of Send, returns through Ret and continues; when it is off, the LED is dark, the effect is bypassed, and the signal passes straight to the next loop or the output¹⁵.

The jacks between the sections decide the routing:

Leave Out 2 and In 3 unconnected and the two sections join into one section of four loops, giving the classic serial connection of four effects¹⁶. Use them and you can split the board, for example running loops 1 and 2 into one destination and loops 3 and 4 into another.

Amp channel switching with Switch A and Switch B

Switch A and Switch B replace the amplifier's footswitches and let MIDI automate channel switching¹. They are connected to relays and are galvanically isolated from each other and from the whole device: they generate no signal of their own, they only close two wires, exactly like ordinary footswitches¹⁶. You wire them with mono 6.3 mm Jack cables into the amp's channel switching connectors, such as Clean/Lead or Volume 1/Volume 2¹. The relay switch connectors are TRS².

Amp compatibility is worth checking before you buy:

• Some amps use one mono connector per switching function¹⁶.
• Some, such as Engl, combine functions in stereo connectors with one common wire¹⁶.
• Mesa Boogie strictly requires galvanic isolation of all control switches, which the isolated relays here provide¹⁶.
• Some Laney amplifiers use a special five-pin connector that is unrelated to MIDI¹⁶.

The related MIDI Agente Relay Plus takes the same idea further, with relays usable for amp channels and a note that amps with pair channel switching on TRS jacks need an appropriate Y-cable⁷.

Programs and the global menu

The unit stores 128 programs, numbered 1 to 128, and any combination of loops and switches can be programmed on each program number¹³. Editing follows a fixed order:

1. Set the program to edit with the Program down and Program up buttons (1 to 128)¹.
2. Set the combination of loops and switches with buttons 1 to 4 and A and B¹⁵.
3. Save permanently with the Save button; the display shows SAV¹.

At power-on the switcher enters working mode and goes to the default program, normally program 1, closing the relays set for that program¹.

Press and hold Save to enter the global menu, navigated with buttons 1 to 4 and A; global mode always starts by editing the channel parameter¹⁶. The menu holds the MIDI configuration:

Beyond the global command, each loop or switch can be assigned its own Control Change number (0 to 127) for individual control. Hold that loop's or switch's button for about five seconds until the display shows IND, set the number, and save with Save. The default is "---", no Control Change assigned¹⁶.

Dots in the upper part of the display indicate reception of a Program Change, Control Change or Note On message¹⁶. The looper also resends all data from MIDI IN to MIDI OUT, so further MIDI devices can be controlled from one source⁵.

Power

The unit runs from a power adapter into its 9 to 15 V AC/DC connector¹. The maker specifies a wide supply range of 9 to 15 V, AC or DC, and recommends the supply be rated for a draw of 250 mA or more⁴. There is no preamp section in this version².

Other Agente Relay Loop versions

Microdesignum builds the Agente Relay Loop in several sizes. The 4L2R1D sits between the smaller 4L1R1D (four loops, one switch) and the eight-loop versions⁴⁸:

The 8L4R1D is the variant with 8 loops and 4 relay switches, and its MIDI interface is on both the front and rear panel⁸. The range also includes an 8L0R1D with 8 loops and no relay switches, and an 8L2R1D with 8 loops and 2 relay switches⁸. The 4L4R1D Rack is the same four-loop, four-switch concept on a 19-inch rack panel⁹, and the 8L4R1D Plus is a further variant in the family¹⁰. An 8L4R loop switcher was used in the rack of a custom pedalboard system Microdesignum built in 2019¹¹. For switching amp channels only, without loops, there is also the MIDI Agente Relay Uno¹².

Questions