The One Control Minimal Series MIDI Dual Stereo Loop, or MDSL, is a MIDI-controlled dual stereo effects loop switcher. It sits between your instrument and your amplifier and gives you two switchable stereo effects loops that you turn on and off remotely with MIDI, either with Program Change (PC) or Control Change (CC) messages, rather than tapping footswitches on individual pedals1.
It belongs to One Control's Minimal Series, which the maker describes as an approach that eliminates waste in the manufacturing process, achieves the most compact size possible, and consolidates simple but sophisticated functionality into each unit1. For a player with a MIDI controller or switcher on their board, the MDSL is a way to bring two stereo effects in and out of the signal path cleanly, and to run a mono instrument into stereo effects without extra splitter boxes.
As of late October 2026, the MDSL is listed as sold out on One Control's product page. Its regular price is $199.99 USD1.
What it does
The core job of the MDSL is loop switching: two effects loops, each with its own send and return, can be engaged or bypassed under MIDI command. One Control says the unit brings players "easy MIDI Loop functionality" in the Minimal Series format1.
The stereo handling is the distinguishing part. Every jack on the unit, the input, the output, and both loops' send and return jacks, is a TRS stereo plug, so a full stereo signal path runs through the whole pedal1. A single L1/L2 switch on the unit sets the routing configuration, and in its top position the signal path is stereo input to stereo send, return, and output1.
For players whose instrument or source is mono, the MDSL can convert mono signals to stereo, in what One Control calls dual mono operation, and send them to stereo effects1. The output side works the same way in reverse: if the mono output signal becomes stereo via an effect connected to the effects loop, it can be output as a stereo signal1. In practice this means a mono guitar can feed a stereo delay or reverb in the loop and come out as a true stereo signal at the output.
The MDSL is part of a small family of One Control MIDI loop products. The One Control Minimal Series MIDI Solo Stereo Loop is a single-loop version, which One Control describes as the smallest stereo 1 loop switcher controlled by MIDI, with a relay-based design the maker says ensures minimum signal loss2. The One Control Minimal Series MIDI Input Selector handles MIDI input selection rather than loop switching3. Compared with the Solo Stereo Loop, which receives on MIDI channels 1 through 4, the MDSL covers more channels and two loops instead of one12.
PC mode and CC mode
The MDSL offers two ways for a MIDI controller to switch the loops: PC mode and CC mode. One Control's guidance is to "use either PC or CC mode to control your loops easily"1.
The mode itself is set by Program Change numbers:
In PC mode, the loops respond to Program Change numbers:
| MIDI message | Function |
|---|---|
| PC# 11 | Turn on Loop 1 (ignored in CC mode)1 |
| PC# 21 | Turn on Loop 2 (ignored in CC mode)1 |
In CC mode, the loops respond to Control Change messages instead:
| MIDI message | Function |
|---|---|
| CC# 102 / Value 21 | Turn on Loop 2 (ignored in PC mode)1 |
The two modes exist so the MDSL can work with different kinds of MIDI hardware. Some controllers send Program Changes easily, others are built around Control Change messages, and the MDSL can be set to match whichever your controller uses. One thing worth knowing when programming: MIDI PC and CC numbers range from 0 to 127, but some devices label PC numbers as 1 to 128. In that case, One Control says to increase the PC number by one3.
The MDSL can use between 1 and 8 MIDI channels to receive control signals, so it can share a MIDI system with other switchers and effects on different channels1.
Inputs, outputs and power
All of the audio jacks are TRS stereo plugs: the main input, the main output, and the send and return jacks for both effects loops1. The L1/L2 switch selects the routing configuration, with the top position giving stereo input to stereo send, return, and output1.
Power comes from a center minus DC 9V adapter, the standard 9V center-negative supply used by most effects pedals. Current consumption is 120mA1.
Batteries are not available for the MDSL, and at 120mA it draws more than many analog pedals, so plan on a proper pedalboard power supply rather than a battery or a low-current daisy chain output1.
Physically, the pedal measures 120W x 60D x 30H mm excluding protrusions, or 125W x 68D x 32H mm including them, and weighs 366g, which keeps it in line with the compact footprint of the rest of the Minimal Series1.
Questions
Does the One Control Minimal Series MIDI Dual Stereo Loop run on a battery?
No. One Control states that batteries are not available for the MDSL, so it needs an external power supply at all times. Like other pedals in the Minimal Series, there is no battery compartment, and the unit draws 120mA, which is beyond what a 9V battery is designed to supply.
What power supply does it need?
It runs on a center-minus DC 9V adapter, the same standard 9V center-negative supply used by most effects pedals. Current consumption is 120mA, so it draws more than a typical analog drive pedal and is best fed from a dedicated pedalboard power output.
How many MIDI channels can it receive on?
The MDSL can use between 1 and 8 MIDI channels to receive control signals. You set the channel to match your MIDI controller or switcher, and the two effects loops are then switched via MIDI Program Change or Control Change messages.
Can it send a mono signal to stereo effects?
Yes. One Control says you can convert mono signals to stereo, in what it calls dual mono operation, and send them to stereo effects. If a mono signal becomes stereo through an effect in the loop, the MDSL can output it as a stereo signal through its TRS output jack.
Which PC number switches it to CC mode?
MIDI PC# 81 sets the MDSL to CC mode. PC# 80 returns it to PC mode, which is the factory setting. In CC mode the loops respond to Control Change messages instead of Program Change numbers.
Is the Dual Stereo Loop still in production?
As of late October 2026 the MDSL is listed as sold out on One Control's product page, at a regular price of $199.99 USD. The page does not say whether production has ended or whether stock will return.
Sources (3)
- Minimal Series MIDI Dual Stereo Loop (OC-M-MDSL), One Control USA
- Minimal Series MIDI Solo Stereo Loop Inspired by Josh Smith (OC-M-SSL-, One Control USA
- Minimal Series MIDI Input Selector (OC-M-MIS), One Control USA
