Hydra – MIDI Loop Switcher

The Oscillator Devices HYDRA is a MIDI loop switcher series (sometimes called MIDI looper switcher, or MIDI controlled loop switcher). They all feature relay based, true bypass loops with clickless switching and muting function. The HYDRA E-devices also feature expression outs to control expression inputs of effects devices via MIDI and connect to switch inputs of amps or control tap tempo.

HYDRA4 and HYDRA2E MIDI loop switchers


  • Low impedance, true bypass loops
  • Clickless switching with individually selectable muting times for each loop
  • Muting after every second loop
  • 14 user presets
  • Master switch to set MIDI channel, save presets and manually select loops
  • MIDI controllable expression outs (HYDRA E only)
  • Isolated control switches on TRS connectors (HYDRA E only)
  • MIDI Clock synchronous functions on EXP and EXT
  • Compatible with all MIDI 1.0 compliant controllers
  • High-quality Amphenol sockets
  • Developed and handcrafted by Oscillator Devices in Germany

HYDRA4: 4-Channel MIDI Loop Switcher

The HYDRA4 features 4 MIDI controlled, relay based, true bypass loops.

HYDRA4 - 4-Channel MIDI Loop Switcher

Connect up to four effects devices to the HYDRA4 and bring them in and out of the signal path via MIDI commands.

HYDRA4 MIDI loop switcher example graph

HYDRA2E: 2-Channel MIDI Loop Switcher + EXP/EXT

The HYDRA2E features two MIDI controlled, relay based, true bypass loops. It also provides two expression outputs for controlling expression inputs of other effects devices and four isolated control switches on two TRS sockets for various functions like amp channel switching or MIDI clock synchronous tap tempo.

HYDRA2E - 2 Channel MIDI Loop Switcher + EXP/EXT

Connect up to two effects devices to the HYDRA2E and bring them in and out of the signal path via MIDI commands. Control expression, tap tempo, channel or reverb switches on amps. The control switches of the HYDRA2E are completely isolated from the circuit and can switch up to ±60V.

HYDRA2E MIDI loop switcher example graph

Master Switch

The Master Switch supports the following functions:

• When pressed shortly while the HYDRA is turned on, the loops are turned on and off in every possible combination.
• When held while HYDRA is turned on, it enters preset save mode to save the current state to one of the 14 presets.
• When held while the HYDRA turns on, it enters MIDI channel mode to set the MIDI channel.

MIDI Connection

The MIDI connections are assigned according to the official MIDI specification of MIDI TRS using MIDI TRS Type A, like pedals from Boss or Wampler. A 1/8″ (3.5 mm) stereo jack plug is used. The MIDI Out socket is a low latency MIDI Thru with a latency of less than 1 ms.

1/8″ stereo jack plug to DIN 5-Pin according to MIDI TRS Type A


HYDRAs are designed without a buffer. This is not necessary due to the low impedance signal path. While the use of an input buffer sometimes makes sense, it’s not always possible because many pedals want to “see the guitar”. If you have the need, just place your favorite buffer into one of the loops or before the HYDRA. For most cases though, a buffer is not necessary at all.

Muting and Clickless Switching

HYDRA devices introduce clickless switching. After every two loops follows a passive muting block, that doesn’t interfere with the signal path in normal operation. For clickless switching the output is smoothly muted a few milliseconds before the actual switching. The muting period is so brief, it’s barely noticeable. The time the output is muted can be selected individually for each loop without complex configuration, or omitted entirely. Since the muting happens after every second loop, later loops are not affected e.g., delay trails of subsequent loops aren’t interrupted when switching previous ones.

This is what every two loops of the HYDRA looks like:

Muting Scheme of Oscillator Devices HYDRA MIDI loop switcher
Every 2 HYDRA loops feature one muting block



Quick StartHYDRA2E and HYDRA4 1.0 (August 2023)English
User ManualHYDRA2E and HYDRA4 1.0 (August 2023)English