Ruppert Musical Instruments RMI Acouswitch Junior

The RMI Acouswitch Junior is a floor unit from Ruppert Musical Instruments that packs several jobs into one box: an A/B input switcher, a high-end preamp, a clean booster, a 4-band EQ, an FX loop switcher and an active DI box¹. With two separately controllable high impedance inputs, Lehle positions it as a control center for players who move between electric and acoustic setups on one pedalboard². It is discontinued: Lehle's product page lists it as such as of October 2026².

What it does

The two inputs, INST A and INST B, each present a 5 MOhm impedance to the instrument, which suits both magnetic and piezo pickups¹. Channel A carries the 4-band EQ and its own volume control, VOL A, whose neutral position is at 12 o'clock and which can boost or cut the signal¹². Toggling between the inputs is possible, and so is mixing them together; for a purely acoustic setup the outputs can be set to be always active². The A/B switch itself can be configured individually depending on the setup².

The unit also has a serial effects loop and a tuner-out output with mute function². The DI output, with a maximum level of about +10 dBu, feeds a mixing desk directly¹.

Modes and controls

The manual describes a set of operating modes selected by flashing indications on the footswitches¹:

The mute / loop boost footswitch manages the effects loop, the mute function and the boost in various combinations². The Tuner Out jack keeps a tuner completely out of the signal path and on all the time, preventing potential sound losses from putting a tuner inline¹.

Switching and build

Inside the Acouswitch Junior, the impulse from the push button triggers a processor based on ARM Cortex-M technology, which controls the switching through high-quality gold-plated relays designed for up to two million switching cycles¹. The relays are part of what Lehle calls its True Sound Technology, alongside a discrete JFET input stage².

The footswitches themselves are Lehle units with an actuator button that activates an internal push button via a metal lever. The manual contrasts this with an ordinary foot switch, which it says will switch up to 20,000 times before wearing out mechanically or electrically¹. Lehle describes the enclosure as extremely robust, with protected controllers and an almost indestructible switching mechanism².

The bigger Acouswitch IQ DI

The Acouswitch Junior sits below the RMI Acouswitch IQ DI, also from Ruppert Musical Instruments and also discontinued⁴³. The IQ DI is an A/B input switcher, high-end preamp, clean booster, parametric EQ, FX loop switcher and DI box⁴. Where the Junior has a 4-band EQ on channel A, the IQ DI's channel A has a 3-band EQ designed for acoustic instruments, with bass, semiparametric mids and treble controls⁴¹.

The IQ DI's MUTE footswitch mutes the LINE OUT and DI OUT for quiet tuning or stand-by, and its A/B footswitch toggles between input INST A and INST B and between channel A and channel B⁴. Its PRE/POST button takes the EQ and effect loops out of the DI signal path in the PRE setting, and a phase switch inverts the phase of the Mix Loop's return signals if needed⁴.

Warranty and support

The Acouswitch Junior carries a limited product guarantee for two years from the date of purchase, covering free rectification of material and manufacturing defects by repair or replacement at the manufacturer's option. The guarantee is void if the unit is modified or damaged by incorrect use, negligence, disassembly, non-authorized service or non-original parts¹. Guarantee repairs are performed by a customer service organization authorized and approved by Lehle GmbH, with returns to Lehle GmbH, Grenzstrasse 153, 46562 Voerde, Germany¹. Support contacts listed in the manual include support@lehle.com, support@acouswitch.com and jacques@rmi.lu¹.

The manual states the RMI Acouswitch Junior is manufactured, assembled and tested in Germany¹.

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