The Pete Cornish Acoustic Preamp/DI/Mute is a hand-built preamp pedal for acoustic instruments fitted with ceramic transducer pickups, with a built-in DI output and a mute function. Pete Cornish designed it to solve a problem familiar to anyone who has plugged an acoustic pickup straight into an amp: the mismatch of level and impedance in the electrical circuit between the pickup and the amplifier, which the maker identifies as a frequent cause of thin or unreliable acoustic tone1.
For double bass players the maker is specific about what the pedal addresses. Players of acoustic (double) basses, Pete Cornish says, will find their previous problems with lack of low frequencies, poor Arco sound, poor sound with volume or other pedals, poor response to double stopping, and poor DI sound are eliminated12. The heart of the unit is a low noise integrated circuit Class A pre-amplifier, specifically designed to overcome the problems often encountered with acoustic pickups1.
Controls, inputs and outputs
The input jack does double duty: a 1/4 in. mono jack serves as both the instrument input and the power switch, so the unit is on whenever a plug is in the input12. Three outputs sit alongside it:
| Connection | What it does |
|---|---|
| Input / Power On | 1/4 in. mono jack, also switches the unit on1 |
| Output | Main signal to the amplifier1 |
| Tuner | Auxiliary output, identical to the main output signal, for a tuner1 |
| D.I. | Transformer coupled low impedance source on a male XLR connector1 |
The tuner output is a practical touch for stage use: it carries the same signal as the main output, so you can tune silently without a separate buffer or splitter1.
The DI output and its phase wiring
The DI is a transformer coupled low impedance source on a male XLR connector, wired Pin 2 Hot +, Pin 3 Cold -, Pin 1 Gnd1. Pete Cornish spells out the phase relationships: "Pin 2 is in phase with the preamp input; pin 3 is reversed phase and pin 1 is the ground connection"2. That matters if you run the DI to the PA and your amp to the stage at the same time: knowing which pin carries the in-phase signal lets you sort out phase cancellation between the two sound sources rather than guessing at it.
Power and battery
The pedal runs on 9V DC, noise free and fully stabilized, with the adapter capable of supplying 20mA1. The coax connector is 5.5/2.1mm with the center pin negative (-VE), the common center-negative pedal standard1. Pete Cornish recommends the Voodoo Lab Pedal Power 2 Plus as meeting these criteria, or a BOSS PSA series adapter for a single unit1.
An adapter providing an AC voltage output should not be used: it will permanently damage the pedal, and such damage is not covered under warranty. Pete Cornish also advises not to daisy chain other effects with the BOSS PSA adaptor, as this may cause hum problems1.
A battery can be used instead of, or as backup to, the adapter. It is replaced through a removable drawer, alkaline types are recommended, and the MN1604 is the preferred battery2. Because the input jack switches the unit on, the battery only drains while the pedal is in use2.
Where it sits among acoustic preamps
The Pete Cornish Acoustic Preamp/DI/Mute is a straightforward preamp-and-DI box: its published specification centers on a low noise integrated circuit Class A preamplifier with adjustable gain from 0dB (unity) to +20dB, plus separate maximum outputs to an amp (+7dBm into 2 Kohms or above) and to a D.I. (+4dBm into 2 Kohms or above)1. Players comparing formats might look at other units in the same territory, such as the Boss AD-10 Acoustic Preamp, the LR Baggs Session DI, the Radial Tonebone PZ-Pre or the Trace Elliot Transit A. See the full range on the Acoustic Pedals page.
Questions
Can I use an AC adapter with the Pete Cornish Acoustic Preamp/DI/Mute?
No. Pete Cornish states that an adapter providing an AC voltage output should not be used, as it will permanently damage the pedal, and such damage is not covered under warranty. The pedal needs a noise-free, fully stabilized 9V DC supply capable of delivering 20mA, such as the Voodoo Lab Pedal Power 2 Plus or a BOSS PSA series adapter used for a single unit.
How much gain does the Pete Cornish Acoustic Preamp/DI/Mute add?
The gain is adjustable from 0dB, which is unity, up to +20dB. That range lets you bring a low-output acoustic pickup up to line level while keeping the input impedance high enough for ceramic transducers.
Does it take a battery?
Yes. The battery is replaceable through a removable drawer, and alkaline types are recommended, with the MN1604 9V battery preferred. The unit is switched on by inserting the input/power jack, so unplugging the instrument turns it off.
What is the polarity of the power connector?
The power connector is a 5.5/2.1mm coax connector with the centre pin negative. That is the standard centre-negative polarity used by most pedal power supplies.
Can I daisy chain power to this pedal?
Pete Cornish advises against daisy chaining other effects with a BOSS PSA adapter when powering this pedal, as this may cause hum problems. A dedicated supply output, such as one from a Voodoo Lab Pedal Power 2 Plus, is recommended.
Does it have a tuner output?
Yes. Alongside the main output and the XLR DI, the pedal carries an auxiliary output that feeds a signal identical to the main output, intended for a tuner.
Sources (2)
- Pete Cornish Acoustic Preamp/DI/Mute, Pete Cornish, 2016
- Pete Cornish Acoustic Preamp/DI/Mute, Pete Cornish, 2014
