Amplifying an acoustic guitar while accompanying worship songs or within a praise band typically consists of seating the player in front of a mic to get a bit more level, or connecting the internal pickup system to a channel in the mixing board and adjusting the EQ to make the instrument sound halfway decent. Imagine being able to make that guitar or other acoustic stringed instrument sound like it’s being captured by a good microphone, but with the greater SPL and freedom of movement that a pickup affords – accurately conveying the audio characteristics of the particular instrument and the pickup system that is installed within it. That’s what the ToneDexter preamp / DI strives toward, and for the most part accomplishes.
The ToneDexter was released in May, 2017 after several years of development by guitarist/engineers James May and Andy Norrell, with partner Michael Seedman creating the software that runs the user interface. Their basic concept was to use a microphone to capture the acoustic sound of the instrument and use that to modify and “correct” the more colored sound created by the pickup system – and then store this instrument-and-pickup-specific result for later use. We’ll take a look at the details of this process and how well it performs.
Features and Controls
The ToneDexter is about the same size as a typical acoustic guitar preamp, at about six by six inches and 2.5 inches high including control knobs at its tallest. The unit tapers down toward the front, where two multifunction footswitches are located. The generous three-segment display also performs multiple functions during the “training”, tuning, EQ setting, and performance tasks. A power connector on the rear panel accepts 9 – 15 VDC, positive or negative polarity, and an external power supply is included.
The controls include a pickup level trim, an output level, WaveMap selector and “character”
knobs, a low-frequency notch filter for resonances, and bass and treble EQ. The rear panel features an XLR3F mic input that provides 48V phantom power (used only when creating the presets), a ¼-inch stereo headphone out with level control, a ¼-inch TRS effects loop connector, and an XLR3M DI output that is switchable between fixed level and variable – controlled by the unit’s output level control. On the right panel is a ¼-inch instrument input, and a ¼-inch output is on the left. A phase switch changes the polarity of all outputs, and the Option A/B switch accesses the two memory banks.
Creating an Instrument-Specific Preset
The basic process to create an instrument-specific preset with ToneDexter is quite simple, and takes only a few minutes from start to finish. After powering up the unit, plug in a pair of headphones, connect and place your desired microphone to capture the instrument acoustically, and plug in the guitar or other instrument. The recommended mic for the most accurate result is a small-diaphragm condenser, but any other condenser or dynamic mic may be used. Play in your normal style for a few moments while you set the input level control, using the LED display as a guide. Listen to the sound of the mic’d instrument and adjust the mic’s position if needed.
When you’re ready, press the “train” button and begin playing for about a minute while ToneDexter learns the differences between your pickup’s output signal and what the microphone “hears”, and creates a WaveMap – as you listen to the process through the headset. When the learning is complete, you can compare the sound of the raw pickup, the mic by itself, and the newly created WaveMap. If you’re satisfied, scroll to an open memory slot and store the result.
Creating presets can be done at a scheduled rehearsal during the week (and would only have to be done once for a particular instrument), or even just before the service begins for a guest musician. If desired, you can create multiple presets using different microphone positions or microphones, or train additional instruments. For example, in under 15 minutes, I successfully trained and evaluated three instruments – a later ‘80’s Martin with a stock undersaddle pickup, and two handmade acoustics outfitted with an LR Baggs Lyric and a K&K Mini.
When done with a training session, unplug the mic and headphones and note which instruments are assigned to particular presets; the system is ready for use. And you can keep the ToneDexter prepared for a variety of instruments and situations, since each of the two memory banks will hold 11 presets.
ToneDexter During the Service
The system is easy to set up and use on a busy Sunday morning. Just power it up, then connect a mic cable to the XLR output and out to the mixing console, the guitar or other instrument to the ¼-inch tip-sleeve input, and an amp or other monitoring system to the ¼-inch output, if desired. Rotate the WaveMap selector to the preset that matches the particular instrument and pickup, and adjust the input level if necessary while the instrument is being played. A separate control determines the output level for both outputs, unless the XLR output is switched to the “fixed level” position.
To counter any feedback sensitivity at the instrument’s resonance point, a sweepable notch filter covers the range from 73 to 392 Hz (in the GEN version of firmware), with the display temporarily showing the selected frequency as the knob is turned. This notch engages a 12-dB cut, with a 1/12 octave width, and in my experience is quite effective. The two EQ shelving filters provide 9 dB of boost or cut, with the low-frequency inflection point at 125 Hz and the HF at 2kHz. The display will temporarily read out the adjustments in 0.5 dB increments.
When playing, the left footswitch mutes the output, and also accesses a tuner. The right footswitch enables a boost circuit for soloing, with up to 8 dB of level increase possible – with its level control located at the rear of the unit. Over the past three months of performances, the ToneDexter has performed quite well, and I’ve received many positive comments about the acoustic sound of the instruments.
Firmware and Other Details
The latest firmware upgrades for the ToneDexter preamp/DI offer three different versions: for guitar and similarly pitched instruments; acoustic and upright basses; and treble instruments such as mandolin, violin, or ukulele. The same unit can be updated with any of these versions, but will only hold one at a time. The versions provide different frequency ranges for the notch filter and equalizer, and a longer sampling for the bass WaveMap. For example, the bass notch filter ranges between 37 and 165 Hz.
From my experience with the ToneDexter acoustic instrument preamp/DI, the system is a potential game-changer for the live reproduction of acoustic stringed instruments. The sound can be customized to the specific qualities of the instrument and pickup system, yielding the characteristics of a mic’d acoustic with the flexibility and greater SPL before feedback of a pickup. More details may be found on the http://audiosprockets.com web site, and ToneDexter currently can be purchased via this site for $399.
