Audio Sprockets ToneDexter

The Audio Sprockets ToneDexter is an acoustic instrument preamp pedal that solves a problem most piezo and magnetic pickup players know well: the pickup never quite sounds like the instrument does in front of a good microphone. Instead of modeling someone else's guitar, the ToneDexter learns the sound of your instrument through your mic. You play into a microphone while the pedal listens to both the mic and the pickup, and it stores the difference as a WaveMap, a correction it then applies to the pickup signal so it comes out sounding like the miked instrument¹².

MusicRadar described it at launch as a pedal that "promises to make your acoustic's piezo pickup sound more like a mic'd guitar," available for $399 direct from Audio Sprockets³. The original ToneDexter was discontinued in 2022, and Audio Sprockets replaced it with the redesigned ToneDexter II, launched in January 2024⁴⁵⁶.

What the ToneDexter does

Underneath the hood, the ToneDexter is a preamp with tone shaping and anti-feedback controls built around the WaveMap idea. You train it once with a mic and a pickup, and from then on the pedal corrects the pickup so it sounds like the mic. Audio Sprockets puts it plainly: "It creates a stored WaveMap of that miked sound" that you can recall on stage². Because the correction is stored in one of 22 presets, a working player can keep a separate WaveMap for each instrument. Rory Hoffman, who endorses Audio Sprockets, notes that "with the 22 presets available on ToneDexter, now all of my instruments can have their own WaveMap"². Molly Tuttle has used one on stage².

The unit is designed for a wide range of instruments. MusicRadar lists guitar, dobro, viola, cello, bouzouki, mandola, mandocello and baritone guitar, with additional software versions for higher pitched instruments such as violin, mandolin, banjo and ukulele, as well as for upright bass³.

Controls and features on the original unit include:

• Bass and Treble EQ¹
• A Phase switch on the rear panel that flips the polarity of all outputs; one position is usually less prone to feedback, and the position does not affect training⁶
• A notch control for feedback mitigation on firmware V2.0 and later⁶
• A Mute switch that taps into MUTE&TUNE mode; tapping it during training aborts back to MUTE&TUNE⁷
• A rear mic jack providing 48V phantom power for condenser mics⁷

Training a WaveMap

Training is the heart of the pedal, and it is simpler than it sounds. You plug a mic into the rear mic jack, which provides 48V phantom, set levels, and play while the unit compares the two signals⁷. The display shows LV during the level setting phase and TL during the learning phase, and you can tap the right switch to audition the live mic signal on headphones⁶. Training normally takes about a minute; if it takes much longer, the mic signal is probably excessively hot, and there is no mic gain adjustment⁶.

A few practical points from Audio Sprockets' own guidance:

• Where to train: almost anywhere. "You can train in your living room, in your kitchen, and yes even in your car," because the WaveMap picks up very little of the room sound⁶.
• What to play during level setting: a repetitive chord or notes without low resonances. For guitar, repeatedly strum the upper four strings at the 5th fret; for violin, middle range double stops; for upright bass, arco open A or D string⁶.
• A hot mic: turn on the mic's built-in pad, move it further away, use a less sensitive mic, or use an inline 10dB attenuator⁶.
• Feedback handling: on firmware V1.66 and below, an algorithm automatically finds the instrument's hot spots and dials them back; training from slot 22 bypasses it for a studio quality mic sound. On V2.0 and later, feedback mitigation is no longer automatic and the notch control is used instead⁶.

Recommended mics. Audio Sprockets recommends a small diaphragm condenser, naming the Shure SM81, sE Electronics sE8, Slate ML-2, Rode NT5, Line Audio CM4, Marshall MXL-600 and Sterling ST-31. Large diaphragm condensers also work well, dynamic mics can yield usable results, and tube mics are not recommended. Cardioid and omnidirectional patterns both give excellent results, and active ribbon mics may be used; passive ribbons work so long as they tolerate 48V phantom⁶.

The ToneDexter II simplifies this process: it automatically sets instrument gain and mic gain in Train-Level Set mode to preserve headroom, training takes about a minute with a progress bar and headphone monitoring, and you can successively tap the Boost switch to audition the WaveMap, the raw pickup, and the live mic sound before storing⁸. Audio Sprockets says the general training principles are the same, "now with simpler training and enhanced WaveMap quality and control"⁷.

Power and connections

The ToneDexter works from 9 to 15V and tolerates either the effects pedal standard of negative center or the more general positive center standard⁶. The catch is current: it requires about 5 to 6 watts, more than many adapters can provide. The supplied power supply is a 12V DC 1.0A unit (input 100 to 240V, 50 to 60Hz) with four international socket adaptors⁶. For pedalboard use, Audio Sprockets recommends the Voodoo Lab Pedal Power Digital or Mondo (paralleling two outputs together), or the Strymon Ojai or Zuma⁶.

Connections cover four modes: Training, Live, Studio and Reamping¹. The signal path is a 1/4" high impedance (1MΩ) pickup input and a 1/4" line output with a level pot on the front panel, with latency under 1ms¹. A MIDI controller can select WaveMap presets if you select MIDI on the rear panel control select switch, using a Type A MIDI to TRS cable wired with DIN pin 5 to tip, pin 4 to ring, and pin 2 to sleeve⁹.

Firmware updates and versions

Firmware history matters on a used unit, because behavior changed across versions:

Updates load from an SD card, and the card format is the common stumbling block. FAT32 is required: on Windows choose FAT32, since FAT16, FAT and exFAT are not the same thing; on Mac choose FAT, which in the Mac world does mean FAT32. An ERR message during update usually means the card is not actually FAT32. FAT32 is only possible on cards of 32GB capacity or less, and Toshiba and SanDisk 2GB cards do not work. Power the unit off for at least 15 seconds before powering up with the card in the slot to start the update⁶.

WaveMap banks are split by instrument: the lower bank (slots 1 to 11) has EQ control ranges tailored for guitar, and the upper bank (slots 12 to 22) is optimized for higher pitched instruments like mandolin, violin, ukulele and banjo. Slot R22 gives the most mic-like sound without feedback adjustments, for studio recording⁶⁷. General maps and bass maps each live in their own distinct memory space inside the unit¹⁰.

From ToneDexter to ToneDexter II

After the original ToneDexter was discontinued in 2022, Audio Sprockets launched the redesigned ToneDexter II in January 2024⁴⁵⁶. Like the original, it is an acoustic instrument preamp pedal, and it is available now¹². It expands the WaveMap storage to 32 slots, with all parameters automatically stored and recalled with each one¹². For players weighing the two, the ToneDexter II page covers the current model in detail.

For the original unit, Audio Sprockets still provides the version 2.0 user guide, circuit board removal and re-installation instructions for repair, and a factory footswitch replacement service at $100 including return shipping in the US for both switches¹³¹⁴⁶. The footswitches are tactile switches mounted on the PCB under spring-loaded actuators; the replacement part is the Alps Alpine SKHCBHA010, with the plastic nib snipped off before installing⁶.

Videos

Click to load

Click to load

Click to load

Questions