The Keeley 30ms Automatic Double Tracker is a stereo pedal from Keeley Engineering that creates up to two additional voices of your playing, tuned "doubles" of your guitar part, the way studio engineers thicken a track by recording the same part twice1. Released in 2015, it was announced at Summer NAMM in Nashville and priced at $19923. Instead of a conventional chorus, it uses very short delays and slight detuning, built on the Haas or Precedence Effect, a delay of 30 ms or less that does not sound like an echo or reverb1.
Keeley describes it as an automatic track doubling device that creates two or more additional voices, and the press materials pitched it as an array of studio style doubling effects for creating thicker, fuller sounding instruments12. Delicious Audio characterized the circuit as a short delay stereo design combined with a chamber reverb and an "altered and detuned effect"4.
How it works: the Haas effect
The pedal's name comes from the principle behind it. As Keeley explains, the Haas or Precedence Effect is a very small delay, 30 ms or less, that does not register as an echo or reverb1. When a copy of your signal is delayed by that little and mixed back in, your ear blends the two into one perceived sound rather than hearing a repeat. Add slight detuning to the delayed copy and it reads as a second player doubling your part, which is the effect engineers got in the studio by recording a part twice on two tape decks.
Dimension, Abbey and Slap Back modes
The pedal has three modes, each a different take on doubling1.
| Mode | What it does | Controls |
|---|---|---|
| Dimension | Creates two additional voices, one tuned up and one tuned down, delayed 0 to 30ms and combined with the dry signal, for a stereo double tracked field15 | Voice (level of the doubled voices, up to equal volume with the original), Tune (pitch, by up to ten cents), Time (0 to 30ms of delay)1 |
| Abbey | A recreation of the Automatic Double Tracking made famous by The "Liverpool Group"; a delayed signal between 0ms and 30ms is modulated very slowly at a somewhat random rate by up to 2ms in depth1 | Rate (rate of the random pitch shifting), Depth (depth of the pitch shift)1 |
| Slap Back | A double tracked echo with the two altered voices, aimed at rockabilly sounds; two "Tuned-Voices", up to 10 cents, delayed anywhere from 30ms to 120ms15 | Time (30 to 120ms of delay)1 |
Dimension Mode is the most flexible. Keeley says it sounds great on acoustic or electric guitars, vocals, keyboards, "you name it," and the pedal was designed from the start to work with guitar, bass, keyboard and even vocals12. You control the tuning the way studio engineers do, by up to ten cents, with the Tune control1.
Abbey Mode is the tape-machine take. Premier Guitar's launch coverage described it as offering something more similar to a conventional chorus in that it simulates synched tape decks running in parallel with varying tape speeds, a wide, lush sound without sounding like a conventional chorus pedal5. The slow, somewhat random modulation of the delayed signal is what gives it that drifting tape feel.
Slap Back pushes the delay times out to 30 to 120ms, turning the doubling into a double tracked echo. Premier Guitar noted the team at Keeley created it for rockabilly sounds51.
The Abbey Verb reverb
The pedal also includes a reverb that simulates the famous chamber in Studio Two, which Keeley calls the Abbey Verb52. In mono operation the reverb is part of the signal path, so a mono rig still gets the doubled voices plus the chamber sound2. In Stereo Double Tracker Pro mode the unit drops the reverb channel in favor of complete control over the double tracked voices5. For players shopping Keeley's reverb line, the same Studio Two chamber idea appears in the Keeley Abbey Chamber Verb, and the broader range is covered on the reverb pedals page.
Power, size and connections
The 30ms runs on a standard 9V DC center negative supply with a 65mA+ draw, and outputs mono or stereo through a TRS cable, which is not included3. Its footprint is 112 x 60 x 30mm3.
Stereo output requires a TRS cable, which does not come in the box. Plan on supplying your own if you want the full stereo double tracked field3.
What reviewers said
Guitar.com's review in February 2016 noted the pedal was already shifting 1,000 units since its announcement at Summer NAMM in Nashville, and listed it at £1493. Delicious Audio, comparing it with the TC Electronic Mimiq in 2017, concluded of the two double trackers: "Both are fine pedal."4
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Questions
Is the Keeley 30ms stereo?
Yes. The pedal works in mono or stereo, and in Dimension Mode you can create up to two different voices for a stereo double tracked field. Stereo output uses a TRS cable, which is not included with the pedal. In mono, the built-in Abbey Verb reverb is part of the signal path.
Can you use the Keeley 30ms on vocals or keyboards?
Yes. Keeley says Dimension Mode sounds great on acoustic or electric guitars, vocals, keyboards and more, and the pedal was designed to work with guitar, bass, keyboard and even vocals. The voices are tuned doubles of whatever signal you feed it.
What is the Haas effect?
The Haas or Precedence Effect is a very small delay of 30 ms or less that does not sound like an echo or reverb. Instead, the ear perceives the delayed copy as part of the original sound, which is what makes the 30ms's doubled voices sound like a second player rather than a delay.
Does the Keeley 30ms have reverb?
Yes. The pedal includes a reverb that simulates the famous chamber in Studio Two, which Keeley calls the Abbey Verb. In Stereo Double Tracker Pro mode the unit drops the reverb channel in favor of complete control over the double tracked voices.
How much current does the Keeley 30ms draw?
Guitar.com's review lists a 65mA+ draw on a standard 9V DC center negative supply. That is modest by modern pedal standards, but it means the pedal runs on a power supply rather than a battery.
Sources (5)
- What is a Keeley guitar effect pedal, robertkeeley.com, 2015-07-04
- Keeley Engineering announces 30ms Automatic Double Tracker pedal, MusicRadar, 2015-09-01
- Keeley Electronics 30ms Double Tracker, Abbey Chamber Verb & Memphis Sun Reverb reviews, Guitar.com, 2016-02-22
- TC Electronics Mimiq And Keeley 30ms, Delicious Audio, 2017-02-21
- Keeley Electronics Launches 30ms Double Tracker, Premier Guitar, 2015-08-27
