Keeley Electronics Hydra. Reverb & Tremolo.Stereo


The Hydra gives super hi-fi stereo reverb and tremolo with spring, plate, and room reverb options are Hydra’s trademark sounds. TRS and external tap tempo switching

Requires 9V DCventre negative supply. Draws approx 115 mA

(1 customer review)

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Keeley Electronics Hydra

The Keeley Electronics Hydra is a stereo reverb & tremolo

Combining both high-fidelity Reverb and Tremolo, the Keeley Electronics Hydra Stereo Reverb & Tremolo adds space and dimension to your guitar, bass or synth.

After completing the powerful, versatile and stellar Eccos delay and looper, the Keeley Electronics team set out to craft the perfect companion pedal and with this feature-rich little blue box, they have well and truly accomplished exactly that and so much more.

The Keeley Hydra In Use

Bathe your sound in Spring, Plate or Room Reverb, then add tap-tempo enabled Harmonic, Vibrato, or Sine Wave Tremolo with the press of a button.

You can easily change the order of effects or the character of the Tremolo or Reverb with Hydra’s smart Alt Controls.

You can even create an Infinite Hold Reverb Trail! Save up to three presets with ease using our intuitive save feature. Engage Reverb Trails on the fly, no more internal dip switches.

The Hydra can be used with pro remote switching systems and offers both TRS Expression Pedal and External Tap-Tempo inputs. T

The HYDRA is a complete end-of-pedalboard solution that fits perfectly in any musician’s rig, regardless of genre.

Experience next-level processing power in this pedalboard-friendly enclosure. The sky, or more appropriately, the ocean floor, is the limit with the new Keeley Electronics Hydra!

See it in use here.


Primary controls

RATE – Sets the rate of the Tremolo. Turn left for slower speeds, right for faster.

DEPTH – Sets the maximum amount of volume reduction for the Tremolo.

DWELL – Sets the length of the Reverb trail. Turn left for less, right for more.

COLOR – Sets the tone of the Reverb. Pressing this control grants access to alternative settings and presets.

MIXER – Sets the level of the Reverb. Turn left for a lower Reverb volume, right for higher Reverb volume.

TOGGLE SWITCH – Selects between Spring, Plate and Room Reverb types.

Secondary Controls

COLOR – Press and hold the COLOR knob while manipulating the other controls to change the settings
marked in dark grey on the Hydra.

TREM SYNC – Sets the stereo output of the Tremolo for either panning, synced, or wet/dry. CCW of noon is stereo panning where the signal will alternate between the two outputs. At noon both outputs will be in sync, pulsing at the same time. CW of noon will run the dry signal through the Stereo Out jack and Trem through the Mono Out jack.

TREM LEVEL – Controls the output volume of the Tremolo. At full CW there is a +6db boost to compensate for the perceived volume drop inherent in Tremolo.

WET/DRY – Sets the stereo output of the Reverb for either stereo Reverb or a wet/dry setup. CCW of noon is stereo Reverb while CW of noon is the dry signal only on the Stereo Out and Reverb on the Mono Out.

REVERB MODIFIER – Modifies the Reverb depending on the mode selected.

On Spring this will control the spring age, being bouncier and more pronounced echoes with the control full CW and more diffused and smooth at full CCW. On Plate this sets the amount of shimmer introduced into the Reverb.

Full CCW is no shimmer with full CW giving a large cascade of octave up. On Room this controls the room size, going from a small closet at full CCW to a large cavern at full CW.

TOGGLE SWITCH – Selects between Sine, Harmonic, and Vibrato Tremolo


Featuring gorgeous Spring, Plate and Room reverb algorithms, plus a tap-tempo enabled Harmonic, Vibrato and Sine Wave Tremolo – are all accessible at the press of a button – Hydra will add space and dimension to any instrument.

To alter the response of this killer Tremolo/Reverb combination, the effects order can be easily changed.

In addition, the Hydra’s Alt Controls let you access in-depth parameters to shape the character of both sound engines. Plus, Hydra even offers an Infinite Reverb Trail!

With expression control, remote bypass, 3 presets, analog-dry-through, kill-dry and a ridiculously low power-draw, this pedal is sure to add immense flexibility and gorgeous sounds to any rig.

  • Stereo high-fidelity Reverb and Tremolo effect pedal
  • 3 memory presets, subdivisions, trails, infinite hold reverb trail
  • 3 reverb (Spring, Plate and Room) and 3 tremolo modes (Sine, Harmonic, Vibrato)
  • Huge array of tone and time-based controls with the Alt Hold feature
  • Bypass and Tap Tempo on-board or remotely with any style pedal-switcher
  • Expression pedal assignment over any parameter and in any direction •
  • Pro Rig designed, remote control thru 1/4″ jacks for live use with pedal switcher systems
  • 100% analog dry signal, audiophile designed input to output
  •  Stereo True-Bypass/Trails, switchable on the fly

Powered by a regular 9V DC PSU (centre -, 2,1 mm, low ~115 mA current draw)

Additional information

Weight .35 kg
Dimensions 12.5 × 7.5 × 6.1 cm
Analogue or Digital

Analogue & Digital




115 mA



Pedal Type

Reverb, Tremelo

Power Connection Type

Centre Negative

Silicon or Germanium




EAN 13






1 review for Keeley Electronics Hydra. Reverb & Tremolo.Stereo

  1. Jim G (verified owner)

    Very good.

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