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Electro-Harmonix Platform Stereo Compressor Limiter Pedal

Image 0 of Electro-Harmonix Platform Stereo Compressor Limiter Pedal

Electro-Harmonix Platform Stereo Compressor Limiter Pedal


The PLATFORM is a sophisticated, professional stereo compressor limiter that includes volume swell and tape reverse, plus overdrive. It's powerful for studio or post production work, yet compact enough to take to a gig!


• High-quality compressor/limiter
• Selectable hard/soft knee function
• 8-segment LED gain reduction meter
• Foot switchable overdrive with volume, tone, and gain controls
• Volume swell function
• True stereo input and output
• Stereo buffered bypass

• Input impedance for each input: 1M
• Output impedance for each output: 300
• Current draw: 125mA
• Maximum input signal level: +7.2 dBu


Compressor Mode: Adjusts compression ratio. As you turn the SUSTAIN knob clockwise, the compression ratio increases. This ratio determines how much compression is applied to a signal once it crosses the threshold. Threshold is the volume level at which the compressor begins working on the signal. In compressor mode, the Platform’s threshold level is fixed at a constant -35dB.

In practical terms, compression ratio determines how much the compressor squashes the signal level and thus how much it levels out dynamics. The higher the ratio, the more it reduces the peaks and valleys in your signal level to yield a more consistent output volume.

Limiter Mode: The SUSTAIN knob adjusts threshold level. As you turn the SUSTAIN knob clockwise, the threshold level decreases and forces the limiter to act sooner on your signal. The compression ratio is constant and practically infinite in Limiter mode.

The ATTACK knob sets the amount of time delay before the compressor/limiter is activated once the input signal level reaches or exceeds the threshold setting. Turn the ATTACK knob clockwise to increase the attack time from fast to slow.

Slow ATTACK settings emphasize the initial attack and add greater pop to your notes (this is great for guitarists who like to chicken pick or play funk). Fast ATTACK settings produce a more even compression where the initial attack is compressed along with the sustained portion of your notes.

While the compressor/limiter is acting on the signal, the input may drop below the threshold setting and cause the compressor to cease working on the signal. The compressor does not stop working immediately, though. Rather, it gradually stops over a period of time that is set by the RELEASE knob. As you turn this knob clockwise, release time increases, or slows. Slower release settings generally result in smoother, more transparent compression with little or no audible artifacts. Slower release settings also reduce the overall output volume. Fast release settings allow for louder volumes and typically yield more noticeable compression effects such as “pumping,” which is audible as unnatural level changes.

VOL Knob [Main Output Level]
This control—located in the upper left corner of the pedal—is the master volume for the entire pedal. Use this control to balance your level between bypass and effect mode.

KNEE Button
The KNEE button changes the compression/limiting curve to produce a compression sound that is either more or less transparent. When KNEE is lit, soft knee compression is enabled, and the result is a softer, subtler compression. When KNEE is off (unlit), the compressor operates with a hard knee response and produces a more dramatic compression effect.

HARD KNEE – is recommended for instrumentation where you want a more obvious compression sound. Most effect pedals employ hard knee compression. Hard knee works great with guitar, bass, drums and keys.

SOFT KNEE – is recommended for delicate instruments or passages. It’s great for vocals, strings, pads and other similar instruments where it is often important for the use of compression to be as transparent as possible.

Press the LIMITER button to engage the limiter. The button lights green to indicate that the limiter is active. A limiter is a compressor that is fixed at an extremely high—practically infinite—ratio. As a result, the signal level does not increase past the threshold setting. The ATTACK knob can still be used to delay the limiter’s attack.

The states of the KNEE and LIMITER buttons (as well as the DRIVE footswitch) are saved in flash memory and restored each time the Platform is powered up.

Bar Graph LEDs
The eight gain reduction LEDs indicate the actual amount of gain reduction in real time. The more LEDs that are lit, the more gain reduction occurs. Each LED represents 3dB of gain reduction. The green LEDs indicate a light to medium amount of compression/limiting. The yellow LEDs suggest a heavy amount of compression. The red LED represents maximum compression.

BYPASS Footswitch & LED
Press the BYPASS footswitch to toggle the Platform between buffered BYPASS and EFFECT mode. The status LED, located above the BYPASS footswitch, lights when you are in EFFECT mode. When in bypass, the entire pedal is bypassed, including the Drive section, no matter the state of the Drive LED.


This knob controls the input gain of the overdrive section. As you turn DRIVE clockwise, the amount of overdrive saturation increases to give you a more distorted sound. Set Drive to a lower setting for a clean volume boost.

The TONE knob adjusts the frequency response of the overdrive’s hi-cut filter, allowing you to dial in the perfect overdrive tone.

VOL Knob [Drive Level]
The Drive VOL knob is located on the left side of the lower row of knobs, and controls the output volume of the Drive section. Use this knob to balance the output volume between Drive on and Drive off.

DRIVE Footswitch & LED
The DRIVE footswitch allows you to engage or bypass the overdrive section. When Drive is engaged, the white LED above the DRIVE footswitch lights up. The last state of the DRIVE footswitch is recalled upon power-up, as with the KNEE and LIMITER buttons.

NOTE: The Platform must be in effect mode for Drive to be heard. The Drive section will not be heard if the pedal is in bypass mode. 

The Swell algorithm is triggered every time a new note is played. The normal attack of your instrument is replaced by a sound that fades in slowly. The Swell function is located after the overdrive and compressor functions in the signal chain, but before the main VOL knob. Swell has just one control, the SWELL knob. Swell mode works best on instruments that have a quick attack and long sustain, such as a guitar, bass, synthesizer or organ.

Adjust fade-in time with this knob. As you turn SWELL clockwise, the fade-in time increases. When SWELL is set to zero, the Swell effect is bypassed.


Input -> Compressor/Limiter -> Overdrive -> Swell -> Output

MONO/L INPUT Jack – Instrument/Line level 1/4" unbalanced input jack that accepts a maximum signal level of +7.2 dBu. Plug your instrument or output from another effects pedal into this jack. If you use just one input, we recommend using the MONO/L input. The input impedance presented at this jack is 1MΩ.

R INPUT Jack – Instrument/Line level 1/4" unbalanced input jack. Plug your instrument output or another effects pedal into this jack. Use this jack with the MONO/L INPUT jack for stereo use. The input impedance presented at this jack is 1MΩ. The maximum allowable signal level into this jack is +7.2 dBu. If you do not use the R INPUT jack, the Left input signal connects to the R INPUT jack.
MONO/L OUTPUT Jack – 1/4" unbalanced output jack. The Left output signal is sent through this jack. In Bypass, the dry signal at the Left input jack outputs to the MONO/L Output jack. The source impedance of the MONO/L OUTPUT is approximately 300Ω.

R OUTPUT – 1/4" unbalanced output jack. The Right output signal is sent through this jack. In Bypass, the dry signal present at the Right input jack is output to the R OUTPUT jack. If a plug is not inserted into the Right input jack then the Left signal is output on the R OUTPUT jack in both effect and bypass modes. The source impedance of the R OUTPUT is 300Ω.

9V Power Jack
Plug the output of the factory-supplied EHX9.6DC 200mA AC adapter into the 9V power jack located at the top of the Platform. The Platform draws 125mA at 9VDC with a center negative plug. The Platform accepts Boss® and Ibanez® style AC Adapters capable of delivering at least 150mA.  
MONO IN & OUT: Left In -> Left Out: when using the Platform in mono, connect to the Left Input and Left Output.

MONO IN, STEREO OUT: Left In -> Left Out & Right Out: same connections as mono in and out but add the Right Output. The Right output signal will be identical to the Left Output both in effect and bypass modes.

STEREO IN, STEREO OUT: Left In & Right In -> Left Out & Right Out: The left and right audio signals remain separate through all effects “blocks,” including the Compressor/Limiter, Overdrive and Swell. The compressor’s sidechain—which is the signal path that controls the compressor’s gain reduction—sums together the left and right input signals to make one balanced mono signal in which to control the compressor. The sidechain acts on both left and right gain control equally so that sudden changes in the left or right input signal will not ruin the stereo balance of the source material.

NOTE: Swell remains completely separate for the left and right inputs, and so left and right fade-ins are triggered independently from each other.


1. When used as a guitar pedal, compressors typically perform their best near the beginning of an effects chain, usually before distortion pedals. Having said that, feel free to experiment with the Platform’s location in your pedal chain; new uses for compression are waiting to be discovered!
2. If you are in compressor mode with SUSTAIN at maximum and you feel like you need even more of a compression effect, turn on the LIMITER.
3. If you hear pumping and would like to reduce it, try the following settings in this order:
• increase the RELEASE knob setting
• decrease the ATTACK knob setting
• decrease the SUSTAIN knob setting
4. If you hear clicking or too much pop at the beginning of your notes, try the following adjustments in this order:
• decrease the ATTACK knob setting
• increase the RELEASE knob setting
• decrease the SUSTAIN knob setting
5. The Drive section can be used as a clean volume boost: turn the DRIVE knob down below 9 o’clock, set the Drive’s VOL knob to 2 o’clock or above and set TONE to taste.