Presonus – ACP 88 Eight Channel Limiter/Compressor

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Product Details
Brand: Presonus

Eight Channel Limiter/Compressor

Classic Dynamics Control

One of our all-time most popular products, the ACP88 delivers the classic analog compression that helped establish PreSonus as a leading signal-processor manufacturer. With eight independent, full-featured compressor/limiters and gates, the ACP88 can solve a host of thorny studio and live-sound problems. A switchable power transformer enables international use.

Each channel provides a fully variable compressor with a sidechain send and return to enable spectral processing and ducking. In addition to the usual attack, release, ratio, threshold, and makeup gain controls, each compressor offers selectable soft- or hard-knee compression and an Auto Attack feature. A six-segment LED meter displays the amount of gain reduction, and pair of LEDs indicate gate position (open/closed) and compression threshold (above/below).

Outstanding Audio Quality

At the heart of the ACP88 is the highly respected THAT 4301s VCA. This VCA has unsurpassed dynamic range, extremely low distortion characteristics, and virtually no noise. With its top-shelf components and classic analogdesign, it’s no surprise that the ACP88 delivers best-in-class audio quality.

The Auto button places the compressor in Auto Attack mode. In this mode, the Attack and Release knobs are inoperative, and preprogrammed Attack and Release curves are applied.

Full-Featured Noise Gates

The compressor/limiter is followed by a full-featured gate with attack, release, and threshold controls; a gate-range switch, which determines the amount of level reduction that occurs when the gate closes; and a sidechain/key insert loop that enables the gate to be opened, or “keyed,” in response to a modified version of the program signal or some other external source.

Each channel of the ACP88 has a separate dynamic noise gate that can be used to gate an entire drum kit, isolate an instrument, or separate a vocal from background noise. Parameters include Attack, Threshold, Release, and Range.

The Attack control is variable from 10 microseconds to 100 milliseconds.

The gate Threshold sets the level at which the gate opens, as indicated by the Open LED above the Threshold knob. The Close LED above the Threshold knob indicates when the gate is closed (i.e., the signal level is below the threshold). If the Threshold is set fully counter-clockwise, the gate is turned off (always open).

As the Release time is lengthened (clockwise), the Close LED reflects the close time.

Gate range determines the amount of level reduction that occurs when the gate closes. If the Range switch is set at 15 dB, there will be a slight change in the signal as it crosses the Threshold. If the Range switch is pushed in, the signal will be reduced by 60 dB. The Close LED above the Threshold knob indicates this by changing brightness relative to the Range amount that has been selected. When the Range is set to 15 dB, the Close LED will show half illumination. When the Range is set to 60 dB, the Close LED will illuminate to its brightest level at the end of the release period.

Gates with Chains, No Less!

Each channel of the ACP88 includes a sidechain send and return for the gate.

Sidechaining is useful for numerous applications, including removing sibilance from vocal tracks (de-essing), spectral processing, compression keying, and automatically ducking (lowering the level of) music tracks behind a narrator in a service, broadcast, or performance.

Sidechaining is often used for frequency-dependent gating, in which you put an equalizer or filter before the gate to, say, cut only the lower frequencies of a kick drum.

When multiple ACP88 channels are , the sidechain send for the master channel contains a mix of all the channels in the link—a very cool feature that allows control over multiple channels of processing with one sidechain send/return.

Channel Link Rules!

With eight independent dynamics processors in one unit, you can employ tricks that aren’t possible with lesser processors. The Channel Link feature lets you lock together as many channels as you wish, so that all processors follow the setting of the master processor. Since you can create multiple simultaneous link groups, you could link a stereo pair of channels plus a group of four processors and still have two unlinked channels for other applications.

The ACP88’s Link feature creates a master-slave relationship between channels such that the master channel’s settings are applied to all slave channels. It is possible to link multiple channels to one master channel.

When a Channel Link button is engaged, the channel is slaved to the channel to its immediate left. All controls for the linked channel are disabled, and gain reduction is indicated by the master channel’s meter. (The slave channels’ Link LEDs and meters still operate and act as signal-presence indicators.)

If multiple Link buttons are engaged, then the channel furthest to the left of the linked channels becomes the master for those channels.

Independent Bypass For Each Channel

Each ACP88 channel can be independently bypassed so you can audition signals with and without processing. Activating Bypass effectively removes all processing and returns the signal to unity gain. Bypass affects both the gate and the compressor. When bypassed, the Link function is interrupted for that channel.

Works Great with Semipro and Pro Gear

The ACP88 is designed to work smoothly with a variety of professional and semipro gear. You can select +4 dBu or -10 dBV operating levels independently for each channel.

The ACP88 operates internally at +4 dBu. Each channel has a +4/-10 switch that adjusts the channel’s internal operating level. When the channel is connected to line level (0 dB = -10 dBV) gear, place this switch in the -10 position to adjust the signal by 11.2 dB in order to take advantage of the lower noise floor of the ACP88’s internal circuitry. The signal level is then lowered on the way out to match the line-level gear’s input.

When the switch is in the +4 position, the signal is not changed, since this matches the ACP88’s optimum internal operating level.

Old Skool Rules

Some people say they don’t make signal processors the way they used to. Nonsense. The ACP88 is a superb old-skool processor, with physical knobs and switches for every parameter, shoehorned into two rackspaces, and it delivers a pure analog sound that will always be in style.

So if you want a professional analog dynamics processor that is every bit as powerful and sonically pleasing as the famous vintage processors were “back when,” try the ACP88. Because great sound never gets old.

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