- Number of Channels: Eight
- Dynamic Range: >115dB
- Signal to Noise Ratio: >95dB
- +24dBu, Unbalanced
- +18dBu, Balanced
- Frequency Response: 10Hz to 50kHz
- Crosstalk: <82dB @10kHz
- Compression Threshold Range: -40dBu to +20dBu
- Compression Ratio: 1:1 to 20:1
- Compressor Attack Time: 0.02ms to 200 ms
- Compressor Release Time: 0.5ms to 500ms
- Auto Attack and Release: Program Dependent
- Gate Threshold Range: -70dBu to +20dBu
- Gate Attack Time: 0.01ms to 100ms
- Gate Release Time: 0.02ms to 2 sec
- Gate Attenuation Range: -15dB or -60dB
- Input Impedance: 10k Ohms
- Output Impedance: 51 Ohms
- THD + Noise: <0.02%
- Output Gain: -20dB to +20dB
- Compression Curve Types: Hard and Soft Knee
- Compression Metering: Above/Below Threshold LED
- Gate Metering: Open and Closed LED
- Sidechain Output Impedance: 51 Ohms
- Sidechain Input Impedance: 10k Ohms
- Internal Operation Level: +4dBu=0dBu
- Input Range: +4dBu or -10dBu
- Input Connectors: 1/4" TRS, Balanced or Unbalanced
- Output Connectors: 1/4" TRS, Balanced or Unbalanced
- Compressor Sidechain Connector: 1/4" TRS
- Gate Sidechain Connector: 1/4" TRS
- Power Supply: Internal, Linear Supply
- Power Requirements: 100V AC to 120V AC or 200V AC to 240V AC
- Power Connection: IEC Receptacle
- Size: 2U Rack
- Dimensions: 19" x 3.5" x 7"
- Weight: 12lbs
ACP88 Architectural & Engineering Specifications
The compressor/limiter/gate shall have eight identical channels, each with an audio frequency response of 10Hz to 50kHz, an electronically floating balanced input impedance of not less than 10k Ohms, balanced and a maximum input level of not less than +24dBu unbalanced and +18dBu balanced, into a minimum load impedance of 51 Ohms and 1/4" TRS type connectors. The unit shall also have a compression sidechain with an input impedance of not less than 10k Ohms and an output impedance of not less than 51Ohms. Sidechain
input/output jack shall be a 1/4" TRS jack. Total Harmonic Distortion plus Noise shall be less than 0.02%. The unit shall have an Equivalent Input Noise level of not more than -96dBu unweighted, and a dynamic range of not less than 115dB. Ouput gain adjustment shall be variable from -20 to +20dB. The compression threshold range shall be variable from -40 to +20dB and the compression ratio shall be variable from 1:1 to infinity:1. The compressor attack and release times shall be selectable for either program dependent or manually adjustable, scalable operation. The compression ratio characteristic shall be selectable for either the hard or soft knee curve type with a maximum compression of no less than 40dB. The noise gate shall have a threshold of - infinity to no less than +20dBu. The gate attack time shall be variable from 10 microseconds to no more than 100 milliseconds. The gate release time shall be variable from .02 to no more than 2 seconds. The gate range shall be preset for either -60dB or -20dB reduction. All input, output and sidechain signals shall be via the rear panel. The stereo link shall be of the true RMS summing type with the previous unlinked channel as the master when linked. The unit shall have the following front panel switches for each channel: Soft/Hard knee, auto, link, range and bypass. Each channel shall have the following identical controls: Compressor threshold, compressor ratio, compressor attack, compressor release, gate threshold, gate attack, gate release, and channel gain make up; and the following identical metering and indicator LEDs for each channel: Below/Above compressor threshold, compression gain reduction, gate open/close, and link engaged/disengaged. There shall be a rear panel switch for each channel to select nominal input and output operation levels at 10dBV or +4dBu. The power requirements shall be 100-120-VAC 50/60Hz or 200-240VAC, 50/60/Hz, 20W via a detachable IEC type AC cable. The size of the unit shall be19" X 3.5" X 7" and a weight of 10lbs. (4.54kg). The 2U high, full rack width eight channel compressor/gate shall be a PreSonus ACP-88.
Q Hi. I have a quick question regarding the ACP88 and how I can use it with my current PA system. My mixer is the digital Yamaha O1V. As you probably know, this type of board doesn't have insert channels. So I'm wondering if I can send my mics straight into the ACP88, use the compression/gate/limiter functions and THEN go into the board. In other words, does the ACP88 function properly if it is used before the mic preamp?
A The ACP88 will not work before the mic preamp of your console because it is a line level device only and plugging a microphone into it will require a mic level input. You will have to either run external mic preamps before the ACP88 or come into it from a line level source like an aux send or a subgroup.
We have had customers use one of our M80 eight-channel mic preamps in front of the ACP88 and then into the line inputs of digital consoles and that works great. While the M80 will improve the sound you are getting from stock mixer preamps, I realize this may or may not be cost effective for you.
Q What is the feature/sonic difference (improvement) from the ACP8 to the ACP88?
A The biggest changes to the ACP88 were in the gate circuit. The ACP8 had a FIXED ATTACK (gate opening) timing of 50 microseconds and a VARIABLE RANGE attenuation knob. On the ACP88 we scrapped the VARIABLE RANGE in favor of VARIABLE ATTACK TIME (10 microseconds to 100ms) and put the RANGE ATTENUATION control on a two position switch ( -60dB or -20dB). The result is a gate that performs better on a variety of applications because of the ability to slow down the opening time. On the back we added a SIDECHAIN for the gate instead of just the gate KEY. This allows for frequency triggered gating by inserting an equalizer.
Q I purchased an ACP88 and the only thing that is not clear to me is the +4/-10dBu button on the back. What is the difference between "pro levels" and "line levels"?
A +4 and -10 refer to operating levels. +4 is considered "pro" and -10 is often considered consumer level. An operating level indicates what a zero reading on a meter equals. On a VU meter that is on a device set up to operate at -10, a reading of zero on the meter indicates an output level of -10 db. A +4 system at zero on the meter is actually putting out 4 db of signal. In a +4 system, .775 millivolts across 1 watt causes a reading of zero on the meter. This is how the meter is calibrated. If you are using the ACP at the inserts of a channel of a mixer, the usual level is -10. You should check the manual of the device you are using your ACP 88 with to ascertain the o-operating level of the device and adjust the 88, accordingly. If you are unsure, the -10 setting on the 88 outputs and handles lower level signals than the unit would were it set to operate at +4.