The Purple Audio MC77 is a compressor that faithfully recreates the audio circuitry of the revision E 1176, utilizing modern components matched to the original design. The MC77 is designed with a focus on quality, longevity, and flexibility, making it a versatile tool for compression in various audio applications.
Key Features
Discrete Transistor Audio Path Electronics: The MC77 employs a discrete transistor audio path, ensuring a high-quality signal flow.
Single Element Class A Output Amplifier: The unit features a single-element Class A output amplifier, contributing to its overall performance.
Transformer Balanced XLR Inputs and Outputs: The inputs and outputs are transformer-balanced XLR connections, providing reliable and high-quality signal transmission.
Zener Shunt Regulated Audio Power Supply: The audio power supply is regulated using Zener shunt technology, contributing to stable and clean power delivery.
Compression Ratios: The MC77 offers multiple compression ratios, including 4:1, 8:1, 12:1, and 20:1, providing flexibility for different compression scenarios.
Fast Attack Time: The compressor features a fast attack time ranging from 20 to 800 microseconds, allowing for precise control over the compression envelope.
Release Time: The release time is adjustable, ranging from 50 milliseconds to 1.1 second, enabling customization of the compression characteristics.
Gain of 45dB: The MC77 provides a gain of 45dB, allowing for significant signal amplification without limiting.
Ruggedized Design: The design includes features such as a PCB stiffener and chassis mounts, ensuring durability and robustness.
Purple Anodized Aluminum Front Panel: The front panel is made of purple anodized aluminum, providing an aesthetically pleasing and durable interface.
True Bypass: The unit includes a true bypass function via a sealed relay with a front panel switch, allowing for unaltered signal flow when bypassed.
Improved Stereo Linking: The MC77 includes a front panel switch for improved stereo linking, enhancing its capabilities in stereo applications.
Sidechain Insert Loop or Key Input: The compressor features a front panel switch for selecting between a sidechain insert loop or key input, adding versatility to its functionality.
Buffered VU Meter: The buffered VU meter can monitor either input or output levels at +4dBu, providing visual feedback on signal levels.
LED Meter Lights: The unit includes LED meter lights designed for longevity, ensuring reliable metering over time.
Heavy Gauge Black Cold Rolled Steel Enclosure: The enclosure is constructed from heavy-gauge black cold-rolled steel, providing durability and protection for the internal components.
155V/230V Operation: The MC77 is switchable between 155V and 230V operation, offering flexibility for different power requirements.
PRODUCT SPECIFICATIONS
Input:
Constant Impedance Input Attenuator
Transformer Balanced and Floating
Input Impedance:
600 ohms at all input gain settings
Maximum Input Level:
+30dBu with limiting active and input cranked up full
(Prolonged exposure to signal levels in excess of +30dBu may burn up the input attenuator)
Maximum Gain:
45dB ±1dB (with limit action switched off)
Frequency Response:
15Hz to 80KHz ±1dB typical
Output:
Floating Transformer Balanced
Output Load:
150 ohms or higher
Load Dependence:
The Output Level as measured while driving into a bridging load will
drop by no more than 1/2 dB when a load of 600 ohms is added there will be a loss in
headroom
Maximum Output Level:
+24 dBm into 600 ohm load (12-1/4 volts RMS)
+30 dBu into bridging load (24-1/2 volts RMS)
Distortion:
Less than 0.5% THD+noise 22Hz-22KHz with limiting activeRelease time set to
1.1sec (fast release times will increase distortion at low frequencies) - NOTE: The VU meter
is now buffered from the audio and adds no appreciable distortion.
S/N Ratio:
>81dB at threshold of limiting 22Hz - 22KHz unweighted
Attack Time:
Less than 20µsec for full limiting action
adjustable to 800µsec with front panel control
Release Time:
Minimum 50msec adjustable to 1.1sec maximum (for 63% recovery) with
front panel control
Threshold and Ratio:
With the input control fully clockwise and the output gain control
set 10dB below maximum (at about 6 on the dial)
The overall gain (before limiting) should be 35dB (±1dB)
The threshold of limiting is defined here as 1dB of limiting
at 20:1 the threshold of limiting will occur with an input of -24dBu (±2dB) and yield an
output level of +10dBu
at 12:1 the threshold of limiting will occur with an input of -25dBu (±2dB) and yield an
output level of +9dBu
at 8:1 the threshold of limiting will occur with an input of -26dBu (±2dB) and yield an
output level of +8dBu
at 4:1 the threshold of limiting will occur with an input of -30dBu (±2dB) and yield an
output level of +7dBu
Note: lower ratios make the limiting action kick in sooner
Dimensions:
2U 19" rack mounting enclosure (19" wide 3-1/2" high)
Depth behind front panel is 8" (not including connectors)
Finish:
Front Panel is 1/8" thick aluminium purple anodized
with some variation in color - this can be viewed as a feature and lends a certain
individuality to each unit - Case finish is black powder coat. Legends are silk screened in
white.
Weight:
12 pounds – loose, 15 pounds – shipping weight.
Start with the customer – find out what they want and give it to them.
