Purple Audio MC77 Limiter

 

The MC77 is a standard 19″ two space rackmountable limiter. The MC77 recreates the audio circuitry of the revision E 1176, using modern components matched to the original.

 

One significant component is the input attenuator. The input attenuator that was custom made for the original revisions A-F 1176 and for the Purple MC76 by Clarostat was discontinued in 2002. It was a J series T-pad attenuator with two 600 OHM “build out” resistors to keep a constant 600 OHM load on the source and primary of the input transformer. Clarostat changed carbon manufacturers and the new carbon manufacturer was unable to make the part. Purple temporarily stopped making the MC76 to find a solution. We tried several three deck Clarostat 70 series pots in different configurations to achieve the same loading and to match the taper. We found a solution that matched the original. Based on that feedback, from hundreds of satisfied MC76 users we incorporated useful new features into the new MC77.

 

• True Bypass via sealed relay w/front panel switch

• Improved stereo linking w/front panel switch

• Sidechain insert loop or key input w/front panel switch

• Buffered VU meter can monitor input or output level at +4dBu

• LED meter lights that don’t burn out

• Heavy gauge black stainless steel enclosure

• 155v/230v operation switchable from rear panel

 

• Discrete Transistor Audio Path Electronics

• Single Element Class A Output Amplifier

• Transformer Balanced XLR Inputs and Outputs

• Zener Shunt Regulated Audio Power Supply

• Compression Ratios – 4:1, 8:1, 12:1 and 20:1

• Fast Attack Time – 20 to 800 microseconds

• Release Time – 50 milliseconds to 1.1 second

• Gain of 45dB (full gain with no limiting)

• Ruggedized Design – PCB stiffener, chassis mounts

• Purple Anodized Aluminum Front Panel