Related Manuals for Purple MC76
Summary of Contents for Purple MC76
- Page 1 Purple Audio Inc. MC76 Peak Limiter Effective with serial number 001 The MC76 is a Monaural FET Peak Limiting Amplifier...
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Page 2: Unpacking And Installation
*3 Year Warranty UNPACKING AND INSTALLATION Your MC76 was packed with care at the factory. The packaging was designed to protect the unit from rough handling. However, once the unit leaves us, it may pass through the hands of those who have no idea what is in the box, may not be happy with work, may like to throw things, don't care.. - Page 3 The carton we ship out contains: *One MC76 Limiting Amplifier *This Manual *One six foot (two meters) IEC Cable *Warranty Card The unit can operate safely and within specification over a range of ambient temperatures from 0°C (+32°F) to +50°C (+122°F). Humidity is generally not a factor unless there is condensation.
- Page 4 6) Select Meter to +4 (or +8 if 0VU in your facility is referenced to +8dBu) and look at the level coming out of the MC76. Set the Output Gain to a level that makes sense for you and then return the Meter Select to GR after you set the output level.
- Page 5 OPERATING INSTRUCTIONS The Attack Time of the MC76 is the time it takes for the detector circuitry and FET to respond to a signal as it exceeds the threshold. This parameter is variable by the user since the adjustment may have a significant effect on the sound of the program material.
- Page 6 DESCRIPTION The MC76 is a gain limiting amplifier. Units of this type have been used for many years to provide precise and automatic control of peak signal levels in recording studios, disc mastering facilities, broadcast stations and sound reinforcement applications.
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Page 7: General Definitions
Amplifiers with compression ratios of up to 8:1 are often considered to be Compressors, while those with ratios higher than 8:1 are called Limiters. The MC76 can function as a compressor or a limiter since it has compression rations from 4:1 to 20:1. -
Page 8: Specifications - Electrical
SPECIFICATIONS - ELECTRICAL Note: the dB voltage level measurements listed here are referenced to 0.775 Volts RMS. We have seen dB measurements referenced to 0.775 Volts RMS labeled interchangeably as dBu or dBv (note the little "v") while dBV (a big "V") uses 1 volt as a zero reference... - Page 9 SPECIFICATIONS - ELECTRICAL - continued 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 should be switched to GR mode in normal operation as it is unbuffered and will add distortion to the signal if left hanging across the output in the +4 or +8 settings S/N Ratio: >81dB at threshold of limiting 22Hz - 22KHz unweighted...
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Page 10: Specifications - General
1/16 Amps Line Frequency can be 50-60Hz Temperature: The MC76 can operate safely over a temperature range of 0°C to +50°C The MC76 can be stored over a temperature range of -20°C to +60°C... -
Page 11: Description Of Front Panel Controls
DESCRIPTION OF FRONT PANEL CONTROLS Input Level Control: Continuously adjustable rotary attenuator Output Level Control: Continuously adjustable rotary potentiometer Attack Time: Continuously adjustable rotary potentiometer Ranges from the slowest attack time of 800µsec to the fastest attack time of 20µsec at the full clockwise rotation Limiting In/Out: The Attack Time control has a switch position at its full counter-clockwise rotation. -
Page 12: Back Panel Connections And Controls
Lithium Cells are harder to find but many camera/photo stores carry them. VU Meter: If you drop your MC76 the VU meter may fail even if there is no other obvious damage. -
Page 13: Repairs And Warranty
(used for stereo offset) and meter lamps. We will not repair damage that results from misuse, abuse or neglect. We do not guarantee that the purple color of every unit will match the purple of every other unit. -
Page 14: Internal Service Adjustments
MAINTENANCE - continued INTERNAL SERVICE ADJUSTMENTS These controls have been set at the factory and should not require adjustments except after service work. If re-calibration is necessary, the test procedure that follows should be performed very carefully, and adjustments performed in the exact manner and order specified. - Page 15 Disconnect R44 Voltmeter across R74 Calibration 1. Zero MC76 "GR" meter with R71 (Thru front Panel Zero Adjust) 2. Adjust pot R75 for 0.0 Volts across R74. 3. Repeat 1 & 2 until both conditions are met. 4. Set controls as follows: Input = "24"...
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Page 16: Cleaning The Limiter
Adjust R86 until the minimum amount of distortion is achieved. CLEANING THE LIMITER The front panel of the MC76 may be cleaned with a non abrasive cleanser such as Formula 409, or "Fantastic" applied with a soft clean cloth. Additional protection of the anodized panel can be afforded through a light application of a spray wax preparation such as Pledge. - Page 17 PRE-AMP 6.8K 100uf/25v C815 .1uf C816 2N3391A .1uf C600 560K T1 UTC 0-12 or Equivalent 2N3391A 100uf/25v 2N3391A 620 1/4w C817 .1uf 620 1/4W 27pf 1uf/50v 2N5457 250K 2W 100uf /25V Output F.P. 100uf/25v 6.8K 2.2M P.C.B. 200pf 200pf 2.2M 56K 1/4W 68K 1/4W 56K 1/4W...
- Page 18 OUTPUT AMP .0047 8.2K 10pf BROWN BLUE 1.2M 1uf/50v YELLOW 2.7M 2N3053 BLACK ORANGE 2N3391A 2N5088 C8 .15 C819 C601 .1uf 100uf/25v C818 100uf/25v WHITEBLACK GREY 200K .1uf utput F.P. 1.5K .033 WHITERED VIOLET 2.7M IN4148 270pf 470 1/4W 560 1/4W 1.5K 1/4W 1.5K 1/4W 12:1...
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