Ashly SC33 User's Manual
Contents
1. The Ashly SC 33 Stereo Noise Gate is a versatile two channel noise reduction system requiring only 1 of rack space designed to control leakage and background noise in recording and sound reinforcement applications Acting much like a level sensitive switch it auto matically attenuates audio signals which fall below a user selected threshold while passing audio that reaches or exceeds the threshold FEATURES Fast attack time 10s Rugged 16 gauge steel chassis 60 AB threshold range Two stage release circuit Stereo tie patch point for accurate tracking of two or more gates Inputs and outputs may be used balanced or unbalanced Extremely low noise and distortion In out bypass switching The SC 33 s operation can be broken down into two functional building blocks a voltage controlled omplifier VCA which performs the actual task of muting or passing the audio signal and a detector circuit which is responsible for providing the control voltage that determines the gain of the VCA Use of a VCA as a gain control element provides several advantages in a noise gate including supe rior audio fidelity accurate tracking of two or more units tied for stereo operation and attack release speeds much faster than those possible with optic ally coupled devices The Ashly VCA used in the SC 33 is a Class A device exhibiting extremely low distortion low noise low contr2. ol voltage feedthrough turn on click and excellent thermal stability The detector circuit encompasses all of the front panel controls and generates a control voltoge which gives the SC 33 its turn on and tum off char acteristics Through the use of unusually wide range time constant options and a unique dual release time circuit a great vanety of gating effects can be achieved A very fast 10 microsecond attack time insures that the leading edge of fast transient material such as snare drums will never be lost and the fade contre offers smooth linear fade times of up to 30 seconds The hold control offers a wait before fading option to prevent premature initiation of the fade cycle useful when processing material that contains natural pausos such as speech and instrumental solos The threshold range is greater than 60 dB making the SC 33 useful for both professional and semi pro signal levels Other thoughtful features include detector symmetry to within GB a hysteresis circuit to absolutely prevent chattering near threshold high siew rate circuitry throughout active balanced inputs and a 16 gauge steal chassis oeecIoe METRICAL SPECIFICATIONS FREQUENCY RESPONSE THD 20 20 kHz 10 dBV inputs 02 IM Distortion 20 20kHz 40 dBV Input 02 Crosstalk from Key input tkHz 85 dB Noise 20H7 2NkHz AS dhVY GAIN Unity DETECTOR SYMMETRY 0 25 dB Control Voltage Feedthrough 65 dBV
3. typical MAX INPUT OUTPUT LEVEL 200BV Slew Rate gt 410V per microsecond Threshold Range 40 dBV to 20 dBV 0 2 dB Attack Time per 40 dB gain increase 10 microseconds to 30 seconds Hold Time 40 milliseconds to 12 seconds Fade Time per 40 d8 gain decrease 15 milliseconds to 30 seconds Noise Attenuation Floor 0 dB to 75 dB Input Impedance 10k 22 Balanced Bridging Active Output Impedance 10042 terminate with 600 Q or greater ADDITIONAL FEATURES Key Inpul switch selectable Notse Gate Bypass switch Stereo interconnect via rear panel jacks LED Threshold Indicator
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