527 Compressor/Limiter Operator's Manual API, 8301 Patuxent Range Road, Jessup, MD 20794 Tel: 301-776-7879 www.apiaudio.
API 527 Compressor Features • Feed-forward or feed-back compression • Hard or soft knee compression • Patented THRUST® switch for frequency dependent side chain control • Continuously variable detented THRESHOLD control • Continuously variable detented ATTACK and RELEASE controls • Continuously variable detented OUTput level control • Continuously variable detented RATIO control • 10 segment gain reduction (GR) meter • Side chain input • LINK switch for multiple unit interdependent compression linking (ste
API 527 Compressor The API 527 Compressor takes its place alongside the family of API VCA based compressors, the 225L and the 2500 Stereo Bus Compressor. Anyone familiar with those units will immediately be at home with the 527. Features common to the line like "feed forward" (NEW) and "feed back" (OLD) gain reduction methods selectable on the front panel, provide a choice of "that old way", or "the new way" of compression, for the highest level of flexibility in signal gain control.
Compressor Controls API 527 Compressor 527 OUT - Continuously variable 31 position detented output level pot VU OV GR -1.5 3 -4 2 -6 1 0 O U T -8 0 -10 -1 -12 -3 -15 -5 -17 -7 -19 -10 -23 -20 00 dB 0 VU 10 1 1.5 15 7 METER -6 T H R E S H -20 dBu 4 GR -3 10 2 5 .5 IN 25 3 RELEASE S .3 1 ATTACK mS TYPE OLD 2.5 HARD 3 4 6 KNEE SOFT 1.5 IN THRUST IN ATTACK/RELEASE - Continuously variable 31 position detented controls 20 2.
API 527 Compressor OUT OV 0 O U T 00 dB OUT: Sets the output level of the 527 · Continuously variable 31 position control 10 THRESHOLD 0 4 7 10 -3 -6 T H R E S dBu -20 H THRESHOLD: Sets the level at which compression begins · Continuously variable between +10dBu and -20dBu · Detented 31 position rotary pot for easy recall · Turning clockwise results in more Compression ATTACK and RELEASE 1 1.5 15 2 5 .5 20 2.5 .3 1 ATTACK mS 25 3 RELEASE S 15 5 20 1.5 2 .5 2.5 .
API 527 Compressor RATIO 3 2.5 4 6 1.5 10 1 RATIO 00 RATIO: Sets the ratio of input vs. output levels for signals that exceed the set THRESHOLD · Continuously variable between 1:1 and infinity (hard Limiting) · A Ratio of 10:1 or greater is generally considered to be a limiter · Detented rotary pot for easy recall METERING - Gain Reduction GR VU OV -1.
API 527 Compressor METERING - Output Level GR VU OV -1.5 3 -4 2 -6 1 -8 0 -10 -1 -12 -3 -15 -5 -17 -7 -19 -10 -23 -20 An OUTput level meter is provided to indicate the 527’s output in VU when the METER switch is in the VU position. The audio output increments provided are: · · · · · · · · · · GR METER VU IN LINK +3 dB +2 dB +1 dB 0 dB Note: 0Vu = +4dBu -1 dB -3 dB -5 dB -7 dB -10 dB -20 dB NEW TYPE In addition, a PEAK (OV) LED is provided that will illuminate at +27 dBu.
API 527 Compressor LINK GR LINK: The LINK switch activates the DC control voltage summing with other units. METER VU IN LINK NEW TYPE OLD IMPORTANT NOTE! HARD KNEE SOFT IN THRUST IN R The Link function of the 527 does NOT operate as other master/slave linked compressor pairs do, where the master unit’s controls become the master control for both units while the slave unit’s controls are disabled.
API 527 Compressor COMPRESSION TYPE The 527 Compressor can be set to operate in two circuit topologies: · OLD: Feed-Back topology: The RMS detector receives the signal from after the VCA · NEW: Feed-Forward topology: The RMS detector receives the signal from before the VCA GR METER VU IN LINK NEW TYPE OLD HARD KNEE The compressor circuit topology is selected using the TYPE switch.
API 527 Compressor NEW: Feed-Forward Compression In a feed-forward compressor, the RMS detector normally gets its signal from a split of the input signal. With this method, the RMS detector sends a signal to the VCA that is an exact ratio of the desired compression set by the RATIO control. This is how many new VCA based compressors work. This can yield more aggressive compression and a harder, more affected sound.
API 527 Compressor KNEE Soft Knee Compression SOFT: Rounded response curve · Gradual onset of compression (fade-in up to the set ratio) · Similar to an “over-easy” type knee · Generally considered more transparent Hard Knee Compression HARD: Sharp response curve · Immediate onset of compression (sudden transition to set ratio) · More aggressive and noticeable Page 10
API 527 Compressor THRUST® SOFT IN THRUST IN R The 527 Compressor includes API’s patented THRUST® circuit that can be switched in or out as needed. This places the THRUST® filter before the RMS detector that decreases the compressor’s reaction to low frequency content. The result is a noticeable increase of punch and low frequencies, but a uniformly compressed signal.
API 527 Compressor IN/OUT Switch IN: The In/OUT switch inserts or removes the 527 from the audio path via a relay bypass. When the switch is in the OUT position, a relay connects the audio Input to the Output – completely removing the 527 from the audio chain.
API 527 Compressor SPECIFICATIONS Input Impedance: High Level In 160K ohms Low Level In: 80K ohms Output Impedance: High Level Out 85 ohms Low Level Out: 50 ohms Nominal Operating Level: -2dBu or +4dBu Maximum Input Level: +26dBu Maximum Output Level: +26dBu Output Fader Control Gain: -Infinity to +10dB Attack Times: 1 millisecond to 25 milliseconds (typical) Release Times: 0.
= F E A P I , 8 3 0 1 P a t u x e n t R a n g e T e l: 3 0 1 - 7 7 6 - 7 8 7 9 R R o a d , J e s s u p , M D 2 0 7 9 4 w w w .a p ia u d io .c o m In a c o n s ta n t e ffo r t to im p r o v e th e s u b tle d e ta ils o f o u r p r o d u c ts , s o m e a m o u n t o f c h a n g e is in e v ita b le .
