API AUDIO TCS-II Channel Strip

512C Preamplifier Section

The input section is equipped with the legendary API 512C preamplifier with microphone, instrument, and line inputs. The 512C preamplifier is designed to provide an unusually good sounding front-end for all types of audio recording applications. Sonically, it offers the distinct API sound, high-quality performance, and low noise.

• Microphone preamp with 14 to 68 dB total gain range (with -20 dB pad)
• Instrument preamp with 14 to 50 dB total gain range
• Line preamp at unity gain
• -20 dB microphone pad
• -6 dB line pad
• Switchable 48V phantom power
• Polarity inverter
• +22 dBu preamp output peak indicator
• Routable to the 10-segment LED level meter
• Rear-panel XLR balanced, low-impedance mic input
• Front-panel 1/4" -10 dBu unbalanced, high-impedance instrument input
• Rear-panel 1/4" TRS balanced, +4 dBu low-impedance line in
• Rear-panel 1/4" TRS balanced +4 dBu, low-impedance line preamp out
• Low noise (-129 dBm EIN)
• Famous API 2520 op-amp and transformer

527A Compressor Section

The API 527A compressor takes its place alongside the family of API VCA based compressors, the 225, 529, and the 2500+ stereo bus compressor. Anyone familiar with those units will immediately be at home with the 527A.

• Type switch for feed-forward or feedback compression
• Knee switch for hard- or soft-knee compression 
• Patented THRUST function for frequency dependent side chain control
• Continuously variable detented threshold control
• Continuously variable detented attack and release controls
• Continuously variable detented ratio control
• 10-segment gain reduction (GR) meter
• In/Out switch
• Comp bypass activates hard relay bypass when engaged
• Post EQ routing moves the 527A to after the 550A equalizer
• Link activates multiple unit compression linking (stereo/multichannel compression)
• DC Link to interface with other 527As for stereo/multichannel operation
• Side-chain input for external keying
• Audio circuit uses API 2510 and 2520 op-amps

THRUST Circuit

The 527A 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.

DC Link Function

The 527A compressor in the TCS-II can be linked with 527/527A compressors in other units for stereo and multichannel applications. When connected together and the LINK switches are engaged, the DC control voltages from all units are summed together.

This results in the same control changes being applied to all compressors. Because this is not a master/slave configuration, the threshold, attack/release times, and ratio of all units should be set to the same values to prevent one channel from generating a disproportionate contribution to the summed control voltage.

550A Equalizer Section

Few equalizers enjoy the respect and admiration of the coveted API 550A equalizer. Designed by the legendary Saul Walker in the late '60s, the 550A equalizer was first used as a modular OEM equalizer.

• 3 bands of classic API equalization
• Each band offers seven API selected frequency centers
• Reciprocal and repeatable filtering
• Maximum 12 dB of boost/cut per band
• Low and High EQ bands offer shelf/peak switching
• Proportional Q narrows filter Q at extremes
• Band-pass filter (-3 dB at 50 Hz and 15 kHz)
• High headroom +30 dB clip level
• Traditional API circuit design using the 2520 op-amps

325 Line Driver Output Section

The output section of the TCS-II includes an insert, output level potentiometer, soft mute (CUT), and the API 325 line-driver output circuit (a 2520 and 1:3 output transformer) taken directly from API console designs. The 10-segment LED level meter can be switched to monitor the output level of the TCS-II or the output of the 512C preamp.

• Insert: switchable insert return
• Cut: soft output mute
• Output fade with full attenuation to +10 dB of gain range
• Routable 10-segment LED dBu level meter displays 512C output or main output level
• High headroom +30 dB clip level
• API circuit design using the API 2520 op-amp with output transformer

General

Inputs/Outputs

Power

Physical