As APL detailed loudspeaker equalization solutions are intended to be used for the utmost critical applications, it was nothing short of our obligation to create an equalizer unit that is respective of that – the APL1s. The APL1s unit is designed to meet even the most critical demands in audio signal processing quality – with a 96kHz sampling rate, 117 dBA dynamic range, and ultra-low latency – 0.15 ms for digital in, analog out (in synchronized mode), ultra-low jitter of 136 ps by double PLL, AES/EBU balanced, SPDIF coaxial and TOSLINK optical digital inputs and outputs. The 16 presets are controllable by a rotary switch on the front panel, and powerful analog outputs are capable of driving hundreds of meters of cable. The APL1s also features a very compact, half-rack enclosure. All this is served by a two channel, 4096 tap, FIR equalizer engine that is capable of delivering any equalizer curve with maximum precision. APL Workshop and APL TDA EQ software are available as tools for loudspeaker measurement and FIR equalizer curve synthesis for the APL1s unit’s FIR engine. The user can also use his own synthesized FIR filters in .wav format to supply to APL1s unit’s FIR engine.




  • 2 channel 4096 coefficient FIR equalizer processing.
  • FIR filter file upload by USB interface.
  • 16 preset internal memory selectable by the rotary switch on the front panel of unit
  • Bit Depth: 24 (up to 56 bit custom FPGA processing)
  • Sampling frequency 48/96 kHz depends on firmware version
  • Anti-Pop power on/off protects your ears, nerves and speakers
  • Ultra-low jitter double PLL clock system.


  • 136 ps (bandwidth 5Hz-20kHz)
  • 75 ps (bandwidth 20Hz-20kHz)


48kHz sampling rate.

  • Digital input (synchronous)- analog output: 0.3 ms
  • Digital input (asynchronous)- analog output: 2.5 ms
  • Digital input (synchronous)- digital output: 0.08 ms
  • Digital input (asynchronous)- digital output: 2.25 ms
  • Analog input - analog output: 1.62 ms

96kHz sampling rate.

  • Digital input (synchronous)- analog output: 0.15 ms
  • Digital input (asynchronous)- analog output: 1.25 ms
  • Digital input (synchronous)- digital output: 0.04 ms
  • Digital input (asynchronous)- digital output: 1.1 ms
  • Analog input - analog output: 0.8 ms

Analog inputs:

  • Type: balanced
  • Connectors: XLR
  • Impedance: 10kOhm
  • CMRR: >60dB
  • A/D converter: AK5394A

Analog outputs:

  • Type: balanced, transformer less galvanic decoupling, 10kOhm impedance to ground
  • Connectors: XLR
  • Impedance: 150 Ohm
  • Load capability: 600 Ohm, 15 nF, up to 200 m of a balanced cable
  • D/A converter: CS4398

Operating signal levels (jumper selectable):

  • +4dBu nominal, +20dBu max
  • -10dBV nominal, +6dBV max
  • Frequency response (20Hz - 20kHz) +0.0/-0.3 dB
  • Signal to noise ratio: 117 dBA
  • THD (1kHz at nominal level) 0.0003%

Digital I/O:

  • SPDIF coaxial
  • TOSLINK optical
  • AES/EBU balanced professional
  • Input sample rates: 22kHz-108kHz, supported by SCR4192 sample rate converter
  • Output sample rate: 48/96kHz


  • Complete sync to external clock at 48/96kHz digital input sampling rate.


  • 7.5V DC, 1.1A


  • 222x41x170 mm
  • Weight: 1055 g