AP-1

Microphone/instrument amplifier, Envelope follower, Opto compressor

The AP-1 consist of three parts:

• Microphone/Instrument amplifier
• Envelope follower
• Opto compressor

Preamp section

The preamp section consist of a low noise /high speed gain booster for signals to an adequate level for the opto compressor. Two audio inputs are accessible; the mic input provided by a balanced XLR socket and instrument input provided by 1/4 '' single ended socket. The mic input can be powered by the phantom voltage (48 Volts) for driving condenser microphones. The mic amplifiers wide gain range (from 1 to 71 dB) is ideal for amplification of week signals (ribbon microphones and dynamic microphones) and a high output level condenser microphones. The instrument amplifier has 6 dB lower gain range than the microphone amplifier and it's ideal for amplification of signals from high impedance sources, such as guitar pick-ups, piezo-transducers and other weak to moderate level signal sources.

Envelope Follower

The Envelope Follower extracts the amplitude of amplified signal to DC signal as CV for control of opto compressor. The Envelope follower has three controllable (manually and by dedicated CV inputs) parameters; Attack Time, Release Time and selectable input high- and low pass filter.

Opto Compressor

The Opto Compressor is build around an opto-electric device and low noise /high speed gain booster (pro-audio, j-fet op-amp for both instrument amplifier and compressor). The gain reduction is controlled by an extracted DC signal from the Envelope Follower. The amount of compression is controlled by the strength of input signal, gradually from soft compression (soft knee) to limiting for high level input signals. The opto compressor is completed with 15dB make-up gain. The Compressor's side-chain is coupled to the envelope followers input filter in purpose to make compression less sensitive to filtered signals by the envelope filter.

http://cwejman.net/ap-1.htm