Basic Compressor Design Applies THAT4305

This is a basic implementation of audio signal compressor based THAT4305 analog audio engine that applies the attack & release time control. The RMS detector applies a very small CTIME (C6) to result very fast response at approximately 1 ms. To make a possible shorter attack time setting, the output of RMS detector knee is hardened with use a two-pole LPF that handled by U3A. The lowest threshold is approximately -40 dBU. The highest threshold is approximately +20 dBU.

The AR (attack-release) control circuit has two non-inverted logarithmic rectifiers with different polarity, one has the positive output polarity handled by U5C + Q1 as the attack timing resource, and one another has the negative output polarity handled by U5D + Q2 as the release timing resource. This AR control circuit also has an active envelope capacitor control (consist of C11, U5A, U5B, R16, and R17) and so it can result constant attack and release time with the last known user settings and it can also be applied with use smaller envelope capacitor. The attack time can be manually set by the user via RV3. The release time can be manually set by the user via RV4. The shortest attack time is approximately 1 ms. The longest attack time is approximately 500 ms. The shortest release time is approximately 5 ms. The longest attack time is approximately 1800 ms.