You Can DIY! Designing a Powerful Speech Compressor

This project describes a dynamic compressor circuit working in reverse. Instead of limiting the maximum volume level of an audio signal, it leaves loud parts alone and instead raises the volume when it’s too soft. The project uses a famous VCA circuit designed by David Blackmer of dbx fame, developed in the 1960s, whose patent expired long ago. The resulting original design is useful for transcribing conference meetings, court reporting, or any other situation where the volume level of recorded speech can vary by a large amount.

During the 137th International Audio Engineering Society (AES) Convention in Los Angeles, CA, a session on the Broadcast & Streaming Media Track discussed “Loudness for Streaming and Radio.” Thomas Lund (TC Electronic), an expert and longtime promoter of the loudness standards currently implemented in TV broadcast, chaired the session, which included an interesting angle from Bob Orban (Orban) and Frank Foti (Telos/Omnia).

Everyone else’s doing it, so why shouldn’t an historic brand like dbx do it as well? With the new model 676 Tube Mic Pre Channel Strip, HARMAN’s dbx offers a Class A vacuum tube-based microphone preamplifier combined with its classic compressor/limiter designs and dynamics processing in a vintage-style solution.