dbx Model 160 and 161 Compressor/Limiters

Message Board - dbx Model 160 and 161 Compressor/Limiters

The dbx 160 and 161 are single-channel compressor/limiters combining sophisticated technology and user-oriented features in a compact package. Unique circuit designs, such as true rms level-detection and feed-forward gain reduction, place the 160 and 161 in a completely different class from conventional compressor/limiters.

The dbx technique of true rms level-detection gives you audible benefits. Most compressor/limiters use some form of peak detection, with fast response characteristics that can have a disturbing effect on program material. True rms level detection closely simulates the response of the human ear. Even at high compression ratios, the gain changing action of the 160 Series is highly listenable and natural sounding.

Because of the unique feed-forward approach, dbx 160 and 161 limiters can achieve infinite compression with complete stability and inaudible distortion. The dbx approach is quite unlike gain reduction in a conventional compressor/limiter. Traditional gain reduction is accomplished by sensing signal level at the device's output and applying a correction signal, via a feedback loop.

At progressively higher compression ratios, the feedback loop's gain increases, distortion increases, and eventually instability or oscillation occurs. To avoid this problem, many conventional units restrict the maximum amount of feedback, thus restricting the maximum compression ratio to somelower ratio, such as 10:1 or 20:1. The dbx 160 and 161 are free of the instability of excessive loop gain, and can provide infinite compression (approximately 120:1).

In addition to increasing the stability and the available range of compression, dbx's feed-forward approach makes it possible for the attack and release times to "track" the signal envelope. In conventional compressor/limiters, the attack and release times depend on feedback loop gain, which means they constantly must be readjusted for optimum results at different compression ratios. Since the attack and release times of dbx units vary automatically with the rate of level change in the program material (the envelope shape), operation is simplified; no manual attack/release adjustments are required. At the same time, the "naturalness" of any given sound is better preserved.