So anyways, I purchased this 80's looking used dod rackmount compressor at guitar center recently for $50 and it actually works quite well. I'm just curious what the de-ess knobs do..? It's the first time I've seen this on a compressor and it can be combined with the compression (and with a sidechain). The model on the compressor is R-825 and any info is appreciated My guess is that it's something to do with recording analog, but I could be wrong.. It actually sounds best with de-ess level and output being maxxed on my amp setup. Thanks.