I'm going to review these two pieces together becasue they are virtually identical units as far as I'm concerned; the only difference between them is the 'peak punch' mode on the DS-501. These sound like you would expect them to. Nice and snappy, make your drums sound like the 80s. Really dig these on Toms to bleed noise, or snare top if the drummer isn't busy and you're going for that gunshot sound. Highly variable controls, you can completely shape the envelope of the sound. The range feature is very useful to reduce dynamic range by raising the noisefloor while the unit is 'out.' It also helps to make the effect less noticeable. They come equpied with an internal sidechain filter (Low Pass and High Pass in series.) This allows you to tune the frequency range you want the gate to respond to (i.e. 20-100Hz for kick drum, 150Hz-1.12Khz for snare, etc.) to prevent accidental triggering. You can listen to what the sidechain detector circuit is hearing by engaging the 'key listen' on the output. Now you can really tune the response. If you leave the unit in 'key listen' mode it becomes an effect, a dual LP/HP filter stepped at 18db! The 'peak punch' (only on DS-501) is a way of accenting the attack of the transient and can be quite dramatic with settngs above 3. 'Peak punch' can be used in either full range mode or tuned to a specific frequency. They take some time to setup, and I've used them a few times tracking with some sucess, but you really have to be gentle and tenative. In a live situation I can see how these would be great for controling vocal feedback in stage monitors and FOH. These can also be used as effects boxes to create glitchy unnatural effects, if you're into experimental music. At the date this review is written you can probably have one of these for about $200 on ebay or locally on craigslist or what have you. The reason for that is there are some really great VSTs out there (I like Sonalksis) that can do a pretty darn good job and are a little easier to use due to the visual aspect of VSTs. Still, these things have their own character and have many uses; did I mention you can use them as ducking compressors? Oh yes they can. This is a classic piece of gear that used to cost a lot of money, and people are practically giving them away. For what they're worth, you may as well pick one up just to experiment with. There are many ways this unit can be appropriated.