Yes, it can work with Pro Tools 5.1 although it is not fully tested. 1. You need DirectConnect to hook up Soft SampleCell's outputs with Pro Tools. Typically this means that for a TDM system you have to have MIX hardware because DirectConnect is not available for Merle (DSP Farm) DSPs. For Pro Tools LE systems you can use the RTAS version of DirectConnect. 2. Starting with Pro Tools v5.1 we have made RTAS plug-ins available on disk tracks (i.e. Audio Tracks) in a Pro Tools TDM system. This means you can use any RTAS plug-in on a disk track but not on Aux tracks or master faders. It doesn't matter if you are using a Pro Tools MIX or a Pro Tools 24 system.Now that DirectConnect is available as RTAS plug-in also (see 1 again) and with the RTAS on disk tracks option (see 2) you will in fact be able to use DirectConnect on a Pro Tools 24 system.Please be aware that there are caveats. -Soft SampleCell has not been fully tested with DirectConnect RTAS on Pro Tools 24. Use at your own risk!-As the feature name suggests, you can use DirectConnect on disk tracks (i.e. Audio Tracks) only, which is not the standard way of working. For example, if you try to record the DirectConnect source you have to route from one disk track to another disk track (inserts are always in the playback chain).