Alright...I'm discovering some interesting things...Lostinspice, what soundcard are you using? Mine, right at the moment, is just the onboard Laptop card with yamaha codecs, and it can only be used in mme, so my experiments aren't going to be so great.
HOWEVER, I can use the aux buss...with noticeable latency. The latency in my aux buss is such that I hear the dry effect and then a slight delay before hearing the wet effect. It's not useful to me this way at all...but, like I said, until I can try this on my Layla, with the asio drivers I've been using...I am not sure if it will be as noticeable. See, I bring my laptop to work every day, as it is probably the nicest computer in our building, as we can't afford to keep our computers as updated as they should be. I bought this for school, and couldn't be happier. At home, I can hook mine up to the Layla with the PCMCIA card, but usually, I leave the Layla hooked up to my desktop...so until I can do this there, I will have some unanswered questions as far as my own setup and maybe yours.
If I have my buffers in the audio panel down to 2, then the lowest latency this card can get it 10ms. The SIR makes my computer drop out at this point. It won't work AT ALL. Now, if I set the buffers to 4, and the latency at the lowest setting moves to 30, and now I can use it, but it's still stuttering. The higher I move either the buffers, or the latency slider, I get better sounding performance, but the latency is exactly the same, at least to my ears, in that the delay time between dry and wet signal does not appear to get longer or shorter, whether I change any of these settings, or the milliseconds buffer setting in the global panel.
So, the effect may just not work in the aux buss properly, no matter what you do. Now, if you stick it in the A (main stereo) or in the track as an insert, then it seems to work fine. I'm kind of assuming at this point, that since no matter what I did with the latency sliders in the audio dialog panels, the only thing that improved was the quality of the sound, not the actual latency, that on my home computer, likely, the same result will happen. but, maybe the asio driver or wdm driver would make a difference here.
As far as plugin delay compensation...I'm not sure I understand what this is exactly, since we seem to have two different types of latency with the SIR, depending on what kind of insert you use it as. So, if I were to buy the DirectiXer today, and it has plugin compensation...is anyone getting this to work with the aux buss? Or, is the plugin delay compensation just something to avoid putting the sample slide an all the OTHER tracks.
Would it help to make some mp3s today, of real short piano clip and you can hear the difference between the aux buss and the insert and the 2 buss? (or A---now I have some new lingo

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I've got the setup pretty much ready to mixdown if you want me to. I'd have to put them on my nowhere site, but I have unlimited space there, so that's no problem. Let me know! I may just do it anyway and link to it. I just copied a couple of measures from some screwing around chords that got recorded into a new track, with 3 of the same tracks. One has the insert in the track, one is set up with sir on the aux, and the other would be soloed with the sir in the Abuss. I would solo each one, and title them. It also might be useful to hear some of them together, so we can see how things match up in actuality.
-Kirstin