Sync Error in certain scenarios in Cubase and Reaper - not in Pro Tools


I have the following setup:
Kick IN
Kick OUT
Snare TOP

All of these (kick and snare subgroups + tom, floor, hh and oh) are bussed to a drums group.

I’m trying to have PI at the last effect slot on each oh the tracks. (Why? because I want to have, for example, both snare top bottom be aligned individually, as well as their respective group, where I might be using eq/compression/distortion which causes phase shift).

In both Cubase and Reaper that scenario causes a Sync Error, regardless of whether they are in different groups (within Pi, that is). If I deactivate the instances of Pi that are on either the kick and snare tracks or on the subgroups it’s ok again, but if it seems that when I have a track with Pi that is bussed to a group with Pi I get the error.

The strange things is that Pro Tools doesn’t behave that way.

I tried tweaking the buffer in the settings window but to no avail.

I’m guessing that there must be something illogical in terms of delay compensation and the inter-plugin communication that causes things to get screwed, and yet somehow Pro Tools seems to handle it just fine with delay compensation intact.

I have both a cubase and a pro-tools session to demonstrate that I can send, as well as some screenshots. I can easily create a reaper session to demonstrate the same problem.

Here is that scenario, working just fine in Pro Tools:


Here’s the same scenario. not working on cubase:

However, here it is OK when deactivating the plugins on the kick and snare tracks, not subgroups:

Sorry for the multiple posts - it won’t let me post all photos in the same post, being a new user, so I found a workaround :slight_smile:

Hi Oded,

Using Pi on auxiliary channels along with the regular channels will create an internal feedback loop in Pi and will cause Sync Errors. To solve your issue, please remove Pi from your Kick and Snare Subgroups.

If you’re still having problems feel free to contact me at [email protected].



I get that, and that’s what I said that in my post.
However, how come in Pro Tools this exact scenario works just fine?

Pi is running a background phase mixing engine, where each Pi instance transmits the audio stream to the background mixing engine which then calculates the optimal phase position for each track, then controls the phase rotation of the individual Pi instances to set the optimal phase position for each moment.

​Using Pi on a group track as well as individual tracks may cause it to go into internal feedback which will cause Pi to malfunction. If the tracks reach Pi after they’ve been mixed into a group, Pi won’t be able to optimize the phase of the individual tracks to the mix. It may not produce sync errors in Pro Tools but it is not ideal for Pi’s operation.