Logic and PI and lack of PreFader Inserts


A while ago I am sure I read in the manual re issues with Logic and PI in which it was insisted that users put PI on an Auxiliary (unlike other DAWs) - this advice seems to be missing in latest Manual? - a reason?
I’ve torn my hair out over getting PI to work in Logic (shifting image placements - eg Bass or Vocals audibly shifting from Left to Right etc) - I recall the issue is Logic’s lack of Pre-Fader insert on tracks - so I’ve created Pre-Fader sends for each track to Auxiliaries where I have placed PI- a lot of work but it appears to work and produce stable results,
Any thoughts?



Hi Andy,

Welcome to the Sound Radix forum!

I do not recall a version of the manual where we recommended the use of auxiliary tracks. In fact, we recommend not to use Pi on auxiliary channels along with regular channels as it will create an internal feedback loop in Pi and will cause Sync Errors.

Having said that, as long as you’re not mixing instances of Pi on regular and auxiliary or group channels that should be perfectly fine as long as you do not see Sync Error messages.

Btw, setting the sends to Pre-fader will be the same as using Pi on a regular channel insert. To create a workaround for Logic’s missing post-fader feature, set the send to Post-fader so Pi will see the true level of your channel in the mix.





Thanks for the reply - but are you not slightly contradicting yourself?

“To create a workaround for Logic’s missing post-fader feature, set the send to Post-fader so Pi will see the true level of your channel in the mix.”

This implies there is an issue in Logic and this implies that I need to use Auxiliaries (via Send) to rectify it?

Maybe it was not the Manual but there definitely some official comment in a Forum somewhere?

Anyway could you clarify this use of Pi in Logic (perhaps by someone who uses Logic) as it has been unusable till now.

Perhaps more clarity generally on how Pi works and what circumstances it will or not work -e.g. as a Plug-in in Ozone?
This is a stunning product when it works but very frustrating when it doesn’t



Hi Andy,

There’s no contradiction. Preferably, Pi should be used on a post-fader insert. This way Pi will receive the actual level of the channel in the mix. Unfortunately, Logic doesn’t have post-fader inserts. To overcome this limitation, we’ve included CHNL GAIN in Pi to allow setting the average gain for the channel.

Alternately, routing each channel output to its own auxiliary and inserting Pi there as you’ve described may work, however, using it this way may result in Sync Errors depending on the project and the plugins being used. Here’s why (Or how Pi works - The short version):

Every instance of Pi routes the audio stream on the channel it lives on to a background phase mixer, where it calculates and optimizes the phase for the individual audio streams.

If Pi is inserted on a channel and on an aux that has the same audio (i.e. Individual drums routed to a drum bus), it will receive the audio twice and it will create a feedback in Pi and it will display a Sync Error.

To work its magic properly, Pi has to receive from the DAW the same chunks of time from every audio channel. If there’s a discrepancy in the sample position Pi sees or if it doesn’t receive the samples in time, Pi won’t be able to do its magic and will display a Sync Error. These discrepancies can happen between individual and auxiliary channels. To make things even more complicated, every DAW uses different internal architectures to compensate for latency induced by plugins in the mix.

For these reasons, we generally do not recommend using Pi on auxiliary and group channels. However, if all the conditions for Pi are met (No feedback loops, samples are received in a timely manner, no discrepancy in between individual channels and auxiliary channels), it could be done.

If I left anything unanswered, bring it on.





Excellent, this information helps enormously - I don’t know how I got the other thing from re Logic but I’m enjoying Pi immensely at the moment - it’s just a shame not enough people cottoned on!