Problem with tempo change and multiple Amps



  • After updating to ProTools 2020.3, I've run into a bug in BIAS FX 2 which prevents the use of more than one instance of a BIAS amp - or even a dual amp config in a single BIAS instance - if there are any tempo changes in the PT session. A tempo change in such a condition always, immediately, results in an alert saying "Pro Tools ran out of CPU power. Try de-activating or removing Native plug-ins. (AAE -9173)".

    Even with the simplest possible test case - one track, one BIAS plugin in, not even any audio recorded - when a tempo change is encountered on playback, I get this error. Switch the BIAS preset to single amp, it works fine. Even with a buffer size of 2048 the error still always occurs when two amps are present. With no tempo changes, my setup can handle at least 6 concurrent BIAS plugins easily.

    This is a modern (2019) iMac with 6 cores and plenty of RAM, running macOS 10.15.3. Up-to-date Pro Tools (2020.3), up-to-date BIAS FX 2 (2 2.1.9.4900).

    I'm reasonably sure this is a BIAS bug since no other plugins have a problem at tempo changes (or anywhere else, for that matter). This just started happening when I updated PT to 2020.3.

    Also, I see recent items in the BIAS FX revision history that seem related to the problem I'm reporting:

    BIAS FX Desktop 1.5.8.2732
    -- Dual Amp setting + tempo change in DAWs = click noise in right channel

    BIAS FX Desktop 1.5.7.2577
    -- Fixed click noise issue under Dual Amp setting + tempo changes in DAW's

    I have a request in at Positive Grid. Meanwhile, I'm wondering if anyone else has run into this, and if anyone knows a workaround. (Avoiding tempo changes is a kind of workaround, I guess, but it's not realistic for the music I make.)

    Thanks.