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Quantum pops and crackles at 32 samples/44.1 kHz

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asked Apr 20 in Thunderbolt - Quantum by nathanimal (270 points)
I have a Quantum, which I run with Logic Pro X 10.4.1 on a 2017 iMac 27" i7. macOS 10.13.4. It's a single-thread monster, and didn't quite expect to be overloading a single core at 44.1k/32 samples with fairly modest CPU loading - as in an amp sim, a compressor, and some basic room reverb. My previous (class-compliant USB) interface never even got close to overloading with this kind of a channel strip set-up with the same buffer size. Granted, RTL was like 5.6 ms with that interface at 44.1/32... not 2.0ms as reported by Logic with the Quantum.

Granted, this isn't exactly a dealbreaker, since 64 and 128 sample buffers are perfectly usable most of the time... it's just that I have some instruments/external effects that incur their own latency when I play through them, and it helps a lot to minimize overall RTL as much as possible with those.

I guess I just expected that the CPU loads would be identical for the same buffer sizes. And I expected that 32 samples would be mostly usable at all samples rates, with the Quantum - this has turned out to not be the case... 32 samples is effectively unusable for me.

Has anybody else seen this problem?

1 Answer

0 votes
answered May 15 by connorguiberteau (16,090 points)
selected May 18 by AlexTinsley
 
Best answer
I have been able to use 32 samples on various machines.

The majority of the CPU load is most likely coming from trying to run those plugins at the same time. Some 3rd party plugins don't play nice at low buffer settings. Personal experience points to high-end reverb emulations eating up headroom in the CPU.

There are some things you can do in Logic to account for this.

Go into Audio Preferences> Devices and try these changes (if they aren't already changed on your system)

Processing Threads: Highest number available for your machine.
Process Buffer Range: Large
Multithreading: Playback and Live Tracks

Hopefully, that will balance out your CPU load a little better in Logic Pro X.
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