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Old 03-30-2020, 07:05 PM   #7
phoo
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Join Date: Dec 2010
Location: Hampstead, NC
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Big BINGO on the aliasing. After converting the project in question to 88.2khz and rendering out, and opening it in Audition, the HF showed up in all its glory.

The screenshot of Adobe Audio in spectrum view shows a lot of energy above the nyquist frequency of 44.1khz. There also appears to be some (maybe) dithering up around 35khz, even though dithering in the rendered mix was not enabled. This is straight out of Reaper.



Converting the project after the fact didn't get rid of all the artifacts, unfortunately. Some audible aliasing artifacts are in a few the original wav files, as those are 44.1k. Can't fix these with filtering or resampling, but I can go back and rerender a few as 88.2khz. Most of these are from a couple of mellotron and synth VSTs. I still have the originals in Reaper, having rendered them to wav for the main project.

While experimenting with this I discovered that the main desktop recording computer can't play the project at 88.2hz because it hits the CPU way too hard. The desktop does support it, as I have recorded a few tracks at that sample rate this week. There is just too much going on, resampling of the underlying wav files probably. That said, the laptop is happy playing at 88.2khz. The onboard audio, as crappy as it is, supports that playback sample rate and the CPU is indeed more powerful than the desktop and has more RAM. Might be time to start thinking about a replacement for the desktop. The motherboard is from 2004. It's still doing great at 44.1k, and even higher sample rates if there aren't many tracks. Because of all that, I have to render on the laptop, but have to mix at 44.1khz on the desktop for the good speakers. It's a compromise I must learn to live with.

But, now I know what the problem is and can easily avoid it in future projects.

Thanks everyone for your help, thoughts, questions, and answers.
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