HDX card questions

[bakedbeansrecord]

I have been running PT Ultimate on a 2021 purpose built Win 10 machine with top of the line i9 CPU, SSD's, 128 GB RAM since 2021. I use an Orion 32 HD interface digilinked into an AVID HD Native thunderbolt box. Running well for the last 3+ years overall, but I cannot get my buffer below 256 reliably except with low track counts or high sample rates. Not worried about latency with mixing and generally I can push the system hard in that realm by bumping up the buffer to 1024. However, when tracking with high track counts, esp. if there are plugins on some of the tracks, the system chokes and requires a higher buffer, inducing borderline latency issues for the musicians.

I'm aware that very few newer plugins are coded to use the HDX DSP, but that is not my issue. My question is, would I see less tracking latency with high track counts by switching from the HD Native thunderbolt box to an HDX PCIe card? Will the HDX card work with my Orion (which has digilink outputs) or would I need to by an AVID interface?

Would hate to lose my Orion, as it gives me 32 in.

[LDS]

How many Pro Tools voices are you using in your large sessions?

[Darryl Ramm]

The Orion will work as good with HDX as it does with HD Native.

But I would pay attention to whether HDX 1 is enough for your needs. LDS can help you there.

Have you really really optimized and troubleshot this system? Do you use freeze/commit to reduce load?

[bakedbeansrecord]

Hi Darryl and LDS,

I pulled up a session with 25 tracks, including 8 VI tracks. With buffer settings at 256, 128 and 64, it shows 18-23% CPU usage with playback (no recording active). When the buffer is set to 32, the CPU jumps to 70% (no, I never attempt to set my buffer that small!).

36 of 2048 voices used.

I can certainly commit more tracks (then choose "Hide and make inactive" to the original tracks) as a session progresses, but often those tracks that have been hidden and made inactive will need to be reactivated to make further changes as the song develops (a pain in the butt).

So, if not using DSP plugins, is there any latency benefit to switching from HD Native Thunderbolt to HDX core card. In other words, will a Core card free up any computer resources if I'm not using plugins written for HDX DSP?

[LDS]

HDX doesn't really 'free up computer resources' per se. It provides a DSP-based low latency mixer that runs side by side your native system. The standard use-case is to flick your sound sources from the native side during playback, to the DSP side when tracking. This allows you to set the native sample buffer at whatever you like, as the DSP-based mixer latency is totally independent from it.

If you can't flick your sound sources from native to DSP, there probably isn't much point in HDX. Virtual instruments and native plugins will always be subject to native sample buffers.

Have you tried using low latency monitoring in the HD Native box?

[bakedbeansrecord]

"Have you tried using low latency monitoring in the HD Native box?"

I confess, I don't know how to enable that...

[Darryl Ramm]

Options>Low Latency Monitoring. Read the Pro Tools Reference Guide to understand what this is doing with the hardware mixer built into the HD Native Hardware. It's not only disabling software monitoring like with typical CoreAudio/ASIO interfaces but it is enabling the hardware mixer.

[bakedbeansrecord]

I will do that next--thanks much - you taught me something there.

But, I found this article on Window 10 optimization (https://www.totallytechnical.com.au/...ow/#enable_dep). I knew most of these things before, but there were several things in this that I have not seen or tried before, such as disabling hyperthreading, turbo boost, and C-state (whatever that is) in the BIOS. I also updated my networking and video drivers and what a difference it made! I just recorded 3 virtual instruments and 64 audio tracks at once with my buffer set to 32 (44.1 KHz and 24 bit) with no hiccups. At 24 bit / 88.2KHz I could do the same with a 64 buffer. I'm thrilled to have this working right.

[Darryl Ramm]

OK good you found that, those things can make huge differences, or not much, it all depends.

You should have been aware of these, the official optimization documentation is here: https://avidtech.my.salesforce-sites...oting/en367983 as always that's linked under "Help us help you" up the top of every DUC web page. Some of that doc could do with some cleaning up but it's a very useful resource.

One thing you did not mention is processor affinity that can be helpful https://avidtech.my.salesforce-sites...finity-Windows but if you are running reliably now then it may not be worth looking at (these things all kinda need you to be running "on the edge" to know if changes really help or even possibly hurt). Make sure you have ignore errors unchecked when making these optimizations/adjustments so you see any errors... and I would always leave that unchecked.

If you are able to track at 32 or 64 samples then I doubt you need hardware monitoring, but you should play with it and see what it can do.

---

There has been several folks asking if they should upgrade to HDX recently, and this is a great example of making sure the current setup is working well. HDX has a purpose, but it's not a silver bullet for all latency or CPU load related issues, and not something I would rush into unless it's really needed.