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Comment by MomsAVoxell | Hacker News Reader

This is an awesome project.

I have a long-in-the-tooth investment in Fireware audio devices (Presonus) in my studio - 19” rack interfaces with 10 I/O’s, as well as the StudioMix mixer with 20 or so .. I’ve been keeping an aging iMac around to use all of this with and it still just plain works, but having the option to replace it with an rPi is really appealing. The system is mostly used for tracking, so having REAPER on the rPi, connected to all that FireWire gear, just seems such a nice idea…

I wonder what the load will be like, though? Can the latest rPi with PCI hat and Firwire interface handle 40 channels of audio over FireWire, I wonder? I know the issue would mostly be SD-card write speeds and so on .. maybe this disqualifies the rPi - but certainly there are other ARM-based SBC’s that this same technique could be applied to ..

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Audio shouldn't be a big problem for the Pi unless you're pumping it through tons of heavy filters. The Pi 5's CPU can hold its own against 2010-2015 era iMacs, and a good microSD card easily holds 40-50 MB/sec writes.

For better performance, I'd plug in a USB SSD (USB 3.0 can put through 300 MB/sec or more), or even use built in Ethernet, good for writing 100 MB/sec out to a NAS or another networked computer.

Do you have any preferred SD card brands and models? Speedy and durable cards suitable for RPi

I used to buy SanDisk Ultra (if I didn't need speed), Samsung Pro+ (if I did), or SanDisk Industrial (if I needed more reliability... not sure how big a difference it makes but I've never had one fail).

But since Raspberry Pi launched their own microSD cards, I've been buying them. They haven't failed me yet and are pretty fast.

The Industrial lineup is dog slow though. That's the trade for SLC.

Fwiw, it is also possible to make a Pi boot from usb.

For cheap yet snappy cards, I have been using Kingston Canvas Go Plus with great success. When used in a Raspberry Pi 5, I personally don't feel any lag. A couple of them are serving 7/24/365 in my RPi5 systems without any problems for more than 2 years.

I don't hammer them with I/O though. For heavy writes, I'd consider Sandisk's higher tier cards (esp. Extreme Pro), which I use in my cameras and never managed to break one.

If you want to use the RPi instead of fixing the RPi becoming a new hobby, the preference is to avoid SD cards and write to USB SSD/network as OP recommended.

Is there a reason you couldn't use the USB audio and MIDI gadget drivers to pass through FireWire audio interfaces as class-compliant USB devices?

You could even use a virtual MIDI interface as a convenient way to control features beyond those supported by the USB audio class, along the lines of

https://github.com/michaelforney/oscmix/wiki/Protocol

I have a Focusrite Saffire that has lots of nice, quiet preamps and ADC channels. I managed to get an old Mac to connect over FireWire and using the Focusrite Control app, I configured the routing to map all the analog inputs to ADAT. That works great but it's always at the wrong sample rate, and I can't change that without getting the old Mac out. Maybe I'll look into one of these rPi shields too. Anyone got any reverse engineering tips for the control protocol?!

The control protocol might be MIDI Sysex .. once you get Linux wired up to your FireWire interface you can wireguard the interfaces and see if you recognize SYSEX packets ..

Out of curiosity, what version of the OS is that iMac running? Using it as essentially dedicated piece of audio equipment instead of a daily driver would be fine by me. I've done it with the 2012 cheese grater MacPros running 10.6 for eternity essentially as a dedicated video capture device. It just happens to look like a computer, but it remains in use for one singular purpose. No more updates. No WAN access.

It’s an ancient iMac from 2011, so whatever is the last supported version from Apple .. it never gets updates. (Don’t have it handy at the moment to find the exact version, sorry..)

Yeah, its just a dedicated DAW in the rig, used only for recording multiple tracks for later transfer to other modern machines for further work ..

I looked it up, it’s 10.3. So, very, very long in the tooth - no longer supported, and even homebrew has given up on it.

So it is essentially just an appliance for the purpose of streaming FireWire audio to disk for use on other systems .. and in that capacity it serves well. But I think I’d like to replace it with a raspberry Pi ..

Yeah, that's pretty much the life of the MacPros I described. The equipment is well paid for, and are only profit makers. They require no IT time. They require no maintenance. To replace them with anything else will cost money, and time retraining muscle memory on how to operate new device. Plus, all of the quirks of the new device would need to be caught/learned and workflows updated to include these.

Sometimes, the devil you know...

Replacement doesn't have to be a raspberryPI.

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