Advice needed: Passing through Voice/Fax Expansion Modules in a virtualized Home Server?

[jalah93190]

Hi everyone,
I’ve been a long-time reader of the guides here, and they have been absolutely instrumental in helping me transition from a chaotic mess of Raspberry Pis and external hard drives to a proper, centralized home server build. I finally pulled the trigger on some new hardware last month, and for the most part, the migration has been smooth sailing.
However, I have run into a bit of a niche roadblock, and I’m hoping there is someone here who has dabbled with more "legacy" communication hardware.
My goal for this build was total consolidation. I wanted to move my routing, storage, and home automation onto one machine. But I also have a specific requirement: I need to handle Voice and Fax capabilities natively on the server. I know, I know—who uses Fax in 2024? Unfortunately, for my freelance administrative work, I still deal with a few government offices that treat email with suspicion but trust a fax machine implicitly.
Instead of keeping my old, clunky ISP router just for its phone ports, I decided to look into professional Network Devices and Expansion Modules https://serverorbit.com/network-devices ... ice-fax-en. I picked up a refurbished interface card (a PCIe voice/fax module) that was originally meant for enterprise PBX systems. The plan was to plug this into the server, pass it through to a VM running a software PBX (like Asterisk or 3CX), and handle all my calls and faxes digitally.
This is where the headache started.
While the host OS sees the device on the PCIe bus, actually getting the expansion module to function correctly within the virtual environment has been a nightmare. It seems like these specific expansion modules are very picky about how they receive power and clocking signals, which virtualization sometimes messes up. I’ve tried tweaking the BIOS settings for PCIe passthrough and messed around with different driver versions, but I’m getting inconsistent results—sometimes the line is active, other times the card just drops offline entirely.
Personal Insight:
I honestly thought the storage configuration was going to be the hardest part of this project. It’s ironic that I can stream 4K video to any device in the house effortlessly, yet trying to send a single page of black-and-white text over a phone line is bringing my entire setup to a halt!
Has anyone here successfully implemented these types of Voice/Fax expansion modules in a home server setup? Or am I trying to force enterprise hardware into a consumer use case where it doesn't belong? I’m starting to wonder if I should just give up and buy an external VoIP gateway, but I really loved the idea of an "all-in-one" box.
I’d appreciate any thoughts or experiences you guys might have!