Just found this interesting gem on Gearslutz! This guy may have solved timing issues once and for all:
https://www.gearslutz.com/boar…s-pops-timing-issues.html
This post is how Focusrite and I, not Access, resolved issues that I have experienced with my Virus TI2 desktop for the last several years. Focusrite has great tech support, and my hats off to them for suggesting something that is not mentioned anywhere in the Virus TI2 manual, and what basically shouldn't even work!I thought about putting the "punchline" and the resolution here, but I'm going to make y'all read a bit! Prepare for a long story. But I think the details may help out some folks that are experiencing similar issues. To know where to go, you need to know where you've been.
Act I: Backstory:My Virus TI2 has always given me grief. Because I love to use Virus Control (VC) and the audio-over-USB feature to give me three stereo channels plus a side-chain channel, I did not give up and resort to the whole "scrap that USB connection and use a MIDI cable and audio cables" idea which is plastered all over the Internet, including the Virus forums.Several years ago, huge spikes in audio-latencies caused massive amounts of pops and crackles in the audio stream, which were coincidentally caused by a Gigabyte brand mobo interfering with a Nvidia graphics card. Swapped in a Radeon card, and it worked better, but not great. Retired the Gigabyte board and bought an older-model ASUS board, while still running the Nvidia graphics card. Things improved for a while, but never 100%. Forcing the graphics card via registry hacks to always run in full-power mode improved latencies, pops, and crackles quite a bit, but again never 100%. Fast-forward about a year from that point in time. I built and upgraded my PC, purposefully seeking out a motherboard tested to have the lowest latencies available: an MSI board. Coupled with the same Nvidia graphics card, the pops and crackles still remained! Intermission:Let me break the story here to discuss my particular, studio setup. In the setup I have, of course, the PC running either Ableton or Sonar as my DAW. Connected via USB cable is the Virus TI2. Connected via Firewire cable is a Focusrite Saffire Pro 24 interface. An Alesis AI3 analog-to-optical ADAT interface connects via TOSLINK fiber-optic to the Saffire. A gaggle of synths connect to the AI3. Now, in order for it all to work, the Saffire is configured in MixControl to sync to ADAT. The Alesis AI3 provides the master clock signal, as it only has one ADAT connection. (NOTE: It can indeed operate as a slave, but since the Saffire only has an ADAT-in port, this configuration is not possible). All projects in Ableton/Sonar use 48kHz. Other sampling rates do not play nicely or just don't work at all.
Act II: Back to the Backstory:Now with that out of the way, here is where I mention the weird stuff. With my particular setup, with the Virus TI2 playing (and soloed), I would get one audio "pop" every 74 seconds. This would happen even with the most simplest of patches. So scratch what the forums say about the DSP being overloaded. Anyway, the "pop" would happen on the nose at every 74 seconds--only in the Virus TI2 audio stream--all other clips and sounds in Ableton/Sonar play error-free. But why 74 seconds? Perhaps it's a clue.So maybe it's a timing/sync issue? With that in mind, I changed the sampling rates of projects in Ableton Live. Though the audio inputs don't work from the AI3 (some being just harsh static noise), now the "pop" occurs at a different time while playing just the Virus TI2, i.e. the interval is something other than 74 seconds! (I don't recall the exact number). Ah ha, another clue!!!The second test is to take the ADAT-sync completely out of the equation and set the Saffire to be the master-clock. Though the AI3 is now completely inoperable in this configuration, absolutely no "pops" occur while playing the Virus TI2! To confirm, I set the Virus to play a MIDI loop for 10 minutes straight. Not one "pop" was heard.So now what? I need the AI3 to be the master, yet it seems the Saffire is not syncing properly for some reason. Is "timing jitter" the problem? How so if all audio except the Virus TI2 plays flawlessly? It's as if Virus Control and/or the driver is not grabbing the correct clock-source and sending it via USB to the Virus TI2 hardware.So a problem with Virus? Then contact Access. Their cookie-cutter response back to my inquiry was this: "Have you tried connecting the Virus to a different USB port?" Not knocking Access or its tech support; they're good people and give timely responses, but trying a different USB port, including buying a PCIe multi-TT USB card, has been done years ago! It is not the solution I'm looking for! Been there, done that! So maybe it's the Saffire interface? Then contact Focusrite. And here, folks, is the solution...
Act III: The Grand Finale:Connect the S/PDIF-Out on the Saffire to the S/PDIF-In on the Virus TI2.
Act IV: Conclusion:The solution is simple yet ridiculous, but it worked. It's ridiculous because it's something that was never considered...not by me after all these years and not by Access, the manufacturer of the product. After all, the USB connection to the Virus TI2 should be the end-all-be-all connection, right? Another cable should not be required, especially for timing and sync. But it worked. No more "pops" at 74 seconds. No more crackles. Even the arpeggiator and timing effects (e.g. tape delay) are dead on with no out-of-pitch anomalies.NOTE: Use a S/PDIF cable, not just an RCA-plugged unbalanced audio cable. A S/PDIF cable is a 75 ohm impedance coax cable.It freaking worked. A solution reported nowhere as far as I can tell, scouring the Internet high and low for help. A solution unwritten in the Virus manual, FAQ, or known to Tech Support. And this is huge...possibly helping many people with similar issues all over the world. Think about how many Virus TI and TI's were sold after their owners abandoned hope.Thank you Focusrite. P.S. - Hope you enjoyed the read...
Addendum: I should clarify that the S/PDIF cable is connected to the Virus in addition to the USB cable. But that's it! Well, I guess there is a little bit more, so check the following:In the Virus' CONFIG menu, make sure the Audio Clock Source is set to AUTO. With the USB connected, the Frequency should show SYNCED TO HOST. This setting cannot be changed if the USB is connected.When the S/PDIF cabled is connected, the LCD screen on the Virus will momentarily display a message. Though it seems odd, in my case, the message is "Clock problem at SPDIF Input." Despite this error message, the timing indeed syncs to the S/PDIF, which is in fact the Master Clock (i.e. ADAT-slave) signal output from the Saffire. I'm running the latest OS, version 5.1.1.0.
