Synchronization Hell

[dgatwood]

So at this point, my studio is torn down. I can't get two pieces of S/PDIF gear to lock to each other. System is a quad G5 running Mac OS X 10.4.6 (was running 10.4.3 until about halfway through today's debugging session from hell).

M-Audio FireWire 1814
Presonus FirePod

If I set the FirePod to be the slave:

• If it gets a message to change to a particular sync rate, it starts ignoring the sync source and the FW1814 gets disabled.
• If it doesn't (normal initialization), a constant note sounds like daaah-daaah-daaah-daaah as though there were gaps in the audio.

If I set the FIrePod to be the master:

• If I set the FW1814 to external sync from S/PDIF, it can't lock to the signal, and thus doesn't show up in my list of inputs.
• If I set the FW1814 to internal sync, the FirePod plays cleanly, but the FW1814 does the stutter thing. This is even with aggregate devices turned on, regardless of whether resampling is enabled.

Whichever one is the slave device ends up making a constant stuttering sound like the frequency is WAY off of 96kHz. The M-Audio doesn't even -try- to sync to the FirePod, pretty consistently showing no sync, then randomly jumping between sync rates.

I guess the next thing to do is hook up the Behringer V-Amp Pro by S/PDIF and see which one can sync to it, then assume the other one is either broken or badly designed.

This setup has never worked correctly with both interfaces since I switched to a new machine and lost the Delta 1010LT as my master clock source. I hate to throw money at a clock generator, though, since there's no way to know if that will work correctly, either. With my luck, I'd just be throwing good money after bad.

Any thoughts? Anybody in the Bay Area with a clock generator they could loan for a five minute test?

 

[dgatwood]

I send the following letter to Presonus tech support last night. I'm pretty sure the FirePod is electrically challenged in some way.

I'm not sure when things went haywire (possibly from day one), but I've had trouble recording pretty much every time I've tried to use your interface in conjunction with other audio interfaces on my quad G5 (Mac OS X 10.4.x). In desperation, this weekend, I tried various combinations of the FirePod as the master via S/PDIF, the other interface as the master, etc. I also updated from 10.4.3 to 10.4.6 to reduce the odds that this is some bug in AppleFWAudio. Just in case my last firmware flash failed in some bizarre and subtle way, I downloaded and re-flashed a fresh copy of the latest firmware (to no avail).

Here's what's happening:

* With your interface as the master, the other interface can't lock to the signal, though at 96kHz, the other interface occasionally locks for a few seconds at 88.2kHz, then gives up.

* With your interface as the slave, everything looks like it works, but when I try to play back any audio, your interface sounds like what happens when you play back audio recorded at one rate at a different rate---that phasey sort of sound. Turns out that CoreAudio is assuming that your device is in sync with the other device, but it really isn't.

* Both interfaces work fine independently.

Tonight, to narrow down the problem to one interface or the other, I enlisted the help of a Behringer V-Amp Pro, which has an S/PDIF output. Unless fed with an external word clock, its internal clock rate ticks at a very modest 44.1kHz. Easy syncing.

Results:

* The other company's audio interface was able to sync correctly at 44.1kHz without incident, which suggests that your interface is not sending out valid S/PDIF data at all (since the other interface was not able to sync to your interface's S/PDIF output).

* Your interface, upon switching to S/PDIF sync, dutifully continued to report 96kHz sampling rate, in spite of the 44.1kHz clock coming in from S/PDIF.

Just in case there was some conflict between the latest firmware and the (earlier) switcher app, I downloaded the latest (universal) version of the sync switcher app. While the previous version of the app remembered the interface's state between executions, the latest version always says "internal" every time I launch it, which, while consistent with the device's behavior, isn't particularly useful....

Finally, to virtually eliminate any possibility that this is anything other than a failure of the device itself, I hooked it up to my iBook G3/900, which has never had the FirePod attached to it previously. I downloaded a copy of the sync source switching tool from your website, attempted to switch the sync to S/PDIF, and it failed in exactly the same way that it did when attached to the quad.

At this point, it looks like your interface isn't generating S/PDIF output at all and is failing to switch from internal to S/PDIF for its sync source (without any error messages). Unless either the 2.14 firmware is colossally broken or Mac OS X 10.4.3 and newer are fundamentally incompatible with multiple versions of your switcher app, I think I've pretty thoroughly ruled out everything other than a rather spectacular hardware failure in the FirePod itself. Unit was purchased 10/29/2005.

Please advise.


Thanks,
David

I think I pretty much ruled out everything but the interface. *sigh*

 

[dgatwood]

Well, the (almost certainly misinformed) Presonus tech said that the current firmware doesn't support S/PDIF input. Yeah. I think they'd have gotten sued in the 7.5 months the new firmware has been out if that were true, especially considering that there are no warnings to that effect anywhere on their firmware download page.

Either way, he sent me a firmware downgrade tool to downgrade to the firmware I started with. It did downgrade the firmware to the previous revision, but still no joy (as I expected).

There is one slight change, though. With this firmware, it now visibly switches to external sync (alternating red and blue when there is no signal present). However, it still is not able to lock to either the signal from my M-Audio FW1814 or my Behringer V-Amp Pro, and switches thoroughly back to internal sync if you power cycle it.

I'd say this Firepod is pretty much toast. Fortunately, it's still under warranty for another 5 months.... Scary.

I will refrain from posting any more recommendations for their gear until this problem is solved and remains solved for several months.