And will the true culprit please stand up...

I'm pretty sure I just finished debugging a really bizarre audio problem with my computer based home theater system that was starting to drive my and my gal batty. We started to get audio dropouts while watching TV - they were only a few seconds but were happening about once a minute. I have a pretty high tolerance for such things, knowing that eventually I'll figure it out, but my gal quickly gets really irritated and blaming things - tech that doesn't work is like an employee that doesn't work - she just wants to fix it or fire it.

I checked the obvious things - like some other process kicking in every minute and ruled that out. I also noticed if I paused TV playback and waited for a few seconds and continued it was fine - so it wasn't the content, it really was some period of no audio. Since I recently built a new computer that was the first culprit my gal was blaming - but I knew it had been working for at least a month with no problems at all. Yeah it could be something gone bad, but I didn't think so. "You've got a driver problem", she proclaimed. Yes, I had done a lot of fiddling with drivers, especially related to my SATA ACHI issues, and had probably dropped in a new audio driver along the way to. But this problem hadn't started right after I did it - it chose to show up a couple of weeks later. Still I duly upgraded to the very latest 1.83 drivers from Realtek and low and behold the problem was still there. Then I downgraded to the older version that was included with the system disk and still on the Gigabyte site. Nope, that didn't fix it.

Now today I finally had another clue - I went to watch some TV and audio was dropping out almost every 10 seconds, now this was really irritating! Then I discovered it wasn't just TV audio, it was any audio. Even if I shut down everything else on the system and played some music with Windows Media Player the problem was still there. Hmmmm, sounds like a big clue to me.

After much futile fiddling with audio settings I resolved to solve the problem once and for all.
I took another try at shutting down everything else on the system, including every non-essential service and that made no difference, but there was nary a blip on the performance during the outages. It really didn't seem to be process related, could still be a driver problem though, but it just seemed odd that no one else was having this problem.

So I got some headphones out and plugged them in - it took me a while to figure out how that works with this new fangled HD-Audio stuff Windows uses, but eventually I got music over the 'phones and waited. Sure enough when the audio from my amp went out the headphones were still going strong. So then I raced upstairs and got my computer speakers from there and plugged them in the back - same experience. So it really seemed like a digital audio path only problem because my normal amp is hooked up to the computer via the optical TOSlink for SPDIF output. I checked the optical connections at each end - it seemed unlikely there was a problem, these cables are just a piece of clear plastic (not glass fiber as you might imagine). Nope, that didn't fix it either.

So then I began to think it was my Samsung HT-DM150 amp which is now about 5 years old but has been very reliable. Of course I've been longing to replace it because it doesn't have discrete inputs, only the digital input and ultimately I want something that can handle HDMI for high def audio (since TOSLink is really crippled in terms of bandwidth - fortunately those DTS and Dolby Digital streams are highly compressed to fit down it).

My theory was there was something wrong with the digital path so I should find another digital signal source to throw at the amp - if that was okay then I'd have to blame my computer instead and start begging Realtek to find a cure, which I'm sure could take ages, long enough that I'd be forced to install the accursed Creative sound card I'd just gladly left behind in my old system (although to their credit it did seem like after 5 years they finally got some decent drivers for it!).

Anyway as I was fishing around the back of my amp I noticed it had a fan - I'd seen it when I bought it and never thought much of it, I didn't recall ever hearing it running so it didn't bother me. Now when I looked with a flashlight I could see it definitely wasn't running and yes, sure enough the unit was pretty toasty. In fact when I checked the top surface it was hot, too hot. Not burning hot but very hot. So I removed the shelf about it in my rack and went looking for that other digital audio source. The music kept dropping out as I worked and I was just getting close to having the other audio source working when bingo - no more dropouts. It had taken about 10 minutes but the music was now definitely playing uninterrupted. The player didn't seem that much cooler yet but I know it only takes a small change to put a circuit back within operating range.

So, here is my theory - the amp was getting so hot that the clock circuit got out of tolerance and could no longer stay in sync with the incoming 48khz data stream - the hotter it got the quicker it went out of sync. It would then resync and then carry on. I guess that it could also be some digital processor crapping out and resetting but I think the would probably have designed the entire system to shut down before that happened. Now I have no idea how long the fan hasn't been working but I went and did some googling and quickly found that a bunch of people were complaining about fan and overheating problems in early production units. I'm not sure if that included mine but I could easily imagine a fan might fail in five years.

Why did it just start happening? Well it could have been the fan failing - or it could be that in the last few weeks we've been having our heater on and that blows hot air right by where the amp is, and also I've been home more during the day so the amp has been on vs. in standby much more which gives it plenty of time to warm up.

Anyway, I moved the shelf up in my rack to give a clear three inches above the amp and hopefully that will let it stay cool enough until I can find a replacement fan. Since the fan is external - bolted onto the back in a box it shouldn't be hard to make one with computer components if necessary, assuming the system is still output voltage to turn it on since it could actually be a sensor that has failed.

So this all goes to show, you shouldn't always blame the computer for problems, especially when audio is concerned.