I borrowed this BR from a friend, and when listening to certain loud passages my center channel produced that horrible "Scratchy" sound. When I swithced over to HDMI out from my Oppo it was ok. Then I figured out a DTS HD MA 5.1 track is available also, I switched back to analog with the 5.1 instead of 7.1, and the problem solved. Has anyone experienced anything like that, why would downmixing cause such a problem? I know 7.1 is new, but I hope all future releases contain a 5.1 lossless track as well.

I believe on the Toy Story 3 BD, the 7.1 mix is entirely new just for the home video release, while the 5.1 is the theatrical mix. So there could be more differences between the two than how the surround channels are handled.

Is your receiver is set to down-mix 7.1 to 5.1 when receiving the signal over HDMI? If that's the case, it sounds to me like there's a bug in the Oppo's firmware. Be it in the DTS decoding (kind of likely, it's had bugs in the past with both DTS and DD), or in the digital summing of channels that is causing the clipping.

I'd contact Oppo and report your findings. Check for firmware updates, and make sure it is repeatable first.

Actually, TS3 was a 7.1 mix in the theaters - one of the first of its kind. Only select theaters had upgraded in time to produce all 7 channels, but that's a separate story. The 7.1 mix on the Blu ray is supposed to be bit for bit identical to the theater soundtrack.

The disc also includes a separate 5.1 mix, which probably sums the two rear channels and places them in the side surround channels, as ClubNeon stated. It is a totally separate soundtrack from the 7.1 track, according to the disc specs.

Since it the center channel, and not a surround channel, I wonder if there is an error in the 7.1 center channel mix or in the decode process peculiar to that mix that is causing the scratching. But I bet it's not a down-mixing issue.

I bet its just a really hot mix that sent your center channel amp into clipping.

Oh, that's right TS3 was 7.1 in (select) theaters.

That's another point, if the mix is maxing out in the digital domain, and you're using +dB trim settings on your Oppo's center channel, you could induce clipping there too.

I always try to make my least efficient speaker be as close to 0 dB trim as possible. So the more efficient ones get negative trims. This may be more or less of a problem depending on how the trim adjustments are applied.

Its very odd, I downmix 7.1 to 5.1 via HDMI, but this issue only happened when I was using my analog outputs of the Oppo through the 7.1 input of my Marantz. Once I changed from DTS HD MA 7.1 to DTS HD MA 5.1 the problem was gone. The oppo has all speakers set to small (80Hz crossover in analog output) with the center trim at -.5 dB. Just wondered if anyone else experienced it, perhaps it is a mixing issue on the 7.1 track center channel.

Can you give time markers when it happens? I'll give a listen on my set up, but I'm running DTS -> LPCM conversion in the PS3 over HDMI to my receiver.

Its the very beggining Neon, when the bridge explodes, woody jumps in the train and hits the brakes, and shortly after when the green t-rex comes out of the ground and gives his best Jurassic Park roar. Then when the red monkeys fall...I didnt listen to it after that before I solved the problem, it was too unbearable.

It's late now, but I'll give a close listen to those parts (to see if I hear any form of distortion, or to give a guess as to why it may be happening) tomorrow after I get home from work.

I'm curious about the answer, too. I just bought the 10 disc Blu Ray box set for the kids for Christmas - hence, it'll be another couple of months before we open 'er up for a demo.

I hear nothing bad at any of those points. One thing that's in common with them all it there are huge bursts of LFE.

Do you have any other movies that are known to be LFE heavy? You might want to see if the problem shows up there too.

Possibly the x-over hand off to the sub is set too low on the center?

Thinking more after I posted, he said the problem goes away when playing the 5.1 track. I probably should listen to that too, to see if the LFE is as intense.

I have a bad feeling that the 8 channels of PCM are not being handed off correctly to the DAC inside the Oppo. The I2S interface between the DSP and DAC would have the sub and center channels paired (I2S multiplexes two channels, usually lefts and rights, but in the case of the center it is paired with the sub).

I really would contact Oppo, first by phone to see if they are aware of the problem, and if they are not say you'd like to submit the details by e-mail so they can keep you updated. They have an excellent track record of acquiring discs for testing purposes.