Perhaps I’m just fooling myself

I’m reviewing a bunch of home theatre receivers for Sound and Image and as I go I fill in a ‘feature table’. This is a continually evolving thing in which new features make it onto the table and old ones — ones that are simply expected and will attract adverse comment if omitted — are removed. For the most part these are features the presence of which I confirm.

For example, I use the Oppo BDP-83 to output an SACD down HDMI in DSD format to see if the receiver decodes this all right. If the receiver is getting PCM, then that suggests that the receiver can’t decode DSD and has informed the Oppo, which is then decoding the DSD to PCM.

I also check whether the unit decodes 192kHz PCM. But there’s a problem with this. I can feed this signal to a receiver, but how do I know that the receiver is fully decoding it?

Answer, I don’t, and I can’t. Let’s say it can deal only with 96kHz (lying in the spec sheet), then all it need do is ignore every second sample. There is no way I could tell that by ear — the bandwidth would still be greater than 40kHz, which is far beyond the capabilities of my hearing and my system.

I could try to invest in a 192kHz sound card for the computer, but even this wouldn’t really help. The 192kHz recordings I have are real world recordings, and I’d be very surprised if there is any signal above the noise floor by the time you get to 40kHz, let alone 80 or 90kHz.

So I guess I’ll just have to trust them on this.

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