Graeme, it isn't "only" PCM; pulse-code modulation is the standard digital encoding format for audio, and newer formats(e.g., Dolby True HD)have to be decoded into PCM for further processing and then conversion to analog for amplification. Since your player decodes the Blu-ray audio formats into PCM, your 661 doesn't need to have that decoding capability and you get the full benefit of the True HD or whatever.

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Enjoy the music, not the equipment.