Yamaha Pure Direct Digital Input?

[FatStrat85]

I have a Yamaha RX-V659. I originally was under the impression that "pure direct" mode bypassed all the digital circuitry and passed a basic analog signal from your source to your left and right main speakers.

Then I connected my PS3 to the receiver via the optical digital TOSLINK connection. To my surprise, pure direct mode worked just fine. How does pure direct mode, supposedly an all-analog mode, produce sound when the source is connected via a digital connection?

Then I connected my Explorer 8300HDC cable box to the receiver via a coaxial digital RCA connection and tried the pure direct mode. Since a digital connection worked from my PS3 with TOSLINK, I assumed it would also work from my cable box via coaxial digital. It did not. No sound was produced when I switched over to pure direct mode.

What's going on?

 

[Adam]

It's not an analog-only mode, but one that bypasses unnecessary circuitry. From the description on Amazon (probably taken straight from Yamaha):

Pure Direct is a special receiver mode that causes the signal to bypass all but the most basic audio circuitry, and even turns off the display to prevent any chance of noise interference. It provides the purest possible high-fidelity sound from all sources including USB and HDMI inputs.​

The RX-V663 manual doesn't say anything about it not working with the coax input (as far as I've found so far), so I'm not sure why it didn't work for the other source. I'll keep looking, though. Perhaps Pure Direct only works with two-channel audio?

Adam

 

[Adam]

This might help, from Yamaha's FAQ:

Pure Direct bypasses the units’ decoders and DSP processors as well as shuts down the video circuitry, allowing for the highest possible audio fidelity from analog and PCM sources. Direct Stereo bypasses the units’ decoders and DSP processors to allow for the highest possible audio fidelity from analog and PCM sources. Straight switches the sound fields off and bypasses the DSP processor.​

Was the PS3 signal PCM, but the cable box was not? If the cable box was sending a bitstream, then the Pure Direct mode would not be able to handle it because it doesn't use any decoders.

 

[FatStrat85]

That makes sense. The cable box was outputting Dolby Digital, but it didn't give any information other than that. I know the PS3 has options for PCM and I have them enabled, so that's probably what's going on. Thank you for the quick and helpful responses, Adam.

 

[Adam]

Glad that helped! Turns out, I was looking into buying a 663 this morning, so I had the manual and the Amazon page right in front of me.

 

[FatStrat85]

I have another quick question while I have your attention. I know TOSLINK originally had bandwidth of 3.1 Mbps. Then it was upped to 125 Mbps. Will the PS3 output PCM at the higher bandwidth and will the receiver accept it? The receiver says it's receiving 48 kHz PCM when I play a Blu-Ray. I guess I'm wondering if the receiver can get the LFE channel through PCM or if would make more sense to use one of the compressed multi-channel formats like Dolby, etc...

 

[Adam]

Hmmm, that is an interesting question. I don't know the answer, but I'll look around a bit on the web. Somebody else on here might have the answer for you in the meantime. I'll definitely post again if I find anything.

 

[Adam]

Although not directly answering your question, this thread at avsforum might be useful to you. It specifically mentions LFE for the PS3 using PCM.

 

[FatStrat85]

I should probably start a new thread because this has gotten quickly of-topic, but I'll let it go a bit linger.

I played around with it and PCM is only 2-channel from the PS3. You can set it to 44.1, 48, 88.2, or 176.4 kHz. I set it to 44.1 kHz so it is native for CDs and there is no up-sampling. To get a LFE channel to the receiver, I have to set the PS3 to output Dolby or DTS multi-channel, but then the signal is compressed over the TOSLINK. I'm not sure which is better. Uncompressed PCM, or compressed multi-channel. I have a subwoofer and my receiver down-mixes everything to 2.1 for me. That LFE channel is kind of nice, but is it worth the compression? What do you think?

 

[Adam]

I'd say experiment to find out which one that you like the best. I've always used the bitstream approach with my DVD players and receivers because I prefer how that sounds.

 

[FatStrat85]

Thanks again, Adam. I'm continuing the off-topic discussion in the following thread.

http://forums.audioholics.com/forums/showthread.php?t=45290

If anyone wants to add anything regarding my initial question about pure direct, then feel free to post here. If you want to discuss uncompressed PCM vs. compressed multi-channel Dolby and DTS, then please post to the other thread.