Marantz AV7705 AV Receiver: HDMI out to external DAC

OP:

There is no point in going from the AV processor to your T+A besides convenience of keeping your 2 channel amp.

The only two ways I’ve ever seen of doing what you are asking for is via Theta Digital’s digital output board and via an Oppo mod which replaces the 8 analog output channels with 4 x 2 channel digital S/PDIF instead.

Most TV’s now have S/PDIF outputs, but to deliver it to your amp you’ll need to set it to 2 channel mode, which will disable the surround information.

For once, I agree with @soix.  Jeez, driving the front channels with the T+A's preamp & DAC would CERTAINLY make a difference.  In fact, when the T+A arrived last week, I did a direct comparison, with hirez SACD stereo sources, running the Oppo HDMI through either the Marantz DAC/pre or straight through the T+A and -- yes, just as @soix suggests -- the difference was dramatic.

And, uh, @deep_333 , I appreciate advice given in good faith, but let's not make assumptioins.  Both my stereo and my HT components are already plugged into $10,000 of Audioquest Niagara power conditioners & AC cords and the topology I'd hoped for would not lose any of the functionality you mention. I mean, we're talking about a system with $4000 Wireworld speaker cables. Most of the old-timers here know that I'm no newbie -- my first speakers were DCM Time WIndows, which I later upgraded to Quad ESLs.

@erik_squires I usually agree 100% with what you post, but this time, I think you didn't understand what I was hoping to do.  There is certainly a "point" in effecting a dramatic improvement in front-channel SQ of a 5.1 system, whether you're talking about Netflix, Blu-ray, or SACD sources. In fact, simply substituting the T+A's power amp for my old $1500 Class D amp has already increased the realism of 5.1 Blu-ray soundtracks & streamed content.  It's just a shame that I won't be able to replace the entire FR/FL/Sub Marantz signal paths.

I'm not familiar with the Theta board, but it doesn't seem like the right fit.  Again, the hope here was to configure the T+A as an HT bypass, but only when playing multichannel sources.  Gotta have a single volume control for all channels.  But the Theta would provide no 5.1 volume control, and not even any 5.1 if fed with 2-channel S/PDIF.  And the Oppos already have multichannel digital outputs a-plenty -- why add another multichannel S/PDIF output to a player that already has HDMI?   But maybe I'm just not understanding what you're proposing...

Hey, look, bottom line is that we've now confirmed, I think, that the only way to embed a higher-end integrated into a home theater, in order to improve the SQ of front channels, is to do what I wound up doing: routing analog FR/FL output from the Marantz HT to an HT Bypass input of the integrated.  You can't get around the HT receiver's DAC & pre.  If there are amps that can configure digital inputs as HT bypasses, I haven't found them.  Just to satisfy my curiosity as an ex-engineer, does anybody have technical documentation explaining why this function doesn't seem to be possible?

Anyway, despite not being able to get my question across to everybody, I do appreciate the conversation and advice.  I didn't find the solution I'd hoped for, but I did get some straight answers, and that's rare enough these days to have value. The system is set up now and I'm about to start zip-tying cables

And again, if the integrated-amp form factor is for you, in the $15-20K range, I can't recommend the R 2500 R too highly.

Thanks!

I think you didn't understand what I was hoping to do.  There is certainly a "point" in effecting a dramatic improvement in front-channel SQ of a 5.1 system, whether you're talking about Netflix, Blu-ray, or SACD sources. In fact, simply substituting the T+A's power amp for my old $1500 Class D amp has already increased the realism of 5.1 Blu-ray soundtracks & streamed content.  It's just a shame that I won't be able to replace the entire FR/FL/Sub Marantz signal paths.

Yes, I understand it and I'm saying it's almost impossible.  Theta Digital makes an output board for the Casablanca processor which has S/PDIF outputs, I think Datasat may also have digital outpus I can't quite remember.AFAIK, those are the only two ways of going from HDMI in to multiple 2-channel discrete S/PDIF outs.  Everything else I know of is a downmix from the multichannel to stereo.

OK, wait, wait. I get it.

A digital HT bypass could work ONLY IF the sending unit could control the volume of the digital signal before it hit the DAC in the receiving component.  But it's not possible to control the volume level of an encoded digital signal -- at least not at the level of technology we’re talking about.

So that’s the reason why HT bypass will work only with decoded analog signals. Now that I get it, it’s head-slappingly obvious.  Sigh.

So, like most other people in the world of multi-channel, I’ll have to live with an AVR’s preamp & DAC for all 5.1 channels.

@erik_squires Yeah, you’re right that a 5.1->2.0 mixdown wouldn’t do the job. But as mentioned above, even the Theta board wouldn’t get me past the real sticking point: A digital input can’t be configured for HT Bypass. My mistake was not thinking hard enough about the issue to realize the existence of that constraint.

So one option is to simply route the Oppo’s FL/FR analog output to any T+A input configured for HT bypass. But from a system-design perspective, it makes more sense to send 5.1 audio (via HDMI) from the Oppo to the Marantz. That way, all FL/FR analog signals arrive at the T+A’s HT Bypass input decoded and pre-amplified the same way. Again, only the T+A is in the signal path when playing stereo content (aside from things like phono stages & disc transports).

Regardless, I appreciate your input. I’ll probably research the Theta board further tonight. Even if I never need one, it’s an intriguing product.