Marantz AV7705 AV Receiver: HDMI out to external DAC

@audiotroy 

I'm still not sure what you're trying to say: "get an integrated amplifier to power your mains then  mains then by adding a Dac to the Marantz."  Sending the AVR's digital output to the T+A is "adding a DAC to the Marantz," right? Or do I misunderstand?

Let me make sure I'm coming across.  I'll be using ONLY the T+A when playing all "serious" stereo content -- vinyl, SACD hirez stereo, streaming digital. No HT electronics would be in the signal path (although hirez SACD stereo would be routed to the T+A DAC via HDMI from the Oppo). 

The T+A's embedded DAC/streamer is a class above the Oppo & Marantz DACs, as you'd expect from a $19,000 product designed by a company like T+A.  So my goal was to ALWAYS use the T+A to drive the front channels & sub, regardless of source.  The Marantz AVR would enter the picture only when decoding multichannel content, sending analog line-level output to the C & rear external power amps and routing a digital front/sub signal to the T+A.

The problem arises when using the T+A to drive the front channels & sub of multichannel content -- such as 5.1 Netflix streamed by the Marantz AVR or multichannel SACD content extracted by the Oppo. It looks now like there's no way to use the T+A's great little DAC & preamp in such cases.

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The Marantz and Oppo are not sending DD-encoded signals.

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@erik_squires  Yes, routing the analog output of the Marantz to the T+A would enable HT integration.  But that defeats the purpose of inserting the integrated into the home-theater topology, taking advantage of the T+A's power amp, but only after routing the signal through the AVR's DAC and preamp.  An analog connection has been my Plan B all along, and I verified that it works, but my OP was posted in hope of figuring a way around that.

Your last sentence I think hits the nail on the head.  In general, digital connections cannot be configured as HT bypasses?  That's a surprise, but if you're sure of that, I'm SOL.  Too bad nobody mentioned that in the lengthy threads I posted here over the last few months describing what I was trying to do.  Kinda late now to be rethinking everything, but here we are.

I think the most likely outcome will be that multichannel playback will have lesser SQ than T+A-only "critical listening" stereo.  So long as I don't compromise the stereo SQ, I guess I can live with that.

And to be clear, I still love the T+A.  It's an incredible piece of grear in so many ways.  It'll be interesting to read the first reviews in TAS / Stereophile.

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!

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.

OK, solved the problem. Save for future reference.

Stereo sources go directly to the T+A amp, which drives the main speakers and the wireless input of the sub (which is processed by the sub’s internal crossover). No home theater components in the signal path.

But the Marantz is the gatekeeper for all multichannel sources. It sees the front speakers as "small," and assigns them a fairly high crossover that is complementary to the LFE crossover. The LFE channel goes to the sub’s LFE input (which bypasses the sub’s internal crossover). In this mode, the T+A amp is still nominally sending output to the sub, but it receives so little low-end content that there’s virtually no redundancy between the sub’s two inputs. This configuration also drives the sub, during MC playback, with a true LFE signal, not a mixdown of other channels.

Even the Oppo disc player fits into this relatively simple setup. Multichannel content goes directly to the Marantz via HDMI. Hirez DSD & PCM stereo goes directly to the T+A, via the Oppo’s second HDMI output -- thus, no HDCP constraints when playing SACD hirez stereo.

Of course, the proof is in the pudding, and it took a bit of fiddling and room-correction to nail down crossover frequencies & channel levels that make this all work. But it’s sounding mighty good right now.

The only thing I couldn't do is bypass the Marantz DAC & preamp for FL/FR output when playing multichannel.  But that doesn't seem to be possible without some significant compromises in functionality.  Oh well.

Regardless, I think we can safely say: "Problem solved."