Hi!
I posed three questions for us to consider in post 134 above 4 days ago. Having done some reading and thinking, I can take a try at answering these questions here together, at least for the DRA-800H. To answer these questions I relied on three source docs: the DRA-800H user manual, the analog and digital block diagram for DRA-800H from post 117, and the service manual for AVR-S950H/X2600H. The full DRA-800H service manual isn’t readily available to me, however comparison of the AVR-X2600H block diagram with that of the DRA-800H indicates that both share the exact same three DAC stack, Audio PLD, and ADC + DIR, so it is very reasonable to make inferences for DRA-800H using the X2600H service manual. Further, the X2600H block diagram gives much more detail of the PLD, showing key digital connections. Below I will also review and then extend in further detail on my previous posts in this thread. The key motivations here are to understand the workings of the DRA-800H to interpret the DAC measurements in Post #1, remaining questions, and how possibly to move forward to answer those questions.
The analog and block diagram for DRA-800H indicates there are three DAC chips, “DAC AK4458”, “Network DAC (Z2) PCM5100A”, and “Downmix DAC PCM5100A”. So two of the DACs are the same model PCM5100A chip. The PCM5100A (Dynamic Range 100dB, SNR 100dB, and THD -90db) is a lower spec DAC chip compared to the AK4458 (Dynamic Range 115 dB, SNR 115 dB, THD -107 dB).
The “Network DAC (Z2) PCM5100A” does network only—with no other possible digital source-- based on the internal connection map of the Audio PLD. This DAC can provide analog output to Zone 2 pre-out via the 7in/3out matrix switch, as shown on the DRA-800H analog audio block diagram.
The “Downmix DAC PCM5100A” receives digital input from the Digital Signal Processing (DSP) chip by a 2ch-only connection that is distinct from the separate DSP to AK4458 connection. The “Downmix DAC PCM5100A” is used for audio signal destined to Zone 2, as shown in X2600H service manual. Unlike the “Network DAC”, the “Downmix DAC PCM5100A” can receive many different digital inputs. Its analog output goes to the 7in/3out switch and can then proceed to Zone 2 pre-out. When using “Downmix DAC PCM5100A”, the Zone 2 audio can be from the same or a different source from what is being played in Main Zone but even if they’re the same digital source, each zone uses its own distinct DAC.
A bit a trivia, but I believe use of the term ‘downmix’ for one of the PCM5100A dacs is a holdover term from surround AVRs, such as AVR-X2600H, that share the same electronics. For DRA-800H ‘downmix’ doesn’t make sense since the HDMI in this model can only accept 2ch PCM and not other formats such as DSD, Dolby True HD, and DTS Master Audio. There isn’t anything to “downmix” to for the DRA-800H but Denon retains the term to be consistent with identical electronics in the surround AVRs.
The DRA-800H digital block diagram shows the AK4458 receiving digital audio from the PLD, and outputting analog for L, R, and sub. The AK4458 is implemented in dual differential mode, so utilizing 6 of the 8 available channel outs (There are 2 unused channels), and then getting reduced back to the 3 channels, L, R, and sub. The analog L and R from AK4458 (but not the sub) splits into two paths (this split is not a switch), one path going to Main Zone amp plus speakers, with the other path going to the 7in/3out switch. At this switch there is a POSSIBLE connection of the analog out of AK4458 to Zone 2 pre-out. Hence, the split and switch together make possible simultaneous playback in Main Zone and Zone 2, downstream from a single DAC, the AK4458.
Interestingly, for network digital (HEOS) there is a pathway from the LEGO network module to the “Network DAC (Z2) PCM5100A” as described above for Zone 2, but also a pathway to the Main Zone via DSP and AK4458. So it’s pretty likely HEOS network in the Main Zone goes via AK4458.
ANALOG signals can enter the 7in/3out matrix switch (all connections are physically possible in 7 by 3 matrix but perhaps not all are implemented) from 1 of 7 possible ANALOG inputs including:
1) Phono
2) Tuner
3) CBL/SAT
4) CD
5) “Downmix DAC PCM5100A”
6) L and R only from AK4458
7) “Network DAC (Z2) PCM5100A”
The 7in/3out switch has 3 possible outputs to:
1) Either: a) L and R amp & speaker OR b) Analog-to-Digital Converter AK5358 →DSP
2) ADC for LEGO network (probably bluetooth headphones etc)
3) Zone2 pre-out
OUT1 can be used to take :
a) any analog input 1-4 and direct it to L & R amp + speakers for ‘direct mode’. OR
b) Alternatively any analog input 1-4 can be routed to the ADC → DSP → AK4458 → L, R, sub main zone speakers for ‘stereo mode’. I believe it’s a situation of Direct mode vs Stereo mode: ‘a or b’, NOT ‘a and b’ . I cannot understand the purpose of an ‘a and b’ configuration.
OUT2 is about bluetooth.
OUT3 can be used to take:
a) any external analog input 1-4 (such as CD player, input 4) and direct to Zone 2 pre-out. OR
b) any analog input 5-7 from one of the DACs and direct that to Zone 2 pre-out. In other words, the matrix switch allows Zone 2 to receive analog output from any one of the three DACs: “Downmix DAC PCM5100A”, L&R AK4458, and “Network DAC (Z2) PCM5100A”.
A KEY QUESTION FOR THIS DRA-800H REVIEW THREAD IS THIS:
WHICH OF THE THREE DACS WAS IN USE WHEN AMIRM MEASURED FROM THE ZONE 2 PREOUT?
In the measurements amirm did, Zone2 was definitely not getting its analog signal from the “Network DAC (Z2) PCM5100A” because he did not use network (HEOS) as the digital source (he used HDMI), and network (HEOS) is the only possible digital source for this DAC. Therefore, amirm was taking measurements from Zone2 preout based on either the lower spec “Downmix DAC PCM5100A” or the higher spec AK4458 in dual differential mode.
I believe amirm was most likely taking his measurement from the “Downmix DAC PCM5100A” and not the AK4458. I provide three (interconnected) reasons for this. None of these is proof in of itself, but rather when taken together point toward “Downmix DAC PCM5100A” as the most likely DAC feeding Zone 2 during the measurements.
1) amirm stated in his initial setup “there is Zone 2 which can program to mirror the main zone output so that is what I did.” The instruction manual for DRA-800H on page 106 states “Setting the input source of ZONE2 as the “Source” allows you to play the same content in MAIN ZONE and in ZONE2, regardless of the type of input signal.” The input source of Zone 2 can be set using the second button from the left on the front panel which in this case can be set to “Source”. It’s weird that the word ‘source’ is both in the name of the button itself, and also the name of one of the selections the button cycles through. Based on what he wrote above, perhaps after reading the manual, amirm probably used the second button from the left on the front panel and selected “Source”. It would be great if
@amirm can definitively confirm or refute this.
In any case, choosing “Source” as the input source of Zone 2 would cause digital signal coming from the DSP to go to the “Downmix DAC PCM5100A”. This assertion is based on pages 140, 152, and 153 of the service manual (See Figures 7a and 7b showing signal path and p140 showing user controlled settings to make path happen that way) for AVR-X2600H which shares the same basic electronics as the DRA-800H including exactly all three DACS, the Audio PLD, etc. Those pages show the signal path going to Zone2 pre-out via “Downmix DAC PCM5100A” when “Source” is the chosen as the input source of Zone 2.
2) There is another user operation than in #1 above in which Zone 2 and Main Zone can play the same music source. And that is to press the “Option” button on the remote control, and select “All Zone Stereo” while listening to the desired music source. I am proposing that when the user invokes “All Zone Stereo”, this causes the 7in/3out matrix switch to direct the analog output from the AK4458 L&R to Zone 2. Main Zone is already getting the same L & R analog output from AK4458, as it always does. The DRA-800H block diagram is consistent with this scenario with the L&R analog output from the AK4458 taking two paths all the time: i) Main Zone L&R amp + speakers and ii) the number 6 input (InA/B6) for the 7in/3out matrix switch. So in this proposal, “All Zone Stereo” allows both the Main Zone and Zone 2 to play analog signal from a single DAC source, the AK4458. This #2 path is what one would want to ensure that both Zone 2 and Main Zone are playing the music synchronized, ie not with a relative delay between the two zones. In contrast, by going with #1 you’re using two different DACs to play the same digital source, so treating the digital source differently, and so apt to be different, including a possible relative delay.
For playback of the same digital source in both Main Zone and Zone 2, there are two physically different paths shown in the block diagrams (corresponding to #1 above and this one #2), AND there are two methods given in the manual to accomplish those two distinct paths. Therefore it makes sense that each path corresponds to a given method. The service manual reveals that “Source” as Zone 2 Input Source as going through “Downmix DAC PCM5100A” (#1) leaves us to assign path here in #2 to “All Zone Stereo” by the process of elimination.
3) The SINAD and other measurements taken from the Zone 2 pre-out were much more consistent with a lower spec PCM5100A compared with the higher spec AK4458 which is implemented in the DRA-800H in dual differential mode.
In summary, the overall hypothesis here is that amirm did his measurements using #1 above, ie by choosing “Source” as the Zone 2 input source. This choice ensured the Zone2 preout received analog signal from the lower spec “Downstream DAC PCM5100A”. Further, this hypothesis points to a real world next step, which is to re-test the DRA-800H from the Zone 2 preout.
If amirm still has access to the DRA-800H, I would propose he compare measurements from the two different methods for dual zone playback of the same source: “Source as Zone2 input” or “All Zone Stereo”, to invoke respectively either PCM5100A or AK4458 as the DAC upstream of the Zone2 preout. Under this hypothesis, we would predict that “All Zone Stereo” (AK4458) would produce better DAC measurements compared to “Source” as Zone 2 input (PCM5100A), which would be reproduced from the measurements amirm reported in post #1 of this thread on Sept 19, 2021. There are other hypotheses that could be ruled out by this type of testing, including the alternative hypothesis that “Source as Zone 2 input” and “All Zone Stereo” are physically the exact same thing and utilize the “Downmix DAC PCM5100A”. This alternative hypothesis can be readily falsified if the two methods result in different measurements. Perhaps amirm, a Denon expert as suggested by
@GiBo61, or anyone else could comment on these various hypotheses or propose new ones, with respect to further testing. In addition, any factual corrections with rationale would be very welcome, to bolster the discussion.