Denon AVR-X4700H 2020 AVR Review

[bigguyca]

Most opamps are able to drive 2 kOhm, the NE5532/4 can drive 600 Ohm - both at full output swing (23 Vpp = 8Vrms when fed with +/- 15V). With a much reduced output swing like at the preamp outputs of most AVRs (less than 2 Vrms) even a load of 500 Ohm (150 Ohm for the NE5532/4) should be OK (same current as the standard load at full output swing).

Unfortunately the input impedance of the internal power amp in an AVR is unknown, so if it cannot be disconnected it's better to stay with an external power amp having an input impedance of 10 kOhm or higher - just in case...

The Denon AVR's don't use NE5532's or any other IC opamp as an output buffer. In fact there is no separate output buffer. The RCA preamp output is in parallel with the internal power amplifier input and is driven by the output of the CMOS based 8-channel NJR NJU72343. This connection to the internal power amplifier exists whether a speaker is connected to the internal power amplifier or not.

The NJR unit is rated with a 47k ohm load. The minimum acceptable load, likely with reduced distortion performance, is probably between 10k ohms and 20k ohms based on the datasheet. While these CMOS-based volume controls provide reasonable performance at a reasonable price, their outputs aren't robust. In addition to low current output capabilities vs. say the NE5532, like most CMOS devices these IC's run at low voltages, +/- 7V for the device above.

The input impedance of an internal power amplifier channel in a Denon is about 33k ohms (maximum). In parallel with the following input impedances of an external power amplifier attached to an RCA output the resultant impedance would be as follows:

An impedance of 33k ohms for an internal power amplifier channel in parallel with:

50k ohm external RCA load = 19.9k ohms

33k ohms = 16.5k ohms

20k ohms = 12;.5k ohms

10k ohms = 7.7k ohms

It is quite easy to place a heavy load on the volume control compared to its output capabilities.

The impedance calculations shown above are why it is important for Denon to change their designs such the any small signal output channel from a volume control can be connected to an RCA output and be disconnected from the power amplifier channels. This should provide improved performance at all RCA output levels.

The ability, for example, to connect the L, C, and R channels to RCA outputs and have these same channels not connected to internal power amplifier inputs would allow improved quality for the L, C, and R RCA channels, and still allow use the internal power amplifiers for the remainder of the channels.

This same change in design would avoid the serious performance impact on the maximum voltage output performance of a RCA output when the associated, connected internal power amplifier channel clips.

 

[bigguyca]

Agreed on this one. To me I would avoid HDAM unless one plans on using power amps with input impedance lower than 10 kOhms and need pre out voltage well above 2 V RCA, such as amps rated >200 W with gain below 28 dB. Even then, we are just assuming HDAM in fact will do the job, but ASR and HTHF's bench tests on the Marantz AVPs (at least 3 measured so far) did not show that they helped, no direct evidence anyway. If anyone has seen anything to that effect I would appreciate a link to the test results.

HDAM's will have essentially the same problems as the outputs from the volume control in the Denons when the internal power amplifier they are connected to clips. The Audioholics measurements of the Marantz SR8012 showed this sort of limitation, although in that case Marantz may have limited the output of the volume control to 1.2V or so to avoid the distortion.

The Marantz AVR's/AVP's needs the same sort of ability to disconnect small signal outputs (in this case the HSAM's) on an output by output basis, from internal power amplifiers when the RCA (or XLR) outputs are used.


Use of the HDAM's forces physical layouts that lead to many compromises in the Marantz AVP's. Use of IC opamps and re-layout of the AVP's would allow a single board to provide: DAC IC, to DAC filter, to volume control, to IC opamp buffer with a second opamp to provide the (-) leg of the XLR output, to physical XLR and RCA outputs. Not likely to happen, but desirable. Get rid of analog video to help pay for any added costs.


Marantz also needs to select a reconstruction filter in the DAC IC (just different value into a port) that conforms to standards. The filter Marantz currently uses is an "unforce error" that would cost $0 to remediate. Even better step would be to allow a choice among the filters offered in the AKM DAC IC's.

 

[valerianf]

On the electronic design point of view, it is bad design to take an internal signal and to bring it to an outside connector (RCA) without any buffer.
Any noise from the outside world is then polluting the inside signals of the AVR.
How is it possible to do such a thing on a $$$ AVR?

 

[bigguyca]

One difference between the 3xxx and higher series is AL32 processing. It is explained here:
https://denon-uk.custhelp.com/app/a...6/~/alpha-processing-and-what-types-are-there
”AL32 Processing: Denon has further developed its proprietary AL32 Processing, an analog waveform reproduction technology, to support the 192 kHz sampling frequency. AL32 Processing, thoroughly suppresses quantization noise associated with D/A conversion to reproduce the low-level signals with optimum clarity that will bring out all the delicate nuances of the music.”
Possible it could be doing more harm than good?

ALxx has always sounded like marketing nonsense. Measurements of the AKM DAC IC's in their respective evaluation boards show excellent THD and noise characteristics. These boards don't have the mythical AL processing. Products that use the AKM DAC's such as those from RME and numerous others show excellent performance without ALxx.

As you note, hopefully Denon isn't doing some processing, in say the DSP chips, that does cause problems.

 

[rccarguy]

If you could elaborate, that would be cool. The verified specs are 350wRMS power handling, 0.5% THD 22Hz-500Hz with a 1W (98dB SPL) drive, 0.2% above 500Hz, max SPL 128db at about 5% THD. -3dB down at 22Hz at 96db SPL.

Do be honest, I don't know if these specs are what's important or not for what you mean. I don't say them to try to sound cool, just that's what they are...

What speakers are they?

 

[Gedeon]

Agreed, but for use with AVR without the ability of disconnected the power amp, I wouldn't recommend going with input impedance of lower than 10 kohm, a little lower okay but not much lower.

So I guess I would change my request on Amir to hook up a 6k ohm resistor, if the results look bad, then try 8 or 10K. To do just a couple of test shouldn't take much more time.

My knowledge is pretty limited regarding to how seriously could measurements be affected if the ohms load is way lower than usually expected in power amps input connections.

Just a question due to my ignorance ...

Relatively low ohms at the measurements output could drive to higher distortion reaults, since in that scenary more power than expectes is demanded than when attaching a 33kohms external power amps ?

Thanks for your patience.

 

[peng]

I hear you but it may then look like I am trying to find fault with this one product now.

Haha, good point, I hear you too. Perhaps you can keep the results to yourself but just advice us if there is valid concerns in matching such AVRs to power amps with input impedance lower than X kOhm.

I really don't think 10 kOhm load in parallel with the internal amps would bring SINAD down below 75 dB at 2 V, may be a few dB, who knows, just what the bigguy said/how he interpreted the data sheet of the volume chip. If it was such a significant factor, I highly doubt Denon would have used the same scheme for the AVR-X8500H.

 

[RichB]

Haha, good point, I hear you too. Perhaps you can keep the results to yourself but just advice us if there is valid concerns in matching such AVRs to power amps with input impedance lower than X kOhm.

I really don't think 10 kOhm load in parallel with the internal amps would bring SINAD down below 75 dB at 2 V, may be a few dB, who knows, just what the bigguy said/how he interpreted the data sheet of the volume chip. If it was such a significant factor, I highly doubt Denon would have used the same scheme for the AVR-X8500H.

Testing inputs at 10K ohms is a good idea since it is a representative real-world load.
I am not a EE, but it seems analogous to testing amps with 4 Ohm loads.

If HDAM produced measurably better results, even higher output, then, perhaps, one could assume improvement in the AVR-8500H. More amplifiers, greater power, and additional channels are the goal and these present additional performance challenges.

- Rich

 

[tparm]

The Denon AVR's don't use NE5532's or any other IC opamp as an output buffer. In fact there is no separate output buffer. The RCA preamp output is in parallel with the internal power amplifier input and is driven by the output of the CMOS based 8-channel NJR NJU72343. This connection to the internal power amplifier exists whether a speaker is connected to the internal power amplifier or not.

The NJR unit is rated with a 47k ohm load. The minimum acceptable load, likely with reduced distortion performance, is probably between 10k ohms and 20k ohms based on the datasheet. While these CMOS-based volume controls provide reasonable performance at a reasonable price, their outputs aren't robust. In addition to low current output capabilities vs. say the NE5532, like most CMOS devices these IC's run at low voltages, +/- 7V for the device above.

The input impedance of an internal power amplifier channel in a Denon is about 33k ohms. In parallel with the following input impedances of an external power amplifier attached to an RCA output the resultant impedance would be as follows:

An impedance of 33k ohms for an internal power amplifier channel in parallel with:

50k ohm external RCA load = 19.9k ohms

33k ohms = 16.5k ohms

20k ohms = 12;.5k ohms

10k ohms = 7.7k ohms

It is quite easy to place a heavy load on the volume control compared to its output capabilities.

The impedance calculations shown above are why it is important for Denon to change their designs such the any small signal output channel from a volume control can be connected to an RCA output and be disconnected from the power amplifier channels. This should provide improved performance at all RCA output levels.

The ability, for example, to connect the L, C, and R channels to RCA outputs and have these same channels not connected to internal power amplifier inputs would allow improved quality for the L, C, and R RCA channels, and still allow use the internal power amplifiers for the remainder of the channels.

This same change in design would avoid the serious performance impact on the maximum voltage output performance of a RCA output when the associated, connected internal power amplifier channel clips.

I've sorta lost my way on this thread. So, are you saying; a) the X3700 would be superior in that you can run it in full pre-mode using external amplification for all channels (9 in my case) but since the architecture of the boards, op-amp, volume buffer etc is interior to the X3600 the pre-amp mode advantage may be moot? I recently bought a new X3600 but am in my return window. I like the X3700 has discrete sub outs, 2 Audyssey memory slots and pre-amp mode, but I don't want to take a step backward from my X3600.... Thank you and the other who are great and educated contributors here. Hopefully @amirm receives the X3700 today and can get it tested fairly quickly.

 

[peng]

My knowledge is pretty limited regarding to how seriously could measurements be affected if the ohms load is way lower than usually expected in power amps input connections.

Just a question due to my ignorance ...

Relatively low ohms at the measurements output could drive to higher distortion reaults, since in that scenary more power than expectes is demanded than when attaching a 33kohms external power amps ?

Thanks for your patience.

I have no concerns whatsoever with a 33 kOhms load, or even 15 kOhms. bigguyca said the input impedance of Denon AVR's internal amps was about 33 kOhm (no idea how he knows as I don't think the SM has that info). So if you add an ext amp with input imp 10 KOhms, the equivalent imp of 10K in parallel with 33 K would be below 8K but should still be high enough for that vol control chip to remain on spec. Not saying it would be low enough to absolutely not affect distortions in any significant way, just can't be 100% sure without seeing actual measurements.

On the other hand as I mentioned before, Marantz has the HDAM unity gain buffer amp, but the 7705's SINAD still dropped to only about 75 dB at 4 V XLR, equiv to 2 V RCA. bigguyca seemed to attribute that to noises, but I don't remember Amir cited that as the reason. If he's right, then the often talks about how dedicated processors are better than AVRs in terms of minimizing noises/interference etc. (i.e. the toroidal tx, copper shieldings blablabla would not make much sense any more..

Below are examples of typical input impedance specs of a few popular power amps:

ATI class AB amps...................................28 kOhms (Expect Monolith's the same)
ATI N core amps......................................47 kOhms
Outlaw monoblocks.................................16 kOhms RCA
Outlaw 5000/7000................................ 40 kOhms
Outlaw 7900.............................................>10 kOhms
Marantz M8077.......................................22 kOhms RCA, 30 kOhm XLR
Parasound A21.........................................33 kOhms RCA, 66 kOhm XLR
Anthem MCA............................................10 kOhms RCA, 15 kOhm XLR
Emotiva A-300.......................................... 27 kOhms RCA
Emotiva XPA Gen 5..................................23.5 kOhms RCA, 33 kOhm XLR
Bryston 4B3.................................................30 kOhms
NAD M22.....................................................17 kOhms + 200 pF RCA

So it would seem that most power amp probably have input impedance >= 10 kOhms, and that's why I picked that value, just to be conservative.

 

[peng]

If HDAM produced measurably better results, even higher output, then, perhaps, one could assume improvement in the AVR-8500H. More amplifiers, greater power, and additional channels are the goal and these present additional performance challenges.

- Rich

The AVR-X8500H does not have HDAM though, so could it even do 60 dB SINAD? Who knows, without measuring.. ? I wish I have the instrument to measure it myself. Or if someone has a direct line to Denon, please ask them what is the minimum load impedance for the pre out to maintain 75 dB SINAD at 2 V, without preamp mode or amp assigned to pre out. If I were the go by ears type, I would have no worry because even the X3400H sounded as good as my separate preamp/power amp, but I only believe in specs and measurements.

 

[RichB]

I have no concerns whatsoever with a 33 kOhms load, or even 15 kOhms. bigguyca said the input impedance of Denon AVR's internal amps was about 33 kOhm (no idea how he knows as I don't think the SM has that info). So if you add an ext amp with input imp 10 KOhms, the equivalent imp of 10K in parallel with 33 K would be below 8K but should still be high enough for that vol control chip to remain on spec. Not saying it would be low enough to absolutely not affect distortions in any significant way, just can't be 100% sure without seeing actual measurements.

On the other hand as I mentioned before, Marantz has the HDAM unity gain buffer amp, but the 7705's SINAD still dropped to only about 75 dB at 4 V XLR, equiv to 2 V RCA. bigguyca seemed to attribute that to noises, but I don't remember Amir cited that as the reason. If he's right, then the often talks about how dedicated processors are better than AVRs in terms of minimizing noises/interference etc. (i.e. the toroidal tx, copper shieldings blablabla would not make much sense any more..

Below are examples of typical input impedance specs of a few popular power amps:

ATI class AB amps...................................28 kOhms (Expect Monolith's the same)
ATI N core amps......................................47 kOhms
Outlaw monoblocks.................................16 kOhms RCA
Outlaw 5000/7000................................ 40 kOhms
Outlaw 7900.............................................>10 kOhms
Marantz M8077.......................................22 kOhms RCA, 30 kOhm XLR
Parasound A21.........................................33 kOhms RCA, 66 kOhm XLR
Anthem MCA............................................10 kOhms RCA, 15 kOhm XLR
Emotiva A-300.......................................... 27 kOhms RCA
Emotiva XPA Gen 5..................................23.5 kOhms RCA, 33 kOhm XLR
Bryston 4B3.................................................30 kOhms
NAD M22.....................................................17 kOhms + 200 pF RCA

So it would seem that most power amp probably have input impedance >= 10 kOhms, and that's why I picked that value, just to be conservative.

Great amp list.

10 kOhms is a good target. At one time, I think @bigguyca mentioned that test gear is at 100 kOhms or greater. Manufacturers may have suitable designs so there may be no issues but they also know, if tested, that this will be load.
Should @amirm run a 10 kOhms test and the SINAD drop in a meaningful way, there will be another sh$t storm.

The shielding needed to be in the unit, not at the bottom.
Many high performing processors (and some amps) have moved to switching power supplies. This reduces weight, heat, and power consumption which is going to be seen as a negative during the ubiquitous unboxing video's. Instead of "wow, from the heft, this is really built" we go to "It was surprising light, is there anything in the box?"

Removing amps presents an opportunity to improve performance, not a guarantee.

- Rich

 

[peng]

HDAM's will have essentially the same problems as the outputs from the volume control in the Denons when the internal power amplifier they are connected to clips. The Audioholics measurements of the Marantz SR8012 showed this sort of limitation, although in that case Marantz may have limited the output of the volume control to 1.2V or so to avoid the distortion.

But that's why I kept referring to the AV7705 for reference because it does not have internal power amps.

The Marantz AVR's/AVP's needs the same sort of ability to disconnect small signal outputs (in this case the HSAM's) on an output by output basis, from internal power amplifiers when the RCA (or XLR) outputs are used.

Understood the AVRs part, in fact I started a thread on AH to try and gauge how many people would be interested in a FW upgrade (if Denon would even consider it) to make the pre-amp mode on individual channel/output basis, instead of the universal all or none preamp mode.

@Dj7675 confirmed that the AVR-X8500H has that exact feature!!

I don't understand your ref to the AVPs though, do you mean you want to see a feature that allows HDAMs to be disconnected on an output by output basis? If yes, I would love that feature too, so that if I am using it with an amp that has relatively high input impedance and sensitivity of >=29 dB I could disconnect the HDAM to minimize noise/distortions regardless of how insignificant the difference is, because less is better, even if not audible.

Use of the HDAM's forces physical layouts that lead to many compromises in the Marantz AVP's. Use of IC opamps and re-layout of the AVP's would allow a single board to provide: DAC IC, to DAC filter, to volume control, to IC opamp buffer with a second opamp to provide the (-) leg of the XLR output, to physical XLR and RCA outputs. Not likely to happen, but desirable. Get rid of analog video to help pay for any added costs.

Fully agreed, by the way, below is part of my conversation with Dr. Rich that touched on the HDAM vs IC OPA topic:

https://hometheaterhifi.com/technic...vr-audio-video-reciever-build-quality-part-v/
He said:

"Marantz could replace all those HDAM modules with the NE5532 and apply the savings to run the left, right and center in balance with an added NJU72343.

The Emotiva Pre/Pro is the next step using balanced Cirrus CS3318 volume chips and balanced CMOS switches. That product uses NE5532 opamps with no performance loss."

I included the irrelevant 2nd paragraph just to highligh the fact that Emo, according to Dr. Rich, uses the CS3318, a very capable vol control chip with much better specs that D+M's JRC and Rohm chips, yet it still couldn't beat the AVR-X3600H, but then again as you pointed out, the real difference may revealed though, if a real world like load resistor is connected for the measurements. Like you said, regardless of the known difference in parts and layout etc., we need measurements.

Marantz also needs to select a reconstruction filter in the DAC IC (just different value into a port) that conforms to standards. The filter Marantz currently uses is an "unforce error" that would cost $0 to remediate. Even better step would be to allow a choice among the filters offered in the AKM DAC IC's.

I emailed them on the issue before, and their engineering team replied back that they did it by choice/design. Obviously they believe that's the right choice for them so I don't think there is any chance they would select a different filter. From what I could see comparing measurements of the older and new models, it would seem that they only went with the slow roll off filter since around 2015.

 

[lashto]

I hear you but it may then look like I am trying to find fault with this one product now.

Political correctness is an excellent choice in some cases. But I somehow doubt that it can bring back the much loved "2$ sandwiches" .
OTOH, that won't be the first time I was wrong. Not even first time I was wrong about political correctness.

 

[lashto]

ALxx has always sounded like been marketing nonsense.

Fixed that for you

I am not aware of any Denon documentation that truly explains what ALxx is, how it works and why it should be (at least in theory) effective. Does someone know a source? (and no, marketing brochures do not count as source)

Also not aware of any kind of test done for that ALxx stuff. Not even asking for DBT/ABX here, just the simplest Alxx on/off test done by anyone anywhere would suffice.

ALxx is actually so obscure that even the youtube "reviewers" forgot to yell about it

 

[peng]

ALxx has always sounded like marketing nonsense. Measurements of the AKM DAC IC's in their respective evaluation boards show excellent THD and noise characteristics. These boards don't have the mythical AL processing. Products that use the AKM DAC's such as those from RME and numerous others show excellent performance without ALxx.

As you note, hopefully Denon isn't doing some processing, in say the DSP chips, that does cause problems.

The SINAD of the X4700H wasn't that bad even with the HDMI inputs though, >90 dB with optical. So either AL32/DDAC are not relevant in direct mode, or they don't cause problems as such?

 

[GXAlan]

Appreciate the sentiments. It is indeed difficult to do these "background projects" while also keeping up with the normal review load. Just spent another 3 hours on this project.

It's always a winning proposition for them, but that's not true for you.

1. Denon cannot replicate your results: Denon "wins" since they show that their products are great.
2. Denon replicates your results: Denon "wins" since they have shown that under certain conditions it's as good as the X3600, and now they got free expertise in fixing the problem

Hopefully, Denon replicates your results, identifies the glitch (like the jitter test throwing the unit into a abnormal state that requires a system reset) and gets to do the marketing of thanking you, showing their commitment to measurements, and then releasing something that breaks the 100 db SINAD level.

I am not aware of any Denon documentation that truly explains what ALxx is, how it works and why it should be (at least in theory) effective. Does someone know a source? (and no, marketing brochures do not count as source)

It's an interpolation algorithm which worked GREAT in the 16-bit CD era. It became a defining characteristic of the brand (imagine McIntosh and autoformers, JBL Pro/Klipsch Heritage and compression drivers). It's unclear how much it helps in the modern day as DAC chips have become more advanced and "Alpha" has grown to be a brand rather than a single technology.

It used to be a dedicated Digital Filter chip proprietary to Denon. Now the math is done in the DSP.

See attached PDF.

http://mobile.denon.com/pages/GlossaryDetail.aspx?GId=13
https://denon-uk.custhelp.com/app/a...6/~/alpha-processing-and-what-types-are-there

 

[lashto]

It's an interpolation algorithm which worked GREAT in the 16-bit CD era. It became a defining characteristic of the brand (imagine McIntosh and autoformers, JBL Pro/Klipsch Heritage and compression drivers). It's unclear how much it helps in the modern day as DAC chips have become more advanced and "Alpha" has grown to be a brand rather than a single technology.

It used to be a dedicated Digital Filter chip proprietary to Denon. Now the math is done in the DSP.

See attached PDF.

http://mobile.denon.com/pages/GlossaryDetail.aspx?GId=13
https://denon-uk.custhelp.com/app/a...6/~/alpha-processing-and-what-types-are-there

many thanks, that is more than I was able to find. Admittedly, I did not try much.

Had a look at both links and although they seem/wish to sound technical, both are just marketing disguised as tech-talk.
The first one even uses that awful jagged-sinewave pic that Sony also put into their CD and HiRes marketing leaflets. Already thoroughly debunked in Monty's videos (of vorbis/flac fame) as pure marketing garbage. That is, if anyone needed extra debunking for something that obviously contradicts Nyquist & co.
In the second "tech paper" Denon has the audacity to call their own lalala-tech "the famous ALPHA processor". If that's not a marketing leaflet I don't know what else is.

Guess I was right to assume that Denon's ALxx was just marketing lalalaa and not even look into it much. Anyway, feeling much more 'informed' now

 

[Head_Unit]

Trashing a product and shaming the company rarely achieves your desired result of making a better product for consumers.

Oh I dunno, once upon a time a disgruntled customer put a bullet through an Alpine radio and sent it back to the company. The director touring me around said that spurred them to take quality control more seriously-that radio is in their museum in company headquarters (near a red Lamborghini that hasn't been driven since the 80s).

I didn't read the original posts as "trashing" or "shaming"-I guess that's a matter of intent perception. They just seemed to me a complaint of "this is not too good" and "why is your stuff getting WORSE?!?!" which are perfectly valid; I read similar criticism not so infrequently in car and even stereo magazines. Do companies respond? It depends how much they have their head up their @-ss.

 

[Head_Unit]

It is silly to expect them to have the same performance measurements at a tenth of the cost.

Where did you read that expectation? I must have missed that. Anyway, it does NOT seem "silly" to me to expect a newer product to have the same or better performance than the previous product. THAT is how product development is supposed to work.

I remember being annoyed that H/K receivers back when had a "CD" input S/N of only 80 dB. It seems to me something designed to reproduce a media (CD, DVD, Blu-ray) should be able to reproduce the best of that media. Otherwise, hey, let's have "mini-Blu" 64mm discs with only 10 bit audio because when all those blockbuster movie explosions are happening, we are being deafened anyway and won't hear the difference, and let's cut the video data too because most people don't calibrate their TVs...