This is a review and detailed measurements of the Denon AVR-X6700H "8k" 11.2 channel Audio/Video Receiver. It is kindly loaned to me by a local member and costs US $2,499 on Amazon with free shipping.
AVRs look the same these days and the AVR-X6700H is no exception:
Inside though, is quite full as indicate by large number of amplifications with speaker terminals in the back:
I did not invoke the ECO mode. Without it, the unit runs quite warm. Some instrumentation on this later.
I tested the 6700H a couple of weeks ago and found what I considered performance issues. I ran the subset of those measurements by Denon. They examined them and confirmed that the measurements are correct for the unit I have and is due to capacitor substitution. They provided me with this statement to share with you:
“Denon is pleased to work with ASR once again, who kindly shared his Denon AVR-X6700H measurement results with Denon engineering. The initial results ASR shared were surprising and prompted an investigation, which resulted in Denon engineering identifying measurement irregularities caused by a particular capacitor used in the initial production run to mitigate a supply issue caused by the COVID-19 pandemic. The latest production units have the capacitor Denon typically uses, which does not show the same measurement results.
Even with the previous production units affected by the capacitor constraint, Denon sound masters approved the audio quality in the initial AVR-X6700H production run and we’re confident it sounds just as good as the latest production units. However, if you purchased a Denon AVR-X6700H and have concerns, please reach out to Denon customer support after August 5, 2020 and we will verify if your unit is affected and offer a replacement if merited. “
They will be sending me a newer unit without this issue for testing in the future. I will be updating this review when I get that sample and test it.
AVR DAC Audio Measurements
As usual we start by feeding the AVR over HDMI a 1 kHz tone and see how much noise, distortion and unwanted signals are present in the pre-amp output. I set the volume to 82.5 which produces the nominal 2 volt we see from stereo DACs (see later for performance at other levels):
Note that the amplifier for the two channels being tested is turned off to avoid its clipping behavior impacting the DAC portion. We see a distortion spike rising up to -88 dB which is high enough to dictate SINAD which is a sum of noise and distortion to the same level. This is quite a regression relative to AVR-X4700H to the tune of 8 dB.
I tested using Coax and got the same performance so this is not HDMI channel mixing issue we have dealt with before.
While troubleshooting this behavior, I noticed that the level of distortion varies with time. See this second measurement for example:
So I powered the unit down, let it cool some and then measured SINAD over time:
The instant the test is started, SINAD is nearly 90 dB but drops after a minute or so to 86 dB.
As noted, Denon engineering traced this to a faulty capacitor in early units (I provided the serial number for this sample and they confirmed that it does use this faulty cap).
Running with what we have, this is the ranking then:
We are now in the "red" category of DACs which I don't consider to be good. The AVR-X3600 from last year now enjoys a commanding lead, bettering the AVR-X6700H by a whopping 12 dB. Hopefully the manufacturing fix narrows and closes this gap.
Lowering the output level does not change the equation much:
Here is our signal to noise ratio:
Intermodulation test vs level shows a saturation problem as early as -20 dB:
32-tone test resembling "music" shows dramatic increase in intermodulation distortion as frequencies rise: (label should say 6700)
This manifests itself in THD+N versus frequency just as well: (label should say 6700H)
Unimpressive out of band filtering in the DAC contributes to above: (label should say 6700H):
On less depressing note, Jitter performance is good:
Linearity suffers from secondary power supply tone close to test frequency of 200 Hz:
AVR Analog Input Amplifier Measurements
The CD input on Denon AVRs is not digitized which makes for a good input to test the amplifier's raw performance outside of digital processing:
This is above average performance for all amplifiers tested regardless of type:
Within AVRs, it lands in the crowded middle:
Frequency response is flat and bandwidth quite wide:
Crosstalk is reasonable:
Signal to noise ratio could be better at 5 watts (like to see 16 bits of dynamic range there):
The most important measurement here is power output so let's get into that using 4 ohm load driving 2 channels simultaneously:
Lots of power at 180 watts. One channel has worse distortion though.
Allowing for more distortion at 1% we get this much max and short-term power outputs:
That's 600 watts of short-term power which is nice! You get a benefit from a power supply that is designed to drive a lot more channels than two in this test.
Switching to 8 ohm we get:
Rated spec is at higher distortion than I allow so we are good here.
Edit: forgot to include this measurement in the original review:
Overall for the class, this is very good power and general performance.
Eco Mode Amplifier Performance
I measured the effect of leaving Eco mode in auto versus On (above tests were with ECO=OFF):
As with my previous tests, auto mode has no impact on performance. The switching seems well, seamless.
Turning on the ECO mode not only limits power to just 38 watts but also raises the noise level some. So auto mode would be the preferred mode of operation if you need the power saving and heat reduction.
HDMI Input Amplifier Performance
Since majority use HDMI as the chose input, I ran a separate test on its performance:
There is essentially no impact because the DAC performance was a few dBs better.
Multichannel Amplifier Power Response
I ran a test where I increased the number of channels driven from 1 to 5 channels using 8 ohm impedance (did not want to press my luck with 4 ohm load):
Above is using 1% THD+N. You still have over 100 watts of output with all five channels running.
The testing as is standard in the industry is at 1 kHz. I thought I run a sweep from 20 Hz to 20 kHz and step through the channels just the same. Alas, after adding the third channel, the AVR went into protection mode immediately and shut down. This tells me the actual available power in bass where most of the action is, is lower than the above bar chart indicates. When I get the second sample from Denon, I will run this test again and verify this issue.
EDIT: Forgot to include these in the original review.
Thermal Performance
As I have been commenting, these Denon/Marantz AVRs run pretty warm. So I thought I take a snapshot after my testing using my IR camera:
As we see the hottest area is the row of heatsinks. Zooming in we get the peak temperature:
As we see the peak temperature is 72 degree C (161 F) and this is the heatsink. The junction temperature for the power output transistors will be much higher. And this is with the AVR in "open air" and not in any kind of cabinet. So be careful about amount of airflow.
Conclusions
Stepping up in Denon AVR line gets you progressively more power and that is indicated in my measurements. Amplifier running out of power is a key aspect of sound quality suffering so this is good.
Alas, the performance of the pre-amp output is disappointing in the way it has regressed relative to other units in the line. Hopefully the later production units perform better. Until I can verify that, I can't recommend the Denon AVR-X6700H.
-----------
As always, questions, comments, recommendations, etc. are welcome.
The number of messages I get in my forum inbox has exploded as of late. I need to hire someone to impersonate me and answer them. I can't find anyone as good looking as myself but since people can't see my image in these messages, maybe I have some hope of finding someone to do that. They won't work for free though so please donate what you can using : https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
AVRs look the same these days and the AVR-X6700H is no exception:
Inside though, is quite full as indicate by large number of amplifications with speaker terminals in the back:
I did not invoke the ECO mode. Without it, the unit runs quite warm. Some instrumentation on this later.
I tested the 6700H a couple of weeks ago and found what I considered performance issues. I ran the subset of those measurements by Denon. They examined them and confirmed that the measurements are correct for the unit I have and is due to capacitor substitution. They provided me with this statement to share with you:
“Denon is pleased to work with ASR once again, who kindly shared his Denon AVR-X6700H measurement results with Denon engineering. The initial results ASR shared were surprising and prompted an investigation, which resulted in Denon engineering identifying measurement irregularities caused by a particular capacitor used in the initial production run to mitigate a supply issue caused by the COVID-19 pandemic. The latest production units have the capacitor Denon typically uses, which does not show the same measurement results.
Even with the previous production units affected by the capacitor constraint, Denon sound masters approved the audio quality in the initial AVR-X6700H production run and we’re confident it sounds just as good as the latest production units. However, if you purchased a Denon AVR-X6700H and have concerns, please reach out to Denon customer support after August 5, 2020 and we will verify if your unit is affected and offer a replacement if merited. “
They will be sending me a newer unit without this issue for testing in the future. I will be updating this review when I get that sample and test it.
AVR DAC Audio Measurements
As usual we start by feeding the AVR over HDMI a 1 kHz tone and see how much noise, distortion and unwanted signals are present in the pre-amp output. I set the volume to 82.5 which produces the nominal 2 volt we see from stereo DACs (see later for performance at other levels):
Note that the amplifier for the two channels being tested is turned off to avoid its clipping behavior impacting the DAC portion. We see a distortion spike rising up to -88 dB which is high enough to dictate SINAD which is a sum of noise and distortion to the same level. This is quite a regression relative to AVR-X4700H to the tune of 8 dB.
I tested using Coax and got the same performance so this is not HDMI channel mixing issue we have dealt with before.
While troubleshooting this behavior, I noticed that the level of distortion varies with time. See this second measurement for example:
So I powered the unit down, let it cool some and then measured SINAD over time:
The instant the test is started, SINAD is nearly 90 dB but drops after a minute or so to 86 dB.
As noted, Denon engineering traced this to a faulty capacitor in early units (I provided the serial number for this sample and they confirmed that it does use this faulty cap).
Running with what we have, this is the ranking then:
We are now in the "red" category of DACs which I don't consider to be good. The AVR-X3600 from last year now enjoys a commanding lead, bettering the AVR-X6700H by a whopping 12 dB. Hopefully the manufacturing fix narrows and closes this gap.
Lowering the output level does not change the equation much:
Here is our signal to noise ratio:
Intermodulation test vs level shows a saturation problem as early as -20 dB:
32-tone test resembling "music" shows dramatic increase in intermodulation distortion as frequencies rise: (label should say 6700)
This manifests itself in THD+N versus frequency just as well: (label should say 6700H)
Unimpressive out of band filtering in the DAC contributes to above: (label should say 6700H):
On less depressing note, Jitter performance is good:
Linearity suffers from secondary power supply tone close to test frequency of 200 Hz:
AVR Analog Input Amplifier Measurements
The CD input on Denon AVRs is not digitized which makes for a good input to test the amplifier's raw performance outside of digital processing:
This is above average performance for all amplifiers tested regardless of type:
Within AVRs, it lands in the crowded middle:
Frequency response is flat and bandwidth quite wide:
Crosstalk is reasonable:
Signal to noise ratio could be better at 5 watts (like to see 16 bits of dynamic range there):
The most important measurement here is power output so let's get into that using 4 ohm load driving 2 channels simultaneously:
Lots of power at 180 watts. One channel has worse distortion though.
Allowing for more distortion at 1% we get this much max and short-term power outputs:
That's 600 watts of short-term power which is nice! You get a benefit from a power supply that is designed to drive a lot more channels than two in this test.
Switching to 8 ohm we get:
Rated spec is at higher distortion than I allow so we are good here.
Edit: forgot to include this measurement in the original review:
Overall for the class, this is very good power and general performance.
Eco Mode Amplifier Performance
I measured the effect of leaving Eco mode in auto versus On (above tests were with ECO=OFF):
As with my previous tests, auto mode has no impact on performance. The switching seems well, seamless.
Turning on the ECO mode not only limits power to just 38 watts but also raises the noise level some. So auto mode would be the preferred mode of operation if you need the power saving and heat reduction.
HDMI Input Amplifier Performance
Since majority use HDMI as the chose input, I ran a separate test on its performance:
There is essentially no impact because the DAC performance was a few dBs better.
Multichannel Amplifier Power Response
I ran a test where I increased the number of channels driven from 1 to 5 channels using 8 ohm impedance (did not want to press my luck with 4 ohm load):
Above is using 1% THD+N. You still have over 100 watts of output with all five channels running.
The testing as is standard in the industry is at 1 kHz. I thought I run a sweep from 20 Hz to 20 kHz and step through the channels just the same. Alas, after adding the third channel, the AVR went into protection mode immediately and shut down. This tells me the actual available power in bass where most of the action is, is lower than the above bar chart indicates. When I get the second sample from Denon, I will run this test again and verify this issue.
EDIT: Forgot to include these in the original review.
Thermal Performance
As I have been commenting, these Denon/Marantz AVRs run pretty warm. So I thought I take a snapshot after my testing using my IR camera:
As we see the hottest area is the row of heatsinks. Zooming in we get the peak temperature:
As we see the peak temperature is 72 degree C (161 F) and this is the heatsink. The junction temperature for the power output transistors will be much higher. And this is with the AVR in "open air" and not in any kind of cabinet. So be careful about amount of airflow.
Conclusions
Stepping up in Denon AVR line gets you progressively more power and that is indicated in my measurements. Amplifier running out of power is a key aspect of sound quality suffering so this is good.
Alas, the performance of the pre-amp output is disappointing in the way it has regressed relative to other units in the line. Hopefully the later production units perform better. Until I can verify that, I can't recommend the Denon AVR-X6700H.
-----------
As always, questions, comments, recommendations, etc. are welcome.
The number of messages I get in my forum inbox has exploded as of late. I need to hire someone to impersonate me and answer them. I can't find anyone as good looking as myself but since people can't see my image in these messages, maybe I have some hope of finding someone to do that. They won't work for free though so please donate what you can using : https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
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