MEASUREMENTS: Yamaha RX-V781 Receiver (a look at the pre-out quality)

With the upgrade recently to a 4K TV, it was alas also time to upgrade the surround receiver system I was using. A number of years ago, I bought a used Onkyo TX-NR1009 which I wrote about. It has served me reasonably well over the last few years but not without some issues. The most bothersome was the fact that the HDMI board died last year and it had to be sent back to Onkyo for a board replacement. Thankfully, despite the machine being released around 2011, Onkyo still honored the repair as apparently this is a common problem acknowledged by the company. Not good that the product was defective due to an engineering oversight (soldering & overheating issues), but at least the company "manned up" to the problem.

These days, to make full use of the surround sound system connected to a full-featured 4K TV, the best way is to upgrade the receiver to be compatible with the latest HDMI 2.0 specification with allowance for 4K/UHD @ 60Hz, HDCP 2.2 copy protection compatibility, as well as passing through the full video signal - including full color information (Rec. 2020/BT.2020 and HDR). (For those new to this kind of AV talk, you might want to review the 4K tech article from a few months back.)

Unfortunately, the Onkyo was only good to HDMI 1.4. It was time to upgrade to one of the new receivers... And this is what I found on sale locally:

It's a new model year 2016 Yamaha RX-V781 (current price ~US$700).

Other than the fact that I found it at a good price locally, it fulfilled all the features I needed. The video features are almost all there: HDMI 2.0 4K/60Hz support, HDCP2.2, HDR pass through with expanded color gamut for "deep color", reasonable number of HDMI inputs (5 rear + 1 front, 3 of which support HDCP2.2), and 2 HDMI outputs (1 for the TV, and another if I ever needed a secondary zone or output like a separate digital audio split). By the way, for the more advanced users, if you want to send the receiver RGB / 4:4:4 HDMI video signals (and also 4:2:2), you should switch the receiver to "Mode 1" (see user manual), this is what I did. By default, the machine is set to "Mode 2" which is fine for most input including UHD Blu-Ray players that are 4:2:0 chroma sub-sampled (this will also help if your HDMI cables aren't up to HDMI 2.0 standard, I'll talk more of this another time I think).

I said that the video features are almost all there. The limitation I found was that it doesn't seem to pass through framerates >60fps. On my Vizio P75-C1, the HDMI5 input is meant for gaming (low input lag, minimal video processing, no HDR ability) and can handle 1080P at 120Hz. Unfortunately, at this time, the Yamaha does not appear to pass the 120Hz high frame rate from the computer to TV. For me this isn't a big deal since I bought a 4K+HDR TV not to get high frame rate 1080P. I've heard that current Denon (like the awesome Denon AVRX6300H) and Sony receivers can handle 120fps though, so maybe check those out if you need this feature. By the way, 120Hz looks great on a big screen TV - you can see the difference the moment you note the smoothness of the mouse pointer gliding across the screen :-). I wonder if a firmware upgrade for the Yamaha could make this available...

The other big feature I needed was a receiver that has surround decoded analogue pre-outs. The reason for this is so the front stereo channels can be fed into my Emotiva XSP-1 preamp so it can be forwarded to the monoblocks using the "HT bypass" mode. It's about having my cake and eating it as well :-). A high quality, capable analogue pre-amp with bass management (XSP-1) for all my 2-channel needs, plus the ability to play 5.1 surround with the Yamaha receiver acting as surround decoder and amplifier for the center channel plus 2 rear channels (5.1 system). The RX-V781 is the least expensive model in the Yamaha lineup that provides these RCA pre-outs. As a reminder, for those who are looking for higher end receivers, Yamaha offers their AVENTAGE line. Considering features, this model looks like it's similar to the Yamaha RX-A860 (~US$900) but with less power though I'm sure the workmanship and parts are better on the AVENTAGE side...

Here's the receiver just taken out of the box:

Yamaha RX-V781... There's a rather plasticky remote control sitting on top; works fine and easily programmed into my Harmony remote.

Note that this is a 7.2 channel receiver capable of the usual surround formats (eg. DD/ DD+/AC3/EAC3, DTS, DTS-HDMA, Dolby TrueHD) and now also "object-oriented" Dolby Atmos and DTS-X decoding. One attractive option in my room would be a 5.1.2 arrangement (with 2 ceiling "presence" speakers although 4 channels would be ideal with a more fancy receiver). Other arrangements like biamping with unused channels are possible... There's also the phono input for you vinyl listeners. Seriously, the flexibility and options available with modern receivers are staggering and more than I can speak about here! Truly the AV receivers these days are amazing "jacks of all trades".

The Yamaha is smaller and lighter than the Onkyo it replaces:

The main reason is that the amplifier section isn't as powerful with this Yamaha compared to the Onkyo, nor as many channels. The Yamaha is rated at 95W 2-channels driven into 8-ohms at 0.06%THD (the Onkyo is a 9.2 surround behemoth with rated power at 135W 2-channels, 8-ohms at 0.08% THD). Considering the fact that I'm only using 3 of the channels - Paradigm Signature C3v3 center speaker and two rear Paradigm Studio 80v3's, this is plenty of power.

I spent a couple evenings fooling around with the settings to the way I want them. Like any of the network connected electronics these days, there are firmware upgrades and I'm up-to-date as of early December 2016 (firmware 1.26). The OSD works well enough to adjust settings and I haven't had any issues with passing 4K/60Hz/HDR signals through the receiver to my 4K TV (initially the Sharp LC-75N8000U and now the Vizio P75-C1). CEC works smoothly with both the Sharp and Vizio TVs.

Although there's much that can be measured and evaluated, for today's post, I thought it would be interesting to have a look at the pre-outs from this device to examine the quality of the DAC using HDMI input - the fact is that I'm not likely going to be using any other digital interface with a receiver these days.

Here's what the measurement chain looks like:

Skylake i5 HTPC --> 12' generic HDMI (2.0) cable capable of 4K video --> Yamaha RX-V781 receiver (front stereo channels pre-out RCA) --> 6' shielded RCA --> Focusrite Forte --> 6' USB --> Windows 10 laptop

Pretty straight forward and typical of the measurements I've presented here over the years... We'll just be looking at the front stereo output channels.

Unless noted otherwise, all measurements of the Yamaha will be done in "Direct" mode with all DSP processing like room correction and bass management turned off.

Part I: Digital Oscilloscope, Digital Filter, Impulse Response

As usual, let's start with a look at the analogue output through the digital oscilloscope:

A small amount of channel imbalance can be seen. The right channel (blue) is a little bit softer than the left. Peak voltage is at 1.62V. You can see that there's a little rise at the leading edge of each square wave. This asymmetrical morphology suggests we're looking at a minimum phase digital filter being used... Voilà:

Yup. The impulse response is in the form of a sharp minimum phase digital anti-imaging filter. Polarity is maintained. I'm not sure what DAC is inside this machine but the specs sheet does state that it uses a Burr-Brown chip capable of 24/192 for each channel. It also is capable of DSD64 (2.8MHz) and DSD128 (5.6MHz) decoding - neither of which I have tried to this point. Here's the "digital filter composite" graph:

This does look like the digital filter signature I've seen over the years for TI/Burr-Brown DAC's. For example, it is quite similar to the HiFiBerry DAC+ Pro which uses the PCM5122 chip. It looks a bit like the "Low latency IIR" setting although with a bit more noise in the ultrasonic noise floor especially around 60-70kHz (likely because of the complexity of this device and all the internal electronics). Overloading of the high amplitude white noise is seen. As expected by the amount of ringing, the filter is rather sharp as demonstrated by the drop-off above Nyquist (22.1kHz), and good ultrasonic suppression of aliasing products seen with the 19 & 20kHz signal.

Part II: RightMark Tests

Let's now have a look at the resolution that this internal DAC is capable of. As usual, we start with the most basic and easy 16/44 test signal:

The above is the summary table with direct objective comparisons with the Raspberry/HiFiBerry DAC+ Pro, Surface 3 with Light Harmonic Geek Out V2, Logitech Transporter, TEAC UD-501 connected to my HTPC, and finally the Oppo BDP-105 blu-ray player which I had the occasion to repeat measurements on recently using the Focusrite Forte measurement set-up these days.

Across the board, 16/44 resolution is a piece of cake for essentially any but the cheapest DACs these days (or the most unusual/boutique DAC!). Honestly guys, I would be suspicious of anyone claiming that their DAC has any special sound quality at 16/44... Unless it's an admission that they're not after high fidelity and they're imparting some kind of coloration that makes it "better".

The usual graphs now:

Notice that the Yamaha compared to the others doesn't fare as well in the noise department although numerically when averaged looks great. There's actually a bit of 60Hz hum there which is still of a relatively low level at -100dB down but obviously sticks out compared to the others (and can be audible of course when putting your ears close to the speakers with volume up). Also, from 1500Hz up, the stereo crosstalk obviously deteriorates (I've been using the same 6' RCA cable for these measurements). THD+N also higher compared to the more expensive DACs but better than the Raspberry Pi 3 & HiFiBerry DAC+ Pro combo.

24/96:

Going into hi-res territory, we see that the Yamaha receiver is indeed capable of quite low noise level. Though perhaps not as impressive as the others, it's really quite good for such a complicated and feature-filled machine.

Note the ~37kHz noise is due to the Focusrite Forte, not to do with the test devices.

Graphs above look very good still and again the main "issues" we see are the extra 60Hz hum in the frequency response, elevated crosstalk, and suboptimal distortion characteristic. Notice too that the frequency response does droop a bit more with the receiver down at -0.5dB @ 20kHz and -1dB at 30kHz (in practice no big deal).

24/192:
Finally, here's 24/192. The Transporter is not capable of this high sampling rate so it's off the table.

Again, same story as above. Decent noise level except for 60Hz hum. Stereo crosstalk likely going to be the same as above as suggested by the numerical values... Alas, RightMark doesn't quite plot out the 192kHz graphs properly for crosstalk and THD+N.

Part III: Jitter

Looking back, I had explored HDMI jitter a number of years ago. As you can see, in October 2013 when I first looked at the Onkyo TX-NR1009, I noted that the Dunn J-Test results clearly left much to be desired. However, jitter was higher not just for HDMI but also coaxial and TosLink input with that device. As we look at the Yamaha in 2016, here are the Dunn J-Test FFT's, first with the 16/44 version:

Here's the 24/48 version:

And finally, we go 2x samplerate and look at 24/96 to exacerbate anomalies (see here, here, and here for some comparisons):

What we see is that compared to the Onkyo, this Yamaha has significantly improved jitter results. Not much "skirting" at the base of the primary frequency, minimal sidebands to be concerned about. The 96kHz result typically brings out the sidebands and even with this test, the levels are extremely low and there's nothing IMO to worry about.

In sum, don't worry about jitter even with HDMI using this 2016 receiver. I didn't test S/PDIF input on this unit.

Part IV: Yamaha's YPAO (Yamaha Parametric Acoustic Optimizer)

Alright, this is Yamaha's multi-point automatic EQ system much like Audyssey. I have it turned on and subjectively it seems to work quite well in my room. I made measurements at 5 locations (max 8 locations) around the sweet spot on my sofa in the AV room and ran the results through the RightMark measurement software. Here's what the summary looks like when I run a 24/192 test signal:

Interesting, so we get 2 observations. First, it looks like it's operating at 24-bits. The "noise level" remains low which is what we see when the DAC is functioning beyond the 96dB threshold of a 16-bit device. Secondly, as expected, the frequency response is no longer flat - that "+6.37, -4.21" result. YPAO is doing it's work with frequency equalization, compensating for the room acoustics. For now, I have not taken out my measurement microphone to run a few sweeps to check how well this works... Maybe another time.

Here's what the frequency response looks like plotted out with and without YPAO active (24/192 signal):

What we see here is that the YPAO signal truncates above 40kHz. Cool. Evidence that this algorithm is operating likely in 24/96. I haven't checked in the last couple years, but in the past, most room correction algos on receivers were working at 24/48. This suggests to me at least that for the 2016-year Yamaha receivers, the internal DSP is powerful enough to run beyond the standard 1X resolution.

Let's also look at the noise floor:

We see that the 60Hz hum is still there and at the same level around -100dB. No difference when YPAO is turned on. We can make out a few low-level extended peaks around 550 and 650Hz for example; nothing too impressive and looks like turning on the DSP doesn't worsen the noise floor. Nice.

Conclusions:

Subjectively, the AV amplifier sounds good to me when I run it using my set-up - front stereo pre-outs to my preamp and monoblock amps, receiver powering my center channel and rears. Front channels sound very good when playing 2.0 stereo (knowing from objective measurements that there are compromises of course), and a nice cohesive sound when running 5.1 after the necessary calibrations. Since I'm not asking the receiver to pump out much power at all (fronts powered by my Emotiva XPA-1L monoblocks), the center channel and surrounds are nice and clear even with higher volumes. Unfortunately, I have not collected many multichannel albums in awhile and many of the recent remasters don't really sound that good (eg. Beatles 1+ DVD/Blu-Ray is at best OK). There are recent gems such as the Steve Wilson remasters of King Crimson albums like Red, Larks' Tongues in Aspic, or In The Court Of The Crimson King. Excellent use of the spatial potential in a multichannel set-up and a nice gift for classic progressive rock fans.

Movie soundtracks were great. Nice explosions, collision effects, space noises on Star Trek Beyond with crystal clear center dialogue. Bone rattling bass especially with the Paradigm Signature Sub 1 turned on :-). As a reference over the years, the DTS Omaha Beach scene in Saving Private Ryan continues to impress as an exercise in brutal realism achievable with proper set-up and calibration.

From an objective perspective, we see that the RCA output quality obviously is not as good as what we see with higher quality DACs like the TEAC UD-501, Logitech Transporter, or Oppo BDP-105. As the old saying goes, "jack of all trades"... But even if the Yamaha's internal DACs may not achieve "master" quality, it certainly gives it a good try! I'm seeing >17-bits of dynamic range through most of the audible spectrum so it can at least benefit from 24-bit hi-res audio data. But it does have more 60Hz hum in my system, the stereo crosstalk and THD can be improved as well. As for jitter, using the HDMI input, this receiver is an improvement over the Onkyo TX-NR1009 it replaced. No, the 16-bit and 24-bit J-Tests are not as ideal compared to a good asynchronous USB or ethernet DAC, but IMO the imperfections are most likely completely inaudible (as I believe the vast majority of audiophile jitter phobias are).

Finally, I haven't spent much time optimizing the YPAO room correction yet, but the preliminary listening tests and the measurement results suggest an encouraging 24/96 algorithm being used.

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Alright guys, I might or might not get a chance to post much more as we get closer to Christmas... Lots of local events and family shindigs to get involved in :-). Hope the weather is good where you are and stay safe in the cold for those of us living in the almost-winter parts of the world.

Listening to The Hamilton Mixtape (DR7, 2016) this past week (recommended by a friend). Interesting "mix" of pop, R&B, rap. The Regina Spektor & Ben Folds rendition of "Dear Theodosia" sounds very sweet... Will have to check out the Lin-Manuel Miranda musical at some point live. The Broadway Cast Hamilton soundtrack recording is excellent as well (DR9, 2 CDs).

Also, I've been spending time playing with my new nVidia GeForce 1080 graphics card with the 4K TV. Phenomenal performance from these new nVidia graphics cards, finally capable of good framerates in real 4K (full 60fps!) with settings set to "ultra" in essentially every game I've thrown at it. Consoles like Xbox One S and Playstation 4 Pro look great but from a hardware perspective, we're looking at upgraded 1080P resolution GPUs in these game machines mixed with novel rendering/upsampling techniques (like the PS4's "checkerboard rendering"). We'll have to wait for Microsoft's Xbox Scorpio next year for the "real deal" in 4K gaming (perhaps just barely). I was somewhat tempted to grab the PS4 Pro if they only had UHD Blu-Ray playback - Sony blew it IMO since this could have been a great home theater/game package for the 2016 holiday season.

Speaking of the GTX 1080 graphics card, of course there's a price to pay for playable games in full 4K currently :-). Remember, here in the Archimago household, we don't mind spending money... I just need to know that it makes a real difference first!

Wishing everyone a most wonderful holiday season with overflowing cups of good cheer while enjoying the sounds and sights...

PS: Titanfall 2 PC on a 75" 4K screen looks stunning! I really like the Microsoft Xbox Play Anywhere initiative - a single purchase for both Xbox One and Windows 10 games while potentially bringing more A-grade titles to the PC (Gears of War 4 and Forza Horizon 3 should be fun as well). "Prepare for Titanfall!"