MEASUREMENTS: Onkyo TX-NR1009 "WRAT" AV Receiver Class AB Amplifier... Plus Pi / LP / Resolution miscellany.

I currently have 3 AV receivers here at home. The Denon AVR-3802 is my oldest machine, purchased back in 2001 and being used in the living room for stereo playback. My newer Yamaha RX-V781 (2016) is currently in use for movie playback with Atmos/dts:X decoding. This leaves the Onkyo TX-NR1009 (2011 model) that I bought used in 2013 which has actually been sitting unused for the last few years mainly because it's an older HDMI 1.4 device which did not support full 4K/HDR/60fps switching:

It's a shame because I think of the 3 receivers, subjectively this is probably the best sounding (no blind test done, just a suspicion), has the highest power rating (135W into 8Ω, 1kHz, 1%), THX Select2 Plus certified, can amplify 9 channels (9.2 decoding), and when new, was also the most expensive of the three. I'm sure at some point I'll find a use for this 41 pound monster - maybe if/when the old Denon breaks down :-).

I don't think anyone can fault the external build quality which also looks quite handsome. Onkyo did unfortunately have some electronics failure issues with this generation of receivers however and back around 2016, I sent this unit back to them for an HDMI board replacement (here's a thread on the issue a few years back).

For this post, I think it would be interesting to explore the sound quality of this device as a 2-channel amplifier (especially compared to the little Yeeco TI TPA3116 amp last week). It'll give us an idea of how well a good receiver could perform and give us a peek at a modern Class AB device sitting in the higher end of the consumer price ladder (Class AB receiver amplifier designs have not changed that much in the last number of years). These days a similar tier THX model with equivalent power would be the newer Onkyo TX-NR1030 and TX-RZ1100.

I. Basic Amplifier Characteristics

This AV receiver is run off a relatively thick 2-prong IEC cable to the mains. For the tests today, I'm going to use the "AUX" RCA input, measuring the front L and R amp outputs, and the amp will be turned to "Pure Audio" mode for presumably best performance with Audyssey MultEQ XT room correction DSP, EQ, bass management, and other features turned off.

Amplifier Gain was measured as 36dB with the volume knob up to "82.0" which the amplifier also identifies as the "Ref(erence)" level. I can push this up to "100" which results in a gain of 54dB!

Amplifier Damping into 4Ω looks quite stable through the audible band:

Notice however that the damping factor is not particularly high. Onkyo states that this device uses their WRAT (Wide Range Amplifier Technology with a range of 5Hz - 100kHz frequency response) amplifier and is stated to have a "3-Stage Inverted Darlington Circuitry" which is supposed to employ "low negative feedback". Perhaps the relatively low damping factor is a result of this? We can see in the online brochure that the damping factor given by Onkyo is 60 at 1kHz into 8Ω which is good but still not high compared to many solid state amps.

Here's the Frequency Response of the amplifier comparing the 4Ω load and the Sony SS-H1600 speaker:

Though the damping factor is not particularly high (ranging 11-16 across the frequencies into a 4Ω load), notice that this is fine for the Sony speaker which has a higher impedance, with only slight frequency fluctuation from an ideal flat response. The "gain spread" for the Sony speaker is less than 0.25dB through the audible spectrum.

We can have a look at the Phase Response as well, output to 4Ω load:

That looks great. The frequency response is flat down to 20Hz and less than 0.25dB dip into 20kHz. Notice the flat phase response from 20Hz to 48kHz as well.

II. Single-Tone Harmonic Distortion and Noise

Moving along, with the DAC output set at 1Vrms, we can have a peek at a few 1kHz THD(+N) FFT's across a few power levels:

As you can see, I've selected 6 power levels to show the THD+N pattern. The amp is straining by 29V (~210W) into 4Ω with around -50dB THD+N. Notice that there's a small amount of 60Hz mains hum with hum harmonics in the lower frequencies adding to little "needles" in the noise floor.

The harmonic distortion other than at 16mW contains low second-order products and we see that it's the 3rd harmonic that predominates across the power levels and from 1W and beyond, the odd-order harmonics predominate. If you've read hi-fi magazines over the years, you've no doubt been aware of the tendency towards odd-order harmonics with solid-state devices and this has been said to be a factor as to why some prefer tube amplifiers (for example, here's KEF's comment on this recently posted in August of this year).

Harmonic Distortion vs. Frequency in the Stepped Sine graph - here are 1W and 100W power levels:

We can clearly see the odd-order predominance on the Stepped Sine graphs. For example, notice how high the 3/5/7/9th harmonics are compared to even the red 2nd harmonic in the 2Vrms graph.

Let's now see how much power this amplifier can produce. Here is the THD+N vs. Voltage curve:

For those not familiar, I've included THD+N in % and also Power Out in W as well. Clearly this is better than the little Yeeco amp from last week. We see that THD+N stays below 0.1% THD+N up to 28Vrms or 196W.

I've seen older measurements such as this one by Sound & Vision magazine from back in 2012. Using their AP test system they claim to have measured 0.1% THD+N into 4Ω at 218W. I didn't see anything as low as their reported 0.0035%/-89dB THD+N into 8Ω at 5W.

My simple Crosstalk procedure using 300Hz and 4kHz tone in either right or left channels resulted in an average of -69dB. That's certainly more than good enough. Up to 100W output, I was unable to detect a difference in THD+N whether both channels were driven vs. single channel. No surprise that for a 9-channel amplifier, there's plenty of power to drive 2 channels without showing any signs of stress.

III. Multitone Testing - Intermodulation Distortion and Triple-Tone TD+N

A few IMD tones for your consideration:

Again, obviously much better than the inexpensive $30 Yeeco TI TPA3116 "chip amp" last week. SMPTE -65dB, CCIF/ITU-R -76dB, Linkwitz -80dB with 48kHz bandwidth.

Here's the TIM test tone using the Tektronix Cookbook recipe accelerated x 2 to 96kHz bandwidth using 1kHz square + 12kHz sine:

As you can see with a low 2Vrms output level, there are no 2kHz sidebands around the 12kHz tone to be found (all we see are low-level "needles" originating from the 60Hz mains hum and harmonics). By 14V output, we indeed see 2kHz spaced noise popping up but this isn't bad as we're looking at levels down below -110dB off the 1kHz square wave. Remember that this test comprises of a square wave that's swinging ~28V from positive to negative in <10μs with the sine wave riding along. Remember that for Class AB amplifiers, the 2V test could still be in pure Class A while by 14V, assuredly in Class AB with potential crossover distortion.

I suppose if I pushed it to 20Vrms, things could get uglier... I'm just not impressed that there's a need to strain the amp that much with such an artificial non-musical signal.

And finally, we have the Triple-Tone Total Distortion and Noise graph at the standard 2Vrms level into 4Ω:

Remember that I'll be using the measurement above (-73.1dB) for my Distortion Factor summary score due to the importance of the "First Watt" principle. Nonetheless, we can have a peek at other, higher output levels like this:

IV. Square Wave and Wideband Noise

That's a pretty nice square wave ("non-aliasing", 24/384 signal) indicative of good extended bandwidth - as per Onkyo's "WRAT" acronym. Notice the excellent channel balance as well with essentially perfect overlay of right and left channel waveforms.

Here's the wideband FFT all the way out to 1.5MHz to look for very high frequency noise:

Nothing much to see all the way out to 1.5MHz.

And for fun, here's what a low amplitude +/-150mV 1kHz square wave looks like:

We see the oscilloscope running at 1gigasample/s is picking up a little bit of spurious noise, but notice how clean this is compared to the inexpensive Yeeco Class D amp last week.

V. Impressions and Conclusions

So let's wrap this up. With the Onkyo TX-NR1009 "WRAT" amplifier, we can see the performance level of a modern Class AB AV receiver. While this is not the latest generation with all the whiz-bang features of 2019 like HDMI 2.0 capability, the amplifier in this model is certainly highly capable and powerful, able of pushing a 28V (~200W) 1kHz sine wave through a 4Ω load achieving 0.1% THD+N distortion.

Here's the summary AMOAR Score:

Notice that while the average Damping Factor of 12.7x isn't particularly high, it is consistent across the audio spectrum unlike the Yeeco last week which catastrophically dropped off in the high frequencies. As a result, we don't see that problematic high frequency lift with the Sony speaker. It's also nice to see how flat the frequency response is with the 4Ω power resistor.

With a Triple-Tone Distortion Factor, 2Vrms into 4Ω result of -73dB, that's indicative of a clean sounding amplifier. A finding worth noting is the relative predominance of odd-order harmonics as seen in Section II.

As I mentioned at the start of this article, I believe this Onkyo is the best sounding of my 3 receivers despite the low damping factor and I would have loved to see lower mains hum harmonics. Maybe at some point I'll have a look at my Yamaha "Natural Sound" receiver for comparison which I'm somewhat curious about as well.

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Let's end off with a quick-fire round of comments.

On Raspberry Pi 4...
Over the last few months, some of you have E-mailed me about the Raspberry Pi 4 and whether I'll have a look at this SBC for music streaming. I currently do not have one of these. As far as I can tell looking into it when it came out, clearly the CPU performance is better and the gigabit ethernet looks good. However it does run hotter than the Pi 3 and power consumption is higher. I think I'll just pass on this device as I don't have any great need for it. Maybe the next generation or perhaps incremental versions would be worth getting if it's able to reduce power consumption. I'm sure it's a great platform for audio streaming for those who have one!

On measurement of vinyl gear and LPs in general...
I've also received E-mails to look at measuring phono preamps and more about analogue playback. Hmmm, as you can see, I'm not much of a vinyl guy. Admittedly, I was more interested back in 2014 - 2016 (articles like this, and this) and I still will play albums with my Technics SL-1200 M3D once awhile especially when friends come over and want to check out the novelty. Truth be told, I visit LP stores much less these days, come to think of it, I haven't bought a used record in more than a year!

With the hype in the last few years, prices have increased for both new and used stuff to the point where I'm just not finding as much value for the dollar. Furthermore, I'm just not sure I want to buy any new, frail, 180g plastic discs for entertainment given environmental concerns these days. This is especially heart-breaking when I see people playing the discs with toy turntables, poorly configured and cheap cartridges, literally destroying the product. Over time, I see vinyl playback as being highly regressive in more ways than one. We'll see, but I suspect new vinyl sales will plateau and decline in light of these various factors.

As published here, vinyl playback is to me very much "defective by design" if we're aiming to hear the most "transparent" reproduction of our favourite music. Some albums sound great, others don't. As such, exactly how "accurate" a phono preamp measures so long as it's within the general expectations of the RIAA curve, and the noise floor staying reasonably low, probably isn't very useful knowledge given the limitations of the analogue playback system itself. Remember, vinyl is not "high resolution". It never was. It never will be. Enjoy it for what it is.

This doesn't mean I won't check out the objective results of various LP-playback gear in the future, but given the quality of even inexpensive digital technology, almost all of what analogue gear has to offer would generally be disappointing objectively IMO.

On bashing the importance of "resolution"...
Finally, I saw this poorly reasoned and formatted article yesterday - Stephen Mejias' "Undercurrents No. 3: The Promise of What". The fact that he wrote this:

Only among audiophiles does the word “resolution” conjure some relationship between reproduced music and the live event, some measurable level of fidelity to the original audio signal.

tells me that he actually doesn't understand. By the way, isn't he some kind of salesman for AudioQuest?

Tell me... If "resolution" isn't important for the audiophile hobby; which implies that high performance technical factors like low noise, accurate data transmission integrity, low jitter, etc. are not really worth seeking in this pursuit, then why would "Garth Powell Discuss(es) Electrical Noise" and want to sell us expensive power products made by AudioQuest? If maintaining resolution isn't important, why should we "Do No Harm" when buying cables from AQ? To me, resolution is actually the cornerstone of high-fidelity and the raison d'être of the hobby itself. Without objective "resolution", all we're left with is "preference". This is analogous to having "opinions" about everything, but no "facts"!

Remember folks, high resolution / high-fidelity is ultimately not about a correlation between the reproduced music sounding like a live event as per Harry Pearson's concept of the "Absolute Sound" (notice that a "subjectivist" made this correlation). Resolution is about maintaining a high quality reproduction of what's on your CD, digital file, even vinyl all the way to your headphones / speakers. The recording might sound "live" if that is the artists' and audio engineers' intent along with one's gear, speakers, room and placement allowing the recording to convey that intent. But many albums will not sound live because there possibly was never anything "live" to begin with and a highly resolving system will show that to be the case as well (just have a listen to some of the music he's listing!). Maintaining high resolution is like what Garth Powell is saying and what AudioQuest's "Do No Harm" article is aiming at even if I don't necessarily 100% agree with their products or claims. The idea is that for audiophiles, it's good to have one's gear be able to reproduce with accuracy what's on the recording. How one perceives that sound - as being "live" or not is up to the individual regardless of how resolving the gear.

I have no idea what Mejias is "selling" or perhaps more accurately, rambling about in that article other than that if it sounds good to him (ie. he perceives it as enjoyable), "it's good" regardless of music format including lossy. That's a fine opinion. Not exactly a deep revelation since I believe few rational audiophiles claim they can hear remarkable things beyond CD-quality 16/44.1 or insist on 24/96+ anyhow. Furthermore, we know that high bitrate MP3 sounds pretty good for years.

Probably best for Mr. Mejias to stick with opinionating on music recommendations rather than speak to the technical side of things. Maybe I missed his main message, who knows, maybe he's trying to say something deeper about "Communism? ... democratic socialism? ... capitalism?" In any event, it doesn't seem to be about science, technology or engineering - the legitimate foundations of the hardware audiophile hobby with "resolution" being a rather important goal over the decades.

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Listening to the Leonard Cohen postscript album Thanks For The Dance (2019, DR13), RIP.

Happy Thanksgiving Weekend to the friends in America! Amazing - one more month and 2019 will be in the books as we enter the next decade.

Hope you're enjoying the music...