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Review and Measurements of NAD T758 V3 AVR

amirm

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#1
This is a review and detailed measurements of the NAD T758 V3 Home Theater Audio/Video Receiver (AVR). It was kindly sent to me by a member. The T758 appears to have been released last year and costs US $1,399.

The T758 is quite a bit heavier than recently measured AVRs and has a serious, business-like look that I appreciate:

NAD T758 Home Theater Audio Video Receiver AVR Review.jpg

As you see, there are hardly any buttons on the front. To change settings, you push the Menu button and then navigate using the 4-way control. I am used to such controls have a center "enter" button but this one does not. Instead you had to push the right button to go into that setting. And left to get out. I could not get used to this and kept pushing the thing in.

The 4-way control is almost too responsive. It can double select easily so it would be nice if it had a bit more "key debounce" control. Nothing major though.

The menus are all text and continue the business-like feel of the unit which I was fine with. No need to wait 5 seconds for the slow CPU in these units to draw a picture of a living room for you.

The back panel shows a modular architecture where all the digital AV switching is on a vertical card to the left:

NAD T758 Home Theater Audio Video Receiver AVR Back Panel Review.jpg

Given the thin margins on these products, I have yet to see a company provide any upgrades of such modules in the future that makes economic sense. I did like the organization though of having them grouped in one place, and the amplifier/analog ins and outs elsewhere.

The speaker terminals are a little less flimsy than some of the other AVRs I have tested but still won't give you a feeling of luxury.

I get a kick out of IEC inputs that lack safety ground. I guess they give you modularity and ability to change to a different power cord compared to the cheap units of the past with the wires coming out of the unit. Similarly it is cute to see the switched outlet in there. I can see an old-timer at NAD insisting on having this connector even though the consumer will likely never use it as he has a lot more than one other device to connect (cable box, etc.).

I could not find any "pure" or "direct" mode to bypass internal processing. There is such a mode though but it is hidden as you will see in testing.

There are hefty, albeit small heatsinks inside. They are quite far from the top of the unit so can't feel them for how hot they get. The top of the unit though was hardly warm even through my testing. I am assuming some kind of power supply rail switching (i.e. Class G) is used in the amplification to keep power consumption low.

The NAD T758 comes with Dirac Lite room equalization which if it works right, should make it audibly perform better than many AVRs that use lesser systems.

Despite my complaints here and there, my overall impression of the NAD T578 was a positive one. It definitely sets its apart from mass-market brand AVRs.

AVR DAC Testing
For testing, I started with S/PDIF coax input since my analyzer can control it without issue unlike HDMI. HDMI results will come in the next section. For output, I used the convenient pre-amp output. Here is what the "DAC" portion performs:

NAD T758 Home Theater Audio Video Receiver AVR Audio Measurements.png


No, your eyes are not deceiving you. When set to 0 dB volume on the unit, you get massive harmonic distortion with the third harmonic dominating. As a result, the NAD T758 takes the dubious crown of worst measured DAC of any product I have tested:
Best Audio DACs Reviewd and Measured 2019.png


We can get much better results by dialing the input level or volume control by 6 dB:

NAD T758 Home Theater Audio Video Receiver AVR -6 dBFS Audio Measurements.png


But now, we have an unfair comparison as the output level has dropped to just 1 volt. But even going with this, the T758 cannot escape the fourth and worst quadrant SINAD of any DAC tested.

Notice that even at this lowered volume, we have issues with noise. The FFT noise floor is quite high and SINAD is determined by that, rather than distortion products. A problem that we see when we measure its dynamic range:

NAD T758 Home Theater Audio Video Receiver AVR Dynamic Range Audio Measurements.png


The problem with rising distortion with level shows up clearly in intermodulation distortion versus level:

NAD T758 Home Theater Audio Video Receiver AVR IMD Audio Measurements.png


As you see, you best avoid the last 6 dB of your dynamic range. Even putting that side, the high noise level lowers performance significantly at lower input levels.

Linearity test shows improper signal processing in conversion of 24 bit samples in the input signal to something lower:

NAD T758 Home Theater Audio Video Receiver AVR Linearity Audio Measurements.png


You are barely good enough for 16 bit content.

Distortion products are quite visible in 32 tone intermodulation test:
NAD T758 Home Theater Audio Video Receiver AVR Multitone Audio Measurements.png


If you want your signal to be free of distortion products, you only have 70 dB or 11.6 bits to work with! I have seen tube products with less distortion than this.

To see what is going on, I set the sampling rate to 192 kHz and ran a frequency response sweep. Ideally we would see 96 kHz of flat response:

NAD T758 Home Theater Audio Video Receiver AVR Frequency Response Audio Measurements.png


But we don't. Response ends at 48 kHz or so, telling me perhaps the input is resampled to 96 kHz. If so, this is twice as good as the recent Pioneer VSX-LX504 I tested so by itself is not bad. Then again, someone sticking a S/PDIF cable into this receiver doesn't expect to see it resampled by half.

The resampling process seems to also reduce low frequency response as we are down 0.7 dB at the low end, and 0.9 dB at 20 kHz. Small numbers to be sure but in this day and age, I better get flat response from 20 Hz to 20 kHz when I running at 192 kHz sampling rate.

THD+N versus frequency shows what we already know:

NAD T758 Home Theater Audio Video Receiver AVR THD vs Frequency Audio Measurements.png


Except that now we see a rise in high frequency distortion to boot! And no, this is not caused by ultrasonics. It is the clipping behavior I showed in the dashboard.

Could it commit any more sins? It can in the form of jitter:
NAD T758 Home Theater Audio Video Receiver AVR Jitter Audio Measurements.png


OK, this is not end of the world but clean it isn't. Thankfully, likely it is not "audioble." :)

DAC filter response is fine but plateaued at just -60 dB:
NAD T758 Home Theater Audio Video Receiver AVR DAC Filter Response Audio Measurements.png


HDMI DAC Performance
I routed the output of my PC through the T758 so that I could then send audio to use using WASAPI exclusive mode in my Roon media player. Here is our dashboard again, this time with HDMI as the input to the unit:

NAD T758 Home Theater Audio Video Receiver AVR HDMI Audio Measurements.png


Overall distortion are there and set the SINAD limit to similar value. But in addition, we have a ton of "junk" thrown in there for good measure.

Jitter test generates similar outcome to S/PDIF input:

NAD T758 Home Theater Audio Video Receiver AVR HDMI Jitter Audio Measurements.png


This says that we don't have input specific jitter but rather, just garbage leaking into the output of the DAC from various sources. There is a pattern in there which may indicate data dependent jitter (which is worse that random).

Based on these results, we know that our S/PDIF input is representative of HDMI performance.

AVR Amplifier Audio Measurements
The amplifier in these products is wideband, giving us an opportunity to diagnose further how the audio pipeline works. Let's start by feeding the unit analog input through CD jack and measuring the frequency response. And the compare the same to using multi-channel input:
NAD T758 Home Theater Audio Video Receiver AVR Amplifier Frequency Response Audio Measurements.png


Ah, we see that the roll off is gone when you use multichannel input. So it seems that the NAD's notion of "pure" or "pure direct" is to use the analogy 7.1 input -- a relief for people who have sources such as SACD players for this type of use.

The digitization of the CD input is quite harsh at just 44.1 kHz. Why not humor us with something higher than this?

Alas, we are limited by the performance of the power amplifier so using multi-channel input versus CD doesn't make much of a difference:
NAD T758 Home Theater Audio Video Receiver AVR Amplifier Audio Measurements.png


NAD T758 Home Theater Audio Video Receiver AVR Amplifier Multichannel Audio Measurements.png


This gives pretty poor scores in ranking of the amplifiers we have tested:
Best Audio Amplifiers Reviewed and Meaured.png



Multichannel input has lower noise floor though:
NAD T758 Home Theater Audio Video Receiver AVR Amplifier SNR Audio Measurements.png


Most important test is power versus distortion+noise. Here it is at 4 ohm:
NAD T758 Home Theater Audio Video Receiver AVR Amplifier Multichannel Power Into 4 Ohm Audio M...png


That is healthy amount of power so putting aside the high noise floor, this is not too bad.

Power drops as expected into 8 ohm:
NAD T758 Home Theater Audio Video Receiver AVR Amplifier Multichannel Power Into 8 Ohm Audio M...png


Peak power is much more as expected:

NAD T758 Home Theater Audio Video Receiver AVR Amplifier Multichannel Peak Power Audio Measure...png


But far short of the spec although they use a different standard than what is used in my testing.

Stability was excellent at 50 watts into 4 ohm. Unlike the Pioneer amplifiers I have tested, there was no massive pull-back after a few seconds.


NAD T758 Home Theater Audio Video Receiver AVR Amplifier Multichannel Warm Up Audio Measurements.png


Conclusions
The overall fit and finish of the NAD T758 V3 was to my liking as I reported earlier. Alas, objective performance is quite shameful. It appears that no testing was performed for the digital processing or even simple distortion measurements. No wonder that outside of the amplifier, NAD doesn't provide any specifications. It appears that even after you spend $1,400, you get distortion and noise factory in these AVRs. A $9 Apple dongle easily outperforms what these devices produce.

These companies need to have a reset, go back to the drawing board and have proper architectural review and design verification. It won't cost any money to get better performance. Despite being a 20 year old part, the DAC chip they use is spec'ed at 96 dB SINAD for example. Toiling that down to just 55 dB is insulting.

As much as I hate to say it given the good looks and feeling of the NAD T758 V3, I cannot recommend it.

------------
As always, questions, comments, recommendations, etc. are welcome.

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#2
Well I'm very disappointed in that! I had a NAD T752 (still do - but it's been modified into a power amp now as the DACs failed) and I'm sure it would have measured far better than this.
Incidentally, I have a NAD2200 which is class G, and that is still quite warm at idle. I wonder if this NAD isn't class D?
 

maty

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#4
As much as I hate to say it given the good looks and feeling of the NAD T758 V3, I cannot recommend it.
Looking for images of inside I found this comment:

https://www.audiosciencereview.com/...buck-for-avr-with-pre-output.2387/post-105623

by Kal Rubinson
NAD 758 v3 is my suggestion.
Maybe your AVR has something wrong. I can not believe the first measurement, although I could not with the TotalDac, so I fear the worst: the problem is generated by NAD and maybe cheap ensamblers? It is an incredible bad measure.
 
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amirm

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#6
Incidentally, I have a NAD2200 which is class G, and that is still quite warm at idle. I wonder if this NAD isn't class D?
It isn't. Here is the 1 kHz FFT showing no switching components:

1567881793451.png
 

amirm

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#7
Maybe your AVR has something wrong.
Don't think so. Kal doesn't measure the gear. I do. :)

Subjectively with Dirac in there, it likely sounds very good.
 
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#9
@amirm Yeah I found an image of the internals and it does look like a regular Class A/B design, as I could see the inductors in series with the speaker outputs.

nad-amp.png
 

audimus

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#10
Thanks for reviewing this unit. It is a fair assessment and disappointing. Not sure how much of that translates to audible issues (except at very high volumes).

But from an engineering viewpoint, sad to know NAD still hasn’t mastered digital hardware/software.
 

amirm

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#14
I see a big transformer so unlikely I would have thought?
Rail switching lowers power consumption at lower output levels. For max power, you still need the same amount of power delivered to the amplifier.

Note that rail switching is not the same as a switching power supply. It simply means the power supply has 2 or more output levels to feed the power stage. It is still linear otherwise.
 

jsrtheta

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#15
I have only a slight understanding of some of these measurements, as I am not very technically literate.

But I come away with two impressions from this and the Pioneer test that you recently did: One, the claim from many that AVRs are capable of the same performance one expects from dedicated separates (and I will include integrated amplifiers with the "separates", as they indeed are just as good as separates, and better than AVRs), and: Two, my history of being unimpressed with NAD products will continue.

I realize this is unfair to the extent that it's based here on only two manufacturers' models. So the overall impression is provisional, and obviously inexpert. But Pioneer and NAD are not fly-by-night operations. They are companies with long histories and successes. I doubt they are anomalies.
 
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#16
Rail switching lowers power consumption at lower output levels. For max power, you still need the same amount of power delivered to the amplifier.

Note that rail switching is not the same as a switching power supply. It simply means the power supply has 2 or more output levels to feed the power stage. It is still linear otherwise.
Yes that's the very definition of Class G, or a commutating power supply.

The NAD2200 is class G - it has a 62-0-62 rail and a 95-0-95 and there are commutating diodes which switch in the higher rails on demand (see attached relevant part schematic). - disclaimer: massively over simplified explanation.

nad2200.png
 
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audimus

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#17
Good comparisons to do at this price range would be the separate Outlaw combination 976 pre/pro + 7000x and the Denon x4500h on the mass-market side.
 

amirm

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#18
It is still early days in our journey into testing AVRs. As we get more data, we will have better calibration of the entire market. But yes, early signs are not good at all.

I hope you all send some goodwill to members who send these large and heavy boxes in for review. The postage cost is not trivial.
 

Timbo2

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#19
This was on my short list to replace my dying AVR.

Looks like it's time to move this one off the list. I really appreciate you taking the time to review this.
 

Blumlein 88

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#20
This was on my short list to replace my dying AVR.

Looks like it's time to move this one off the list. I really appreciate you taking the time to review this.
So far the problem is whether or not any AVR belongs on that list. Agreed we don't have the measure of the market, but until there are products better than tested so far it does not appear there are any good AVR products. Like already mentioned, look at all the stickers on the front about the great capabilities, but it fails at the most basic level.
 

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