Review and Measurements of NAD T758 V3 AVR

[speedy]

I have also just submitted a support request to NAD explaining how interested I am in replacing my Marantz 7703 with their M17 processor but am now having serious reservations after reading this review. I would love to own a reasonably priced processor with Dirac DSP onboard, so far my experience with the Audyssey Editor app has been very disappointing. Asked if this unit was defective would appreciate a response to either myself or ASR. We shall see

I'm looking forward to Amir's tests of the M17, but I've owned both of these processors and subjectively compared them side by side (purely personal preference) and significantly preferred the M17 to the AV7703...

If you're actually considering replacing your AV7703 with an M17 then I'd highly recommend picking one up from somewhere that will let you return it if you don't end up preferring it; I'd imagine that you'll be as impressed as I was.

With that said, it may test horribly though because I also owned a T758 at one point and thought it sounded excellent (I never listened to it at the -6 levels though that Amir mentioned)

Can someone maybe answer my question if the T777 is using the same DAC as the T758?

I have owned both of these receivers and had opened them up at one point and confirmed that they use different DACs. I didn't note which DACs they used, but I don't think these results have much to do with the DACs that are used in them, but rather their implementation in the receiver.

@amirm, is this likely more of an issue with the DSP implementation or the DAC implementation?

 

[peng]

Yes, I don't know if HDAM has been the very same these many years, but all HDAM gear has the same specs, and it would seem to be the culprit.

HDAM was updated since the model numbers SR7010, AV7702 and AV8802.

 

[jhaider]

I still have my Marantz AV7701 available. It is now a few generations behind, on the other hand the specs have not changed at all - indeed they are identical for all AV77xx and AV88xx so chances are high that newer models perform similar. I could do these measurements

The current generation has significant changes in its analog circuitry. See Dr. Rich's latest installment of his "AVR Build Quality" series. https://hometheaterhifi.com/technic...vr-audio-video-reciever-build-quality-part-v/

 

[peng]

The current generation has significant changes in its analog circuitry. See Dr. Rich's latest installment of his "AVR Build Quality" series. https://hometheaterhifi.com/technic...vr-audio-video-reciever-build-quality-part-v/

I told him that in my last several posts, but thanks for the proof. I saved part1 through 3, didn't know there is a part 5. Thanks again!

 

[restorer-john]

HDAM is just a name for what was originally a discrete FET buffer stage, and Marantz has updated, changed and plastered the name all over stuff since the CD player days.

An early "HDAM" circuit is here below. In machines without HDAMs, they simply left out the circuitry and placed a link/resistor between the IV/LPF and the final line driver/output. AS you can see, the design is essentially identical several years apart.

It was and is marketing hype and BS in my opinion, and it seems ArnieK (RIP) thought the same:

https://www.avsforum.com/forum/173-2-channel-audio/1509244-help-understanding-marantz-hdam.html

Here's an early CD-63 implementation- one of the first to use it IIRC

 

[Blumlein 88]

I told him that in my last several posts, but thanks for the proof. I saved part1 through 3, didn't know there is a part 5. Thanks again!

I've not disputed there were changes. How do you explain Marantz quoting the same specs for years, and for measurements to more or less match those specs? One common factor is the HDAM in use for all of them. As restorer-john has shown not anything really special. That is why I thought the HDAM or basic analog output circuitry was a bottle neck. Maybe it isn't, but they are getting similar good, not great results for quite some number of years.

The specs in the manual for the 8805 and 7701 are carbon copies. Results of testing aren't quite carbon copies, but close. Usually test results exceed quoted specs just slightly in the few examples I've seen.

The Marantz results are respectable, but not exceptional. I was somewhat appalled that the basic performance of the $5000 8805 is no better than a several year old model that sold for $1500. OTOH, it appears the Marantz does better than any others tested around here so far. I suppose until someone tests one that is better, the Marantz is SOTA for pre/pro units. Of course the Oppo players had some far better results, and I do believe one can feed those directly out which would make them the benchmark in home theater MCH.

 

[Labjr]

2SK170 & 2SJ74 were low noise JFETs made by Toshiba. Possibly the best ever made. Not sure why they discontinued them.

 

[Blumlein 88]

The current generation has significant changes in its analog circuitry. See Dr. Rich's latest installment of his "AVR Build Quality" series. https://hometheaterhifi.com/technic...vr-audio-video-reciever-build-quality-part-v/

I noticed this paragraph in the article you linked to.

Our first measured performance of these new chips is on our upcoming review of the Marantz AV8805. In that product we saw the improved noise performance but not the distortion. Marantz follows the New Japan Radio chips with additional electronics which may be the source of the distortion.

 

[restorer-john]

2SK170 & 2SJ74 were low noise JFETs made by Toshiba. Possibly the best ever made. Not sure why they discontinued them.

No-one was buying them except Nelson Pass...

They had been in production for nearly 30 years...

 

[peng]

I noticed this paragraph in the article you linked to.

Our first measured performance of these new chips is on our upcoming review of the Marantz AV8805. In that product we saw the improved noise performance but not the distortion. Marantz follows the New Japan Radio chips with additional electronics which may be the source of the distortion.

He's likely referring to other things than the HDAMs, but that's just my educated guess, as in the review of the av8802a he praised the updated HDAMs that used 10 transistors, vs the 7701/8801's 6 transistors + two low grade OPAs. It really hurt reading his comments on the 8801's preamp vol IC and HDAMs, shorting after I paid over $3,000 for it, but facts are facts. I have the service manual.

 

[Labjr]

No-one was buying them except Nelson Pass...

View attachment 32939

They had been in production for nearly 30 years...

I think Ayre bought like a million $ worth of them too. Not like it was superseded by a better part. I don't believe a better or even equivalent JFET exists. Linear Systems licensed the design, but they're expensive and yields are low.

 

[peng]

I've not disputed there were changes. How do you explain Marantz quoting the same specs for years, and for measurements to more or less match those specs? One common factor is the HDAM in use for all of them. As restorer-john has shown not anything really special. That is why I thought the HDAM or basic analog output circuitry was a bottle neck. Maybe it isn't, but they are getting similar good, not great results for quite some number of years.

The specs in the manual for the 8805 and 7701 are carbon copies. Results of testing aren't quite carbon copies, but close. Usually test results exceed quoted specs just slightly in the few examples I've seen.

The Marantz results are respectable, but not exceptional. I was somewhat appalled that the basic performance of the $5000 8805 is no better than a several year old model that sold for $1500. OTOH, it appears the Marantz does better than any others tested around here so far. I suppose until someone tests one that is better, the Marantz is SOTA for pre/pro units. Of course the Oppo players had some far better results, and I do believe one can feed those directly out which would make them the benchmark in home theater MCH.

Just curious, have you read the reviews of the 8801 and 8802 by hometheaterhifi.com? You can see that the 8802 has significantly lower THD in almost every measurement categories. The measured distortions were also much lower than the specified 0.005/0.008%.

Obviously even the 8801's were very low already, the 8802's were just lower. So if the 8805's are similarly low, but better in noise as Dr. Rich hinted, that's pretty, consider the only major change appeared to be from the LSI volume IC to the MSI one.

https://hometheaterhifi.com/reviews...ntz-av8801-11-2-surround-sound-processor-ssp/
https://hometheaterhifi.com/reviews/receiver-processor/processors/marantz-av8802-processor-review/

In the second linked review, Dr. Rich said the following about the updated HDAM circuitry:

"From an internal perspective, Secrets’ Dr. David Rich offered this analysis on the design of the AV8802:

“The AV8802 is similar in design to the AV8801 in the analog path but a significant improvement has been made to the output circuitry. The output circuitry is now a pair of fully discrete, fully complementary, current mode opamps per channel. The first discrete opamp is wired as a unity gain buffer (10 transistors) and interfaces between the Renesas R2A15220FP LSI and the RCA output jack. The output also goes to the positive output pin of the XLR (pin 2).
The other discrete opamp is wired as a unity gain inverter (14 transistors) and is connected from the output of the non-inverting buffer to the negative output pin of the XLR (pin 3). Current draw for the 26 discrete buffers is +/- 320mA.
The buffers are powered by a +/- 12V DC power supply. The unregulated rails for the discrete output buffers are produced by a separate transformer winding which would have had the function of supplying the power amp in an AVR. For the AVR the transformer winding would be at a much higher voltage.
RCA and XLR output anti-pop on power up muting function is performed by relays.
The signal to noise ratio of the AV8802 is improved over the AV8801 with the output stage redesign. The AV8801 output stage had a gain of two. The AV8802 output stage is now unity gain. The noise from the volume control block, which is the dominate noise source in the analog signal path, is not increased by the output stage in the AV8802. The signal at the output of the DAC, which is before the volume control, is doubled in the AV8802 to compensate for the gain reduction at the output."

and he has the following to say about the DAC change:

"The DAC is changed from a TI PCM1795 in the AV8801 to the AKM AK4490 in the AV8802. The worst case signal to noise declines from 120dB to 115dB but worst case distortion improves from 0.001% to 0.0006%. The distortion measurements are for a full scale signal at a data rate of 44.1k samples /sec. The AKM AK4490 supports DSD. The schematic shows data signal marked DSD coming from both chips associated with HDMI and USB."

The AV8805's service manual is downloadable. If you are interested in seeing the HDAM circuit, you can download it yourself as I don't feel comfortable posting the schematic diagram. From what I can see I don't think it is the bottleneck, but I also don't believe it would make any audible differences.

 

[restorer-john]

If you are interested in seeing the HDAM circuit, you can download it yourself as I don't feel comfortable posting the schematic diagram.

Here you go, I did it for you:

It's freely available in the public domain, is required for servicing, and is posted here in the interests of furthering the knowledge on Marantz's "famous" HDAM, it evolution etc.

 

[astr0b0y]

Back to the NAD in question? No need for continuing with Marantz stuff in this thread surely.

Amir, can you test the Roon ready input?

 

[Blumlein 88]

Just curious, have you read the reviews of the 8801 and 8802 by hometheaterhifi.com? You can see that the 8802 has significantly lower THD in almost every measurement categories. The measured distortions were also much lower than the specified 0.005/0.008%.

Obviously even the 8801's were very low already, the 8802's were just lower. So if the 8805's are similarly low, but better in noise as Dr. Rich hinted, that's pretty, consider the only major change appeared to be from the LSI volume IC to the MSI one.

https://hometheaterhifi.com/reviews...ntz-av8801-11-2-surround-sound-processor-ssp/
https://hometheaterhifi.com/reviews/receiver-processor/processors/marantz-av8802-processor-review/

In the second linked review, Dr. Rich said the following about the updated HDAM circuitry:

"From an internal perspective, Secrets’ Dr. David Rich offered this analysis on the design of the AV8802:

“The AV8802 is similar in design to the AV8801 in the analog path but a significant improvement has been made to the output circuitry. The output circuitry is now a pair of fully discrete, fully complementary, current mode opamps per channel. The first discrete opamp is wired as a unity gain buffer (10 transistors) and interfaces between the Renesas R2A15220FP LSI and the RCA output jack. The output also goes to the positive output pin of the XLR (pin 2).
The other discrete opamp is wired as a unity gain inverter (14 transistors) and is connected from the output of the non-inverting buffer to the negative output pin of the XLR (pin 3). Current draw for the 26 discrete buffers is +/- 320mA.
The buffers are powered by a +/- 12V DC power supply. The unregulated rails for the discrete output buffers are produced by a separate transformer winding which would have had the function of supplying the power amp in an AVR. For the AVR the transformer winding would be at a much higher voltage.
RCA and XLR output anti-pop on power up muting function is performed by relays.
The signal to noise ratio of the AV8802 is improved over the AV8801 with the output stage redesign. The AV8801 output stage had a gain of two. The AV8802 output stage is now unity gain. The noise from the volume control block, which is the dominate noise source in the analog signal path, is not increased by the output stage in the AV8802. The signal at the output of the DAC, which is before the volume control, is doubled in the AV8802 to compensate for the gain reduction at the output."

and he has the following to say about the DAC change:

"The DAC is changed from a TI PCM1795 in the AV8801 to the AKM AK4490 in the AV8802. The worst case signal to noise declines from 120dB to 115dB but worst case distortion improves from 0.001% to 0.0006%. The distortion measurements are for a full scale signal at a data rate of 44.1k samples /sec. The AKM AK4490 supports DSD. The schematic shows data signal marked DSD coming from both chips associated with HDMI and USB."

The AV8805's service manual is downloadable. If you are interested in seeing the HDAM circuit, you can download it yourself as I don't feel comfortable posting the schematic diagram. From what I can see I don't think it is the bottleneck, but I also don't believe it would make any audible differences.

No, I've not read the reviews of the other devices. I will do so.

 

[restorer-john]

Back to the NAD in question? No need for continuing with Marantz stuff in this thread surely.

It's called discussion, technical discussion. Things are compared, discussed, dissected and analyzed. That's what we do.

 

[astr0b0y]

Fair point, and I do like discussion. I must have missed where it was related to the thread topic. Not being facetious, just not good at following at that level sorry.

 

[Blumlein 88]

Fair point, and I do like discussion. I must have missed where it was related to the thread topic. Not being facetious, just not good at following at that level sorry.

Well it was maybe not off-topic, but wouldn't help someone reading the thread to learn about NAD.

The relation is whether or not an AVR or pre/pro has good performance. Most have been shown to be not very good in basic performance. With Marantz being the best which was merely okay or merely good regardless of price. So then we got into a discussion about whether Marantz had improved etc. etc.

I think where it might help, is unless you need the latest surround formats, you'll get more bang for buck with a few year old Marantz pre/pro and good amps. Certainly would have saved me wasting money on an Emotiva pre/pro.

 

[Juhazi]

Not right now. I may have a 10+ year old one some place but not sure. Is there a budget one that is popular?

I have had nothing but problems with Denons and Onkyos. Video circuitrys run very hot and obviously caps burn soon, giving noise, hum or silence.

I am surprised that Yamaha AVRs aren't popular in USA, in Europe I see them everywhere. I recently bought a RX-V685 for 550€. It has pre-outs for main L/R channels, which is critical for me as I use diy active speakers. Aventage (RX-A) series is overpriced IMO.

https://scoopjunction.com/audio-vid...ous-growth-in-near-future-key-players/194994/
While there is a number of companies engaged in Audio/Video Receiver (AVR), the report has listed the leading ones in the world. They are

• Sony
• Yamaha
• Onkyo (Pioneer)
• D+M Group
• LG Electronics
• Harman Kardon
• Inkel Corporation
• NAD
• Rotel
• Anthem AV Solutions Limited
• Pyle
• Cambridge Audio
• Arcam

 

[speedy]

Is the general consensus that these review measurements are the primary determining factor of the sound quality of a component in the real world or is there significantly more to it than that?