I've decided it's barely worth considering a surround sound processor which does not have the ability to control the target curve for each speaker. In the Marantz line, the Audyssey App is supported by the AV7704, AV7705, and AV8805 units, and not earlier models such as the AV8802a.
My favorite audio tester, Amir at Audio Science Review, measured a Marantz AV8805 and did not like what he found in this $4500 unit:
At 4 Volts RMS at the XLR main outputs:
1) 91.2dB SINAD at 1kHz (0.0027% THD)
2) Shocker: THD rises dramatically at 5kHz and above, above 1% just above 10kHz
Also he also thought the jitter spectrum looked relatively busy compared to his favorite DAC, but not so much as to be an audible issue.
Now, in my estimation, Amir did something a bit unfair to Marantz, but often addressed by commenters. Amir didn't bother to do any measurements at the official AV8805 Rated Output Level, which is 2.4 volts. He said that was simply a crutch that Marantz used to get better measurements. 4V is the defacto industry standard level for XLR for consumers, and Marantz should be expected to perform well at that level like any top product.
Furthermore, in long discussion which compared the specs and measurements of other Marantz processors done by others, it appears that the 91.2dB SINAD is consistent with measurements done by others at different levels.
For example, Secrets of Home Theater found the AV8802(a) to have less distortion at 2.0V, and more distortion at 5V, which was still below the apparent maximum output. Amir reiterated many times that he turned the level "down" to 4 volts, though he never indicated what he turned it down from.
This other review of the AV8805 didn't do a single measurement, mainly talking about features and giving subjective reactions to various discs.
After much discussion, it appears that the Marantz AV8802, AV8802A, and AV8805 have the same output circuit and cound be considered comparable. The specs are identical, and in fact the specs are also identical for the AV7705 and AV7704. Therefore, conveniently, a review of the audio raw performance of one of these units is equivalent to a review of another. Therefore, despite many people complaining about Amir only doing one measurement (not true) and calling it a day (apparently true, he shipped the unit out to make room to walk around in his laboratory), we can fill in the gaps by looking at measurements done by others.
Though it's not great, I don't think the 0.0027% distortion is that big a deal either. Sure, my Emotiva Stealth DC-1 (another product Amir does not like) measured 0.0003% THD in my testing, which is about 10x (20dB) better, and Amir's favorite dacs (I now use the cheapest one he recommended for measurement purposes) do even better, but few recordings are going to be made that well and no speakers would even come close. Many highly regarded audio products have no better than 0.1% THD, which is often suggested as a limit to the audibility of nearly all distortion harmonics.
I think, and what unfortunately to this moment has not gotten enough discussion is the #2 Shocker.
Amir did some further investigation of this. First, he ran a 10kHz signal and found a ginormous distortion peak approaching 1% at 34kHz. Since this is not an even multiple of 10khz, this got him thinking it might be an aliasing artifact. So, he runs a white noise signal and then discovers only 3dB rolloff at 22.05kHz, where (according to Shannon et all) there should be infinite attenuation from a reconstruction filter. Acceptible levels of attenuation were only ultimately achieved near 40kHz.
Amir looked in vain for any discussion of digital filtering in the manual, or ways to select different digital filtering options. Failing to find such, he pronounced the AV8805 flat out broken.
Such slow reconstruction filters are not at all unusual on audiophile gear nowadays. There's quite a strong following for no filters at all (NOS).
Now the only piece that leaves me wondering about this, even after reading every post in a 24 page discussion (which was quite interesting in itself) is whether the high levels of HF distortion would essentially disappear if Amir had stuck to the Rated Output level of 2.4 volts.
Amir simply believes that such an output level is not worth bothering with, 4 volts is the defacto standard, he tests everything balanced at 4V, and if a unit can't do 4V well that's simply another way that it's broken. Commenters suggest that 2V is more than adequate for many amplifiers and challenged him to suggest one amplifier where this would not be true.
Here's one aspect which wasn't discussed. We can't simply tell the maximum input voltage an amplifier can use from its rated input, sensitivity, and/or rated power. Most power amplifiers have considerable headroom. So even if it only takes 1.5V input for such-and-such an amplifier to reach rated power, it may be able to handle input peaks up to nearly 3V without clipping. This is a good reason for preamplifiers AND surround processors to have at least 4V output, as Amir suggests.
Amir does note that the level of the 10kHz distortion products including aliases does go down at lower levels. And therefore, he admits, the audibility of this problem probably isn't that huge either. But it represents unacceptible performance for a flagship product. I agree.
But I'd also just like to know, if the 2.4v output level fixes things. It seems OK in the AFAIK identical audio circuitry of the AV8802a, as tested by Secrets. They measured 0.002% THD at 10kHz with 2 volt output with 44.1kHz sampling, and lower levels with higher sampling rates. That suggests the Marantz would easily meet it's specified 0.008% THD from 20-20khz at the rated output level which Amir refused to test.
Digging a bit deeper still, Secrets also tested 10khz up to 5V with 24/96 data, with distortion at 0.0036%. Unlike Amir, Secrets did lots of different tests with 10kHz and with pairs of frequencies. Curiously, however, they did NOT report a test for 10kHz with 5V at 44.1kHz, which might speak to the high levels of distortion Amir saw at 4V output with 44.1kHz signal and attributed to aliasing. At the higher sampling rates, distortion reduces at 2V also.
Looking at these high frequency and IM tests, the profusion of products does indeed look like it may fit an aliasing theory. It still bothers me how it seems fine at 2 volts (and possible 2.4 volts) but then distortion products including aliasing products just take off. It seems to me that aliasing products should be there all along and increase linearly.
It was a similar output level limitation that led to my finally ridding myself of my two Integra Research RDC-7's today. When I bought these a few years ago I was hoping they'd make excellent DACs, which I could even use in my laboratory. My first naive measurements at 4V showed such massive distortion I figured my first RDC-7 was broken. It was only later while testing my second unit I discovered that distortion looked basically OK (just OK, perhaps about 0.005%) until 2V balanced or 1V unbalanced. Then, distortion products began rising linearly from the noise floor. At first I thought it must be clipping. But clipping distortion products would rise much more quickly. It almost seem like some kind of soft clipping was being applied.
All these high end surround processors are THX licensed. This means they pass proprietary tests by THX. We don't know exactly what these tests are, and what they required, because they are not public information.
I wonder if THX virtually demands a kind of soft clipping be introduced in the pre/pro above 1v unbalanced and 2v balanced, in order that amplifiers or speakers themselves not be the clipping elements.
Anyway, the way the shocking issue appears in all the information presented does not suggest that soft clipping alone is the source. The products that appear in high frequency and IM tests look a lot like aliases in some cases. However, the rapid rise when levels exceed 2.4v suggests that aliases alone are not responsible. Then it appears the issue may be the combination of two things, the very slow reconstruction filter AND a form of soft clipping that starts just above 2.4V.
Knowing all this, I've somewhat lost interest in the AV8805, which no longer looks like a reference product and isn't worth the high price. (If you want reference, apparently the Trinnov is the unit to get, at 4 times higher price.) However, the AV7705 may be OK for the features, and knowing that the limitations aren't likely ever to intrude on the auditory experience.
Amir correctly blames the lack of competition in the pre/pro world to the introduction of HDMI. Apparently only 2 companies make the require HDMI chips, and they aren't interested in supporting small time manufacturers.
I've never liked the idea of squeezing my audio signal through HDMI, and now it appears (increasing distortion, jitter, etc) that avoiding this would have been good. Given the current market, however, it's unavoidable.
Much of this impasse has also been caused by the myth of perfection. Everyone wants "perfect" digital inputs and outputs to things, as these are considered "lossless." One thing that's lost but barely remembered is openness. Analog inputs are fully open, transparently, and not subject to being locked down by greedy bastards.
If instead of demanding digital I/O, we had stuck with analog I/O and just made it better, we would not be trapped by greedy chipmakers and other proprietary schemes.
I strongly believe that digital conversion is virtually transparent, especially at 24/96, so there would be no harm in sending analog audio signals from CD player to preamp, which could convert them to digital for processing, and back to analog for amplification.
This is the kind of thing I have done for over a decade now for stereo. In some cases, curiously, I find the resampled analog to be BETTER than digital. In not one single case have I found it to be noticeably worse. Sometimes I just use the direct digital because it's supposed to be better, but I've never actually heard that.
But if reference high end products can get away with 91dB SINAD (and far worse at high frequencies), the -120dB added noise from resampling is just not a big deal, and if we still had analog interfaces there could be endless competition, even from people like me. (I recently found a "open source" surround processor project. It hasn't gone anywhere in 5 years, probably due to the HDMI issues.)
I had been thinking the Integra Research RDC-7's would give me this kind of analog processing. For quite some time I was blocked by the fact that they use a snake multichannel input connector, and I never got around to testing the multichannel path because I didn't want to risk getting the wrong kind of snake for it. Well, it turns out I could have seen the issue from looking at the schematic, which reveals that the multichannel inputs are not digitized, they are simply passed directly to the output with volume adjustments. This is the same limitation as on my 2005 Yamaha HTR-5790 receiver. So the glorious Integra Research would not move me one inch forwards, and possibly a few backwards.
I understand that there were some earlier processors by Yamaha and others that did digitize multichannel inputs, at least up to 5.
But to get with the program, and play with all the new surround toys, I'm still tempted to get the AV7705 at a decent price.
My favorite audio tester, Amir at Audio Science Review, measured a Marantz AV8805 and did not like what he found in this $4500 unit:
At 4 Volts RMS at the XLR main outputs:
1) 91.2dB SINAD at 1kHz (0.0027% THD)
2) Shocker: THD rises dramatically at 5kHz and above, above 1% just above 10kHz
Also he also thought the jitter spectrum looked relatively busy compared to his favorite DAC, but not so much as to be an audible issue.
Now, in my estimation, Amir did something a bit unfair to Marantz, but often addressed by commenters. Amir didn't bother to do any measurements at the official AV8805 Rated Output Level, which is 2.4 volts. He said that was simply a crutch that Marantz used to get better measurements. 4V is the defacto industry standard level for XLR for consumers, and Marantz should be expected to perform well at that level like any top product.
Furthermore, in long discussion which compared the specs and measurements of other Marantz processors done by others, it appears that the 91.2dB SINAD is consistent with measurements done by others at different levels.
For example, Secrets of Home Theater found the AV8802(a) to have less distortion at 2.0V, and more distortion at 5V, which was still below the apparent maximum output. Amir reiterated many times that he turned the level "down" to 4 volts, though he never indicated what he turned it down from.
This other review of the AV8805 didn't do a single measurement, mainly talking about features and giving subjective reactions to various discs.
After much discussion, it appears that the Marantz AV8802, AV8802A, and AV8805 have the same output circuit and cound be considered comparable. The specs are identical, and in fact the specs are also identical for the AV7705 and AV7704. Therefore, conveniently, a review of the audio raw performance of one of these units is equivalent to a review of another. Therefore, despite many people complaining about Amir only doing one measurement (not true) and calling it a day (apparently true, he shipped the unit out to make room to walk around in his laboratory), we can fill in the gaps by looking at measurements done by others.
Though it's not great, I don't think the 0.0027% distortion is that big a deal either. Sure, my Emotiva Stealth DC-1 (another product Amir does not like) measured 0.0003% THD in my testing, which is about 10x (20dB) better, and Amir's favorite dacs (I now use the cheapest one he recommended for measurement purposes) do even better, but few recordings are going to be made that well and no speakers would even come close. Many highly regarded audio products have no better than 0.1% THD, which is often suggested as a limit to the audibility of nearly all distortion harmonics.
I think, and what unfortunately to this moment has not gotten enough discussion is the #2 Shocker.
Amir did some further investigation of this. First, he ran a 10kHz signal and found a ginormous distortion peak approaching 1% at 34kHz. Since this is not an even multiple of 10khz, this got him thinking it might be an aliasing artifact. So, he runs a white noise signal and then discovers only 3dB rolloff at 22.05kHz, where (according to Shannon et all) there should be infinite attenuation from a reconstruction filter. Acceptible levels of attenuation were only ultimately achieved near 40kHz.
Amir looked in vain for any discussion of digital filtering in the manual, or ways to select different digital filtering options. Failing to find such, he pronounced the AV8805 flat out broken.
Such slow reconstruction filters are not at all unusual on audiophile gear nowadays. There's quite a strong following for no filters at all (NOS).
Now the only piece that leaves me wondering about this, even after reading every post in a 24 page discussion (which was quite interesting in itself) is whether the high levels of HF distortion would essentially disappear if Amir had stuck to the Rated Output level of 2.4 volts.
Amir simply believes that such an output level is not worth bothering with, 4 volts is the defacto standard, he tests everything balanced at 4V, and if a unit can't do 4V well that's simply another way that it's broken. Commenters suggest that 2V is more than adequate for many amplifiers and challenged him to suggest one amplifier where this would not be true.
Here's one aspect which wasn't discussed. We can't simply tell the maximum input voltage an amplifier can use from its rated input, sensitivity, and/or rated power. Most power amplifiers have considerable headroom. So even if it only takes 1.5V input for such-and-such an amplifier to reach rated power, it may be able to handle input peaks up to nearly 3V without clipping. This is a good reason for preamplifiers AND surround processors to have at least 4V output, as Amir suggests.
Amir does note that the level of the 10kHz distortion products including aliases does go down at lower levels. And therefore, he admits, the audibility of this problem probably isn't that huge either. But it represents unacceptible performance for a flagship product. I agree.
But I'd also just like to know, if the 2.4v output level fixes things. It seems OK in the AFAIK identical audio circuitry of the AV8802a, as tested by Secrets. They measured 0.002% THD at 10kHz with 2 volt output with 44.1kHz sampling, and lower levels with higher sampling rates. That suggests the Marantz would easily meet it's specified 0.008% THD from 20-20khz at the rated output level which Amir refused to test.
Digging a bit deeper still, Secrets also tested 10khz up to 5V with 24/96 data, with distortion at 0.0036%. Unlike Amir, Secrets did lots of different tests with 10kHz and with pairs of frequencies. Curiously, however, they did NOT report a test for 10kHz with 5V at 44.1kHz, which might speak to the high levels of distortion Amir saw at 4V output with 44.1kHz signal and attributed to aliasing. At the higher sampling rates, distortion reduces at 2V also.
Looking at these high frequency and IM tests, the profusion of products does indeed look like it may fit an aliasing theory. It still bothers me how it seems fine at 2 volts (and possible 2.4 volts) but then distortion products including aliasing products just take off. It seems to me that aliasing products should be there all along and increase linearly.
It was a similar output level limitation that led to my finally ridding myself of my two Integra Research RDC-7's today. When I bought these a few years ago I was hoping they'd make excellent DACs, which I could even use in my laboratory. My first naive measurements at 4V showed such massive distortion I figured my first RDC-7 was broken. It was only later while testing my second unit I discovered that distortion looked basically OK (just OK, perhaps about 0.005%) until 2V balanced or 1V unbalanced. Then, distortion products began rising linearly from the noise floor. At first I thought it must be clipping. But clipping distortion products would rise much more quickly. It almost seem like some kind of soft clipping was being applied.
All these high end surround processors are THX licensed. This means they pass proprietary tests by THX. We don't know exactly what these tests are, and what they required, because they are not public information.
I wonder if THX virtually demands a kind of soft clipping be introduced in the pre/pro above 1v unbalanced and 2v balanced, in order that amplifiers or speakers themselves not be the clipping elements.
Anyway, the way the shocking issue appears in all the information presented does not suggest that soft clipping alone is the source. The products that appear in high frequency and IM tests look a lot like aliases in some cases. However, the rapid rise when levels exceed 2.4v suggests that aliases alone are not responsible. Then it appears the issue may be the combination of two things, the very slow reconstruction filter AND a form of soft clipping that starts just above 2.4V.
Knowing all this, I've somewhat lost interest in the AV8805, which no longer looks like a reference product and isn't worth the high price. (If you want reference, apparently the Trinnov is the unit to get, at 4 times higher price.) However, the AV7705 may be OK for the features, and knowing that the limitations aren't likely ever to intrude on the auditory experience.
Amir correctly blames the lack of competition in the pre/pro world to the introduction of HDMI. Apparently only 2 companies make the require HDMI chips, and they aren't interested in supporting small time manufacturers.
I've never liked the idea of squeezing my audio signal through HDMI, and now it appears (increasing distortion, jitter, etc) that avoiding this would have been good. Given the current market, however, it's unavoidable.
Much of this impasse has also been caused by the myth of perfection. Everyone wants "perfect" digital inputs and outputs to things, as these are considered "lossless." One thing that's lost but barely remembered is openness. Analog inputs are fully open, transparently, and not subject to being locked down by greedy bastards.
If instead of demanding digital I/O, we had stuck with analog I/O and just made it better, we would not be trapped by greedy chipmakers and other proprietary schemes.
I strongly believe that digital conversion is virtually transparent, especially at 24/96, so there would be no harm in sending analog audio signals from CD player to preamp, which could convert them to digital for processing, and back to analog for amplification.
This is the kind of thing I have done for over a decade now for stereo. In some cases, curiously, I find the resampled analog to be BETTER than digital. In not one single case have I found it to be noticeably worse. Sometimes I just use the direct digital because it's supposed to be better, but I've never actually heard that.
But if reference high end products can get away with 91dB SINAD (and far worse at high frequencies), the -120dB added noise from resampling is just not a big deal, and if we still had analog interfaces there could be endless competition, even from people like me. (I recently found a "open source" surround processor project. It hasn't gone anywhere in 5 years, probably due to the HDMI issues.)
I had been thinking the Integra Research RDC-7's would give me this kind of analog processing. For quite some time I was blocked by the fact that they use a snake multichannel input connector, and I never got around to testing the multichannel path because I didn't want to risk getting the wrong kind of snake for it. Well, it turns out I could have seen the issue from looking at the schematic, which reveals that the multichannel inputs are not digitized, they are simply passed directly to the output with volume adjustments. This is the same limitation as on my 2005 Yamaha HTR-5790 receiver. So the glorious Integra Research would not move me one inch forwards, and possibly a few backwards.
I understand that there were some earlier processors by Yamaha and others that did digitize multichannel inputs, at least up to 5.
But to get with the program, and play with all the new surround toys, I'm still tempted to get the AV7705 at a decent price.
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