Thanks a million for the input.
I think the thing that puzzled me is what Amir wrote:
"We see that the optimal output level is around 0.7 volts which is quite low. If you are buying an external amplifier make sure its sensitive is no higher than 0.7 dB or you will suffer from degradation of the internal DAC and buffer stage in SR7015." I was under the impression, that if I push the 7015 above volume 73 (in full pre amp mode or "mixed mode"), then I start to feed the amp with a clipping signal which would probably be inaudible for my ears but could harm my speakers on a long term.
Indeed my 7015 is from the new batch where the end of the serial number is above 70000, (ones before had the famous HDMI board issue), so I don't think it has the AKM DAC unfortunately, but the ESS Sabre one (or the TI one). I could only confirm it if I opened the lid, but I would rather not.
Amir was right, but he's an EE and in many opinion, he often wrote things in ways that may not be the easiest for everyone to interpret his comments/remarks correctly, or the way he intended to.
I hope the following may help:
The 0.7 V/optimal point - as I mentioned before, try not to focus on one data point but look at the whole SINAD versus output level curve.
"degradation"- that's in reference to the data point at 0.7 V, so it is a relative thing, it doesn't mean that performance would be bad at 2 V or higher.
For example, imagine one that has a flat curve, that shows 90 dB SINAD anywhere between output level of 0.1 V to 2.0 v, versus one that shows 100 dB at 1 V, but everywhere else on the curve is in between 60 to 80 dB, which one would you prefer? The answer would be obvious right?
Clipping at vol 73, clipping? - Maybe, maybe not, you cannot tell because it depends on the output level at 73, if it is at below 4 V, then it is not clipping, Amir may call it clipping because of the standard he chooses to use, but most would not consider the signal is clipping, it SINAD is say, even as low as 60 dB, that is 0.1%, let alone 70 dB that is 0.0316%.
Again, you cannot tell what the pre out level is just by volume setting of say 73, without knowing the signal input voltage and the gain of the preamp. If you want to find out, you will have to use a signal of know level and measure the pre out voltage at volume 73 (your example). Or you can project it to some extent based on:
- You do know that with the test signal at 0 dBFA, volume at 73, the output level is 0.7 V, so at 79, it will be 1.4 V, and at 85, it will be 2.8 V, that is by calculation
For better understanding of digital signal input level:
dBFS - Wikipedia
The level of 0 dBFS is assigned to the maximum possible digital level. For example, a signal that reaches 50% of the maximum level has a level of −6 dBFS, which is 6 dB below full scale.
Sherbourn claimed that the amp can output 150W at 8 Ohm, all channels driven. Funny thing, is that I hardly ever pushed the volume above 65
I am not surprised, the gain of your Sherbourn is 32 dB, that is at least 3 dB higher than that of any of the Marantz AVR's. That means, if you keep the level trim setting the same, the channels driven by the Sherbourn amp will be 6 dB louder at the same volume setting, than the channels powered by the internal amps. Your Emo amp's gain is 29 dB, about the same as the SR7015's.
That's again a misconception. All else being equal, just about any mid range Marantz AVR such as the 6015/7015 can power 4 ohm rated speakers without getting cooked, it depends not only on the impedance of the speakers but also the phase angle characteristics, as well as your seating distances, and largely on how loud you listen. As an example, someone who routinely listens to reference level of 85 dB average may cook the SR7015 even with 8 ohm speakers that has sensitivity of lower than 85 dB/2.83V/m, if his seat distance is 16 ft, yet someone who routinely listens to 10 dB below reference level that is still quite loud, and seating distances of no more than 10 ft, may expect the same SR7015 to run fine without overheating even with 4 ohm rated speakers that doesn't have difficult phase angles in the low to mid range, and have sensitivity in the 90's dB/2.83V/m.
I hope this help, and you are welcome to ask if you have further questions.
