- Written by Chris Heinonen
- Published on 25 August 2011
- Onkyo PR-SC5508 9.1 SSP and PA-MC5509 Nine-Channel Power Amplifier
- Page 2: Design of the Onkyo PR-SC5508 9.1 SSP and PA-MC5509 Nine-Channel Power Amplifier
- Page 3: Setup of the Onkyo PR-SC5508 9.1 SSP and PA-MC5509 Nine-Channel Power Amplifier
- Page 4: The Onkyo PR-SC5508 9.1 SSP and PA-MC5509 Nine-Channel Power Amplifier In Use
- Page 5: The Onkyo PR-SC5508 9.1 SSP and PA-MC5509 Nine-Channel Power Amplifier On the Bench
- Page 6: Conclusions About the Onkyo PR-SC5508 9.1 SSP and PA-MC5509 Nine-Channel Power Amplifier
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On The Bench
When I first tested the Onkyo on the video bench, the results were not great. There was a lot of chroma detail being lost in multiple colorspaces, with only RGB Video working correctly. When I ran it through my Marantz processor, I found that the Onkyo was taking an 8-bit input signal and converting it to a 10-bit signal on output. Because of this, fine chroma detail was no longer making it to my display but getting lost along the way. There is no option to disable this in the menu system, but there is a hidden menu option you can access from the front panel to turn Video Convert to Off. This affects all of the inputs, but it only turns off the video conversion from 8 bit to 10 bit. You can still switch resolutions, and you can still convert Component video to HDMI. If you input YCbCr 8-bit (4:2:2 or 4:4:4 format) you will now get YCbCr 8-bit output, instead of being converted to 10-bit. I'd highly recommend to Onkyo that they add this option in the menu system somewhere instead of hiding it, and disable it by default, since it makes the default behavior of their video section worse than it should be.
After testing the video section of the Onkyo, I tested the pre-outs from the 5508 using the balanced input in Pure Direct mode.
With both 1 kHz and 10 kHz test tones, the fundamental was around 100 dB or more above the noise floor, with distortion right around 0.004% for each.
On both of the IMD tests the Onkyo did very well, with no B-A peak to be seen on the 19 kHz and 20 kHz test, and an IMD reading of only 0.0017% on the 60 Hz, 7 kHz test. Both of these had a noise floor around 100 dB below the tones as well, showing fantastic performance.
To test something new with the Onkyo, I performed the same tests but instead of feeding it the test signal over the balanced inputs, I used the coaxial input and fed it digitally. This let me also test the performance of the DAC section of the Onkyo. All tones were fed from an Oppo BDP-95 using a 24/192 PCM signal.
The THD+N values are very close to those of the analog test, though on the 1 kHz test you can see some 2nd and 3rd order harmonics that are around 90 dB below the fundamental. On the 10 kHz test there is a 2nd order harmonic that is around 85 dB below the fundamental.
With the 19 kHz+20 kHz IMD test, we now see a small B-A peak, as well as very small 2nd order harmonics visible on the test data. These are all still around 90dB below the fundamentals which is still very good performance. On the 60 Hz + 7 kHz IMD test the IMD value is up to 0.0028% but the noise floor is still very low with no harmonics visible at all, which is very impressive.
After testing the 5508 I moved on to testing the matching amplifier. We can look at the 4-ohm test data first.
The THD+N numbers on the amplifier drop as the power output goes up, as you would expect from a Class AB device. As power is increased you can see more odd and even order harmonics appearing, with the odd order going out to at least 13 kHz and the even order stopping around 8 kHz. They are all 90 dB or more below the fundamental harmonic however.
With a 10 kHz tone, the THD+N doesn't drop as much as power output increases, and the 2nd order harmonic is only around 70-75 dB below the fundamental. The noise floor is still overall very low.
Both these tests were only run at 2V of output as I would overload my test device if I went much past that. The 19 kHz + 20 kHz IMD output has a very small B-A peak, and a few harmonics that drop off sharply, providing at least 75dB of headroom over the secondary harmonic. The 60 Hz + 7 kHz test is not as clean with large peaks at 19 kHz and 20 kHz that only provide around 50 dB of headroom, as well as 2nd and 3rd order harmonics at 14 and 21 kHz that are 80dB or more below the fundamentals. The IMD value of 0.01% is a bit higher than I would expect to see from a separate amp as well. Next we have the 8-ohm data for the same tests.
Performance here is almost identical to how it was at 4 ohm, though the THD+N drops even more as the amp handles an easier load.
10 kHz performance at 8 ohm and 4 ohm is virtually identical, with the THD+N dropping slightly as power increases, and that 2nd order harmonic around 75 dB below the fundamental.
Once again, it's virtually the same as with 4 ohm loads, though the 19 kHz and 20 kHz peaks on the 60Hz+7kHz IMD test are 60dB below the fundamental instead of 50dB below. Otherwise the performance is almost identical, though the IMD value of 0.02% with 2V output for an 8 ohm load is higher than on 4 ohm, showing that the performance increases with power output as you'd expect with the amplifier design. The amplifier shows adequate performance in testing, though how it would respond with all nine channels driven instead of the two I used for the bench test I am not sure.
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