All this talk about High frequency content!
I have a Teac UD-501 DSD capable DAC - with variable filtering for different scenarios, also have a Benchmark DAC 2, and a Leema acoustics Elements DAC ( http://www.leema-acoustics.com/product.html?prid=61 ), which is the king of my DAC's ( yes I prefer it to even the benchmark!). The DAC retails for £1200 (same as DAC 2).
Here is a snap-shot of the handbook, that tells it all.
Yes, but no DAC expects to be sent an unfiltered DSD audio signal.
There is a ridiculous amount of high frequency noise that dwarfs the signal with DSD if left in.
You can't just ignore it, it
must be filtered out.
If you bitstream a DSD signal to the DAC, the DAC should filter it out itself, but if you were to convert to PCM without filtering it could potentially damage your amplifier/speakers.
So that filter is very important.
Currently the only effective filter option in Media Center is the 24kHz 48dB/octave option.
What I have requested is more aggressive filtering, increasing the 30kHz filter from a 24dB/octave filter to a 48dB/octave one.
This would extend the high frequency response while still rejecting all the high frequency noise inherent to 1xDSD.
The current 24dB/octave is too weak and allows too much high frequency noise to pass through the system.
The 50kHz filter - though I don't believe it should be used at all - would be better updated to a 30dB/octave filter to have an option which matches the SACD spec. 24dB/octave is too weak.
However, with these agressive filters, the filter needs to adapt to the DSD rate.
If you are using the 24kHz filter - the only once which is currently effective - there will be zero difference between 1xDSD and 2/4/8x DSD.
The
entire point of these higher rates is that they shift the noise into higher and higher frequencies, so the filter should be adjusted to match.
At 2xDSD a 24kHz filter should be moved to 48kHz, the 30kHz filter should be adjusted to 60kHz etc.
Now you could debate whether there is any merit to using those signals at all to begin with, but if you're going to support them - and Media Center does - applying the same filter used with 1xDSD to higher DSD rates is not the right thing to do.
I actually think that PCM is a better format than DSD to begin with - after all, if you're having to filter at 30kHz, that means 24-bit 88.2kHz PCM would outperform it instead of DSD's 2.8MHz sample rate. (no noise with PCM since it's 24-bit instead of 1-bit)
But SACD is often the only way to get high resolution or multichannel versions of certain albums, and I would like to see it handled as best as possible even if the format is flawed.