PCM to DSD (DSC1) vs native PCM

[asdf1000]

7 hours ago, Andy-HandyHifi said:

We are talking SNR differences so small why worry at all???

I'm not worried at all... I was more-so  asking for the measurement because I was wondering (not worrying) if it is even true...

[asdf1000]

7 hours ago, Andy-HandyHifi said:

Not what I was trying to say.  I was really just pointing out how amazing the engineering crew at iFi that chose and developed the iDSD products around the DSD1793 made major accomplishments. 

The Stereophile measurement is not that great for the iFi Pro iDSD.

 

Another reason I asked for measurements.

[Andy-HandyHifi]

6 hours ago, asdf1000 said:

The Stereophile measurement is not that great for the iFi Pro iDSD.

 

Another reason I asked for measurements.

 

What are in the stereophile measurements that are concerning to you? The only thing that befuddled JA was the rise in noise floor at 44.1 in bitperfect mode.  There is a reason for that and it is directly related to using a 20 year old chip that was never meant to bypass its PCM oversampler before the segment DAC.  When used in USB mode, due to the nature and complexities of asych clocking, the sigma delta portion of the DAC that handles 2's complement sample bit below the top 6, runs slower than by design when the PCM oversampler is bypassed, such as in 'bitpefect' mode.  It is by nature third order, but there was no way to prevent the modulator from running too slow, therefore causing the noise shaped quantization to rise earlier than expected.  Other than that JA was complimentary of the measurements. 

 

Sometimes there are real reasons, not just bad engineering or something, that cause certain measurement anomalies.  Also, as I pointed out numerous times, this is an old chip that will NOT measure as well as the latest greatest, was never meant to run over x64 delta sigma, and was never meant by its designers to bypass the PCM oversampler!  iFi has managed to coax things out of it the chip was not designed to do, and they have done it well in spite of any measurements people don't like.  On the whole, the measurements are no impediment to sound quality.  My reference comparison DAC is a measurement darling, and it also sounds excellent, the RME ADI.  They sound very different, but the RME indeed is extremely impressive for its price.  But the iFi sounds like a next level DAC in actual practice, and the price difference, which may still be bigger than warranted, nonetheless gets you better sound IMO, as it should.  

 

I can counter everything JA said with Paul Miller of Hi-Fi News, who is one of the most respected in the industry and one could argue more experienced than Atkinson in these matters.  

 

"Although the Pro iDSD packs a capable headphone amp, the rated 1500mW/64ohm (and 4000mW/16ohm) cannot quite be achieved in practice because of its limited voltage output. While the balanced line outputs achieve 8.45V, the maximum single-ended headphone output is 4.2V (the Pro iDSD was tested at its maximum +18dB gain setting, at full volume and with a maximum 0dBFs digital input). Unlike most DAC/headphone amps, the output is not clipped at this full 0dBFs input/maximum analogue output (just 0.14% THD, in fact), but with the moderate ~3ohm source impedance resulting in a further 0.8dB signal loss, the power output is 578mW/25ohm (or 900mW/16ohm).

 

 

This finite source impedance will also emphasise any swings in headphone response with low impedance models – otherwise the frequency response is determined by choice of digital filter. Importantly, residual noise is very low and the A-wtd S/N extremely wide at 108dB, so hiss, hum and other noise will still be low with sensitive headphones.

 

Distortion depends on digital level, loading and choice of solid-state or tube output. Via the line outputs, THD falls to as low as 0.0003% at –30dBFs (20Hz-20kHz) but is closer to 0.11-0.18% at 0dBFs, merely doubling in ‘Tube’ and ‘Tube+’ modes (these are almost indistinguishable). Via the headphone out, THD increases from 0.009% to 0.09% at low bass frequencies when loaded (10mW/25ohm) and from 0.006% to 0.025% at 1kHz . Ifi Audio’s digital engineering has improved significantly of late [xDSD, HFN Jul ’18] – and this is true here with jitter extremely well controlled down to <25psec with 48kHz-192kHz/24-bit data."

 

 

 Just goes to show that armchair comparison via magazine writers is worth little.  Everywhere I go I make people crazy because I won't stop reminding them to have to actually use and listen to the product to have an opinion.  Maybe some magazine measurements are worth concern.  Others are not, especially when I know the person who did the measurement didn't do their due diligence.  They simply could have asked iFi why there was a certain anomaly which I addressed above.  How do I know?  Years ago I simple asked.  Same issue was present on the original iDSD Micro.  Obviously since then they have tirelessly reworked their analog output so the issue doesn't cause audible intermodulation distortion.  Their work in this matter is reflected in the iDSD Pro.  You won't hear anything anymore in the slightest suggesting any issues.  It has been addressed as best as possible, only occurs in Bitperfect filtering and only at the lowest sample rates of 44.1/48 khz.  The higher the native sample rate, the more the 'anomaly' disappears.  If you want it to disappear altogether and get perfect measurements then use the GTO filter or any other oversampling filter other than bitperfect.  

 

Stereophile insulted the iDSD Pro putting it in class B.  It sounds as good or better than most of the DAC's saved for their class A. 

 

And I am not an iFi fanboy.  

 

Actually, I am fairly upset with the company as a whole for reasons I have already indicated I will not be directly addressing.  Just to clarify, the iDSD Pro is the last iFi product I will have ever purchased.  I have no doubt it will be the pinnacle of their product line as remember years from now when they are probably just another hi-fi memory.