DDC 討論

william02

請問各位CHING意見

近年來CAS受到的重視，令USB DAC 幾近每日有新款，DDC 在CAS 的作用，還有之前的重嗎?

還是DDC 的調整還是比USB 直入的DAC好?

odysseyhk

I have practical experience with DDC and there are customer carried DDC in and compared at our showroom.  I like the improvement DDC brings.  We can analyze the DDC advantage in the following areas.

1/ Galvanic isolation

2/ Re-clock

3/ Clean power (battery and/or high quality LPS)

4/ I2S output vs RCA/Coaxial SPDIF vs AES/XLR interface

5/ Reformat

6/ Upsampling

odysseyhk

1/ Galvanic isolation

- Good DDC offers galvanic isolation which is important
- However, many good USB DAC already include galvanic isolation with the USB interface.  So it is more beneficial to the older DAC without USB galvanic isolation built-in

2/ Re-clock

- Very important feature of DDC using high quality clock to output digital audio stream

3/ Clean power (battery and/or high quality LPS)

- This is key benefit of DDC.  For many DAC, both digital/analog circuits are power by the same power supply (though they may be regulated separated). Having the DDC powered separated by battery or separate high quality Linear Power Supply is beneficial to the sound quality

4/ I2S output vs RCA/Coaxial SPDIF vs AES/XLR interface

- DDC output I2S is significantly better
- RCA/Coaxial SPDIF and AES/XLR digital interface require conversion to DAC internal I2S interface.  This conversion will deteriorate sound quality and not as good as I2S.  However, it is still better than direct USB.

5/ Reformat

- Some DDC perform reformatting.  e.g. USB receive DoP (DSD over PCM) and output to I2S DSD Direct.  That requires reformatting in real time.  In this particular example, Direct DSD over I2S, is great in performance.

6/ Up-sampling

- Some DDC may perform up-sampling. It is less important as most DAC (e.g. ES9018) operates at very high frequency and internally up-sampling it.  DDC up-sampling to say 24/192 would be up-sampled again by the ES9018 for processing.  The signal will therefore be up-sampled twice which is not very desirable.   However, there are some Ching reporting DDC up-sampling giving better sound.  It is not something we could easily be explained.

AS A WHOLE

- I like my DDC indeed.  

william02

odysseyhk 發表於 2014-7-28 23:44
1/ Galvanic isolation

- Good DDC offers galvanic isolation which is important

thx a lot,clear my mind
(Post76 Android 手機版送出)

william02

今日有試過，用一隻可以digit out的dac當ddc已經有d分別，但條可歸咎線的影響

但後來再搵部ddc試，效果好強，但一直整理唔到點解，因為我試ddc嗰part,隻dac差唔多ddc5倍價錢，係我所知的reclock 問題應該答唔到，但講到電我就大約理解了
(Post76 Android 手機版送出)

odysseyhk

william02 發表於 2014-7-29 01:44
今日有試過，用一隻可以digit out的dac當ddc已經有d分別，但條可歸咎線的影響

但後來再搵部ddc試，效果好 ...

It is fun with DDC .  If one want to go beyond USB DAC, adding a good DDC output I2S would be amazing. Even of you DAC does not support I2S, the improvement is still pretty good with spdif.