2. digital
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Things I don‘t know

Digital is very much an emerging transmission form and there are a few questions where I simply don‘t know.

1. In the digital domain it is very easy to shift polarity of recordings and the effects are very audible. Yet few devices offer the capability even in very high end systems. Conversely it seems a standard feature on software for computer based systems. This matters greatly since probably half of all recordings are made out of polarity.

2. In digital accurate clocking is of paramount importance to achieve good leading and trailing edge definition as well as spatial rendition. Yet few Dacs even in high end devices and even fewer streamers or switches offer 10m clock interfaces.

3. Even small RFI/EMI or ground level intrusions are very detrimental to accurate D/A conversion. Yet most Dacs still don‘t provide galvanic isolation on their inputs and often claim to address the issue with error correction in the digital domain. Do designers simply not know better?

4. Recent advances in Class D amplification seem to point the way; yet there seems to be no consensus on optimal sample frequency nor power supply design for these devices.

Finally, while rare exceptions like @atmasphere see their task as clarifying and educating on the issues, the vast majority of designers either don‘t make the effort or just go about shilling their widgets.

While I am sure that this is only the beginning of a list of digital issues worth discussing,the usefulness of Audiogon Fora rests precisely on elaboborating and clarifying on all issues immanent in this new approach to things and in most instances the issues don‘t at all relate to issues discussed purely in the analogue domain.

antigrunge2
spatialking's avatar
spatialking
610 posts
 

Let me see if I can answer some of your questions -

1. Polarity - It has to be in software, reversing it in hardware means all your ones become zeros and zeros become ones.  This isn't analog!   Conceivably, a bit stream could be designed for that but to what end?  If it is done in hardware, then it takes some silicon to covert the phase, so SW is usually the way to go.

2. Clocking - 10m?  I am not sure what you mean by 10m.  I believe the question you need to ask is about jitter.

3. Galvanic Isolation - You are correct, galvanic isolation is the way to go.  The problem is, it is relatively expensive.  If they can achieve similar results in SW, then that is the direction they are forced to go.   Note that the same thing applies to balanced inputs and outputs in the analog domain.  Specs love to quote CMRR but it is CMB on the output device that dictates how good the CM rejection is because excellent CMB is much harder to achieve.  Galvanic isolation on the output is really the way to go, yet it is a cost issue, and many, if not most, audiophiles would ignorantly question a transformer in their signal path.

4. Class D - It is still a young and evolving technology, I do believe it is much too soon to expect standardized clock frequencies or power supply topologies.  Designers need to have the flexibility to improve their design as they see fit. 

asctim
438 posts
 

I’ll have to admit I can’t reliably tell if the polarity is reversed or not, at least not with music. My equipment does allow me to switch the polarity.

antigrunge2 OP
1,338 posts
 

&spatialking,

my point on polarity was that it is determinant of sound quality but being ignored by top equipment designers

10mhz is the standard frequenzy for masterclocks controlling several components in the same system, typically by a 50 or 75 Ohm BNC connection. Most top class devices do not provide a connection for this.

Galvanic isolation cannot be replicated in software.

Agreed on class D, however there seems to be no discussion about different approaches so far.

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