Does Native PCM exist or has existed ?

[PeterSt]

3 hours ago, Mike48 said:

it's implementation quality -- engineering quality in a broad sense -- that makes a DAC superior. It is not a particular chip or technology that is the key, though manufacturers like to advertise those.

 

OK, here's one (manufacturer); he has some comments as well. :-)

 

For a pure PCM DAC (like ours) it sure is the most crucial what "chips" one uses. Thus, when it would be something like the Holo, this is a full (as in "huge") discrete design and each corner of the circuitry requires enormous attention not to do it wrongly (think mostly noise). There's always the impedance sh*t following you, with for key requirement the low output impedance, like a couple of Ohms would be that. With a discrete R2R DAC this is virtually impossible (but t can be done). Voltage vs Current (R2R) ladders ... there's really a LOT to design and think of. That is, if you really want to do it in a best fashion.

 

The discrete way is always very noisy, thus ... it really is not the best way to design a ladder = PCM = (mostly) R2R DAC. If such a DAC can do a resolution of 16 bits (no matter how many physical bits it has), you may prize yourself lucky (as the designer).

But wasn't the Holo tuning the ladders (in real time or otherwise) ? So that will achieve more resolution (if the noise can be held out of the way). You could call this engineering quality, but if you'd ask me this is technology in explicit sense.

 

This brings us to chips ...

Okay, which chips ?

The only 24 bit chips which ever existed are the PCM1704U-K (-K for the better quality version). They are end of life for quite some time now and the only ones still available, well, are in my possession. So ... currently it would not even be possible to design a "PCM" DAC around a 24 bit chip (unless it is me doing it - LOL).

 

The conclusion could be that for a PCM DAC the ladder technology used (be that chip or discrete) is the most crucial of everything.

Next the engineering around it is as crucial, but that counts for all DAC's. However, one could argue that for PCM DACs this is more difficult (for the discrete ladder DACs for sure, and for the chip version still so because of the "to voltage" conversion).

There's the aspect of the output stage which is quite crucial to the sound (a lot of engineering to be done there), but there is even more engineering going on pre-D/A stage, thinking of the reconstruction (digital filtering). For a PCM DAC this is more crucial than for an SDM DAC because what you feed the PCM DAC will be 1:1 for the conversions in the filtering area (16 bits are transferred to 24 bits but the code is and remains PCM). Thus with a PCM DAC you will be hearing much more of what the filter is doing, hence it is there where the sound really is "created". And these days we do that in the playback software ...

 

Those knowing about the Phasure NOS1 DAC know that this is very explicitly NOS/Filterless (as how this was hot, say 20 years ago), BUT that the filtering is (per my requirement) to be done in software. Although more NOS DACs still exist (though not 24 bit - 20 Yes) their manufacturers do not tell you to apply filtering in software. The NOS1 (in today's NOS1a/G3 incarnation) is the only one explicitly wanting that, and their owners know that there's only one filter(-type) sounding the very best - that's what's in the XXHighEnd software, made for it. IOW, any software player can be used, but they all sound way "less" because they don't use the proprietary filtering I made.

... And this is how the "engineering" as such, is very very broad and it even extends to software.

 

Quote

It is not a particular chip or technology that is the key, though manufacturers like to advertise those.

 

So I just did. 🤪

 

On 4/15/2021 at 9:37 AM, Jean Paul D said:

second hand T+A DSD8 and Holo XXX??? on the short list

 

Personally I would take the Holo because it is a much more technically interesting product. Don't ask me how it sounds.

 

Peter

[PeterSt]

3 hours ago, Confused said:

Or maybe the statement refers to non delta-sigma type chips specifically? 

 

Sure it does. 🙂

This is inherent to the "PCM" question. Thus, a CD is encoded in PCM, and it can be 1:1 converted by the "PCM" chip which does not oversample internally (for example, the PCM1792 does that and with that can also do DSD (as a kind of hybrid).

 

Of course each SDM chip will "do" the PCM encoded files just the same, but the internal (SD) modulator is always active (same in the PCM1792).

Some times it is not completely clear what a chip can do, as its functionality is/should be written in the datasheet of it, and certain register settings should depict its possibilities. But this is not simple to try out and usually one just gives up on the particular function, just in case it does not work (mind you, it always requires PCBs and the parts to be sourced and if something was overlooked or uncertain it is all down the drain ($ and especially time).

 

I recall from the 1792 that theoretically it should be able to work in native PCM mode, but it can't shut off its internal filtering (or whatever was "wrong" with it). This makes it again "worthless" for someone who wants the filtering outboard (in advance of it - in-software).

 

Designing a DAC is quite exciting. For example, the PCM1704 has always been specified as being able to do 24/96. Still the datasheet gave hints to otherwise, and I just gave it a try at 24/768 and it worked. Since then the 1704 can officially do 768 (many people still don't know, but alas, the chip is EOL anyway).

Anyway the fun for me : in the beginning of 2011 our NOS1 could do 24/768 as the very first (that I know of). In 2010 it could do 24/384 which was also a world's first, with mind you, a Juli@ soundcard of 24/192 as the base.