Worlds Greatest DAC and what it does differently

[barrows]

My feeling is that there is some "magic" with DSD 256 (and perhaps above).  But of course this is not really "magic" at all.  High sample rates, including high rates of PCM-like quality allow for relatively simple actual conversion paths.  This is how most Sigma Delta style DACs work.  Tthese high rates also allow for even discrete (non chip based) converters, which give designers additional freedom (if they are clever enough) to develop a unique converter topology which may offer advantages over standard chips.

For chips, when one looks at, say, ESS-it oversamples to a very high rate (similar to DSD rates) and 5, 6, or 7 bits, and then converts to analog from this very high rate.  dCS uses a similar approach, but they do the final conversion into analog using a discrete converter.  Chord, again uses a similar approach, again using a (similar to dCS) discrete final converter stage.

Jussi's (AKA miska) DSC-1 DAC design, now adopted in various different iterations by Holo Audio, Denafrips, T+A, among others, is a DSD based discrete converter stage designed to be fed by a very high rate single bit signal, generally DSD 256 and above.

Mola Mola, in the excellent Tambaqui DAC, uses a variation on the discrete converter theme as well, with the final converter stage being a multi-element switch and resistor set up, similar to DSC-1.  Same with Playback Designs, and I suppose Emm Labs...

I am listening as I type to Bricasti M3 DAC, which uses a different, discrete converter stage design of their own, essentially also based on a high speed switch and filter, for single bit DSD input only.

 

Most of these different DACs sound different, but I have experience now with 4 different single bit based DACs, all of which have used some variation on a discrete converter stage.  All of them have seemed to share, in differing degrees, a quality of conversion which sounds more natural, and easy going to me.  I do not mean that they are rolled off, or "soft" sounding, but that they sound more like music, and less like an electronic representation thereof.

 

There are a lot of really good DACs out there these days, but for me, I do seem to prefer the DAC which use discrete conversion approaches, with high rate DSD input.  This can be done on a chip as well, as with AKM DAC chips' "direct DSD" path option.  But, when a designer goes discrete, they have control of the performance, and they may be able to do better than what is available on a generic DAC chip (or not, as the case may be).  

[barrows]

Just now, davide256 said:

Are their source side benefits? I'm told the Mojo doesn't really do DSD, converts to PCM but using Stylus/Roon sounds cleaner to me with DSD 128/256 upsampling than max PCM rate.

I am not sure what you are asking....

Chord DACs, except DAVE, all convert incoming DSD to PCM 705.6 before then upsampling to very high (MHz rates) at, as I recall 5 bits.  the this data goes to their discrete conversion stage.  I would not send dSD rates to a Chord DAC, as it will be down sampled to PCM 705.6 anyway.  If you want to oversample in software with a Chord DAC (again excepting DAVE), I would send PCM 705.6 to the DAC, as this will bypass some of the DACs onboard processing.  Note that this what the mScaler does...

[barrows]

2 minutes ago, davide256 said:

The question is

 

assuming  adequate processor power and memory with competent software, which will be less impacted  as USB source by issues in the source hardware and software,

1 bit xMhz DSD output or 16/24 bit 705khz PCM output?

So, I think you are asking how a given source (hardware endpoint, like an ethernet renderer?). outputting USB audio, would be "impacted" by the different formats?

If I understand the question, then the answer would-be, it depends on the quality of the USB source.  A good USB source should not care either way, it should be equally capable of delivering high rate information.  USB 2 is easily capable of delivering high rate (DSD 512 or PCM 705.6) 2 channel audio.  Now higher data rates do increase processor activity, and power consumption (let's say we are talking about an Ethernet based renderer: Ethernet-USB), and hence noise inside the device.  Whether any of that noise gets to the USB output will be dependent on the competency of the design of the hardware.  In other words, with well designed Ethernet-USB Renderer, the data rate will not matter at all, as the well designed renderer will output a clean and ultra low noise USB signal regardless.

 

Also, it is worth noting that the actual increase in processor activity and power consumption for say, 44.1 vs 705.6, or 44.1 vs. DSD 256 is not very big, on the order of ~10%-15% or so, at least in the Renderers of which I am familiar.

[barrows]

In a "perfect" world, where electronics all acted "perfectly" with no errors or losses' and where digital filters were "perfect", with infinite stop band attenuation and no artifacts, then 16 bit 44.1 kHz sample rate would result in perfect output from a DAC.

 

But nothing in the real world works "perfectly", everything is subject to errors in one way or another:  digital filters produce artifacts (alias products and or ringing), analog circuitry is subject to interferences from high speed processor noises which may produce intermodulation effects in the audible bandwidth.  Electronics are subject to thermal noise at very least, and harmonic distortions.  DACs are mixed digital and analog circuitry in a single chassis, which in itself is a challenge.

 

Higher sample rates, and oversampling overcome some of the real world limitations of how things actually operate.

[barrows]

14 minutes ago, beerandmusic said:

I may pop in from time to time simply to post a thought that entered my mind, that may or may not be applicable, but at the moment I post it, I believe it is applicable, and don't want to forget the thought.....

 

this is such a moment, and just want to share this thought....

 

Part of the problem with DAC design may be the amount of different inputs it has to resolve for, that if the design could concentrate on a limited amount of inputs, the design could be better perfected....along this thought, if 44.1K fully encapsulates our audible spectrum, that if the DAC only had to resolve for example 44.1, 48, and perhaps 96k, it may be easier to perfect the design to accurately reproduce the input signal, if it had less variables to deal with.

 

In most DACs, the actual conversion stage does operate in either a single rate (for those with an asynchronous upsampling section) or at a high rate related to the two base frequencies (usually 16x rate).  So they are already optimized for a given rate.

 

The exception would of course be NOS style DACs, but these are in the minority.

 

Indeed it is correct to think that if a DAC is optimized for certain sample rate, it may be able to more easily deliver the expected performance level.  For example, on my ESS 9038 DAC build I optimized all settings of the ESS chip for DSD 256 input, and then I also optimized the analog output filter to suit this rate as well.

 

This is what I have been thinking about:

 

Single rate DAC optimized for single rate (DSD 256) input

"Perfected" DSC style discrete conversion stage

"Perfected" optical Ethernet input with NAA, ROON RAAT, and DLNA (for old schoolers) capability (no other input)

onboard, by passable, analog volume control

A robust output stage capable of driving any amplifier directly without compromise

 

Such a DAC, made really well, in the USA, with high quality, ought to be able to be produced for under $10K, perhaps even $7K would be possible, given that we are leaving out unnecessary "features".  It would require the owner to oversample in software to DSD 256, but that is fairly easy to obtain these days from many playback softwares.

 

I would even want to make an "one box" version, with amplifier modules as well.

[barrows]

The reason for the DSD 256 conversion rate is because this makes the actual conversion process much much simpler and more accurate.  Resulting in improved sound quality.

And who said we should start with 16/44.1 music recordings, those are compromised to begin with.  I will choose a higher rate file any time I have the option to purchase it, because there is an advantage to higher rate of recording.

 

BTW, right now I am listening to a DSD 128 file of Debussy Piano works recorded by Wave Kinetics records, played by Ilya Itin, through the native single bit discrete conversion of the Bricasti M3 DAC.  It sounds AMAZING!