Which DACs bypass digital filtering?

[Jud]

9 minutes ago, Jud said:

 

What open source software do you work on (just curious)?

 

Got it, never mind.

 

[AnotherSpin]

24 minutes ago, Jud said:

 

mansr provided SDM capabilities for the open source SoX software, then adapted SDM for inline processing in Audirvana+.

 

Thank you, Jud.

[Miska]

16 minutes ago, Jud said:

What open source software do you work on (just curious)?

 

I've been using Linux since about 1994/1995 from 0.x kernel times. "Solely" on open source since 2004, before that only partially.

 

It varies over time. One of the audio related projects was/is JACK audio server ("jack1").

 

For Nokia's Linux-based mobile devices (internet tables, phones) on multimedia frameworks, instant-messaging/voice/video-calls and accounts & single sign-on. Nokia N9 was last product of that line before Nokia decided to hire Elop and switch to Windows Phone.

 

Then later on Glib-based rewrite of the single sign-on framework, Tiny Login Manager "TLM", Tizen OS for some time and now recently on IoT specific distribution.

 

Plus bunch of other stuff across the board.

[Jud]

14 minutes ago, Miska said:

 now recently on IoT specific distribution.

Edited 11 minutes ago by Miska

 

Yep, saw some of the Ostro stuff.  You would find a very interested audience for IoT security among many people in my field at the moment.  But the vast majority would be iOS and Android users.

 

(Sorry for the OT.)

[semente]

3 hours ago, Jud said:

 

I have seen ads for some boards from China - don't know if they're fully populated and what the quality might be.

 

Since schematics and (IIRC) suggested parts lists are available,  another possibility is to pay someone local with decent electronics skills to build one for you.

 

Is it just a hardware thing or does it require programming? 

[Jud]

5 minutes ago, semente said:

 

Is it just a hardware thing or does it require programming? 

 

Just hardware.  Everything you need to do is in software.  But that means you're not getting any fun user interface stuff on the hardware side either.

[jabbr]

25 minutes ago, semente said:

 

Is it just a hardware thing or does it require programming? 

It is literally a USB interface (Amanero) followed by a digital FIR filter (chip registers) followed by an analogue low pass filter. That's it. Simple.Dsc1.pdf

[jabbr]

Edit above "chip registers" -> "the chips are shift registers"

[semente]

17 hours ago, mansr said:

Digital filters are always more flexible than analogue ones. Especially for DSD64 where the noise is quite close to the audio band, a digital low-pass filter followed by remodulation at a higher rate can give an end result superior to using an analogue filter directly.

It's always possible for a poor implementation to do more harm than good. If the implementation is of reasonable quality, I see no downsides.

There is no difference in principle between hardware and software digital filters. A hardware filter is simply a network of multipliers and adders hardwired to perform one function. A computer uses exactly the same kind of arithmetic blocks to do its calculations, only here they are controlled by a program so the function is not fixed. That said, cheap DAC chips might use lower precision arithmetic in order to save silicon space (and power). Good DACs have 32-bit filters whereas computers can easily use 64-bit precision, although the benefit of that is marginal at best. The main advantage of software is the flexibility it offers.

 

What about jitter?

Doesn't it get increasingly higher with higher sample rates?

What's the "current" limiting threshold for DSD? 

[Norton]

23 hours ago, Jud said:

 

I have seen ads for some boards from China - don't know if they're fully populated and what the quality might be.

 

Since schematics and (IIRC) suggested parts lists are available,  another possibility is to pay someone local with decent electronics skills to build one for you.

So the DSC1 really only exists as a design, not even a kit of parts?

 

I would have thought there'd be enough takers for a HQP-tailored DAC to make it worthwhile someone selling as a finished item.  I'd likely buy one.

[Miska]

8 hours ago, semente said:

What about jitter?

Doesn't it get increasingly higher with higher sample rates?

What's the "current" limiting threshold for DSD? 

 

Jitter is more problem with DAC chips, because they need somewhat higher speed clock than the conversion section runs at, to have some more clock cycles per output sample. For example ESS Sabre is commonly run from 100 MHz clock and requires clock at least 3x higher than the input DSD rate. When a simple DAC like DSC1 is run with software processing, it can have 1:1 clock ratio, so for example DSD512 DAC would run from 22.5792/24.576 MHz clock. Such clocks have typically about 10 dB lower phase noise at low frequencies than 100 MHz clock. Yet another advantage for running all the DSP in computer, because the computer's clock has no relation whatsoever with the DACs clock. So the process is truly asynchronous.

 

Apart from ESS, DAC chips run their DSP pipeline synchronously with the conversion. And thus cannot do things like HQPlayer for example does.

 

[Jud]

4 hours ago, Norton said:

So the DSC1 really only exists as a design, not even a kit of parts?

 

With the proviso that hardware in some intermediate state may be available from China, yes, that's correct.

 

4 hours ago, Norton said:

I would have thought there'd be enough takers for a HQP-tailored DAC to make it worthwhile someone selling as a finished item.  I'd likely buy one.

 

A group buy of boards populated with the parts that would be more difficult to DIY has been discussed.  This would make it easier and cheaper to have some local person finish it.  And a group buy could include some or all other parts and a chassis, making up a kit.

 

But nothing's gone past the preliminary discussion stage.

[jabbr]

17 minutes ago, Jud said:

 

With the proviso that hardware in some intermediate state may be available from China, yes, that's correct.

 

Uh, since the Chinese source:

1) has a different circuit, which is allowed under @Miska CERN Open Hardware License

2) however doesn't publish the circuit, which is entirely against the CERN Open Hardware License, I'm not going to discuss nor promote the effort.

3) Who knows what it is? Says DSC1 but who knows...

 

17 minutes ago, Jud said:

 

 

A group buy of boards populated with the parts that would be more difficult to DIY has been discussed.  This would make it easier and cheaper to have some local person finish it.  And a group buy could include some or all other parts and a chassis, making up a kit.

 

But nothing's gone past the preliminary discussion stage.

 

It would be possible to group buy a set of finished circuit boards but there would need to be a number of people interested to make this cost effective. This would be the parts as described. The production facility can then populate the boards. This is particularly good for the SMD parts but can also be done for TTH. The design includes a power supply, and uses the Amanero USB interface all of which could be grouped together, and a case etc.

 

That said, I've already built the DSC1 and am personally more interested in modifications. Since I have a good day job  this is a hobby for me, I enjoy designing and laying out circuits, and and have become very interested in using the Zynq as a universal interface for pre-amp/DAC whatever, particularly to build an Ethernet interface... programming an FPGA requires certain skills (I used this project to learn) and currently slogging through writing a device driver (another skill that I am trying to learn) ... this would all be to replace the Amanero with something better   I think the fundamental DSC1 design is terrific and readily modifiable and await @Miska's promised DSC2 design... he also has many other things on his plate... so in any case if someone wanted to organize a group buy I could assist, but that's not what I do best as a primary skill.

 

That said, I think the very best thing about the DSC1 is that it is a fantastic way to learn exactly what a DSD DAC needs to be -- without frills, and if folks are interested we could start discussing the DSD DAC from a technical/mathematical aspect using the DSC1 as a concrete and easily understandable archetypical example. I could start the discussion in another post so as not to put this very interesting thread completely off topic.

[jabbr]

On 5/29/2017 at 10:54 AM, mansr said:

Got any more insults while you're at it?

My sincere apology for being insulting. I was attempting to avoid an argument by authority and even if I felt insulted myself that is not an excuse for going on the attack -- I did not mean to denigrate your contributions, and I particularly respect your open source contributions. I do hope that these will continue to lead to commercial opportunities. My apologies.

[mansr]

3 minutes ago, jabbr said:

My sincere apology for being insulting. I was attempting to avoid an argument by authority and even if I felt insulted myself that is not an excuse for going on the attack -- I did not mean to denigrate your contributions, and I particularly respect your open source contributions. I do hope that these will continue to lead to commercial opportunities. My apologies.

Apology accepted.

[semente]

Thanks to everyone who participated.

The list of DACs hasn't grown much, though:

 

- Phasure NOS1 DAC

- Teac UD-501 and UD-503

- Aqua DACs

- Lampizator DACs

[Norton]

41 minutes ago, semente said:

Thanks to everyone who participated.

The list of DACs hasn't grown much, though:

 

- Phasure NOS1 DAC

- Teac UD-501 and UD-503

- Aqua DACs

- Lampizator DACs

+ Esoteric DACS and players ( as per TEAC)

+ Mivera

+ Soekris 1541  (if there is filter off option, maybe?) 

[bibo01]

2 hours ago, Norton said:

+ Esoteric DACS and players ( as per TEAC)

+ Mivera

+ Soekris 1541  (if there is filter off option, maybe?) 

Also the Holo e the Denafrips DACs (The Pontus looks interesting) work in NOS mode

[Jud]

iFi micro-iDSD can be used this way (I do).

[AnotherSpin]

1 hour ago, Jud said:

iFi micro-iDSD can be used this way (I do).

 

Jud, would you share more details what micro-iDSD settings you use? Thank you.

 

[semente]

7 minutes ago, AnotherSpin said:

 

Jud, would you share more details what micro-iDSD settings you use? Thank you.

 

 

Probably the analogue filters?

 

Filters
– PCM	Bit-Perfect Processing/Minimum Phase/Standard	Digital filters selectable
– DSD	Extreme/Extended/Standard Range	Analogue filters selectable
– DXD	Bit-Perfect Processing	Fixed analogue filter

[semente]

Apparently here's another one for the list:

 

http://www.audio-gd.com/R2R/R2R11/R2R11EN.htm

 

Audio-gd R2R 11

•True NOS , R-2R discrete ladder DAC
•Built in pre- and headhpone amp
•Built in 2 groups DA-8 R-2R modules with 450MHz ultra speed CPLD
•Unique noise process technology will remove any digital artifact
•DSD native , DXD, PCM up to 384KHz Support
•Amanero Combo 384 USB interface

[George Hincapie]

Add Metrum Acoustics to your list. Yes, I am a fan, but they are wonderful.

[guymrob]

Add Holo Audio Spring DAC switchable NOS mode. I'm been using for months now and it sounds wonderful!

[guymrob]

On 30/05/2017 at 5:49 PM, semente said:

 

What about jitter?

Doesn't it get increasingly higher with higher sample rates?

What's the "current" limiting threshold for DSD? 

DSD noise shaping is always done at the A/D converter while at DAC side, LPF will reduce the ultrasonic noise. Two filters are available, 50kHz(narrow) and 100kHz(wide).