I'd like to try building a DIY PCM/DSD DAC with Amanero and DSD1794/2. I'd like to use Amanero DSD flag to drive the magic "X" circuit that will route the signals to DAC chip and set it in proper mode. Digital is not my thing, so I kindly ask if somebody can give me some pointers how to get it done.
I'm wondering if using DSD1792 with external uC won't be better in this case, as it can control inputs (via Amanero and eg. WM8805) and screen of some kind. I understand I need some digitally controlled switching grid to route signals?
What is the best way to make the routing circuit?
I'm not interested in using newest AK and ESS chips.
I'm wondering if using DSD1792 with external uC won't be better in this case, as it can control inputs (via Amanero and eg. WM8805) and screen of some kind. I understand I need some digitally controlled switching grid to route signals?
What is the best way to make the routing circuit?
I'm not interested in using newest AK and ESS chips.
You already have a real Amanero, not a Chinese clone? If not, you might consider an alternate USB to I2S board that some find preferable to Amanero.
DSD1794A appears to use the common I2C control bus, and looks to be a fairly popular part around here.
On the other hand DSD1792 appears to be designed for Time Domain Multiplexing (TDM) which doesn't seem nearly as popular for most hi-fi use.
DSD1794A appears to use the common I2C control bus, and looks to be a fairly popular part around here.
On the other hand DSD1792 appears to be designed for Time Domain Multiplexing (TDM) which doesn't seem nearly as popular for most hi-fi use.
You can't get a *real* Amanero just anywhere. You can order one from Italy, or maybe order from the US distributor, Twisted Pear. There is a small handful of other distributors spread around the world. Most of the boards that say "Amanero" on them and that are sold on ebay or Aliexpress are fakes. They won't do native DSD, nor ASIO (needed for clean sound from Windows). You can use Amanero though, real or fake. Many people wouldn't use either for the project you have in mind, however, and for good reason.
Regarding 1794A, it is software controlled over I2C bus, look at the register definitions and related info in the data sheet.
Regarding 1794A, it is software controlled over I2C bus, look at the register definitions and related info in the data sheet.
As I know:
PCM1794A - HW control, no DSD
PCM1792A - SW control, DSD capable
DSD1794A - SW control I2C only, DSD capable
DSD1792 - SW control, DSD capable
You can check out dimdim's ak4493 akduino project. You can get a brief of SPI related info from source code. One of the rare opensource dac project I have seen.
AK4493 | Dimdim's Blog
AK4493 | Dimdim's Blog
+1
He also can check out this project. AD1955 is more like PCM1794 than AKM DACs. The source code is for PIC MCU, but C programming language is still C, so it can be easily adapted for newer MCUs.
I2C, SPI, pin control, makes no difference here. There is always stuff to be controlled with modern dacs, just pick a dac chip that does what you want and get on with it. I'm sure we can help the OP as needed, but best to understand the major trade offs first then make major design choices, rather than the other way around.
One preliminary question if that would be okay: is TDM a requirement or not? Again, we don't see it used often in diy projects.
One preliminary question if that would be okay: is TDM a requirement or not? Again, we don't see it used often in diy projects.
If required DSD, so PCM1794A is out of discussion and the cheaper version in this case is PCM1792A which is also TDM capable.
As I understand, DSDxxxx are made from Japan team and they seem to be better.
Even so, looking on digikey, DSD1792A (20 USD) is cheaper than DSD1794A(24USD) and again, user will receive an unwanted TDM function.
As I understand, DSDxxxx are made from Japan team and they seem to be better.
Even so, looking on digikey, DSD1792A (20 USD) is cheaper than DSD1794A(24USD) and again, user will receive an unwanted TDM function.
Thorp, I would suggest to choose the most suitable USB to I2S solution. IMHO for most projects like this one I2SoverUSB will give more performance for lower cost than Amanero. How do other's feel about it?
Some other possible things to consider:
Output stage topology (is it settled?).
User interface goals/requirements (display, remote, etc.)?
Basic power supply needs. (How much isolation between loads, grounding plan, etc.)
System layout, signal and power routing?
Is there going to be a case?
What is/isn't included in the project?
At some point a DAC PCB will need to be laid out (ground plane?, more than 2-layers?, power plane?, etc.)
Somebody mentioned the other day that 4-layers were recommended back in the day for 16-bit audio.
Some other possible things to consider:
Output stage topology (is it settled?).
User interface goals/requirements (display, remote, etc.)?
Basic power supply needs. (How much isolation between loads, grounding plan, etc.)
System layout, signal and power routing?
Is there going to be a case?
What is/isn't included in the project?
At some point a DAC PCB will need to be laid out (ground plane?, more than 2-layers?, power plane?, etc.)
Somebody mentioned the other day that 4-layers were recommended back in the day for 16-bit audio.
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Oh Boy, I'm happy to see all of you chip in.
For now I camed up with an idea to route PCM/DSD signals to DAC chip, see attached. Thats the biggest concern now. Of course I can route it through uC to let it know what is happening in the circuit.
I can change DAC chip, at this stage not a problem. PCM1792A is the cheapest and avaiable in Mouser, so green light for me.
I think I will stick to Amanero, it is more popular here, in Europe, it's cheaper and suits the project better (no need for old R2R DAC formats).
User interface will be made on STM32 BlackPill, it will control a screen, inputs (I will develop this further if it turns out good) and volume.
PCB will probably be 4 layer, we will see. It's not the time yet to decide.
Of course power supply will be adequate to this great chip. Bulk analog power supply with local LDOs and similar solution on the digital side.
In first prototype output stage will be standard opamp one. Output stage is a topic for later.
For now I camed up with an idea to route PCM/DSD signals to DAC chip, see attached. Thats the biggest concern now. Of course I can route it through uC to let it know what is happening in the circuit.
I can change DAC chip, at this stage not a problem. PCM1792A is the cheapest and avaiable in Mouser, so green light for me.
I think I will stick to Amanero, it is more popular here, in Europe, it's cheaper and suits the project better (no need for old R2R DAC formats).
User interface will be made on STM32 BlackPill, it will control a screen, inputs (I will develop this further if it turns out good) and volume.
PCB will probably be 4 layer, we will see. It's not the time yet to decide.
Of course power supply will be adequate to this great chip. Bulk analog power supply with local LDOs and similar solution on the digital side.
In first prototype output stage will be standard opamp one. Output stage is a topic for later.
Attachments
Umm... Don't know if its necessary to switch between PCM and DSD inputs on the DSD1792A? It works with AKM dacs to just wire the two sets of inputs (PCM/DSD) in parallel if they are fed from the same source lines. The main reason for needing the DSD_ON signal is so the MCU can know it needs to program the dac chip to operate in DSD mode. The MCU may also need F0-F3 signals from Amanero to set the dac chip to the correct DSD sample rate (unless maybe DSD1792A auto-detects DSD sample rates? ...I should probably read the data sheet 
).
This thing stands to sound a lot better if external clocks are used for Amanero, along with galvanic isolation, and reclocking of the Amanero output signals. That's how to get the cleanest and highest quality clock and I2S signals if using Amanero. Since I2SoverUSB already has decent clocks, galvanic isolation, and reclocking of I2S its often much simpler to get pretty good sound quality with it. (Or, is worrying about Amanero clocks, and USB computer ground noise, overkill for a dac chip like DSD1792A?)
). This thing stands to sound a lot better if external clocks are used for Amanero, along with galvanic isolation, and reclocking of the Amanero output signals. That's how to get the cleanest and highest quality clock and I2S signals if using Amanero. Since I2SoverUSB already has decent clocks, galvanic isolation, and reclocking of I2S its often much simpler to get pretty good sound quality with it. (Or, is worrying about Amanero clocks, and USB computer ground noise, overkill for a dac chip like DSD1792A?)
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PCM1792A seems to use exactly same pins as Amanero in terms of output, so it may be possible to connect it straight to each other. This is a plus, but... If DSD signal comes before DAC chip is set to DSD mode it will lock in error state (page 41):
https://www.ti.com/lit/ds/symlink/pcm1792a.pdf?ts=1591022485721
Don't know what to think about that one...
Yes, I want to use F0-3 to display Fs anyway. So uC will be able to tell DAC what signals are coming to it.
I understand your point about USB interface, but its Amanero for now. In future iterations I will think about that.
https://www.ti.com/lit/ds/symlink/pcm1792a.pdf?ts=1591022485721
Don't know what to think about that one...
Yes, I want to use F0-3 to display Fs anyway. So uC will be able to tell DAC what signals are coming to it.
I understand your point about USB interface, but its Amanero for now. In future iterations I will think about that.
The MCU should probably have control of the RST pin of the dac in case it ever looses communication. Also, DSD_ON timing of Amanero should probably be measured to see how much time there is before DSD playback starts.
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