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Building the ultimate NOS DAC using TDA1541A
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Old 2nd January 2020, 05:29 PM   #7431
SSassen is offline SSassen  Netherlands
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Evening gents, quick question; I have one of Ianís I2S to PCM boards and was going to hook that to a TDA1541A tomorrow and see whether I can do some measurements to confirm the 15 bit resolution issue as reported here. I would however like to compare it to a known working solution with glue logic. Now Iíve seen several posts referring to a glue logic solution by John (ec-designs) but I canít seem to find that in this monster thread? Any help would be appreciated, thanks!
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Old 2nd January 2020, 08:25 PM   #7432
rfbrw is offline rfbrw
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The I2S to PCM board guide neatly illustrates the issue on page 2. For all the listed devices bar the TDA1541A data is valid on the rising edge.
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Old 2nd January 2020, 09:43 PM   #7433
koldby is offline koldby  Denmark
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Quote:
Originally Posted by SSassen View Post
Evening gents, quick question; I have one of Ianís I2S to PCM boards and was going to hook that to a TDA1541A tomorrow and see whether I can do some measurements to confirm the 15 bit resolution issue as reported here. I would however like to compare it to a known working solution with glue logic. Now Iíve seen several posts referring to a glue logic solution by John (ec-designs) but I canít seem to find that in this monster thread? Any help would be appreciated, thanks!
I donīt seem to remember John making any suggestions to a glue logic solution to Janīs board, but then again I am getting old. What John did was making his own version of an I2S to PCM solution, that does not have the, presumable, issues Jan's board has. Maybe that is what you are serching for?
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Old 2nd January 2020, 09:50 PM   #7434
SSassen is offline SSassen  Netherlands
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Quote:
Originally Posted by koldby View Post
I donīt seem to remember John making any suggestions to a glue logic solution to Janīs board, but then again I am getting old. What John did was making his own version of an I2S to PCM solution, that does not have the, presumable, issues Jan's board has. Maybe that is what you are serching for?
Yes, perhaps I didnít word my post properly? It was my understanding that John had posted a I2S to simultaneous (COB) schematic using glue logic at some point, as obviously heís also running his TDAs in COB mode. I just canít seem to find the schematic in the +700 pages of this topic?
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Old 2nd January 2020, 10:36 PM   #7435
markos4553 is offline markos4553  United States
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Hi SSassen,


Maybe this:
DIY I2S to simultaneous converter PCB.



Mark K.
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Old 3rd January 2020, 04:09 AM   #7436
Hanze Khronye is offline Hanze Khronye  Australia
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Quote:
Originally Posted by SSassen View Post
Evening gents, quick question; I have one of Ianís I2S to PCM boards and was going to hook that to a TDA1541A tomorrow and see whether I can do some measurements to confirm the 15 bit resolution issue as reported here. I would however like to compare it to a known working solution with glue logic.
There is a solution presented here;
Drive NOS AD1865/62,PCM1704/02/63,TDA1541 from FIFO: Universal I2S-PCM driver board
Maybe this can help?.
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Old 4th January 2020, 05:22 AM   #7437
ecdesigns is offline ecdesigns  Netherlands
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Hi JOSI1,

sorry for the late reply,


First of all, I developed an electro / optical digital audio hybrid interface that received the name ElectroTos.

The interlink basically consists of a 1 meter coaxial cable driving an ultra high speed LED. This LED shines directly on the Toslink optical receiver. The relatively large distance between wires inside the LED and wires inside the optical receiver provides superb galvanic insulation and almost zero coupling capacitance.

It can run in compatibility mode, this is very interesting for use with existing DACs that have Toslink input. This way the performance of existing DACs that have a Toslink input can be significantly increased.

In native mode the ElectroTos protocol is used, this offers maximum obtainable performance.

So if you want to improve sound quality of existing DACs (including MOS16, MOS24) you can use the new ElectroTos interface plus translator, it will always outperform Toslink by a large margin while preserving advantages of Toslink like perfect galvanic insulation and low bandwidth output.

Ground loop noise + wired LAN will lead to significant sound quality degradation. This is one practical example off how important it is to have -zero- ground loop noise injection. Direct USB, I2S, coax or AES/EBU connection to the DAC cannot prevent ground loop noise injection.


What makes ElectroTos so special?

+ Superb galvanic insulation, zero ground loop noise injection.
+ Limited bandwidth output, massive noise spectrum reduction compared to USB, I2S, coax, and AES/EBU.
+ Extremely low inter-symbol jitter because of twin bandwidth interface (large bandwidth electrical interlink, low bandwidth optical output) and the ElectroTos protocol.
+ No optical reflections.
+ Extra jitter reduction by PLL.


USB

- Poor galvanic insulation, large bandwidth ground loop noise injection.
- Very large bandwidth output, maximum noise injection into the connected DAC.
- High jitter (has to be fixed with an USB receiver that offers asynchronous feedback).
+ No optical reflections.

S/PDIF coax:

- Poor galvanic insulation, large bandwidth ground loop noise injection.
- Very large bandwidth output, maximum noise injection into the connected DAC.
- Poor S/N ratio.
+ Low jitter.
+ No optical reflections.
+ Extra jitter reduction by PLL.

S/PDIF AES/EBU:

- Poor galvanic insulation, large bandwidth ground loop noise injection.
- Very large bandwidth output, maximum noise injection into the connected DAC.
+ Good S/N ratio.
+ Low jitter.
+ No optical reflections.
+ Extra jitter reduction by PLL.

I2S:

- Poor galvanic insulation, large bandwidth ground loop noise injection.
- Very large bandwidth output, maximum noise injection into the connected DAC.
- Poor S/N ratio.
- Medium to high jitter.
- No jitter reduction by PLL.
+ No optical reflections.

Toslink:

+ Superb galvanic insulation, zero ground loop noise injection.
+ Limited bandwidth output, massive noise spectrum reduction compared to USB, I2S, coax, and AES/EBU.
- Very high inter-symbol jitter.
- Optical reflections (fibre optics interlink).
+ Extra jitter reduction by PLL.



In order to get an idea of large bandwidth noise:

I2S, coax and USB (typically 2GHz and up):

################################################## ############################## (2GHz)

Toslink / ElectroTos

# (25 MHz)

Larger bandwidth noise spectrum will cause much more problems when injected into a DAC. Think of the impact of stray capacitance / inductance and crosstalk. That's why I2S, coax, USB and AES/EBU connection on a DAC will maximise the amount of noise being injected into a DAC and is therefore not a very good idea.

Even worse, when using Toslink, and leaving coax / USB connectors plugged into the DAC, ground loop noise will be injected (bypassing Toslink). There will also be unwanted large bandwidth noise injection into the DAC by the still connected coax / USB sources.


In order to ensure that the Fractal DAC -only- receives one band limited signal (lowest practical noise) and in order to guarantee zero ground loop noise injection, it only has one optical ElectroTos input.

S/PDIF offers the fewest signal changes / second (clock will be recovered from sync codes or preambles), so it will work with lowest practical bandwidth. The single one direction signal is also easy to isolate.

Even if you, by some miracle, find digital couplers that offer zero pF coupling capacitance (input - output), zero noise and zero jitter. These will still inject very large bandwidth noise spectrum (2GHz and up) into the DAC. Once injected into the DAC it's game over, it's like allowing dust to enter a clean room continuously. Once the dust keeps getting into the clean room, there is no way keeping the clean room free of dust no matter what filters you use.

So my different DAC approach forms a noise barrier (air lock) between the source (dusty environment) and the DAC (clean room).



If you want pure involving music reproduction (studio tape quality or better) you use ElectroTos in native mode in combination with the new Fractal / ElectroTos DAC.

This means that the new Fractal DAC will only work with ElectroTos sources. When connected directly to a Toslink source this will result in heavy distortion. So to be absolutely clear, the new Fractal DAC is -not- a Toslink DAC and has totally different properties compared to a Toslink DAC.

The optical receiver in the new Fractal DAC has a standard Toslink socket, but it is -only- intended for use with the ElectroTos interface.

I attached a photograph of an experimental ElectroTos interlink and how it fits into a Toslink optical receiver.



In order to use this new digital audio interface we need a translator. The translator converts USB, S/PDIF coax or Toslink to ElectroTos and reduces jitter. Jumper setting sets either compatibility mode (for use with existing Toslink DACs) or native mode (for use with the Fractal DAC). The translator also contains a special driver circuit for the ElectroTos interlink.

For clarity, when using ElectroTos (compatibility mode) in combination with a Toslink DAC, the DAC will still receive coax signal quality plus superb galvanic insulation. Make sure to pull all other digital interface plugs as failing to do so will bypass ElectroTos, injecting large bandwidth (ground loop) noise. So when comparing sources, always make sure to disconnect all other sources while listening to one specific source!


In order to guarantee maximum performance and minimum interference (crosstalk) we designed two translators:

Asynchronous USB translator based on XMOS 200 series with local low jitter audio clocks. Jumper setting switches between native (for standard Toslink DACs) and ElectroTos (Fractal DAC only).

S/PDIF Toslink / coax translator based on PLL jitter reduction. Jumper setting for Toslink / coax selection and a jumper setting for native and ElectroTos mode. Low jitter coax sources will offer best results. I use an insulation transformer and a differential LVDS receiver for coax in order to get best signal quality and lowest jitter.

The final option is a very clean, guaranteed bit-perfect digital audio source with graphical user interface (PC). This digital audio source has ElectroTos output so it can be directly connected to the DAC. This digital audio source can offer compatibility mode (for existing Toslink DACs) and ElectroTos native mode for the Fractal DAC. One can never be sure what goes on in a PC or streamer, is playback always bit-perfect?



Quote:
Can you provide a sketch showing how these devices are combined/connected.
USB digital audio source -> USB interlink -> USB translator (ElectroTos native mode) -> ElectroTos interlink -> Fractal DAC.
USB digital audio source -> USB interlink -> USB translator (compatibility mode) -> ElectroTos interlink -> Toslink DAC

S/PDIF Toslink -> fibre interlink -> S/PDIF translator (ElectroTos native mode) -> ElectroTos interlink -> Fractal DAC.
S/PDIF Toslink -> fibre interlink -> S/PDIF translator (ElectroTos compatibility mode) -> ElectroTos interlink -> Toslink DAC.

S/PDIF coax -> coax interlink -> S/PDIF translator (ElectroTos native mode) -> ElectroTos interlink -> Fractal DAC.
S/PDIF coax -> coax interlink -> S/PDIF translator (ElectroTos compatibility mode) -> ElectroTos interlink -> Toslink DAC.

UPL digital audio source (ElectroTos native mode) -> ElectroTos interlink -> Fractal DAC.
UPL digital audio source (ElectroTos compatibility mode) -> ElectroTos interlink -> Toslink DAC.


Quote:
Can a Toslink source be directly connected or only via the New digital audio interface.
No it only accepts ElectroTos and is always used in combination with a translator.



Quote:
Can I switch between 2 or more inputs via RMC.
No this causes degrading:

- Large bandwidth (ground loop) noise injection by unused sources.
- Crosstalk
- Jitter.
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Old 5th January 2020, 02:03 PM   #7438
maxlorenz is offline maxlorenz  Chile
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Dear -EC-

Great!

Two questions:

1) Will Fractal DAC have integrated Electro-Tos and Translator inside?

2) When?

Best wishes of Joy and Success.
M.
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Old 6th January 2020, 04:32 PM   #7439
diyiggy is offline diyiggy
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Hi All,


John would be interrested to draw us a TDA1541A standalone DIY PCB yet (as stated long time ago) ?
John if you read us
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Old 6th January 2020, 06:46 PM   #7440
rfbrw is offline rfbrw
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Surely you can do that for yourself.
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