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Old Yesterday, 10:58 PM   #221
chris719 is online now chris719  United States
diyAudio Member
Join Date: Jun 2004
Location: Connecticut
Here you go, another block diagram (Figure 1) that represents how AK4499 and similar parts operate. Note the DAC (and everything after the SAI) is clocked by MCLK.


This is also your answer to the ESS question, because in a way, the ESS approach with ASRC is very similar to Figure 2 and how the cheap Cirrus and TI DACs that have integrated PLLs to recover the MCLK operate.

Last edited by chris719; Yesterday at 11:01 PM.
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Old Today, 07:50 AM   #222
ishizeno is offline ishizeno
diyAudio Member
Join Date: Mar 2015
Default Updated USB and DAC Boards

Here are some updated USB and DAC boards for which the seven regulators (5 NJM78M05 and 2 SMD versions of the BA033CC0T) are mounted directly on the PCB. This will ensure that we do not deviate from the original design of the evaluation board, while reducing the height of the DAC assembly. It will also reduce the BoM of a single DAC board by a cool $90...

The DAC board is certainly a tight fit, and many resistors and capacitors will have to be mounted on the underside. We might also go from 70mm 35mm to 72mm 36mm in order to get a tiny bit of extra breathing room. That being said, I really like the layout as it stands.

The isolated part of the USB board has now been broken down into three sections:

1. Oscillators (bottom right with picture in portrait orientation)
2. Outputs (right)
3. Inputs (top)

As a result, the pins located on the top side and used for isolated inputs will not be used by the DAC board, but they could be used by some other boards. This will ensure that we can reuse the USB board across different bricks.

The four balanced outputs on the DAC board are now provided through four separate sets of three pins, which is probably better than two sets of six pins. That being said, their actual positions might evolve a little bit as we finalize the overall component placement.

On the DAC board, we now have 16 pins for the audio inputs and 16 pins for the controls, which will allow us to provide separate ground references for everything we need, but we lost the two extra GPIOs that we had included in an earlier iteration.

Now that we have a high-level validation of the overall design, we will review every single component of the AK4499EQ evaluation board in order to come up with a full BoM. And when that part is done, we will do the same for the USB board.
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File Type: jpg DAC.jpg (976.4 KB, 9 views)
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Old Today, 10:11 AM   #223
ishizeno is offline ishizeno
diyAudio Member
Join Date: Mar 2015
Default Diodes for DAC

Any recommendation for the D300, D301, D302, D303, D320, D321, D322, and D323 diodes of the AK4499EQ evaluation board? Would the DB2132000L used for D1, D2, D3, and D4 be suitable?

Last edited by ishizeno; Today at 10:19 AM.
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Old Today, 12:37 PM   #224
ishizeno is offline ishizeno
diyAudio Member
Join Date: Mar 2015
Default DAC Board BoM

We have listed all the components for the DAC board on its BoM sheet. This leaves us with a few questions:

- What is the maximum voltage for the 180pF C8, C9, C19, C20, C56, C57, C58, and C59 capacitors?
- What is the maximum voltage for the 0.1μF C39, C40, C41, C42, C47, C48, C68, C69, C70, C75, C80, and C81 capacitors?
- Is R1 a 5.1Ω resistor or a 5.1kΩ resistor?
- What is R7?
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