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Old 18th July 2019, 12:54 PM   #151
ishizeno is online now ishizeno
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Quote:
Originally Posted by Markw4 View Post
A picture of the eval board at: ES9038Q2M Board
if you open the picture, then click on the white X in the lower left corner it will blow up to full size, or you can right click to download at full res.
Under the daughter board are some more electrolytic caps. There are also a few components on the bottom side of the motherboard.

The rows of yellow and green banana plugs along the long sides of the motherboard are alternate power entry points for the adjacent circuitry. That circuitry provides the analog power for dac chip outputs. There are also a few components of that circuitry on the bottom of the board.

The I/V opamps on the daughterboard are powered directly off the incoming +-15v rails, and as such are not quite ideally powered.
Thanks a ton for the link. This picture will be a lot more useful than the low-res version on the AKM website.
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Old 18th July 2019, 12:56 PM   #152
ishizeno is online now ishizeno
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Originally Posted by Markw4 View Post
Only if you will be satisfied with rather compromised sound quality.

Sabre dacs are not easy to get right either. Allo, in India, is expected to come out with a good ES9038Q2M USB dac soon. Probably better sound quality using those, or some you get them to make for you rather than doing a poor version of an AK4499 design.
Of course! But I would not learn anywhere as much by getting someone else do the work for me... I'll work as long as necessary to make it good. And the BoM will be closer to $400, but we'll make sure to make the Sitara SoM optional. Without it, the cube will just be exposed through the XMOS directly.

Last edited by ishizeno; 18th July 2019 at 01:20 PM.
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Old 18th July 2019, 12:58 PM   #153
ishizeno is online now ishizeno
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Originally Posted by Markw4 View Post
The Reference Voltage power should be very, very clean, no noise contamination, and low impedance. ESS recommends putting their equivalent power, AVCC, as close to the dac chip pins as possible for best results. With specified noise and distortion at -120dB or lower, you are getting into an area that requires careful design.
I'll try to fit it all on the DAC board then. That will make for an interesting challenge...
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Old 18th July 2019, 04:30 PM   #154
ishizeno is online now ishizeno
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Default AK4499EQ Evaluation Board Availability

According to AKM, the evaluation board should become available at Arrow and DigiKey sometime in the middle of August. In the meantime, we'll work on the ADC brick.
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Old 18th July 2019, 06:25 PM   #155
ishizeno is online now ishizeno
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Default Additional Capacitors

Here are the other capacitors that we need to mount on the DAC board:

C352, C357, C358, C361 (+15V MVDD): 470μ
C350, C351 (+15V MVDD): 470μ
C300, C306, C320, C326 (+15V MVREF): 470μ
C302, C308, C322, C328 (+15V MVREF): 100μ
C304, C310, C324, C330 (+5V REG): 100μ
C305, C311, C325, C331 (+5V REG): 100μ

The BoM for the DAC brick is being compiled on this sheet.
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Old 18th July 2019, 06:31 PM   #156
sciencesky is offline sciencesky
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Originally Posted by chris719 View Post
I don't know what kind of filtering you've tried on the PoE input, but a common-mode choke is a good idea. There are also some nice 3-terminal "feedthrough" caps that Murata makes we have used to good effect. Could also look into using LDOs with better rejection up to 1 MHz, which seems to be around where the best IC regulators top out.
There is no filtering only capacitors. The PoE part belongs to the board of our client and its the first time that we actually have one of their boards on our desk after nearly 2 years.
There is also an isolated DC-DC-Converter Module after the PoE part but that thing does nothing except voltage conversion and heat production

You really need to be careful with those ready to go regulator modules!
Input and output filtering is a must!
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Old 18th July 2019, 07:09 PM   #157
chris719 is offline chris719  United States
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Quote:
Originally Posted by sciencesky View Post
There is no filtering only capacitors. The PoE part belongs to the board of our client and its the first time that we actually have one of their boards on our desk after nearly 2 years.
There is also an isolated DC-DC-Converter Module after the PoE part but that thing does nothing except voltage conversion and heat production

You really need to be careful with those ready to go regulator modules!
Input and output filtering is a must!
Yes, most of the modules suck. The exceptions being the SIP / IC package types from Linear, TI, and Intel/Enpirion.
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Old 18th July 2019, 07:11 PM   #158
chris719 is offline chris719  United States
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Quote:
Originally Posted by Markw4 View Post
Only if you will be satisfied with rather compromised sound quality.

Sabre dacs are not easy to get right either. Allo, in India, is expected to come out with a good ES9038Q2M USB dac soon. Probably better sound quality using those, or some you get them to make for you rather than doing a poor version of an AK4499 design.
What part of his post is making you think it will be compromised? Just curious. Small size and proximity to the SoC?
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Old 18th July 2019, 07:21 PM   #159
ishizeno is online now ishizeno
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Quote:
Originally Posted by chris719 View Post
What part of his post is making you think it will be compromised? Just curious. Small size and proximity to the SoC?
I do not want to speak for Mark, but I suspect that my original BoM estimate was way off ($200 to $300) and created some confusion. Without Sitara SoM (about $100 when buying 1K), the BoM is already at about $420, and I am far from being done. I expect it to reach anywhere between $500 to $600 when everything is said and done. It's certainly not cheap, but I'm not cutting any corners, at least within the space/volume constraints that I have to deal with. And if these constraints prove to be insurmountable, I'll got to a 2 OTO units footprint (160mm 80mm).

Also, the likelihood that a complete newbie like me could pull this one off must seem very low, but appearances can be deceiving ;-)
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Old 18th July 2019, 07:28 PM   #160
ishizeno is online now ishizeno
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Default Question about PSU

Let's assume that we add a PSU board derived from the AAPSU01 with an extra LT1965 for the +3.3V output. Would using this in combination with the VRED Jung-Didden power supplies and the LT3045-78XX regulators mounted on the DAC board be useful or wasteful (two stages of regulation)?
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