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Old 3rd June 2019, 12:22 AM   #61
spiltmidi is offline spiltmidi
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Hi All,

Need help with part for Freedsp CLASSIC BAL A build.

Freedsp CLASSIC BAL A parts question
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Old 19th June 2019, 02:44 PM   #62
JayShoe is offline JayShoe  United States
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Hello Friends,

On the FreeDSP Guidelines Wiki there is a call to have a distribution circuit for the Master Clocks. Here is what is written.

Quote:
MCLK distribution
All main-boards and slave boards need to be synchronous to a common master clock (MCLK). Therefore future freeDSP main-boards must feature a MCLK distribution circuit, which provides several synchronous but independant MCLK outputs. These will supply a MCLK to the onboard DSP and also to each expansion board via the standard freeDSP expansion connector.

freeDSP main-boards provide MCLK: 24.576 MHz
freeDSPx expansions receive MCLK via standard freeDSP expansion connector
I'm designing a board that will use the FreeDSP Expansion Connector to connect a DSP Main Board, to ADC/DAC Add-on Boards. I'm wondering if there is any more information out there regarding clock distribution, or I2S distribution in general. Upon review of the various FreeDSP boards, the clock distribution, or I2S distribution is done differently. I document my search here on the DiyAudio Thread "Clock Repeater IC, Jitter correction ic, clock distibution". Some circuits are using Gate Buffers for all of the I2S lines... Other circuits are using just a clock buffer.

Options seem to include
- Fan-out IC for Master Clock
- Buffer of all I2S lines

My question for the FreeDSP users is surrounding real world experience. Do any of these circuits provide a more reliable outcome than others? What users are connecting add-on boards using long lines? Are any users out there connecting multiple add-on boards on an unbuffered signal? Buffered signal? Fan-out for MCLK only? What's the outcome? I can tell you that in my breadboard tests I'm finding that if I connect more than one board to my breadboard using 6 inch cables I get problems. I'm wondering if maybe we could come up with a more concrete recommendation and add it to the wiki, something that we can all agree will send I2S a distance. Maybe 6 inches to each board? Maybe 12 inches? 18 inches? Any IC's that incorporate I2S buffering specifically into the datasheet? Something designed to strengthen the I2S lines... That would be really nice wouldn't it be!?
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Old 16th July 2019, 09:13 AM   #63
DarkOne is online now DarkOne  Slovakia
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Default DAC 2&3 noise

Quote:
Originally Posted by Eliani View Post
Hey guys,

I've just recently bought a freedsp smd B board and it's got a distinct noise on oupt 3 and 4.... prety much like pink noise... it' doesn't go away when I use a mut button before the DAC...
Hello, I have exactly the same problem. DAC0 and DAC1 work fine, but DAC2 and DAC3 are extremly noisy. Its a white noise and it is not from ADC (as DAC0&1 work fine). Tried 4 different power supply, USB from PC, 9V power brick, 5V from power bank and 15V PS with 7815 stabilizer. All work more or less the same, there are only subtle differences between them.
I made a project in sigma studio to generate 500Hz tone, that I fed to my ESI Juli@ sound card and analyzed it with REW, results bellow.
Attached Images
File Type: png ADAU1701_Schematic.PNG (9.5 KB, 187 views)
File Type: jpg ADAU1701_DAC0_500Hz.jpg (175.6 KB, 191 views)
File Type: jpg ADAU1701_DAC2_500Hz.jpg (164.0 KB, 192 views)
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Old 16th July 2019, 01:50 PM   #64
theol is offline theol
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Default DAC 2&3 very noisy

Quote:
Originally Posted by DarkOne View Post
Hello, I have exactly the same problem. DAC0 and DAC1 work fine, but DAC2 and DAC3 are extremly noisy. Its a white noise and it is not from ADC (as DAC0&1 work fine). Tried 4 different power supply, USB from PC, 9V power brick, 5V from power bank and 15V PS with 7815 stabilizer. All work more or less the same, there are only subtle differences between them.
I made a project in sigma studio to generate 500Hz tone, that I fed to my ESI Juli@ sound card and analyzed it with REW, results bellow.

Hi,


Same problem for me… DAC0 & DAC1 are very clean output, but DAC2&3 are very very noisy. I don't know why. I tried different configurations in Sigma Studio, different power supply, I checked all the soldering.


Did anyone else encountered the same problem ? How can we solve it ?


Thank you very much
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Old 16th July 2019, 03:49 PM   #65
CyberPit is offline CyberPit  Japan
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Default PCB Layout?

Quote:
Originally Posted by theol View Post
Hi,


Same problem for me… DAC0 & DAC1 are very clean output, but DAC2&3 are very very noisy. I don't know why. I tried different configurations in Sigma Studio, different power supply, I checked all the soldering.


Did anyone else encountered the same problem ? How can we solve it ?


Thank you very much

I don't have FreeDSP classic SMD B board. My design FreeDSP SMD A/B board don't have this kind of issue, so I can say ADAU1701 chip has four very clean audio outputs.

So I checked with SMD B ki-CAD file on Git-Hub. It seems no potential problem in schematic design. But I can see the very very long VOUT2 & VOUT3 tracks along the MCLK lines.
What will happen? if you remove the R44, R45, R46, R47, and/or additionally bypassing U7 clock driver.
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Old 17th July 2019, 06:42 AM   #66
DarkOne is online now DarkOne  Slovakia
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Quote:
Originally Posted by CyberPit View Post
I don't have FreeDSP classic SMD B board. My design FreeDSP SMD A/B board don't have this kind of issue, so I can say ADAU1701 chip has four very clean audio outputs.

So I checked with SMD B ki-CAD file on Git-Hub. It seems no potential problem in schematic design. But I can see the very very long VOUT2 & VOUT3 tracks along the MCLK lines.
What will happen? if you remove the R44, R45, R46, R47, and/or additionally bypassing U7 clock driver.
Are you suggesting its a design flaw?
I don't have hot air station yet, so desoldering or making changes is a problem. Also I purchased the board with all SMD components assembled, so I'd leave it as it is, for warranty (if there is any)
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Old 17th July 2019, 02:05 PM   #67
CyberPit is offline CyberPit  Japan
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Quote:
Originally Posted by DarkOne View Post
Are you suggesting its a design flaw?
I don't have hot air station yet, so desoldering or making changes is a problem. Also I purchased the board with all SMD components assembled, so I'd leave it as it is, for warranty (if there is any)
Hello DarkOne-San,


Well yes!
You can do as you like. Because it's a "DIY"
One of technique to remove SMD resistor which using with two solder irons. (Photo attached)


BTW, I have ordered this hot air tool in last week.

BGA Rework Solder Station 8858 Portable Hot Air Gun Blower 220V EU Plug Hand held Heat Gun With Welding Soldering Repair Tools-in Soldering Stations from Tools on Aliexpress.com | Alibaba Group
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File Type: jpg IMG_2801.jpg (664.1 KB, 146 views)
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Old 18th July 2019, 07:54 AM   #68
DarkOne is online now DarkOne  Slovakia
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Quote:
Originally Posted by CyberPit View Post
Hello DarkOne-San,


Well yes!
You can do as you like. Because it's a "DIY"
One of technique to remove SMD resistor which using with two solder irons. (Photo attached)


BTW, I have ordered this hot air tool in last week.

BGA Rework Solder Station 8858 Portable Hot Air Gun Blower 220V EU Plug Hand held Heat Gun With Welding Soldering Repair Tools-in Soldering Stations from Tools on Aliexpress.com | Alibaba Group
I have more than enough of DIY as you can see on attached inage.

Weird things happened, without any change, all chanels work flawlessly now, noise is gone. I'm not sure if there is something in the grid, or some badly bahaving device in the house that cause interference.

I will test all chanels over and over again in the upcoming weekIMG_20190709_181443.jpg
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Old 18th July 2019, 03:42 PM   #69
CyberPit is offline CyberPit  Japan
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Default Capacitive Loads?

Quote:
Originally Posted by DarkOne View Post
I have more than enough of DIY as you can see on attached inage.

Weird things happened, without any change, all chanels work flawlessly now, noise is gone. I'm not sure if there is something in the grid, or some badly bahaving device in the house that cause interference.

I will test all chanels over and over again in the upcoming weekAttachment 768991

Hello DarkOne-San,


A possibility of MCLK interference is gone.

I guess some oscillation possibility depends on output loads.
Voltage follower's negative input phase can be shift to -180 degrees over 1MHz if the voltage follower's output impedance raise to 30ohms around.

Hope you can succeed to shut the evils...


Regards,
CyberPit
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Old 26th July 2019, 03:00 PM   #70
theol is offline theol
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Hello,


Quote:
Originally Posted by DarkOne View Post
Weird things happened, without any change, all chanels work flawlessly now, noise is gone. I'm not sure if there is something in the grid, or some badly bahaving device in the house that cause interference.
Attachment 768991

DarkOne, I'm glad that the noise is gone on your FreeDSP !



Unfortunately, on mine, I still have a lot of noise on DAC 2&3. I checked once again all soldering, I changed the power supply, but nothing worked…


I'm a little bit confused and I don't know what to do.


If anyone have an idea.



Maybe I'm gonna send back this board and buy a MiniDPS…
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