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DISCRETE R-2R DAC for raspberry pi
#1
Finalised my Discrete R2R DAC 

Here's the built video :

https://youtu.be/7pHpN-J0S8M

https://youtu.be/HsWyG7MWpEo

Resistor matching is really time consuming and tiring .
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#2
A non-oversampling R2R DAC on a HAT board, amazing! Well done!
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#3
(09-10-2020, 09:21 AM)vinnn Wrote: A non-oversampling R2R DAC on a HAT board, amazing! Well done!

Thanks.  Yes, Non over sampling .
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#4
@bigbulb

Sorted, selected, and assembled by hand. Wow. I tip my hat to you!

I've got plenty of patience but I'm too old now to trust my hands and my eyesight anymore. Sad  

Regards,
Kent
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#5
Tell us about the firmware in the Altera and what I2S driver is being used.
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#6
(09-10-2020, 02:24 PM)TheOldPresbyope Wrote: @bigbulb

Sorted, selected, and assembled by hand. Wow. I tip my hat to you!

I've got plenty of patience but I'm too old now to trust my hands and my eyesight anymore. Sad  

Regards,
Kent

Thanks !  Smile
Yes, You can see my clumsy hand, and I'm wearing a magnifying glass .
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#7
(09-10-2020, 03:58 PM)Tim Curtis Wrote: Tell us about the firmware in the Altera and what I2S driver is being used.

This project had been planed for more than a year, I'm not familiar with Linux coding , I ask around on WWW about how to create a custom I2S  driver, and I fail to find any clue to do that. 

I ended up to program the FPGA to accept basic Generic ( R-Pi DAC) driver. 
The Altera is basically a I2S serial to parallel converter, and also a binary to unity counter( thermometer counter ) to correct 4 bit nearest to MSB , and also reduced glitches to -24dB lower than normal R2R DAC. slew rate control in the FPGA further reduced glitches too.

Matching resistors are very time consuming , before matching them , I heat up a batch of 0.1% resistors in oven for 30 minutes and cool it down , and repeat the cycle 3 times. From 0.1%, I have 2 batches of 0.05% sorted, and then from there, I matched down to 0.01 and finally matched down to 0.005% .
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#8
Nice work, again ;-)
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#9
@bigbulb, what are your plans for this unique DAC?

It does not seem like the design lends itself to mass production unless you are setup to do something like Soekris did but I'm sure, myself included, there are audio enthusiasts that would want to buy one of these from you.

Let us know :-)
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#10
(09-15-2020, 01:10 AM)Tim Curtis Wrote: @bigbulb, what are your plans for this unique DAC?

It does not seem like the design lends itself to mass production unless you are setup to do something like Soekris did but I'm sure, myself included, there are audio enthusiasts that would want to buy one of these from you.

Let us know :-)

Is the DAC delivered "soldered" ready?
What should it cost?
How about moode?

Maybe you can make a bulk order to adjust the price.

is just an idea of mine and doesn't have to agree with others .. Smile Smile

Ciao Zeferino
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