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Reference DAC Module - Discrete R-2R Sign Magnitude 24 bit 384 Khz

I have been working on a little side project, now it's time to present it for everybody here....

It's a DAC module based on a discrete R-2R sign magnitude DAC design, with FPGA based reclocking and custom digital filters, < 1 ps jitter clock generator, with 28 bit resolution so there is headroom, oversampling up to maybe 3.072 Mhz. Up to 24 bit / 384 Khz input from SPDIF, I2S and USB (via USB to I2S interface board), with isolation on the I2S interface. The board will be very flexible, with digital volume control and filter parameters that can be downloaded, a possibility is also to add digital crossover filters, but that will probably not be ready for first production lots, although the board is firmware upgradable over a simple serial connection.

The basis R-2R network has an output voltage of 1.4V RMS and output impedance of 625 ohm and can therefore drive a lot of things directly.... There is also onboard balanced output drivers that can drive high impedance (>= 300 ohm) headphones directly. The power supply is also onboard, just add a 5W toroid transformer.

It is a small mostly surface mount PCB, and yes, I have working prototypes, see below.... But it's not really something for home assembly, with the FPGA in BGA package and 600 pcs SMT parts.... So yes, if there is enough interest it will go into real production, with sales though two existing online shops in US and EU.

Performance of first prototypes using 0.05% resistors is better than expected, see 1 Khz -1 db and -60 db FFT plots. I believe that the sound quality will be the absolute best, better than any Delta Sigma DAC, in class with discrete DAC's from totaldac and msb technology. And for way way less cost :)

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Update on Apr 26, 2021:

dam1021 rev 7 is now released, see post# 10146, Reference DAC Module - Discrete R-2R Sign Magnitude 24 bit 384 Khz for details.

Update on Apr 29, 2018:

Vers. 1.19 firmware with with filters now available on Soekris Engineering ApS, R-2R Sign Magnitude Audio DAC
The dam1021 have been shipping as rev 5 for a while, but no major updates, just production related updates.

Update on Oct 14,2016:

The dam1021-12 and -05 are in stock again, still rev 4.

Update on May 27, 2016:

Vers. 1.06 firmware with DSD support now available on Soekris Engineering ApS, R-2R Sign Magnitude Audio DAC

Boards from next production run will be rev 4 and are now in stock, that batch will only be the 0.05% and 0.01%/0.02% resistor version, which will be the only two dam1021 versions available long term. The only other change from rev3 to rev4 is a change in the output buffers, the LME49710/LME49724 is replaced with OPA1602.

Pricing for board rev 4 is:

dam1021-12: USD 295 / EUR 266 (0.01%/0.02% resistor version, in stock)
dam1021-05: USD 195 / EUR 176 (0.05% resistor version, in stock)

Pricing for board rev 3 is:

dam1021-02: USD 265 / EUR 238 (0.02% resistor version, very low stock)
dam1021-05: USD 195 / EUR 176 (0.05% resistor version, sold out)


Shipping cost and any sales tax and/or other local taxes to be added.

They are available to order though two existing webshop:

404 Not Found for American and Asia markets.
Soekris Europe » for EU and European markets.

The main Soekris Engineering ApS (Denmark) website for product and technical information is:

Soekris Engineering ApS, R-2R Sign Magnitude Audio DAC Please don't email soekris.com or soekris.eu with technical questions....

See also post #901 http://www.diyaudio.com/forums/vend...-magnitude-24-bit-384-khz-91.html#post4197094 for a quick drawing with connections.
And post #1108 http://www.diyaudio.com/forums/vend...magnitude-24-bit-384-khz-111.html#post4202602 for SPDIF interface drawing.
And great info here https://hifiduino.wordpress.com/2015/01/30/building-soekris-r-2r-dac/
Post #1486 http://www.diyaudio.com/forums/vend...magnitude-24-bit-384-khz-149.html#post4216998 with filter tools.
Post #3276 http://www.diyaudio.com/forums/vend...magnitude-24-bit-384-khz-328.html#post4421518 Firmware revision 0.99 update
Post #3295 http://www.diyaudio.com/forums/vend...magnitude-24-bit-384-khz-330.html#post4421780 more info on 0.99
Post #3108 http://www.diyaudio.com/forums/vend...magnitude-24-bit-384-khz-311.html#post4392832 Official vref modification
Post #3362 http://www.diyaudio.com/forums/vend...magnitude-24-bit-384-khz-337.html#post4425324 More info on vref mods

Anybody can now order the dam1021 R-2R DAC board from the two webshops.
 

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rredline

Member
2004-10-06 4:40 pm
Very cool project, soekris!
Count me in for one 0.02% version. Otherwise a 0.05% version is fine for me, too.
A fully assembled board is prefered, otherwise I can also solder the SMT parts myself if you have pre-soldered the FPGA.

However, it seems the analog output portion can't be bypassed. Here in diyaudio many of us have our own flavor of analog stage (opamp, discrete, tube, output transformer, etc). It would be much better and certainly would garther more interest if you could add a jumper for us to use the onboard analog stage or our own analog stage. The real jewel of this design is the digital portion.
 
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jean-paul

diyAudio Moderator Emeritus
2002-09-20 7:20 am
Germany
Very nice design, it is quite compact and it is a joy to look at. I think it is the smallest discrete R2R DAC I have ever seen.

Some concern: with a resolution this high and "naked" resistors even some dust can disturb things isn't it ?
 
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Very impressed too ! Count me interested in a board (0.02%).
Please tell us more :)
Digital volume control will be ready for first batch ? how will it be handled (rotary encoder ? i2c ?)
Will firmware will be user updatable through usb ?
Will it be easy plug un upgraded power supply ? what kind of voltage in ?

Ony and I heard the TotalDac ... I guess that there will be lot of interest for your design !
 

esgigt

Member
2013-12-15 10:45 pm
Looks great, measurements too..

Can you provide some more specifications and comparative measurements as well, please?

A 0.05% resistor variant will stretch my financial capability too its limits, but might be worth consideration... a 0.02% version is way too expensive