General HIFI > Other DACs
Reference DAC Module - Discrete R-2R Sign Magnitude 24 bit 384 Khz
Tuyen:
http://www.diyaudio.com/forums/digital-line-level/259488-reference-dac-module-discrete-r-2r-sign-magnitude-24-bit-384-khz.html
"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 optical 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 1.2 Kohm 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 :-) My plans are for two board versions, one with 0.05% resistors for maybe USD 170, and one with 0.02% resistors for maybe USD 240, one with 0.01% resistors is also a possibility, but it might be to expensive....
"
Tuyen:
Thoughts? I'm interested in putting my name down for 1 board. I've always liked the idea of the TotalDAC, but just too costly for my taste. This seems like a cheaper option but based on similar concept. Could be good!?
kajak12:
go for it tuyen
Tuyen:
Indeed I will! Noticed klacto has posted his interested for one too. :)
Seems like DSD will be possible too through the programmable FPGA according to the designer.
"Hi Soekris
i have some question that need to ask . The r2r dac is possible to accept a DSD format file ?"
"At some point, should be easy to convert from DSD to PCM in the FPGA..."
ozmillsy:
--- Quote from: Tuyen on July 23, 2014, 12:04:01 PM ---Seems like DSD will be possible too through the programmable FPGA according to the designer.
"Hi Soekris
i have some question that need to ask . The r2r dac is possible to accept a DSD format file ?"
"At some point, should be easy to convert from DSD to PCM in the FPGA..."
--- End quote ---
Conversions are not ideal. May as well just convert in software.
There are 2 issues with *any* kind of conversion (hardware or software);
1) volumes of the recorded DSD material
2) high frequency filtering
The reason why tools like Audiogate or Saracon are a better option, than an "on the fly" converter (software or hardware based), is you can check the headroom and re-run the conversion to optimise the volume. There are also better dithering and filtering options. These things can and do make a difference, for different types of music. When it is done in hardware, it is generally 1 setting for all, and the type of dithering will be pretty basic.
I like the idea of a purpose built DSD dac, which is optimised purely for DSD playback. Such a device could be quite affordable, if done well. There is no problem having multiple front ends, from my perspective. :)
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