I have finally managed to borrow a Soekris R2R sign magnitude dac to measure. Essentially I bought this dac for a speaker project. I was/am agnostic about the DAC technology, however there is no denying R2R measures more poorly than typical delta sigma. I was particularly interested in its FPGA filtering capabilities for crossover duties. Ultimately it wasnt the solution I wanted so the dac now resides with a friend who has put it in a box with very pleasant subjective results.
Note that I had a few issues with 50Hz and harmonics pick up. I will investigate later, so crap below 1kHz please ignore. I have measured this DAC under other circumstances previously and I know its not an issue with it.
http://www.soekris.dk/dam1021.html
This board is the 0.05% resistor version which will exhibit higher harmonic distortion (maybe 9dB or so) than the more expensive 0.01%/0.02% resistor version
The unit is driven I2S over HDMI cable from a Gustard U12.
FS output voltage is approx 4V rms over the balanced outputs, 2V single ended.
0db - As noted typically for r2r, high harmonic distortion. I probably wouldnt be worried if the levels were below -100dB but I think we are possibly in the territory of colouring the sound. I would say that the 0.01% resistor version probably gets below the level where I would be concerned.
-6dB
-60dB ignoring the 50 hz and harmonics which are a measurement issue, the noise floor is very low.
-90.31dB 16 bit
-90.31dB 24 bit - good waveform, seems to confirm low noise floor
12kHz Jitter - minor sidebands too low to be audible
IMD SMPTE - yikes messy! Imd is related to hd so this is no surprise.
White Noise + 19kHz FR and imaging. Now the stock firmware comes with 5 selectable filter types, however IIRC I loaded a set that were developed by a 3rd party. Thus board allows you to design your own filters. This one is fast roll off.
Im planning to produce a linearity chart a la Amirs latest reports
EDIT: Yer tis
I need to add some more data points but the DAC linearity is good to at least 17bits. Ill give the benefit of the doubt until I re-measure, but Ill say its good to the intermediate 18 bit point.
Reversed to be more consistent with Amirs graphs - I wonder how much this would improve with the 0.01% resistor version???
Note that I had a few issues with 50Hz and harmonics pick up. I will investigate later, so crap below 1kHz please ignore. I have measured this DAC under other circumstances previously and I know its not an issue with it.
http://www.soekris.dk/dam1021.html
This board is the 0.05% resistor version which will exhibit higher harmonic distortion (maybe 9dB or so) than the more expensive 0.01%/0.02% resistor version
The unit is driven I2S over HDMI cable from a Gustard U12.
FS output voltage is approx 4V rms over the balanced outputs, 2V single ended.
0db - As noted typically for r2r, high harmonic distortion. I probably wouldnt be worried if the levels were below -100dB but I think we are possibly in the territory of colouring the sound. I would say that the 0.01% resistor version probably gets below the level where I would be concerned.
-6dB
-60dB ignoring the 50 hz and harmonics which are a measurement issue, the noise floor is very low.
-90.31dB 16 bit
-90.31dB 24 bit - good waveform, seems to confirm low noise floor
12kHz Jitter - minor sidebands too low to be audible
IMD SMPTE - yikes messy! Imd is related to hd so this is no surprise.
White Noise + 19kHz FR and imaging. Now the stock firmware comes with 5 selectable filter types, however IIRC I loaded a set that were developed by a 3rd party. Thus board allows you to design your own filters. This one is fast roll off.
Im planning to produce a linearity chart a la Amirs latest reports
EDIT: Yer tis
I need to add some more data points but the DAC linearity is good to at least 17bits. Ill give the benefit of the doubt until I re-measure, but Ill say its good to the intermediate 18 bit point.
Reversed to be more consistent with Amirs graphs - I wonder how much this would improve with the 0.01% resistor version???
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