This is a Review and Measurements of Soekris dac1421 Multibit DAC. It is on a kind loan from the designer and forum member, Søren Kristensen. In case you are not familiar with this class of DACs, instead of using an off-the-shelf dac chip, this unit uses a custom implemented DAC using a series of resistors and a custom FPGA (digital logic) controlling them. Technical term for their approach is "Sign Magnitude Discrete R-2R." The dac1421 is unbalanced only and has a retail price of around $1,000 (sold in Euros however).
The unit itself has a simple "design language" and fits in the class as far as fit and finish. Here you see it below SMSL SU-8 which I also tested against it:
There is a useful clipping indicator as the volume control can go over reference. For this review, I did not measure the headphone amplifier. Will do that in a future installment.
There is interest in comparing the dac1421 against the Schiit Yggdrasil. For a short period I had both in hand and the measurements below reflect that. A request was also made to compare it to SMSL SU-8 which retails for $250 from what I recall. See its review here: https://www.audiosciencereview.com/...eview-and-measurements-of-smsl-su-8-dac.3778/. And Yggdrasil DAC: https://audiosciencereview.com/foru...measurements-of-schiit-yggdrasil-v2-dac.3607/
I imagine you all are anxious how it did on the bench so let's get into that.
Measurements
All tests are done using USB input and naturally using unbalanced output since that is all the dac1421 has.
Let's start as usual with our dashboard view of 1 kHz, full amplitude signal at 44.1 kHz:
THD+N is 0.006% in one channel at 0.005% in the other. These match what Søren measured prior to sending the unit to me. Both are better than the advertised 0.008% spec. Søren says this is just a unit out of the assembly pipeline as otherwise he would have sent me one that had matching distortion. I believe him.
The dac1421 has an internal switching power supply fed by a two-pronged cord. The case as such is "floating." Teardown will come in a future article. The issue and one that is not unique to the dac1421 is that its case can start to float up causing ground differentials. This shows up in the spike that you see at 60 Hz. There is a 50 ohm resistor between the chassis and signal ground. When I bypassed this with a jumper, it made a significant reduction in mains leakage. Søren says he is not seeing any of this in his testing. Unfortunately the vagaries of unbalanced audio interconnects and grounding in consumer audio is that it is perfectly possible for the two scenarios to exist. Søren is considering lowering the value of that resistor.
The power supply harmonics travel fair bit in frequencies if we look at the FFT spectrum in top right (they get jammed together more and more). Beside that we have a regular train of harmonic distortion. We can see this better if we zoom in and overlay the results on top of Schiit Yggdrasil:
Schiit Yggdrasil has large number of inharmonic spikes going the full audio bandwidth. Soekris dac1421 doesn't have much of this but then has higher harmonic distortion so overall, it winds up with similar SINAD numbers (difference between signal and sum of the distortion and noise products):
Looking at intermodulation distortion we get a mixed picture:
At the highest amplitudes the dac1421 does better. At the lowest, it is noise dominated and similar to Yggdrasil. IN the middle range it loses to Yggdrasil by fair bit. Had one of the channels not been higher than the other when it came to distortion, it would have ranked better. As it is, I will give the nod to Yggdrasil in this test.
Looking at more classical THD+N distortion and noise versus frequency, we have:
The Yggdrasil oddly has rising low frequency distortion and noise as I have reported (NB: this is unbalanced -- balanced output doesn't have this this problem). In that regard, we have yet another mixed performance and no winners.
Of course our classically designed sigma-delta converter in SMSL SU-8 way outperforms both of these DACs, providing much better signal transparency.
As an interesting aside, the SMSL has "different color" settings and on Tube 1, it almost matched that of Soekris dac1421!
Let's look at our jitter and noise at 44.1 kHz sampling:
The Schiit Yggdrasil has a couple of sidebands on each side of our main tone. They are not equal in amplitude so they are likely not jitter but unwanted regardless. The dac1421 doesn't have but the spectrum shows the power supply mains leakage. All of these are at -120 dB and lower so absolutely inaudible.
Finally, everyone's favorite measurement, linearity:
The Soekris dac1421 produces near ideal response with variation of just 0.5 dB at -120 dBFS (20 bits). The limit of measurement is about 0.2 dB so this is almost as good as it gets. Of course, it is worlds better than Schiit Yggdrasil DAC.
Listening Tests
Søren asked me, well pleaded with me
, to also do some listening tests. Regular readers of the forum know that I don't usually perform listening test comparisons on DACs since differences are too small to show up in my casual AB testing. But since he asked, I went ahead and did that against SMSL SU-8 since the Yggdrasil was returned to its owner.
I used Roon to group both DACs and connected their outputs to the two inputs on my Stax SRM-007t headphone amplifier, driving the Omega pro headphones. I then played a series of reference quality tracks from instrumental to classical, jazz, blues and everything else I could. Indeed I am listening to them as I am typing this. The output is simple: there is no audible difference. There just isn't to my ears.
If I could capture the outputs and then perform ABX testing I may be able to tell them apart. But in controlled AB testing, there is no difference that I can detect. Everything sounds as good as the source material allows. Excellent tracks sound superb through both.
Conclusions
Up until now, I had only tested multibit DACs from Schiit. Unfortunately all seem to have glaring design flaws, especially when it came to linearity. Thankfully, there is no such problem with Soekris dac1421. It has excellent linearity, and near absence of inharmonic distortion that plagues Schiit multibit DACs. This tells me the design is thought through and verified.
Alas, coaxing discrete resistors to be as precise as the fewer precision ones inside monolithic DACs is hard. So when it comes to distortion, the traditional sigma-delta DACs produce far better performance.
In my limited listening tests I cannot detect any "multibit magic." If you think you do, or want it regardless, I can recommend the Soekris dac1421.
-------------
As always, questions, comments, recommendations, etc. are welcome.
If you like this review, please consider donating funds for these types of hardware purchases using Patreon (https://www.patreon.com/audiosciencereview), or upgrading your membership here though Paypal (https://audiosciencereview.com/foru...eview-and-measurements.2164/page-3#post-59054).
The unit itself has a simple "design language" and fits in the class as far as fit and finish. Here you see it below SMSL SU-8 which I also tested against it:
There is a useful clipping indicator as the volume control can go over reference. For this review, I did not measure the headphone amplifier. Will do that in a future installment.
There is interest in comparing the dac1421 against the Schiit Yggdrasil. For a short period I had both in hand and the measurements below reflect that. A request was also made to compare it to SMSL SU-8 which retails for $250 from what I recall. See its review here: https://www.audiosciencereview.com/...eview-and-measurements-of-smsl-su-8-dac.3778/. And Yggdrasil DAC: https://audiosciencereview.com/foru...measurements-of-schiit-yggdrasil-v2-dac.3607/
I imagine you all are anxious how it did on the bench so let's get into that.
Measurements
All tests are done using USB input and naturally using unbalanced output since that is all the dac1421 has.
Let's start as usual with our dashboard view of 1 kHz, full amplitude signal at 44.1 kHz:
THD+N is 0.006% in one channel at 0.005% in the other. These match what Søren measured prior to sending the unit to me. Both are better than the advertised 0.008% spec. Søren says this is just a unit out of the assembly pipeline as otherwise he would have sent me one that had matching distortion. I believe him.
The dac1421 has an internal switching power supply fed by a two-pronged cord. The case as such is "floating." Teardown will come in a future article. The issue and one that is not unique to the dac1421 is that its case can start to float up causing ground differentials. This shows up in the spike that you see at 60 Hz. There is a 50 ohm resistor between the chassis and signal ground. When I bypassed this with a jumper, it made a significant reduction in mains leakage. Søren says he is not seeing any of this in his testing. Unfortunately the vagaries of unbalanced audio interconnects and grounding in consumer audio is that it is perfectly possible for the two scenarios to exist. Søren is considering lowering the value of that resistor.
The power supply harmonics travel fair bit in frequencies if we look at the FFT spectrum in top right (they get jammed together more and more). Beside that we have a regular train of harmonic distortion. We can see this better if we zoom in and overlay the results on top of Schiit Yggdrasil:
Schiit Yggdrasil has large number of inharmonic spikes going the full audio bandwidth. Soekris dac1421 doesn't have much of this but then has higher harmonic distortion so overall, it winds up with similar SINAD numbers (difference between signal and sum of the distortion and noise products):
Looking at intermodulation distortion we get a mixed picture:
At the highest amplitudes the dac1421 does better. At the lowest, it is noise dominated and similar to Yggdrasil. IN the middle range it loses to Yggdrasil by fair bit. Had one of the channels not been higher than the other when it came to distortion, it would have ranked better. As it is, I will give the nod to Yggdrasil in this test.
Looking at more classical THD+N distortion and noise versus frequency, we have:
The Yggdrasil oddly has rising low frequency distortion and noise as I have reported (NB: this is unbalanced -- balanced output doesn't have this this problem). In that regard, we have yet another mixed performance and no winners.
Of course our classically designed sigma-delta converter in SMSL SU-8 way outperforms both of these DACs, providing much better signal transparency.
As an interesting aside, the SMSL has "different color" settings and on Tube 1, it almost matched that of Soekris dac1421!
Let's look at our jitter and noise at 44.1 kHz sampling:
The Schiit Yggdrasil has a couple of sidebands on each side of our main tone. They are not equal in amplitude so they are likely not jitter but unwanted regardless. The dac1421 doesn't have but the spectrum shows the power supply mains leakage. All of these are at -120 dB and lower so absolutely inaudible.
Finally, everyone's favorite measurement, linearity:
The Soekris dac1421 produces near ideal response with variation of just 0.5 dB at -120 dBFS (20 bits). The limit of measurement is about 0.2 dB so this is almost as good as it gets. Of course, it is worlds better than Schiit Yggdrasil DAC.
Listening Tests
Søren asked me, well pleaded with me
, to also do some listening tests. Regular readers of the forum know that I don't usually perform listening test comparisons on DACs since differences are too small to show up in my casual AB testing. But since he asked, I went ahead and did that against SMSL SU-8 since the Yggdrasil was returned to its owner.I used Roon to group both DACs and connected their outputs to the two inputs on my Stax SRM-007t headphone amplifier, driving the Omega pro headphones. I then played a series of reference quality tracks from instrumental to classical, jazz, blues and everything else I could. Indeed I am listening to them as I am typing this. The output is simple: there is no audible difference. There just isn't to my ears.
If I could capture the outputs and then perform ABX testing I may be able to tell them apart. But in controlled AB testing, there is no difference that I can detect. Everything sounds as good as the source material allows. Excellent tracks sound superb through both.
Conclusions
Up until now, I had only tested multibit DACs from Schiit. Unfortunately all seem to have glaring design flaws, especially when it came to linearity. Thankfully, there is no such problem with Soekris dac1421. It has excellent linearity, and near absence of inharmonic distortion that plagues Schiit multibit DACs. This tells me the design is thought through and verified.
Alas, coaxing discrete resistors to be as precise as the fewer precision ones inside monolithic DACs is hard. So when it comes to distortion, the traditional sigma-delta DACs produce far better performance.
In my limited listening tests I cannot detect any "multibit magic." If you think you do, or want it regardless, I can recommend the Soekris dac1421.
-------------
As always, questions, comments, recommendations, etc. are welcome.
If you like this review, please consider donating funds for these types of hardware purchases using Patreon (https://www.patreon.com/audiosciencereview), or upgrading your membership here though Paypal (https://audiosciencereview.com/foru...eview-and-measurements.2164/page-3#post-59054).
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