Review and Measurements of Soekris dac1421 Multibit DAC

[DuxServit]

I can't really comment on Amir's measurement, and don't really care that much. I of course base my specifications on my own measurements and are very satisfied with the performance of my DACs.

As an audio consumer I care about Amir’s measurements and pay close attention to the response from a vendor to these measurements.

A great example was John Siau in the Benchmark DAC3 thread. He responded very well to the questions surrounding Amir’s measurements of the DAC, and showed his deep engineering/design skills. I very much respect that. As such, Benchmark is on my “good vendors list”.

 

[soekris]

As an audio consumer I care about Amir’s measurements and pay close attention to the response from a vendor to these measurements.

A great example was John Siau in the Benchmark DAC3 thread. He responded very well to the questions surrounding Amir’s measurements of the DAC, and showed his deep engineering/design skills. I very much respect that. As such, Benchmark is on my “good vendors list”.

My comment was directed to the power supply noise.... I don't get anything in my measurement setup, Amir seems to get some.... There can be plenty of reasons why but as I don't know Amir's exact setup I can't really say much about it, only that my specifications of course are based on my own measurements.

 

[soekris]

Just to show how a stock dac1421 FFT's look like here, just done, no cheating or anything. Measuring Equipment not that fancy but works just fine.

 

[Blumlein 88]

Just to show how a stock dac1421 FFT's look like here, just done, no cheating or anything. Measuring Equipment not that fancy but works just fine.

View attachment 14607View attachment 14608

Thank you for doing this. Your results don't look much different in general than Amir's except for the power supply noise.

Just eyeballing it lets say your noise floor is around - 145 db for that 20 khz band. The FFT gain for the 128k FFT would be 48 db. So your noise floor over that 20 khz would be -97 db which would be the dynamic range. Which isn't bad. I notice you are using a 96 khz sample rate. If arta uses the bins of the FFT over that 48 khz bandwidth then you would pick another 3 db from my eyeball estimate. Putting the dynamic range at 100 db. Which for a multi-bit is good.

 

[gvl]

Atomicbob got some data from the dac1541 which is the TOTL Soekris balanced offering, he got 112dB of dynamic range from SE outputs, mains spikes are much lower than here.

 

[rebbiputzmaker]

Your results don't look much different in general than Amir's except for the power supply noise.

This is evident across a number of reviews. Possibly something in the setup or environment, as previously suggested.

 

[Rthomas]

Let me do a couple of comments:

On my test bed I have zero power line harmonics, can't explain my Amir get so much (relatively), although its below the human hearing limits...

The output buffer is a zero feedback design so it add a little 2nd and 3rd harmonics at high levels, lower the level a couple of dB and they don't dominate anymore.... Still, they're way below what you can hear.

The slight different THD and Intermodulation results between the channels will mostly be present due to the slightly varying values of the resistors, there are 200 pcs of very precise ones.... They have a max specification but are typically significant better than the spec.

One reason I prioritize performance at low levels is the perfect digital volume control, my DACs are designed to be connected directly to a power amplifier or active monitors, or to headphones using the builtin headphone amplifier.

If you want to see a Sine down to -120 dB, one of the other forums had the balanced version, the dac1541, under test... The dac1421 is basically the unbalanced version of the dac1541.

And thanks to Amir for taking his time, results are better than what you could have feared here

This is the way a manufacturer should conduct himself. Hats off to Soren for sending a unit for testing. I'm much more likely to consider Soekris products going forward.

 

[miero]

On my test bed I have zero power line harmonics, can't explain my Amir get so much (relatively), although its below the human hearing limits...

Does the dac1421 have a galvanic isolation on USB input? If not then a ground loop can cause those issues. For example if Amir has connected it to PC with an ATX power supply. But I'd expect that AP has galvanically isolated audio inputs, so there could be another problem. For example two DACs connected to AP at once and each connected to same PC?

 

[soekris]

The dac1421 are fully isolated on all digital inputs, incl. the USB input, like all DACs should be....

 

[miero]

In that case... is it possible that the power line harmonics arise if two DACs connected are into AP?
Notice, there are both balanced & unbalanced inputs connected on the AP:

 

[amirm]

In that case... is it possible that the power line harmonics arise if two DACs connected are into AP?
Notice, there are both balanced & unbalanced inputs connected on the AP:

Quick note on these pictures. I "stage" the units for the pictures. They are not the actual test setups (although sometimes they can be). Often I take the pictures days after the measurements as that is the last thing I do.

So please don't read the tea leaves from them.

 

[gvl]

Perhaps grab a quick 1kHz spectrum over optical to eliminate a possibility of mains pollution over USB?

 

[amirm]

Perhaps grab a quick 1kHz spectrum over optical to eliminate a possibility of mains pollution over USB?

Sure, will do later and post.

 

[garbulky]

@amirm what do you mean the Ygdrassil clips at -20db on the IMD test? Could you elaborate?I think I saw it where you were doing 0db 1 khz sine wave measurements with it and the wave showed no clipping?

 

[miero]

OK. Also check that DAC, AP, computer, monitor, etc. are connected into the same power outlet. I observed issues with measurement using sound card when that was not true.

Another source of power harmonics could be induction into cables from nearby power transformers/adapters, even into balanced lines if they are near to them.

If none of that help, you can try to measure just a single channel.

 

[dir]

I also have a Stax, but I never try to judge line out of DAC's with my Stax. Even best headphones always play for one ear only. When you come to the mastering studio, you'll see only headphones which are used to searching for defects in the recording. That's all.

Why you didn't use speakers for the listening test?

 

[amirm]

Why you didn't use speakers for the listening test?

For detection of small impairments, headphones are by far superior to speakers. They block ambient noise and let you listen to any level you want without disturbing the neighbors. And because each channel plays separately and without room reflection, perceptual masking is heavily reduced, allowing distortions to be better detected.

It is for above reasons that they are the standard in audio research and development community.

 

[Bhargu]

Just to show how a stock dac1421 FFT's look like here, just done, no cheating or anything. Measuring Equipment not that fancy but works just fine.

View attachment 14607View attachment 14608

Do you have graphs of something like -6 or -10 dBFS? Also, do you think it is possible to design a DIY unit with your dam1021 or dam1121 (.01% resistors) in unbalanced mode with similar measurements. I am looking for a new long term hobby project

PS: from where I am, acquisition of the components itself will take a long time, so most DIY projects are long term projects , but that gives me a lot more time to work on my designs.

 

[dir]

They block ambient noise and let you listen to any level you want without disturbing the neighbors

actually Stax has open acoustic design. In other apspects i agree with Ken Rockwell who was told about 007's: "... it sounds great even if the microphones aren't well placed".

 

[soekris]

Do you have graphs of something like -6 or -10 dBFS? Also, do you think it is possible to design a DIY unit with your dam1021 or dam1121 (.01% resistors) in unbalanced mode with similar measurements. I am looking for a new long term hobby project

PS: from where I am, acquisition of the components itself will take a long time, so most DIY projects are long term projects , but that gives me a lot more time to work on my designs.

Sorry, didn't take more graphs, but it wouldn't matter. It's a Sign Magnitude DAC, so the harmonics goes down with the signal, varies a little depending on which resistors are active. So on the -60 dB graph the harmonics are still there, just down 90 dB so they're buried in the noise.... In contrary to a regular R-2R DAC where the distortion is relative to the full level.

All my dams and dacs basically use the same core R-2R networks and will give the same results, you can see the same FFT's for the dam1021 prototype using 0.05% resistors on the DIY thread front page. More precise parts give a little better results, also better long term, but I have seen a few boards using 0.05 % resistors with THD around 0.004 % in my manufacturing test.... Balanced will improve noise and THD with about 3 dB.

And btw, headphones are very good for evaluating DACs, I use a Sennheiser HD800S myself for testing.