All Things Digital Audio

I've collected quite a few DACs over the last few years. Each has a slightly different sound, but I was curious to know if the differences were great enough to measure with equipment I have on-hand. I use my Focusrite Scarlett 2i2 audio interface for acoustic measurements, so I decided to give it a try. If you're the sort of person who loves looking at plots, you may enjoy this write-up of my findings:

What Makes DACs Sound Different?

If you're a fan of Room EQ Wizard, you're welcome to download my sweep files to analyze for yourself here:

https://www.dsnyder.ws-e.com/ts/sweeps.zip (300 MB)

I'm hoping that this inspires you to find out what you can learn by measuring your own equipment. Let me know if you have questions. Please share your results. :)

-- David

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Thanks David, This is very interesting. Especially the poor results on the iFi micro iDSD Signature NOS filter. For more distortion as the frequency sweep goes above 11kHz it has to be because of the steep filter (analog?) being introduced. As the output level goes down above 11kHz the error (distortion) goes up as the noise becomes a greater part of the signal. I’m not sure that’s actually audible as distortion. A near complete roll off above 11kHz has got to be audible even for old people like me as a dulling of the sound! And not using the steep 11kHz filter would create a large number of high level in band distortion products which probably would be audible. Even if a person’s hearing doesn’t extend that high, high levels of high frequency signals can cause problems for some amplifiers. This is why we see amplifier frequency response tests typically done at 1 watt. Back in the 60’s and 70’s some reviewers would do a power bandwidth test where they would sweep from dc to when the amplifier output rolled off. Every now and then an amplifier would go into oscillation, shut down from protection circuits, or just plain fail. Steve Gooding

Hi Steve,

Thanks for having a look. Yes, it is pretty interesting. As far as I can tell, the DAC measurements over at ASR only consider a single sampling frequency, but all of my DACs behave slightly differently at different sampling rates. I remember reading years ago how Benchmark Media Systems decided on an internal upsampling rate of 110 kHz for their DAC: https://benchmarkmedia.com/blogs/application_notes/13127453-asynchronous-upsampling-to-110-khz

Based on this research, it's probably safe to assume that there is a sampling rate that is optimal for any given DAC. This also the idea behind software like HQPlayer, which is configured to use high quality algorithms and filters to optimize the digital signal before feeding it to the DAC.

With most modern DACs, it does not take much upsampling to get into the optimal range, and it's easy to over-do it (with significant negative consequences). I see a lot of folks upsampling to DSD256 or DSD512; however, I've yet to find a DAC that benefits from these high rates, and this adds significant (if not crushing) load to the server, endpoints, and network. Most DACs seem to perform optimally at DSD128 or 192 kHz PCM. Enjoy.

-- David