Someone pointed me to a discussion at
@amirm's site where the Benchmark DAC3 was measured. Among the measurements posted was this one (Fig.1):
Fig.1 @amirm's plot of the Benchmark DAC3 jitter versus the RME ADI-2 DAC.
Later in the thread, John Siau from Benchmark said this (regarding the measurements posted in that thread):
John Siau at AudioScienceReview said:
Amirm,
The sidebands shown in the above test are due to the use of ASIO4All. This "ASIO" driver is not a true ASIO driver and is not a Benchmark product nor is it recommend by Benchmark. Unlike a true ASIO driver, ASIO4ALL does not bypass the operating system's audio system. Software-based sample rate conversion is the cause of the sidebands. They are not being produced by the DAC3.
Benchmark provides a downloadable driver, but this Benchmark driver is not needed with Apple operating systems nor is it needed with newer versions of Windows 10.
The driver is available here:
https://benchmarkmedia.com/pages/drivers
Unfortunately the ASIO4ALL driver has corrupted many of the measurements in this review. The tests should be rerun without using ASIO4ALL.
ADDED 2018-07-18 0949 EDT: I noticed that
@amirm also got similar sidebands when using the DAC3's optical digital input, which should have zero to do with any USB driver issues. Here's what he posted:
@amirm at AudioScienceReview said:
Here is the comparison of unbalanced output with USB vs Toslink. Sadly the same spikes remain:
This was his measurement using the optical input (48 khz):
Fig.1A @amirm's plot of the Benchmark DAC3 jitter, using both USB and optical digital inputs (analog output was unbalaned).
As you can see,
@amirm is getting similar jitter sidebands from both inputs. You can compare this measurement (Fig.1A above) to my measurement (Fig.12 below).
@amirm posted a couple of responses affirming his measurements are fine, concluding
"So until John comes back with different measurements, there is no conflict to resolve."
I decided to do some jitter measurements on the Benchmark DAC3. (Benchmark Media is not a Head-Fi sponsor or advertiser.)
I started with the J-test stimulus via USB. I used the Benchmark ASIO driver with the analyzer:
This is the FFT spectrum plot from the Benchmark DAC3, using the J-test stimulus, 48 kHz, USB digital input, unbalanced analog output (Fig.2 below):
Fig.2 Benchmark DAC3 J-test (jitter), 48 kHz, USB digital input, unbalanced analog output.
As you can see, the measurement above does not show the sidebands that
@amirm's measurement is showing.
I also decided to run the
APx J-Test (Jitter) Measurement Utility downloadable at Audio Precision's website. This test (and its accompanying project file) is pre-configured by Audio Precision. You hook up the DAC (using its various inputs/outputs) and then simply choose which input/output and sample rate you want to test with, and then run the test. (The utility chooses the appropriate J-test stimulus based on the chosen sample rate.)
Because the APx J-Test (Jitter) Measurement Utility does not support USB, I used the DAC3's unbalanced and optical digital inputs, and both unbalanced and balanced analog outputs.
Here are the results:
Fig.3 Benchmark DAC3 J-test (jitter), 44.1 kHz, unbalanced digital input, unbalanced analog output. The measured jitter result was 36.8 ps.
Fig.4 Fig.2 Benchmark DAC3 J-test (jitter), 48 kHz, unbalanced digital input, unbalanced analog output. The measured jitter result was 32.7 ps.
Fig.5 Benchmark DAC3 J-test (jitter), 96 kHz, unbalanced digital input, unbalanced analog output. The measured jitter result was 23.4 ps.
Fig.6 Benchmark DAC3 J-test (jitter), 192 kHz, unbalanced digital input, unbalanced analog output. The measured jitter result was 17.0 ps.
Fig.7 Benchmark DAC3 J-test (jitter), 44.1 kHz, unbalanced digital input, balanced analog output. The measured jitter result was 27.9 ps.
Fig.8 Benchmark DAC3 J-test (jitter), 48 kHz, unbalanced digital input, balanced analog output. The measured jitter result was 25.6 ps.
Fig.9 Benchmark DAC3 J-test (jitter), 96 kHz, unbalanced digital input, balanced analog output. The measured jitter result was 18.6 ps.
Fig.10 Benchmark DAC3 J-test (jitter), 192 kHz, unbalanced digital input, balanced analog output. The measured jitter result was 16.4 ps.
Fig.11 Benchmark DAC3 J-test (jitter), 44.1 kHz, optical digital input, unbalanced analog output. The measured jitter result was 36.0 ps.
Fig.12 Benchmark DAC3 J-test (jitter), 48 kHz, optical digital input, unbalanced analog output. The measured jitter result was 32.4 ps.
Fig.13 Benchmark DAC3 J-test (jitter), 96 kHz, optical digital input, unbalanced analog output. The measured jitter result was 24.0 ps.
Fig.14 Benchmark DAC3 J-test (jitter), 44.1 kHz, optical digital input, balanced analog output. The measured jitter result was 34.8 ps.
Fig.14 Benchmark DAC3 J-test (jitter), 48 kHz, optical digital input, balanced analog output. The measured jitter result was 33.4 ps.
Fig.15 Benchmark DAC3 J-test (jitter), 96 kHz, optical digital input, balanced analog output. The measured jitter result was 21.3 ps.
Because the Benchmark DAC3's optical digital input is rated to 96 khz, I did not include 192 kHz for optical digital input.
I haven't seen Benchmark's measurements of the DAC3. However, in terms of the jitter measurement, it appears
@amirm and I are getting different results.
NOTE: I know, because this is a Benchmark DAC3, this is a bit off-topic with respect to the title of this thread. That said, I think it's relevant in the context of the current discussion. I'll post these and other DAC3 measurements sometime after I get back from CanJam London in an appropriate thread about the Benchmark DAC3.
EDIT 2018-07-18 0949 EDT: I added the
@amirm's optical (toslink) jitter plot above (Fig.1A). You can compare that to my plot in Fig.12 above.
