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The DAC1, DAC2 and DAC3 all have internal pads on the XLR outputs that should be used to set the output levels to the range that is required by the downstream device. This will allow direct interfacing to virtually any pro or consumer product.
The maximum output from all three devices is approximately the same. It is about 27.5 dBu. The calibrated level is +24 dBu at 0 dBFS prior to the pads. Consumer-grade XLR inputs will require the use of the 10 dB pads. Some power amplifiers will require the use of the 20 dB pads. The Benchmark AHB2 power amplifier is designed to accept full studio-level balanced signals (in low gain mode) and the pads should be set to 0 dB.
Turning down the volume control is not a substitute for selecting the proper pad setting!
Excessive use of the volume control skews the measurements by adding excessive noise. This in turn impacts the linearity measurements, which at their low end are really SNR measurements. The tests should be run at or near maximum volume (or the calibrated switch on the back of the DAC1 should be enabled).
At the calibrated volume setting (and any pad position) the DAC1 will deliver a SNR of 114 dB unweighted and 116 dB A-weighted. (19.4 bits unweighted)
In contrast:
At the calibrated volume setting, the DAC2 will deliver a SNR of 123 dB unweighted and 126 dB A-weighted. (20.9 bits unweighted)
At the calibrated volume setting, the DAC3 will deliver a SNR of 126 dB unweighted and 128 dB A-weighted. (21.4 bits unweighted)
The DAC2 and DAC3 are 9 to 12 dB quieter than the DAC1. This increases the effective bit depth by up to 3 bits.
The DAC1 was introduced in 2002, but was definitely ahead of its time. In 17 years we have gained about 3 bits in effective performance. THD has also been reduced. But, the biggest sonic improvement may be the elimination of the clipping intersample peaks that exceed 0 dB FS. The DAC2 and DAC3 have 3 dB of headroom above 0 dB FS. See:
https://benchmarkmedia.com/blogs/application_notes/tagged/inter-sample-overs
for a series of papers on this topic.
There are still thousands of DAC1 converters in daily use in recording studios around the world. Many others have upgraded to the DAC2 or DAC3.
Loving the inputs john, you guys are doing great work for our community and should add on to it by sending dac3 and hpa4 to amir for testing