I'm running some numbers of the Okto DAC8 PRO vs Motu UltraLite-mk5 for use with Purifi amps. Because the UltraLite-mk5 has a decent output signal voltage of 8.6v, it could in theory be used to feed the 1ET400A without pre-gain at 81.2% power (8.6v/10.59v), and also in theory, the net SINAD would be improved by 1.638dB over the Okto DAC8 PRO?...
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Motu UltraLite-mk5
Channel 1 SINAD: 0.000226%
Channel 2 SINAD: 0.000229%
Averaged SINAD: (0.000226% + 0.000229%)/2 = 0.0002275%
Purifi 1ET400A (No Pre-Gain)
Channel 1 SINAD: 0.000391%
Channel 2 SINAD: 0.000392%
Averaged SINAD: (0.000391% + 0.000392%)/2 = 0.0003915%
Combined SINAD: 0.0002275% + 0.0003915% = 0.000619 = -104.166dB
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Okto DAC8 PRO
Channel 1 SINAD: 0.000127%
Channel 2 SINAD: 0.000124%
Averaged SINAD: (0.000127% + 0.000124%)/2 = 0.0001255%
Purifi 1ET400A (With Pre-Gain)
Channel 1 SINAD: 0.000627%
Channel 2 SINAD: 0.000617%
Averaged SINAD: (0.000627% + 0.000617%)/2 = 0.000622%
Combined SINAD: 0.0001255% + 0.000622% = 0.0007475% = -102.528dB
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SNR would also have a net improvement but both combinations would already be beyond audible.
So, provided 81.2% power is sufficient, it's possible the UltraLite-mk5 may be a better match for the Purifi?
Could also go with a custom output voltage for the Okto DAC8 PRO, but everything I'm seeing indicates the noise penalty with custom output voltage is worse than pre-gain.
It would be ideal if Amir happens to test a custom input buffer that doesn't add as much noise, but so far they seem to test worse than stock Purifi buffers.
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Motu UltraLite-mk5
Channel 1 SINAD: 0.000226%
Channel 2 SINAD: 0.000229%
Averaged SINAD: (0.000226% + 0.000229%)/2 = 0.0002275%
Purifi 1ET400A (No Pre-Gain)
Channel 1 SINAD: 0.000391%
Channel 2 SINAD: 0.000392%
Averaged SINAD: (0.000391% + 0.000392%)/2 = 0.0003915%
Combined SINAD: 0.0002275% + 0.0003915% = 0.000619 = -104.166dB
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Okto DAC8 PRO
Channel 1 SINAD: 0.000127%
Channel 2 SINAD: 0.000124%
Averaged SINAD: (0.000127% + 0.000124%)/2 = 0.0001255%
Purifi 1ET400A (With Pre-Gain)
Channel 1 SINAD: 0.000627%
Channel 2 SINAD: 0.000617%
Averaged SINAD: (0.000627% + 0.000617%)/2 = 0.000622%
Combined SINAD: 0.0001255% + 0.000622% = 0.0007475% = -102.528dB
---------------------
SNR would also have a net improvement but both combinations would already be beyond audible.
So, provided 81.2% power is sufficient, it's possible the UltraLite-mk5 may be a better match for the Purifi?
Could also go with a custom output voltage for the Okto DAC8 PRO, but everything I'm seeing indicates the noise penalty with custom output voltage is worse than pre-gain.
It would be ideal if Amir happens to test a custom input buffer that doesn't add as much noise, but so far they seem to test worse than stock Purifi buffers.