The three key parameters that we looked at for evaluating different DACs were the signal-to-noise ratio (SNR), dynamic range (DR) and total harmonic distortion (THD+N). Based on the three main criteria, we decided to limit our final choice to a DAC with a SNR and DR of at least 120 dB, and a THD+N of at least -100 dB. Here’s a list of DACs that meet our specifications:
| Manufacturer | Part # | SNR | DR (dB) | THD+N (dB) |
| AKM Semiconductor | 120 | 120 | -100 | |
| Cirrus Logic | 120 | 120 | -107 | |
| TI/Burr Brown | 132 | 129 | -108 | |
| Analog Devices | 120 | 120 | -110 |
We've also tried to contact a representative of these highly respected manufacturers, Texas Instruments/Burr Brown, Cirrus Logic, Analog Devices, and AKM Semiconductor, for advice. So far the only ones to respond have been Richard Kulavik, Manager of Marketing and Applications at AKM and John Melanson of Cirrus Logic. TI/Burr Brown, and Analog Devices have yet to respond. Could it be that Amplio is just too small and insignificant? Maybe -- that's one of the challenges and frustrations of being a start-up.
have a look at the wolfson codecs like the wm8770 as used by the terratec aureon 7.1 firewire soundcard. The wm8770 comes with an integrated analog volume control.
ReplyDeleteThanks for the recommendation. I have looked at the Wolfson DACs, but they didn't make our final cut. The one you are recommending is actually a combination DAC and ADC, which is typically called a CODEC (for code/decode). The audio performance of the Wolfson WM8770 is also not at the level of those on our list. The WM8770 SNR is 106dB compared to 120dB and -96dB THD+N vs. -100 to -110dB for the others. We also prefer to use multiple stereo DACs instead of a single multichannel DAC. This will also give us better performance. Wolfson also sells the WM8740, which is their flagship or highest performing DAC. It still doesn't quite measure up to the performance of their competition. Wolfson does have a nice analog volume control chip, which is also much better than the integrated volume control in the WM8770. Our goal is to provide DAC performance on par with most of the relatively expensive dedicated stand alone DACs, so we need to spec fairly high end components.
ReplyDeleteWhat about Wolfson WM8728 ?
ReplyDeleteDiego -
ReplyDeleteThe Wolfson WM8728 doesn't meet our spec either. It has a dynamic range of only 106 dB and a THD of -97 dB (0.0014125%). Even though the distortion measurement is pretty good, it isn't as good as any of the others, including the TI/Burr Brown chips, which are -108 dB (0.0004%). We also considered the Wolfson WM8740, but again it didn't measure up. The WM8741 might be worth checking out as well. It has very good dynamic range (128 dB), but only good THD (-100 dB or 0.001%). Still not as impressive as the TI/Burr Brown PCM1792.