It's Sunday and if you would like a cat nap, you may wish to have a read of this.
Technical Notes (3)
Cherry-Picking the Chipset: Going to the nth degree
Selecting the ideal chipset for a DAC is not an easy task for any audio manufacturer.
We are faced with two choices:
Option 1 - select a chipset that is well-known. Sonically very good, newer and with high customer awareness.
Option 2 - select a chipset that we think sounds most gratifying but customers are familiar with is a risk (may be more expensive, existent, etc).
For iFi, since the AMR days we have and will always continue to choose option 2. This somewhat goes against convention and is riskier but we truly believe the sonic results are worth it.
Back in 2000, when we started the development of the flagship CD-77 (USD11,400), we implemented extra steps to extract an additional ~30% more sonic performance from the legendary Philips TDA1541A DAC chipset. We brought to market undocumented features and it was and still is a fully-maxed out sonic performer.
The pictures below give you some idea of the length we went to.
1. Audiophile Level
2. Datasheet Implementation Level
3. Advanced Level
4. AMR/iFi Level
The TDA1541A has a worldwide following and is justified in our opinion for a whole host of reasons. We were not the only people to use this chipset but we researched down to the silicon-die level, to extract the most out of the chipset. Able to confirm to customers that the CD-77 not only has this remarkable chipset but it has been implemented with a dash of “factor X” – is the equivalent of getting a super car and then re-mapping the ECU and uprating the drivetrain. Neat.
Similarly, for the upcoming micro iDSD, the DAC we picked is a direct descendant of the renowned DSD chip, the DSD1700 (Just like in the PCM world, the Philips TDA1541A is legendary, especially in Japan).
The platform we chose for the micro iDSD (and the nano and rest of iDSD range) was the Burr-Brown. Why? Because it is one of the few chipsets that handles DSD and PCM without internal conversion. It keeps things unchanged and whether your music file is DSD or PCM, the whole chain remains as close to original.
In the iDSD micro we go to great length to provide that. Finding a readily available DAC Chip that treats both DSD and PCM fairly was a challenge. Manufacturers generally are quite mum about what goes on inside their chipsets, so often you have to actually test the part in detail to figure out what is really going on.
The DAC Chip we use in the iDSD nano offers a rather unusual way to handle things. It uses a 6-Bit Multi-bit DAC for the upper 6-Bits of PCM Audio and delivers the warmth and slam Burr Brown Multi-bit DAC’s are so famous for. Any bits below this are converted with a low-order 256 Speed Delta Sigma modulator (in effect DSD256) giving PCM playback the smoothness Delta Sigma DAC’s and DSD are famed for.
The Burr-Brown True Native DSD/PCM chipset – handling PCM and DSD natively
When playing DSD the same Delta Sigma Modulator is used as directly to convert the DSD Bitstream to analog. Of course, there is no digital filtering available for DSD and no digital volume control, so we have to add these features in the analogue domain, where they arguably belong.
Conclusion
So if you have a recording that was made in DSD, you can hear it natively on the micro iDSD.
So if you have a recording that was made in PCM, you can hear it natively on the micro iDSD.
To be cont’d. Part 4: DSD and PCM in more detail.
