Schiit Loki - affordable DSD DAC
by, 11-19-2013 at 05:52 PM (3321 Views)
Schiit Loki is an interesting product at very affordable price tag. At this price point, there's not much competition on desktop DAC market and even less (none?) on DSD DAC market.
Loki is based on Asahi Kasei Microdevices (AKM) AK4396 DAC chip and asynchronous UAC2 USB interface is implemented using C-Media CM6631A chip. The AK4396 has been one of the most popular DAC chips in pro-audio converters. Loki is USB-powered. Analog reconstruction filter is optimized for DSD use. Since COTS USB-chip is used the device announces to support all standard PCM rates from 44100 to 192000. But in practice only 176.4 kHz rate is supposed to be used for 2.8 MHz DSD64. Attempt to switch to 192 kHz rate for 3.0 MHz DSD64 results in stuck output due to lack of clock (?). Limiting the advertised rates to the functional ones could solve some possible usability issues...
For listening I decided to partner Loki with Schiit Magni headphone amplifier, very affordable too and built around discrete circuit. Both devices use same case, so it's a neat looking stacked couple. Magni has external transformer wall wart with AC output, so other than transformer, the actual PSU is built-in.
All following measurements are done with Loki connected to my Linux desktop PC.
First measurement is my standard 0-20 kHz sweep with wide band view. We can see that the AKM chip uses a comb filter for reducing DSD noise. This is then further reduced by the following filter stages.
Next is output of 1 kHz tone. We can see that all harmonic distortion products are below -100 dB.
Since dynamic range seemed to be actually pretty good I wanted to see how -60 dBFS and -120 dBFS 1 kHz tones are reproduced respectively.
Next measurement was the standard 19+20 kHz IMD test. Here 1 kHz IMD product is also below -100 dB. Higher order products around the fundamentals are a bit higher, but still relatively low.
And last test was jitter test with 24-bit test pattern. We can see that there's one pair of jitter sidebands and some amount of main lobe widening.
Jitter is weakest point of Loki, it needs clean USB power to perform best. I tested it with two other computers with different SMPS and the jitter figures got about 10 dB worse. All the sidebands seem to be heavily influenced by power feed and only the mainlobe widening would seem to be property of it's internal clock.
Overall, I am impressed by how well this DSD DAC performed for it's price! Especially the audio band noise level was lower than in couple of 3x more expensive delta-sigma PCM DACs.