Hello ladies and gents ,
as many of you heard , we have been working on a new DAC .
We asked ourselves how its possible to bring true HIFI sound to the RPI. We wanted a price point thats accessible to everyone while blowing away any DAC made by anyone under 1000$ .
Lets see if we succeeded
- DAC IC
First we chose a very capable IC , the ess9038q2m . This IC has excellent specs (theoretical THD+N at -120) and the analog stage (output) is left to the designer (more on analog stage below). One extra advantage of the ess9038q2m is DOP
Of course we used super caps and everything in audio path is film caps and thin film R.
Any delta sigma IC is very sensitive to the clocks (jitter). We used the "ultra low jitter clocks from NDK [url]NZ2520SDA[/http://www.ndk.com/en/products/search/clock/1190972_1433.html]. We also made sure that power was filtered by 2 LDOs in series along with a HF filter. Noise tested is in uV. Of course we also used buffers (that also has its power filtered 3 times…)
What we achieved is the lowest jitter ever (390fs)
- Analog stage
There are 2 kinds of analog stages , transfos and opamps. A lot of people swear by trans (with good reason) and others chose specific monolithic opamps. Still the consensus is that transfos are better as far as sound quality (but very expensive and bulky) and that opamps are better as far as THD+N numbers . If Opamps are used the quality of the PSU (opamps need dual rail 15V) is very important .
Still we felt that opamps CAN be better than transfos…
We concentrated a lot of efforts in this analog stage . You see , monolithic (integrated circuits) opamps suffer from the fact that not enough real estate is available on the silicon die .( excellent article sparkoslabs.com/audio-op-amps-g … bandwidth/ )
So our choice was ultimately to build a discreet opamp (with IV stage we got 6 of them) while feeding it from a DC/DC convertor that has filters on input (+ LDO) and filters on output (+ LDOs) and of a course a common mode choke (each rail has independent filtering) for a total noise thats lower than 1mV
However building an opamp is not a trivial task . What we did is partner with Sparkoslabs.com and used his excellent design (thx you Andrew the wizard) . One review of those opamps monoandstereo.com/2014/08/s … eview.html .
Each board is then hand trimmed (individually ) for DC offset (when board is warm to simulate conditions of a board that been running for at least 45 min)) and then programmed for THD+N compensation .
So in essence Katana dac is an excellent implementation of the Ess9038q2m in Master Mode (we are the first to do so) , with a discreet stage made by 6 opamps running in[u] class A amplification[/u] . THD+N numbers (1Khz , 0 dbfs , a weighted ) at -112.75 !!!
Pricing at 249$ (US) and 259Eur (tax included) Release date 17 of July