DSD Playback system, DSF Player + USB DDC + DSD Amplifier

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Hi Sonic, you noticed me that "Why it have to be Switch?". You are right.
I'm thinking dead_time control and I don't like dead_time control idea, it's not for the audio. :(

Maybe I can use good old analog circuit,
(a) logic out, volume(pulse height changed between 0V - 3.3V), DC cut C,
(b1) fixed gain 1Tr amp, diamond buffer Emitter Follower handles pulse, then + LPF.
(b2) Vacuum amp(no NFB) handles pulse, then it's output transformer is natural LPF.

By the way attached original 1kHz wav file "C:\TEMP\1KHz.wav"
and I converted to 1kHz.DSF by my program,
Then convert DSF back to WAV by KORG AudioGate. "C:\TEMP\KORG\1kHz.wav"
very little noise (below -110dB) was added, but should be OK.

and attached current source (dirty but anyway it works)
 

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Please forget Post #22. that is because of 16 bit limit. (final digit error)

I made 44.1/24bit 1kHz Wav file
converted it to DSF format by my program
converted back to 44.1/24 WAV by KORG AudioGate
and there are no noise over -140dB. :)

I wonder my mistake.. I checked final WAV, and there was KORG Tag. OK I'm not looking same file.
0079142c|4c 49 53 54 46 00 00 00 49 4e 46 4f 49 43 52 44 | LISTF...INFOICRD
0079143c|0c 00 00 00 32 30 31 31 2d 31 31 2d 32 33 00 00 | ....2011-11-23..
0079144c|49 53 46 54 26 00 00 00 4b 4f 52 47 20 41 75 64 | ISFT&...KORG Aud
0079145c|69 6f 47 61 74 65 20 76 65 72 2e 32 2e 32 2e 31 | ioGate ver.2.2.1
0079146c|20 28 57 69 6e 64 6f 77 73 20 37 29 00 00 | (Windows 7)..

now I have nice quality PCM to DSD converter, I can add this function to my another programs.
(VST for crossover, ASIO driver, etc)
 

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That's more like it! Try a wav file that is higher in frequency, since DSD it has less capability there. A 22kHz audio sampled with 48 or 96 would be sufficient.

PS: 144 dB is the theoretical limit of PCM 24 bit resolution. No audio DAC on market comes close of that.
 
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Hi, I can not see over 22050, by WaveSpectra.
if I convert 88200/24bit wav, I will see noise curve attached "DSD_noise_Shaper.png".
(my program only handles 44100 now)
I set Zero point at 0.95, 0.74, 0.42 = 20947Hz, 16317Hz, 9261Hz.
These points and noise_floor are trade-off. :eek:
(noise lowered dB * lowered freq area) < (noise shaped dB * shaped freq area)

oh, KORG can handle 88/24. I tested 1kHz-88-24.wav to dsf to wav.
it shows -160dB range.
-101dB: 30000Hz
-88dB: 44000Hz
So, If I use LPF cutoff at 25000, 4th ButterWorth,
Then 44000Hz noise goes to -88dB - 10log(1+(44000/25000)^8) = -107dB.
maybe it's OK.
anyway I can not notice over 18500:(
 

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That should be OK, it's on par with what I know DSD can do...

I don't hear (now) over 18k, but I can tell if the 2nd and 3rd harmonics are "wrong" - to fundamantals in 10-14 kHz range. Tube amplifiers drive me on walls with that, even at medium volumes.

Young people might hear even better - I tested myself when i was 18 and I was hearing up to 21kHz. Very attentuated, I had to raise the volume some 20dB, but I was there.
 
I searched another PCM - DSD converter. any other?
(1) Weiss Saracon. $2500! -147dB S/N. mine looks like almost same performance.
(2) Korg AudioGate, Free but annoying auto-tweet. to unlock, KORG MR-2, $500
(3) Sony VAIO, some model has SonicStage Mastering Studio??

=======================

any math method to use FIR for delta-sigma modulation?
"delta" needs feedback, but maybe there should be some method to use FIR filter.
Then I can improve the high frequency performance, steep noise shaper.
 
Hi Thanks Bunpei san
MATLAB, that is thousands $ software :(
If there are no free & easy WAV to DSF converter, only small number of people will play DSD.
maybe I should brush up DSF converter, and ask some frontend GUI programmer to support it??
for myself I want FLAC (LINN RECORDS etc) to DSF converter.
You Japanese have some DSD download store, I envy you!
 
Hi Sonic, yes,
DSD -> PCM : for signal processing.
PCM -> DSD : I think.. DSD makes DAC job almost done. so using DSD as final signal format can improve the sound.

now my PCM->DSD = oversampling to 2.8MHz + 2048 tap FIR LPF + 7th IIR.
I'm wondering about FIR LPF, because this LPF has no effect < 22050Hz. don't have to be linear.
So maybe I can use 16th IIR LPF instead of 2048 FIR LPF.
This is lightweight code, can be implemented in.. where? ASIO driver?

Or something interesting, "mathematical DAC"
I2S In -> MCU(>100MHz) -> DSD output -> passive LPF
 
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