DSD Playback system, DSF Player + USB DDC + DSD Amplifier
I have some DSD music file from SACD now. I want to listen to them as it is.
So I made prototype of full DSD playback system.
(1) DSD File player (source, DSF hex dump screenshot)
Read DSF format DSD file into memory, make byte(= 8ch) stream, send to USB DSD digital-digital converter.
Now 1 Byte data contains 2 bit (L,R) only, but for future I want to playback 5.1 DSD. so I use 1 byte for 2 bit sample.
(2) DSD DDC (Photo, Schematic, VHDL) Right side of the photo
This is FTDI UM232H + FIFO + FPGA, to make +- output to DSD amplifier.
Made for USB - I2S x 24ch (see "Digital Line" forum).
FPGA is too large for DSD.. only 27 FFs are used.
These (1) (2) are just making bit stream to the (3).
(3) DSD amplifier (Photo, Schematic, Signal Photo) Left side of the photo
MOSFET Driver + MOSFET, 1bit amplifier. just a High Speed H bridge and LPF.
Volume is controlled by Final stage voltage. (0.0 - 6V)
Note: I'm using LOW side driver so Final stage voltage is limited, driver - 5V.
If you use High/Low side driver, you can apply any power.
It sounds. :)
Byte stream, which contains DSD signal, and H bridge + LPF can playback the Audio (as DSD theory is)
I have no experience with SHARP 1 Bit amplifier. This one sounds like SHARP? I hope so.
Bunpei and Chiaki,
How about implementing this to your SD player?
You need different drivers on the amplifier side, so the push-pull don't get to be "ON" in the same time.
You mean Dead-time control? Yes I selected the driver without timing control.
I loss some power (10ns/300ns or so) / I get correct pulse width.
dead time control reduces on-width of pulse = distortion.
same as analog amp, we need some power loss = idle current for quality.
This is prototype so I want to know which driver is the best, or thinking to design adequate driver circuit (for audio) by myself.
Attached, This system - 3 inch full range - USB mic - WaveSpectra, to check THD.
Total system THD @1kHz = 0.2%, should be no terrible problem:)
I made 1KHz DSF file by KORG AudioGate.
IMO with MOS like IRF you get less distortion with a small dead-time. You won't get anyway a "clean" transition there, it's still at zero, being a short-circuit between rails. Reduced voltage dip on rails at zero crossing and lower temperature on finals will help lowering the distortions.
How small can that time be... is up to how fast are those finals.
Sorry, ideea is good, but I found out long time ago that the final stage needs to be analogic. At least this is the state of electronic devices in this decade. 0.2% is nothing to care. Add one more zero and we are talking replacing the analog final stage.
0.2% is including cheap Pioneer 3 inch full range speaker and Samson C01U USB mic.
I crushed my USB audio interface:(
How fast = how small FET, I think this is too large. I just need 4.5V for 6 feet listening.
maybe I need to try more smaller FET / my own fast driver.
As I said, the ideea is good.
Dead-time will help IMO, for reasons exposed above.
But modern DAC's have an easyer job to convert DSD to analog (than PCM) because of the fact that they are Delta-Sigma in essence. So they are pretty good at it.
That is just a difference of our tastes, I want to "reduce".. the DAC chip, I/V, opamp, volume, JFET input, NFB, driver stage and Final stage and emitter register. and multiple toroidal and huge capacitors..
less analog is better for me.
for another idea,
I once made Power DAC (PCM to current, to drive speaker) before.
It was PCM so bit accuracy was weak point, but by DSD I just need 1 current source / 1 current sink, big enough to drive speaker.
Which one do you think better for audio?
switching voltage by DSD, or current push / pull by DSD?
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