Power DAC (like Wadia) full digital amp - diyAudio
Go Back   Home > Forums > Amplifiers > Class D

Class D Switching Power Amplifiers and Power D/A conversion

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 16th September 2007, 04:16 AM   #1
diyAudio Member
 
Join Date: Nov 2006
Default Power DAC (like Wadia) full digital amp

Now I'm designing Power DAC like small Wadia. (Their PowerDAC was $80,000. it sounds GREAT but I'm not a rich)
You may will know PCM63P / PCM1704 well, this project is like huge PCM1704 / differencial driven.

1. Principle
SPDIF to Right justified, 16bit signal
Serial to Parallel conversion
PCM to +(0000 to 7FFF), -(0000 to 7FFF) linear conversion
Voltage Reference (0 to 5V) works as volume control
Analog switch for Voltage Reference, driven by each data bit
Pre LPF after analog switch for each bit
+ side current source, MSB = 250mA, magnitude to LSB
- side current sink, MSB = -250mA, magnitude to LSB, +LSB offset

All Currents merged without any component - drives speaker directly.

2. Notes
Current amplifier can drive any "Low impedance speaker" but can't work with speaker's high impedance frequency area.
So it must have "impedance dumper" . it assures peak voltage < 4V.

register value for Current source will be 0.1%.

There can not be "Post LPF" like PCM1704, because added current drives speaker.
12dB Pre LPF are implemented for each bit.

3. Pros/Cons with PWM amplifier

Pros: Less signal modification. pure direct conversion from PCM to current.
Less Analog Component. there are no coil and capacitor at output terminal.

Cons: TOOOO low efficiency. implementation is nightmare.
now I understand why Wadia's PowerDAC had to be $80,000.
Attached Images
File Type: png powerdac_sch.png (39.8 KB, 1832 views)
  Reply With Quote
Old 16th September 2007, 04:17 AM   #2
diyAudio Member
 
Join Date: Nov 2006
Default nightmare

here is current board image.
it's 12x12 inches..
most left: Left D7 to D0 Current source / sink
2nd left: Left D14 to D8 Current source / sink
(right side as same)
Powers: for OpAmps, Transisters, 5V
DAI / Serial-Parralel / conversion for + and - / AVR / Voltage reference

100xOpamp, 400x0.1uF, 600 resistors, 60 analog switch, etc.

I'd like to ask you this project is value for the money about $600
Attached Images
File Type: png powerdacboard.png (95.5 KB, 1661 views)
  Reply With Quote
Old 16th September 2007, 09:09 AM   #3
el`Ol is offline el`Ol  Germany
diyAudio Member
 
Join Date: May 2005
Location: Bavarian Forest
As far as I know the Wadia Power DAC consisted of 8 true 24bit PCM DACs per channel that worked phase-shifted to get 2.8 MHz without any noise-shaping. These DACs drove a minimalistic Class A power stage and volume control was entirely done in the digital domain.
Do we mean the same product?

P.S:
The term "full digital" refers to amps like TacT/Lyngdorf and the TI chips derived from it.
  Reply With Quote
Old 16th September 2007, 03:00 PM   #4
diyAudio Member
 
Join Date: Nov 2006
like that you mention, only the idea of "current generator based" is like wadia. less bit, less sampling, leeeess power...
Instead better to say it is like discrete PCM63 or something?

anyway what I'm interested is another way of "full digital", multi bit PCM to curent conversion and direct speaker drive.

My DAC (then .. what is the best word to say ) has no oversampling, no noise-shaping, no PCM-PWM conversion, no post LPF, just using 31 circuit module to make 1 channel signal.
(If 24 bits and x4 phase shift, 188 circuits to make 1 signal!)

such a crazy can not be a commercial product. so must be DIYed

attached is more schematic, to make each signal bit from D15 - D0.
Attached Images
File Type: png latchmodule.png (57.0 KB, 1505 views)
  Reply With Quote
Old 16th September 2007, 05:02 PM   #5
el`Ol is offline el`Ol  Germany
diyAudio Member
 
Join Date: May 2005
Location: Bavarian Forest
I guess you would have to do the digital filtering on your own, DSP-based, am I right?
  Reply With Quote
Old 16th September 2007, 06:04 PM   #6
diyAudio Member
 
Join Date: Nov 2006
No, no, there are no DSP or digital filter. Have you ever made R-2R DAC? it has no DSP or filter. R-2R works with magnitude Voltage, my DAC works with magnitude current.
Attached Images
File Type: png powerdac09_latch.png (8.0 KB, 1371 views)
  Reply With Quote
Old 16th September 2007, 06:35 PM   #7
el`Ol is offline el`Ol  Germany
diyAudio Member
 
Join Date: May 2005
Location: Bavarian Forest
Jadis and Kondo had pure PCM no oversampling DACs, but with excessive analog filtering (valve-based). The other extreme is the Wadia Power DAC with only digital filtering. All the others (DIY kits excluded, I don`t know much about that field) have a combination of both.
Both Jadis and Kondo go other ways now. Jadis is using Analog Devices 12-bitters more common in labs than in hifi, still a bit closer to pure PCM than the 5-6 bit mainstream. I don`t know what Kondo is using. I am also not up to date what Wadia is doing now.
  Reply With Quote
Old 2nd October 2007, 10:41 PM   #8
diyAudio Member
 
Join Date: Nov 2006
Default CS8416 Right Justified, 16 bit delay problem

Now I am working with board and having problem with CS8416.
(purchased last month, CS8416-CZZ)
Attached shows LRCK and SDATA with Right Justified, 16 bit configuration.
Last one bit of data is changing "1 clk after" LRCK edge.

//Serial Audio Format = (Right Justify 16bit)
//Bit 7:SOMS = 1, master mode
//Bit 6:SOSF = 0, 64Fs
//Bit 5:SORES1 = 1
//Bit 4:SORES0 = 0, 16 bit resolution
//Bit 3:SOJUST = 1, Right Justified
//Bit 2:SODEL = 0 not effected
//Bit 1:SOSPOL = 0, SCLK Polarity, rising
//Bit 0:SOLRPOL = 0, LRCK, high = Left
WriteData = 0xA8;
ret = I2CWrite(CS8416_ADDRESS, 0x05, &WriteData, 1);

Of course I tried 0b10000000 to 0b10111111 64 patterns, but could not get correct Right justified 16bit signal.
When SODEL = 1, the delay of SDATA is 2 clks

Does anyone see same issue?
Attached Images
File Type: jpg delayed_data.jpg (81.5 KB, 1138 views)
  Reply With Quote
Old 11th October 2007, 05:43 AM   #9
diyAudio Member
 
Join Date: Nov 2006
maybe I made some mistake because CS8416 designer will be more smart than me! but I was tired for thinking.

Dirty Patch by 74HC74 and 74HC04.
(Latch LRCK by SCK and inverted SCK, delays LRCK for one bit clock)

now digital section looks like working.
Attached Images
File Type: jpg p1010225s.jpg (68.6 KB, 870 views)
  Reply With Quote
Old 19th October 2007, 03:41 AM   #10
diyAudio Member
 
Join Date: Nov 2006
This soldering makes me crazy.
Now 3 bit implemented, it shows 500 Hz triangle wave.
can you see 7 step signal (by 3 bit upper/lower)?
It looks like R-2R DAC implementing, but this DAC can drive speaker.

Now I have dsPIC SD-I2S player, and direct sound converter, only by commodity devices. interesting.
Attached Images
File Type: jpg p1010227s.jpg (76.0 KB, 822 views)
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
The Full Digital AMP cac liu Class D 29 27th July 2009 08:07 PM
Full Digital Speaker KOON3876 Class D 32 19th March 2009 09:23 AM
d2audio Full digital audio okkyn Class D 4 1st August 2007 05:17 PM
Tube Output Full digital Amplifier KOON3876 Class D 8 14th December 2006 05:54 PM
full (low cost) digital chain raxy Digital Source 0 17th October 2004 10:26 AM


New To Site? Need Help?

All times are GMT. The time now is 01:48 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2