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Dual Mono DAC AK4490/AK4497
Dual Mono DAC AK4490/AK4497
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Old 2nd February 2016, 08:52 AM   #21
cal1sto is offline cal1sto  France
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Quote:
Originally Posted by manudrz View Post
An other base to mod with ? AK4490 - I2S over USB Audio
Nice board, but this doesn't have implemented like i see on the board the large value capacitor between VREFH-L/R to improve THD performance, refer to the eval board manual.

Anyway now with some input direction from some post there, i will sugest to go with following line:
  1. 4 Layer board (minimum)
  2. Implement a Large Capacitor on VREFH-L/R to improve THD on audio bandwidth... >=2200uF (see attached graph)
  3. Balanced / unbalanced output (mean 2 LPF/mono DAC)
  4. LDO - LT3042 on board for providing the 2 * 3.3V with Ultra low noise and Ultra high PSRR on Digital side. (perfect will be 4 LDO/Line for getting 0.4uVrms noise for up to 800mA max. this should be optimum for the DAC(>=150mA) and/or the XMOS board (>=400mA)
  • Should we made the same integration on board for the 5V/7V Analog part with only 1 LDO/Line (0.8uVrms, 200mA) this as sense but we could over dimension this with 4 LDO/line to stay on the Ultralow noise of 0.4uVrms ???????
  • Then also for the dual LPF for each mono AK449X to get the Balanced output line with +-(12 or 15V) ->this should be able to be switched on board easily depending on Opamp choice, should we there also go on the same idea to provide the ultralow noise UltraHigh PSRR -> this has logical improvement for me.
  • The three before proposition will say we should provide 5 isolated power 2*5V DC for the 3.3V(digital), 2*9V DC for the 5V/7V (selection on board) analog and 2*18V DC for the LPF with +-(12 to 15V) -> Some input of the 7V setting on Analog improve the THD+N but this should be checked before doing it selectable.
  • But i should not forget that the AK4497 need a clean 1.8V , clear this provide one in chip LDO for, but is this better than the LT3042, really not sure so there i will go to provide on same way the 1.8V form the LT3042 and switch off the internal LDO.
Any comment will be great on this direction ?
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Old 3rd February 2016, 12:05 AM   #22
manudrz is offline manudrz  France
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Agree with everything, but you don't plan to put a Xmos on each board ?
Quote:
2*18V DC for the LPF with +-(12 to 15V)
Selectable just with a jumper could be great.

Quote:
Implement a Large Capacitor on VREFH-L/R to improve THD on audio bandwidth... >=2200uF (see attached graph)
Yes I know that, search for a hifiduino link... I didn't remember the DIYinhk had this "tweak" on-board, far away from the DAC but implemented yes...
Ok, I'm waiting for updates now
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Old 3rd February 2016, 12:16 AM   #23
abraxalito is offline abraxalito  United Kingdom
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Quote:
Originally Posted by cal1sto View Post
LDO - LT3042 on board for providing the 2 * 3.3V with Ultra low noise and Ultra high PSRR on Digital side. (perfect will be 4 LDO/Line for getting 0.4uVrms noise for up to 800mA max. this should be optimum for the DAC(>=150mA) and/or the XMOS board (>=400mA)
If the aim is ultra-low PSU noise, then variations in load current absolutely have to be minimized or the regulator's own noise will be swamped by load-current induced noise. Getting the load current variations down is rather tricky when opamps are in play (the SCFs at the output of the chip are generally CMOS opamp based) because opamp output stages don't operate in classA.
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Old 4th February 2016, 01:49 PM   #24
cal1sto is offline cal1sto  France
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Let begin to build the board XMOS isolated (or not isolated) with AK4490 firmware and AK4490 board from DIYINHK.

BOM:
1 - Transformer R-core 2*9V, 2*15V or Toroidale 2*9v 2*15V (2*18V) (>=30VA)
2 - Regulator board 2*3.3V, 2*5V (5 to 7V max), +-12V (+-10V to +-15V Opamp need)
3 - XMOS isolated (or not) with AK4490 firmware
4 - 100uF electrolytic (>=10V) from Panasonic or better is to filter the optional Analog 5V supply.
5 - AK4490 DAC board

Customize the AK4490 board to provide 2*3.3v , 2*5V to split both digital/analog Ops.
Refer to attached screenshot (1) remove the FB1 to split the 3.3V provided , by adding up to the FB1 3.3V power.
Cut the trace (2) to split the 5V provided on board by two separated 5V, new 5V supply provided under the point (3) .
On (3) solder the 100uF capacitor.

The board now should be cleanly powered (with more direct power line than before

Enjoy your DAC and connect everything by controling any pin to match also don't forget the PSN jumper to set the software mode (for operating trough the XMOS board)

Next we will create a new AK4490 board (base for the AK4497 when sample requested by AKM is delivered)
Board D1
- Dual AK4490 on board
- Balanced/Unbalanced analog output
- Ultra Low noise with High PSRR LDO on board (LT3042)

Board X1
- Usb XMOS board (with firmware supporting native DSD 256 and if possible PCM 768khz/DSD256 -> currently i working on)

Board S1
- AK4118 board for Optical, coax .. input selection

.....
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Old 4th February 2016, 03:18 PM   #25
manudrz is offline manudrz  France
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Quote:
Originally Posted by cal1sto View Post
Board D1
- Dual AK4490 on board
- Balanced/Unbalanced analog output
- Ultra Low noise with High PSRR LDO on board (LT3042)
As you plan to use onboard LDO, do you think it'll be possible to use big external PSU in order to power 3 boards together ? One 5V/7V and one +-15V ?
That project seems nice
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Old 4th February 2016, 05:12 PM   #26
cal1sto is offline cal1sto  France
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Quote:
Originally Posted by manudrz View Post
As you plan to use onboard LDO, do you think it'll be possible to use big external PSU in order to power 3 boards together ? One 5V/7V and one +-15V ?
That project seems nice
For sure you could for your 6 channels system the VA should just be right dimensioned on your transformer.
I like to provide one litle transformer by channel for your need one personalized toroide with 6*9V + 6*15V at >=90VA (120VA) then 12 graetz bridges and 12*5600uF all take place but will provide optimum power supply on my point of view , is just my point of view

Last edited by cal1sto; 4th February 2016 at 05:19 PM.
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Old 22nd February 2016, 10:05 AM   #27
cal1sto is offline cal1sto  France
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Back from vacation, I am working now to program the XMOS XUF216-512-TQ128-C20 , already integrated the Vumeter over GPIO as I2S interface, I am just now trying to find out the device address for the AK4490 (diyinhk) to configure the DAC on data type coming from the USB interface to have output depending on sound source.
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Old 24th February 2016, 09:30 AM   #28
cal1sto is offline cal1sto  France
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I got already the vumeter runing (move right by sound input) and could now put on the Oled some information dynamicaly, i will today test and integrate the specific AK4490 configuration to configure on need the DAC register. I hope to have the basic firmware ready til end this week (with volume up/down and filter selection)
After i will optimize everything for performance to be able to reach the max power this DAC is able to deliver -> to be ready for the AK4497 when AKM deliver me the sample.
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Old 24th February 2016, 10:03 AM   #29
androa76 is offline androa76  Slovenia
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Very nice. Inteterested tread. I also wait for your result ak4490 vs ak4497 in terms of sound difference not so interested in spec.
what kind of output stage have you planed to do fot both dac. Any schematic?
Thank you
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Old 31st March 2016, 06:07 PM   #30
Comzone is offline Comzone  Hong Kong
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Quote:
Originally Posted by cal1sto View Post
Hi Manudrz,

This is my first DAC project, i design before a nice powerfull MOSFET (IRF) power amplifier with a passive preamp.
Yes i do everything "modulable" is i think the way for us to have any time the possibility to upgrade, control every part and build a stereo , 2.1, 5.1, 7.1 or more depending on need (i will go surely finaly for a stereo and 7.1 version).
The Xmos board (usb, S/pdif, coax) board is able to deliver 6 channels at 384khz, 8 channels at 192khz and up to 32 channels at 48khz, so to answer on your need only for the DAC boards this is able to deliver the 24bits 96khz you want to deliver over your DSPiy... (The DAC could 16,24,32 bits at up to 768khz) with I2S and I2C interface to have full control + H/W interface.
Very Nice.
However how you control two 4490 in one I2C channel? since the DAC got some ID
Maybe need to use 2 MCU to control 2 DAC
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