Dual Mono DAC AK4490/AK4497

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Dimdim

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Joined 2008
Before we designed the dual mono board we did a test board with a single 4490, just to make sure that the design would work. That's the one shown on my blog.

A full presentation of the dual mono version with the accompanying arduino code is on my to-do list.. I'm waiting on a new set of controller PCBs, so as to do a full presentation. These boards are useless without an Arduino (or similar) controller.
 
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Dimdim

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Joined 2008
That is really hard to tell, since my two test platforms are very different (different power supplies, different clocking setup, reclocking vs. no reclocking, different layout, 4-layer vs. 2-layer boards, and of course, different analog stages).

What I know for sure is that my dual 4490 setup as-is sounds a lot better than my single 4490 test board as-is, but that really does not mean a lot.
 
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Voysto

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Joined 2013
Hello everyone,

It is probably a dumb question but I am in the process of building the JLSounds AK4490 + LME49710 Filter Board + Screen (I will replace the lme49710 opamp) and was wondering if I can directly connect my headphones to the output and use my DAC as a headphones amplifier too ?

Thank you very much

Voysto
 
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Dimdim

Member
Joined 2008
This shouldn't be hard to nail. On my 4490s I do this to set DSD mode:

Code: 
ChangeBit(ak4490, 0x01, 0, true);         // Enable soft mute
ChangeBit(ak4490, 0x02, 7, true);         // Set To DSD Mode
WriteRegister(ak4490,0x00,B00000000);     // Reset
WriteRegister(ak4490,0x00,B00000001);     // Normal operation
WriteRegister(ak4490,0x00,B10001111);     // Set To Master Clock Frequency Auto / 32Bit I2S Mode
WriteRegister(ak4490,0x06,B10011001);     // Set To DSD Data Mute / DSD Mute Control / DSD Mute Release
WriteRegister(ak4490,0x09,B00000001);     // Set To DSD Sampling Speed Control
ChangeBit(ak4490, 0x01, 0, false);        // Disable soft mute
 
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themystical

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Joined 2006
I am getting closer to powering up my dual mono AK4497 set up as an upgrade? to the dual mine Ak4490 so trying to understand some of the register settings. Anybody have any ideas about the "heavy current" setting and under what circumstances it mine appropriate and how it helps?
 
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AIM65

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Joined 2015
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SQ ?

themystical said:
Also can anybody shed any light on the "Sound Quality" Register Options of which there are 5 settings?
Click to expand...

Those SQ setting were also on the 4495 and 4490. On my 4495 DAC, I'm not able to ear any SQ change while using them and AKM datasheet says nothing about them.

About 'Heavy load drive', according to the datasheet it allows to load the output stage down to 120R. Without this option lower load is 8K (see page 11). It's probably a special request of AKM customers. On 4490 min load is 1K (1,5 for DC).

Regards
 
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themystical

Member
Joined 2006
AIM65 said:
Those SQ setting were also on the 4495 and 4490. On my 4495 DAC, I'm not able to ear any SQ change while using them and AKM datasheet says nothing about them.

About 'Heavy load drive', according to the datasheet it allows to load the output stage down to 120R. Without this option lower load is 8K (see page 11). It's probably a special request of AKM customers. On 4490 min load is 1K (1,5 for DC).

Regards
Click to expand...

That is really useful thank you. It looks like I was looking at a really old version of the datasheet and the new version has a lot more and slightly different information.
May I get some help interpreting this - see excerpt below.
AK4497 Datasheet by themystical2012, on Flickr


Am I right in understanding that the "price" of using the better heavy load mode is not in performance but a higher current requirement? That does not seem to be stated anywhere.
Also it seems like there is a 3dB improvement in the A weighted SNR if one uses the higher gain mode which seems like a no brainer. Is the price to pay for this a 3dB worse THD performance as per the datasheet? Doesn't make much sense to me?
 
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AIM65

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Joined 2015
Paid Member
themystical said:
That is really useful thank you. It looks like I was looking at a really old version of the datasheet and the new version has a lot more and slightly different information.
May I get some help interpreting this - see excerpt below.
AK4497 Datasheet by themystical2012, on Flickr


Am I right in understanding that the "price" of using the better heavy load mode is not in performance but a higher current requirement? That does not seem to be stated anywhere.
Also it seems like there is a 3dB improvement in the A weighted SNR if one uses the higher gain mode which seems like a no brainer. Is the price to pay for this a 3dB worse THD performance as per the datasheet? Doesn't make much sense to me?
Click to expand...

Hi,
it seems that the 3dB gap is due to the Gain setup, not Load (GC bits, not HLOAD bit), those are two different parameters.
One thing to spot: all the measurements and official figures in the datasheet are given with HLOAD=0 (load max = 8K). But sometime, tests conditions are optimized to give the best figures, which may not be the bests for SQ.

I just went quickly through the DS. See page 91, there's a (short ! ) description of the SC0,1 bits which configure SQ, there're related to 'internal current'. Maybe those bits change internal config of the dac out stage resulting in a change in SQ (but to be defined...), you will also notice that SC2 is called 'High Sound Quality Mode'...so this will be my default setup :)
 
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