DAC 2496 (AK4393) DAC KIT With CS8416+AK4393+5532 - Page 17 - diyAudio
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Old 9th June 2011, 12:22 AM   #161
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Default Warning!!! For AK4396 version...

Ouch!

I think I've found why the AK4396 version sounds tonally unbalanced...

I was reading the datasheets of AK4393 and AK4396 and the sample output stage (which incidentally is identical to the one of this board...) and they've the same topology but different resistors and caps values...

So for the two DACs a different LPF is required!!!

Then I've checked the one of AK4395 (identical to AK4393 one) and AK4399 (different values from AK4393/95 and AK4396).

So this kit should have different LPF's resistors and caps for the two chips...

Obviously I've found this information the day after I've ordered PRPs for two boards... (if someone with AK4393 version is interested PM me...I'll make a nice price )

I've attached the two output stages and, since to me they're a Sallen-Key filter, two graphs that shows the difference (made with this calculator).

The AK4396 outstage is clearly more rolled-off...
Attached Images
File Type: jpg Outstage.jpg (62.7 KB, 2108 views)
File Type: jpg Oustage - Graphs.jpg (118.2 KB, 2639 views)
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Last edited by ClaveFremen; 9th June 2011 at 12:52 AM.
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Old 9th June 2011, 01:11 AM   #162
YohY is offline YohY  United Kingdom
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Quote:
Originally Posted by ClaveFremen View Post
Ouch!

The AK4396 outstage is clearly more rolled-off...
Wow.... good work Clave !
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Old 9th June 2011, 02:35 AM   #163
sendler is offline sendler  United States
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Default Low ultrasonic noise

Quote:
Originally Posted by ClaveFremen View Post
I was reading the datasheets of AK4393 and AK4396 and the sample output stage (which incidentally is identical to the one of this board...) and they've the same topology but different resistors and caps values...
That is because the level of remaining ultrasonic noise with the AK4396 is so low that it really doesn't need any analog filtering. I find the best sound by far with the AK4395 or 96 comes from running the analog direct out through high quality caps to block the dc. No filters, output Rs or buffers. Now I don't have to worry about which opamp will sound best or if it is properly decoupled as I don't have any in my signal chain.
.
AK4395/4396 ultrasonic noise spectrum graphic
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Old 9th June 2011, 07:33 AM   #164
stifa is offline stifa  Yugoslavia
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^ I heard this somewhere else...
4396 seems to be better chip than 4393 so it is better to stay focused on it.

@Sandler... Ehat exactly do you mean by direct out mod... there's gotta be something to be filtered there... or not ?

@Clave ... it doesnt matter what the figures say...if it sounds good .....

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Old 9th June 2011, 09:56 AM   #165
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Quote:
Originally Posted by sendler View Post
That is because the level of remaining ultrasonic noise with the AK4396 is so low that it really doesn't need any analog filtering.
I don't think so.

IMHO the LPF filter is there not only to deal with ultrasonic noise but also to adjust the frequency response of the output if the DAC, by design, don't handle it completely.

As a matter of fact different sources (PCM or DSD for instance) needs different filters to achieve the (quite) same final frequency response.

And since different AKM DACs are coupled with different LPFs to achieve the same frequency response it can be deduced that the DAC output frequency response is different....

Quote:
Originally Posted by stifa View Post
it doesnt matter what the figures say...if it sounds good .....
To my ears it matters... sounds good but unbalanced...
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Old 9th June 2011, 10:28 AM   #166
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Very interesting info on the filter differences between the 93 and 96 - thanks for doing the homework.

I'd strongly advise anyone to ditch the filtered active output stage anyway. I've used a number of different 600ohm output transformers on the 93 in my src2496, and all have been a massive improvement on opamps. I briefly tried the cap only output using the positive dac output only, but to my ears this wasn't close to the quality of transformers. I suspect this is down to two things: (1) i read that these dacs like to have even loads on positive and negative outputs (2) transformers may add a pleasant colouration.

I have the 93 kit at home unbuilt and the 96 kit on the way. Got a pair of tamura td-1 transformers for the 96 and some bbc ones for the 93. Thinking about all solid polymer caps for one dac and all tantalum for the other. Might even use linear psu on one and a really nice medical smps on the other. I'm on holiday next week so looking forward to playing with all the spare parts i have lying around. Great fun :-)
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Old 9th June 2011, 11:45 AM   #167
sendler is offline sendler  United States
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Default Corner frequencies

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Originally Posted by ClaveFremen View Post
I don't think so.

And since different AKM DACs are coupled with different LPFs to achieve the same frequency response it can be deduced that the DAC output frequency response is different....
I think that you will find the corner frequencies of the filters are so far out of the audio band that there will be no measurable difference to the in band response, or possibly even a flatter extension at the top, without the filter. It is just for the ultrasoninc noise of which there is very little with the AK4396.
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Old 9th June 2011, 11:59 AM   #168
sendler is offline sendler  United States
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Default Direct out with trannies or transformers

Quote:
Originally Posted by stifa View Post
^ I heard this somewhere else...
4396 seems to be better chip than 4393 so it is better to stay focused on it.

@Sandler... Ehat exactly do you mean by direct out mod... there's gotta be something to be filtered there... or not ?

@Clave ... it doesnt matter what the figures say...if it sounds good .....

Cheers
Running a dac chip direct from the analog pins has been discussed here since 2006. Just send the signal through a high quality cap to block the dc, or through a good transformer to eliminate the dc by balancing it on both legs. I find the sound to have the best fine detail through caps. A more pleasant and euphonic sound can come with transformers.
.
AK4396: best solution for output stage
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Old 9th June 2011, 01:49 PM   #169
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Quote:
Originally Posted by sendler View Post
I think that you will find the corner frequencies of the filters are so far out of the audio band that there will be no measurable difference to the in band response, or possibly even a flatter extension at the top, without the filter.
Why AKM bother to specify different filters for different DACs?

Quote:
Originally Posted by sendler View Post
It is just for the ultrasoninc noise of which there is very little with the AK4396.
We agree about ultrasonic noise, it's just a fact, but since there's no noise to filter why the AK4396 filter is more rolled-off?
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Old 9th June 2011, 02:00 PM   #170
stifa is offline stifa  Yugoslavia
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Quote:
Originally Posted by sendler View Post
Running a dac chip direct from the analog pins has been discussed here since 2006. Just send the signal through a high quality cap to block the dc, or through a good transformer to eliminate the dc by balancing it on both legs. I find the sound to have the best fine detail through caps. A more pleasant and euphonic sound can come with transformers.
.
AK4396: best solution for output stage
Well I am not an expert but I was told even though not in audible range , extra frequencies can put a strain on the amplifier if it is a DC amp like Firstwatt F5 which I have...

seems like a easy solution...will give that a try just for fun and see what happens.

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