DAC 2496 (AK4393) DAC KIT With CS8416+AK4393+5532 - Page 35 - diyAudio
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Old 15th July 2011, 07:50 PM   #341
Trebla is offline Trebla  United Kingdom
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I just realised i've got 2.5volts dc on the right +- outputs of the DAC.
Only 1.4mV on the left.
Whats going on there?
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Old 15th July 2011, 09:32 PM   #342
bismuth is offline bismuth  France
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Hi,

@jeffzen:
DC offset may be a problem with a DC coupled amp after the dac because DC will also be amplified and may damage your speakers.

@Trebla:
2,5V is way too much, there must be something bad with your board.

I just rebuilt the LPF filter with correct values for AK4396 as suggested by ClaveFremen with hand matched resistors (to 0,06%), and as a bonus DC offset is now 0mv on both outputs !

I suggest to those with high DC offset to check LPF resistor matching with a multimeter.
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Old 16th July 2011, 06:02 AM   #343
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Hello,
Thank you very much! Are my values considered too much? I'm just asking because in my country it is very hard to find some special quality components. However, if it is mandatory for protecting my speakers from DC, I will not hesitate to buy the necessary parts on ebay.
Thanks,
Jeff
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Old 16th July 2011, 09:00 AM   #344
FOXYE is offline FOXYE  Israel
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I had the DEQ2496, with AK4393 and passive output, the sound was great, warm and very musical.

I'm thinking of purchasing the AK4393 kit and use it with passive output.

What is the difference between AK4393 to AK4396 in terms of sound?
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Old 16th July 2011, 10:33 AM   #345
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Default Schematic

Schematic of the ebay dac board from zoe_tsang (i didn't see one yet?). Nothing new, but helps clarify things when modding.

I just ordered the parts from Clave's BOM, the RS ones. Came to around 35 with postage. Only problem was the Evox-Rifa SMR's, didn't fancy paying the 12 postage from Mouser. I ordered one of the few alternatives available from RS, nothing special, and hope for the best.
Attached Files
File Type: pdf ak4393-6 dac scematic.pdf (23.1 KB, 470 views)
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Old 16th July 2011, 10:42 AM   #346
Trebla is offline Trebla  United Kingdom
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Quote:
@Trebla:
2,5V is way too much, there must be something bad with your board.
Yes.
I sent a message to the seller explaining my findings, but i'm not too hopeful.
Thankfully the board has not been modified yet.

Anyone got an idea what the likely causes of high DC offset are?
Bearing i mind that i am not using the analogue output stage.
My measurements are directly from the dac output.
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Old 16th July 2011, 11:20 AM   #347
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I haven't done the direct out mod, but in terms of fault finding, have you disconnected the analogue output stage at R26 and R32 before tapping the audio signal? I would be tempted to disconnect R24 and R30 also.

If the voltage persists, i'm thinking it must be the AK4396 IC causing it, a faulty chip perhaps ??
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Old 16th July 2011, 11:30 AM   #348
Trebla is offline Trebla  United Kingdom
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Quote:
Originally Posted by mrwireless View Post
I haven't done the direct out mod, but in terms of fault finding, have you disconnected the analogue output stage at R26 and R32 before tapping the audio signal? I would be tempted to disconnect R24 and R30 also.

If the voltage persists, i'm thinking it must be the AK4396 IC causing it, a faulty chip perhaps ??
Well disconnecting the output stage would have been my next move.
But i'm a bit reluctant to make any alterations to it, until i have made contact with the seller. There's always a slim chance he may swap it.
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Old 16th July 2011, 11:38 AM   #349
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Hi Trebla,

Why don't you post a picture of the output stage, top and bottom.

My guess would be one bad solder joint.

Regards
__________________
Greg Erskine
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Old 16th July 2011, 05:24 PM   #350
Trebla is offline Trebla  United Kingdom
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Cheers Greg.
I,ll go over it with a soldering iron later.
This is a ready assembled board, and is supposed to be tested. How much testing it gets is anyones guess.
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