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.
@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.
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.
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.
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.
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 ??
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.
All leds come on for a split second at start up. Then only the power stays on.
If you are playing something at 96k, the 96k led will probably stay on.
I cannot tell you why the No Audio led should blink, unless there is a problem with your source. Hopefully someone else will help.
Is the DAC working ? ie. Can you hear music?
'NO AUDIO" i guess would would mean you are feeding in a non-audio signal over SPDIF, such as AC3. Try plugging in a different source.
Thank you for your replies.
No problem with the source I've tested several which are ok with a PCM1796 DAC.
In fact, there is a random behavior: sometimes POWER, 96K and ERROR are alight when I turn on, sometimes only POWER but it never work.
I've tested all my soldering work, it seems to be ok. I've tested voltage after the 3 LM117 (2x3.3V and 5V) all is ok. I've to replace some composants and the problem is exactly the same. So I suppose there is a problem with one of the 3 CMS chips already soldered on the PCB.
No problem with the source I've tested several which are ok with a PCM1796 DAC.
In fact, there is a random behavior: sometimes POWER, 96K and ERROR are alight when I turn on, sometimes only POWER but it never work.
I've tested all my soldering work, it seems to be ok. I've tested voltage after the 3 LM117 (2x3.3V and 5V) all is ok. I've to replace some composants and the problem is exactly the same. So I suppose there is a problem with one of the 3 CMS chips already soldered on the PCB.
I haven't read all this thread so please excuse me if I missed this.
To the designer (evangelion1999) you said you use the LM4562 output op-amp. Do you have some measurements of this to show better performance than NE5532?
Many people dislike the NE5532 but I have measured the output of a very similar design (not the Mini2496 though) with both 5532 and 4562 and found absolutely no difference. This would suggest to me that both op-amps performance is below the issues the DAC distortion, PSU decoupling and grounding etc.. cause.
Anyway I think this DAC is great for the money. A high quality transformer output or perhaps a 'super-bal' op-amp output such as used in the CA DacMagic would take it to superb (objectively). It is generally my finding that parts swapping does very little, while actual design changes can bring big improvements.
To the designer (evangelion1999) you said you use the LM4562 output op-amp. Do you have some measurements of this to show better performance than NE5532?
Many people dislike the NE5532 but I have measured the output of a very similar design (not the Mini2496 though) with both 5532 and 4562 and found absolutely no difference. This would suggest to me that both op-amps performance is below the issues the DAC distortion, PSU decoupling and grounding etc.. cause.
Anyway I think this DAC is great for the money. A high quality transformer output or perhaps a 'super-bal' op-amp output such as used in the CA DacMagic would take it to superb (objectively). It is generally my finding that parts swapping does very little, while actual design changes can bring big improvements.
Last edited:
Here is my measurements of the Mini2496 at full output taken with my M-Audio Fast Track Ultra. - GREEN
I also tried knocking up a super-balanced configuration of output stage using a dual 5532 for one channel. - RED
Make of it what you will. I can say that the high 50Hz hum and LF harmonics are from the M-Audio interface. Much of the HF spurious noise is also from the computer, but how well circuits deal with such things is important IMO.
I also tried knocking up a super-balanced configuration of output stage using a dual 5532 for one channel. - RED
Make of it what you will. I can say that the high 50Hz hum and LF harmonics are from the M-Audio interface. Much of the HF spurious noise is also from the computer, but how well circuits deal with such things is important IMO.
An externally hosted image should be here but it was not working when we last tested it.
Last edited: