Real or fake?

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New results with ARTA, 991Hz signal. "THD+N" is the DCD-360 (4562 OpAmps) at -0.6dB. "Null" is with the CD player stopped (noise?). DVD-2931 is the PCM1791 with AD8599 OpAmps one. "DCD360" one is at -3dB. Last one is loopback on my X-Fi Platinum bay.
Gosh, 0.011% that's way better! I still suspect a limitation due to my ADC - at some 0.01% now...
 

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Yeah, I know! I have used an Y adaptor from 3.5mm jack (back line out) to RCA (front bay input cables). I wonder if that made it look that bad...
Players are connected RCA-RCA. On front bay I have as output a headphones jack (1/4" type).
Or maybe this how 44.1kHz looks on the output of X-Fi...? The input I think it does not go tru the DSP so it might be "cleaner". I'll try with different frequency settings when I will come back from work.
 
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Well it's clear that the sound cards performance is dominating the measurements. It is possible that some DSP processing is going on somewhere though. Do you know what ADC the X-fi uses?

Using a Y splitter shouldn't make things that much worse.

You mention that the X-fi uses a drive bay to the front of the PC. Does the drive bay contain the DAC/ADC or does the PCI card at the back have them on and then its wires to the front? If its wires to the front, if they are transferring analogue signals then they could be picking up lots of noise. A friend once had awful noise issues when using the microphone socket on the front panel, now obviously a lot of gain was applied afterwards, but we are talking about trying to measure low distortion here, so it's just something to think about.
 
I will take a look inside the bay tonight. The bay has independet ADC and DAC and is connected via SPDIF lines (inside a 40 pin IDE cable) to the PCI card. X-Fi has one more ADC on PCI board itself, but input is via 3.5mm jack. Some say that ADC is WM8775SEDS.
About DSP - maybe the Crystalizer was "on" or something stupid like that. Will check that too.
An externally hosted image should be here but it was not working when we last tested it.
 
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That ADC should be capable to 0.003% and is roughly in line with the performance of the PCM61. Of course the surrounding analogue stuff can ruin that performance.

If possible I would use the 3.5mm input jack on the sound card itself. At least just as a test to see if the drive bay is the real issue.
 
Well, those might be from the ADC?
My X-Fi bay DAC is CS4392, digital receiver for DAC is CS8415A. I cannot figure the ADC - I think is a Philips one, but can't make out the numbers. Can it be UDA1361T??? That has THD+N= -88dB at level -1dB and -40dB at level -60dB.

I did burn a CD with -60db level and I did rotate all the DAC's that I have in one socket. Good news - all worked. Bad news - all had THD between 1% and 0.61%. I was able to "select" from all 8, two with lowest THD. This based on my limited ADC means almost nothing. Time to get a E-MU1212...
 

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That's nice to know, I am just not trusty into those mini-jack inputs.
E-MU121 uses as A/D converter AK5394A.
Equal (on paper) to the ADC in XONAR DX2 (CS5381).
I will "hunt" something on eBay.

There's nothing wrong with mini-jacks :)

Asus also use the CS5382 in their flagship cards, one of which I own and I can testify towards the quality of the line input.

Finding RMAA measurements for the EMU is harder then for the Xonar range, but of the one limited test I did find the EMU did fine.
 
I did aquire a better sound card. E-MU 1820 (same PCI card as 1212 or 1616 but with a different external dock).
I re-measure (at 96kHz samplerate) the PCM61 at 0dB and -60dB and I did a loopback test on the new card (not ballanced thou, didn't have cables for that). I am happy that at lest I have a nice audio measuring tool now. And my PCM61 does not "look" that horrid anymore :)

PS: That E-MU "Patch DSP" is kicking my butt... Not an easy setup like any other regular soundcard.
 

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Correct, I did extend the measured range on purpose. That raise over 20kHz is noise shaping - the difference between a Delta-Sigma DAC (the one in my E-MU dock is CS4392) and a Multibit one (PCM61).
Weird thing is that the odd harmonics on PCM61 are bigger than the even ones.
Also you can see in the first pic, past 20kHz, where the noise floor of the PCM61 drops (filtered, no more analog signal past that) to remain only the level of ADC noise.
PS: In my dock ADC is PCM1804 and OpAmps are NJM2068. I didn't know that only in the "m" versions they have AK5394 (with same OpAmps).
 
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