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Old 17th November 2010, 01:41 AM   #1
diyAudio Member
Join Date: Nov 2009
Location: Vienna
Default Measuring AD1865 DAC2

Dear All,

I have a new measuring toy (Picotech 4424), and I am doing some measures on my gears. Main purpose is to lear how to use the instrument, understand results and put a baseline for further development.

I started measuring signals out of my MAC PRO and I measure the DAC2 designed by Quanchao.

On the latter I got some strange/interesting results. DAC has been fed both with the digital output of the laptop and with the M2Tech Iface, with no measurable difference. For the pictures I used the Iface.

Please see the images attached:
1) The first image is the FFT with no SPDIF connected. Wondering what that bomps are, but this can be not relevant
2) Second picture is a 1kHz signal 44.1 kHz. There are so many odd harmonics, but the measured THD is not so bad.
3) Third picture is the same signal with 96 kHz. The FFT looks much better, but the value of the THD is almose one order of magnitude more.
4) The last picture is a 1kHz square wave. This is where the DAC performs very well. If compared to the analog output of the MAC it is perfetc, while the MAC was showing very evident symmetric ringing.

Any comment ?

One question: for IMD I think I have to feed two signals. What are good frequencies to use ?

Additionally, I noted that the signal generator software really matters. I tries Tongen and SignalSuite. The latter is much more accurate in term of THD.

Best Regards,

Attached Images
File Type: jpg nosignalad.JPG (117.4 KB, 196 views)
File Type: jpg 44ad.JPG (123.1 KB, 196 views)
File Type: jpg 96ad.JPG (124.6 KB, 187 views)
File Type: jpg squareadmac.JPG (53.4 KB, 180 views)
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Old 18th November 2010, 05:15 AM   #2
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Join Date: Nov 2009
Location: Vienna
No input on this ? :-(

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