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SoNic_real_one 5th March 2012 02:01 AM

Measurements
 
I have a new "toy" E-MU 1820 (with PCM1804 ADC) do I decided to do some THD testing of my digital players. Thought to share the results here. I don't know how accurate are ARTA calculations, so I will post the screen-grubs too. The table is my attempt to centralize and interpret the data. Actual resolution is calculated from THD+N results (provided by ARTA).
A quick note - I did those measurements with unbalanced cables, in "consumer" mode (because my players have unballanced outs). That is at -10dB level compared with than the ballanced "professional" mode that can go to +4dB... The loopback was done the same way, I will get a ballanced cable and redo that measurement soon.
LE: Updated table with the 1820m version that has better A/D converter (AK5394A). Updated pictures are in posts #22,23,24:
http://www.diyaudio.com/forums/attac...nts-table2.png

PCM61 & LM4562 (modded Denon DCM-360) - sorry, I didn't realized that the bottom level was shifted (it doesn't matter in calculations):
https://lh5.googleusercontent.com/-t...DCM360_0dB.PNGhttps://lh3.googleusercontent.com/-r...CM360_60dB.PNG

TDA1541 & LM4562 (modded Philips CD-473):
https://lh4.googleusercontent.com/-e...da1541_0dB.PNGhttps://lh4.googleusercontent.com/-1...a1541_60dB.PNG

PCM1791 & AD8599 (modded Denon DVD-2910):
https://lh5.googleusercontent.com/-_...cm1791_0dB.PNGhttps://lh3.googleusercontent.com/-P...m1791_60dB.PNG

2x PCM1791 & NJM2068 (Denon DVD-2930CI, stereo out):
https://lh3.googleusercontent.com/-a...cm1791_0dB.PNGhttps://lh5.googleusercontent.com/-u...m1791_60dB.PNG

CS4392 & NJM2068 (E-MU 1820 output):
http://www.diyaudio.com/forums/attac...m_loopback.png

UPDATE: I did upgrade my external dock to the E-MU 1820m (with AKM AK5394):

https://lh4.googleusercontent.com/-g...0/EMU1820m.JPG

ThorstenL 7th March 2012 04:55 AM

Hi,

Quote:

Originally Posted by SoNic_real_one (Post 2933457)
I have a new "toy" E-MU 1820 (with PCM1804 ADC) do I decided to do some THD testing of my digital players.

Looking at loop-back results and the results for the AD alone, something is grievously wrong in your set-up. So your measurements of external gear are likely pointless.

Could be bad cables, problems with level settings etc, I don't know.

I have several EMU1616m in use for measurements, who share the ADC and circuit of your 1820, AFAIK, I get nearly 120dB SNR in loopback, including DIY breakout box, cables from breakout box to EMU and the cables used in the setup, with their ends connected by an adapter.

Cables are double screened starquad mike cable (tinned) for Breakout Box to EMU and Foil & Braid screened 75R Coax externally with BNC's and BNC to RCA adapters at the end (all connectors NOT goldplated).

I use precisely the same cables on the AP2 that is a few meters away.

Maybe crucial, the DUT is fed floating earth balanced power, as is the PC connected to the EMU (separate transformers) and the same set-up applies to the AP2...

Ciao T

DoktorSteve 22nd March 2012 05:02 PM

Just curious how you got to the LM4562 with the PCM61. Did you also try the NJM2068?

SoNic_real_one 22nd March 2012 10:39 PM

Quote:

Originally Posted by DoktorSteve (Post 2956350)
Just curious how you got to the LM4562 with the PCM61. Did you also try the NJM2068?

I had LM4562 in DIP8 capsule. I didn't install sockets because I did try before (on a TDA1541) the NJM2068 (I have several DIP8) and then I did prefer the LM4562...

studiostevus 28th March 2012 02:34 PM

4 Attachment(s)
Thought I'd give it a try with my emu0404...

Emu0404 loopback @ 0db
Attachment 274253

Emu0404 loopback @ -60db
Attachment 274254

Modded Marantz cd-63se (lm4562) @ 0db
Attachment 274255

Modded Marantz cd-63se (lm4562) @ -60db
Attachment 274256

SoNic_real_one 29th March 2012 02:40 AM

9 Attachment(s)
Received the new and improved 1820m.
New batch of measurements are posted below. They are as expected slightly better due to less contribution to THD+N from ADC. The previous results for the multibit DAC's where erroneous due to a misread of the THD+N at -3dB... They where 10 times worse. Obvious winner is (gasp) the S-D DAC that was read correctly. The results psoed by studiostevus are simular for TDA1541 like mine's. At low level MB THD+N (DNR) results are similar with S-D ones.

http://www.diyaudio.com/forums/attac...nts-table2.png

Pictures below: PCM61+LM4562 @ -3db and -60dB; PCM1791+AD4599 @ -3db and -60dB;TDA1541+LM4562 @ -3db and -60dB.

sgrossklass 29th March 2012 04:10 PM

Your -60 dB results still look bad. I know nearly nothing about ARTA, but if I had to hazard a guess I'd say you're recording in 16 bit.

studiostevus 2nd April 2012 05:16 PM

Loopback results suggest otherwise....

SoNic_real_one 2nd April 2012 09:03 PM

Quote:

Originally Posted by sgrossklass (Post 2965015)
Your -60 dB results still look bad. I know nearly nothing about ARTA, but if I had to hazard a guess I'd say you're recording in 16 bit.

The SOURCE is 16 bit because is a CD. I did want to measure CD transports. I could make a 24 bit DVD to measure the Denon DVD universal player (with PCM1791). I didn't do it yet because I tought it would not be fair/relevant comparation to the multibit DAC's that are limited to 16 bit CD resolution.

wwenze 3rd April 2012 12:05 AM

About the unusually high THD, seems that ARTA doesn't limit the bandwidth to 20kHz (or 22kHz.... blah blah), but uses the entire full bandwidth of whatever sampling rate you choose.

http://img831.imageshack.us/img831/7...xarta48khz.png
http://img834.imageshack.us/img834/7...xarta96khz.png

So those THD/THD+N numbers depend on the sampling rate and can be seriously hurt with most filters that don't remove stuff above audible frequencies.

And actually I have some doubts over how it calculates THD and THD+N too, but then I doubt everything.


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