1
\$\begingroup\$

I cannot achieve a 2.1 Vrms mentioned in their datasheet (pages 4 and 9). I can only output 1.04Vrms from the 1kHz source. Do I measure it wrong or this is what I should expect? Or maybe I get such measurements because it could possibly be a counterfeit chip?

enter image description here

PCM5102A schematic: enter image description here

Update:

I tried to play different sine wave tone (0 dBFS) generated from Audiocheck and now I can see 1.88 Vrms and 5.64 Vpp when there is no load. Is this something I should expect? I'm playing this sound at the full volume over bluetooth since I use CSRA64215 chip as a source for PCM5102A. I also checked CSRA64215 config and it's output level is already set to max.

enter image description here

\$\endgroup\$
  • 1
    \$\begingroup\$ What's your code, bits, and schematic and test points? \$\endgroup\$ – Erik Friesen Jan 27 at 15:40
  • 1
    \$\begingroup\$ And the link to the datasheet and page reference? \$\endgroup\$ – Transistor Jan 27 at 16:03
  • \$\begingroup\$ 2.1Vrms is 6Vpp @ 1kohm and you are getting 3Vpp @ ? \$\endgroup\$ – Sunnyskyguy EE75 Jan 27 at 17:25
  • \$\begingroup\$ @ErikFriesen updated the main post with the schematic. I did those measurements directly from OUTL/OUTR and GND nearby. By the way, what do you mean code & bits? \$\endgroup\$ – user1258202 Jan 27 at 17:26
  • \$\begingroup\$ @Transistor updated the main post with the links and page references. \$\endgroup\$ – user1258202 Jan 27 at 17:27
0
\$\begingroup\$

To be able to measure the full-scale output, you have to input a full-scale sine wave.

I do not know what signal generator app you used, but https://www.audiocheck.net/audiofrequencysignalgenerator_sinetone.php certainly is buggy and does not generate a 0 dB FS waveform.

As far as I can see, https://www.wavtones.com/functiongenerator.php works correctly. (Even a 16-bit file will bring you to within 0.01 % of the limits.)

\$\endgroup\$
  • \$\begingroup\$ I got the same measurements even with this generator, but then I tried to generate the sine wave using Audacity and it does this job quite well - now I get 1.58 Vrms @1k and 1.91 Vrms @ 10k. I also monitored what the bluetooth module is outputting - for some reason it outputs -0.95dBFS, I checked everything in DSP chain and everything was already bypassed. But I think we can calculate Vrms like that: -0.95dBFS is 0.896396, so 1.91 Vrms @ 10k / 0.896396 = 2.13V. Is it correct? \$\endgroup\$ – user1258202 Jan 29 at 21:08
  • \$\begingroup\$ Yes, -0.95 dbFS is about 89.6 % of full scale. \$\endgroup\$ – CL. Jan 30 at 7:28

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.