Search found 59 matches

by robiwan
Mon Nov 20, 2017 12:34 am
Forum: Stereo soundcard for the Raspberry Pi
Topic: Low input sensitivity
Replies: 13
Views: 6121

Re: Low input sensitivity

Furthermore, here is an Oscilloscope screenshot of the output of the soundcard. The datasheet states 1.0Vrms*(AVdd/3.3) and as the AVdd is 3.3V, the output should be peak +/- 1.4142V, which the scope screenshot verifies. So the problem is on the input side.
by robiwan
Mon Nov 20, 2017 12:22 am
Forum: Stereo soundcard for the Raspberry Pi
Topic: Low input sensitivity
Replies: 13
Views: 6121

Re: Low input sensitivity

Ok, I've done a loopback test where I playback (with aplay) a 0 dB fullscale WAV file, and the result is recorded with arecord. I would have expected that the result would be approx. 0 dB peak, but it is far from it. The result is at least 6 dB lower than fullscale. See attached files. Could it be a...
by robiwan
Wed Sep 06, 2017 4:40 pm
Forum: Stereo soundcard for the Raspberry Pi
Topic: Low input sensitivity
Replies: 13
Views: 6121

Re: Low input sensitivity

Yup, I have everything set to max, still having this issue. I will try to do a measurement of the exact levels, analog and digital.
by robiwan
Wed Aug 30, 2017 9:36 pm
Forum: Stereo soundcard for the Raspberry Pi
Topic: Low input sensitivity
Replies: 13
Views: 6121

Low input sensitivity

Hi Matt, I have a solution now which streams audio, but I notice that full output from a USB audio device couple to the input of the I2S card does not even remotely reach +0db peak level, more like -20 dB peak. Is there a way to set the PGA of the WM8731 for higher sensitivity ?
by robiwan
Sun Aug 27, 2017 6:45 pm
Forum: Stereo soundcard for the Raspberry Pi
Topic: Lowest possible latency
Replies: 42
Views: 20456

Re: Lowest possible latency

The latencies we are talking about here are typically within the DMA process in ALSA. Typically Codecs have 1 sample of latency. I imagine that the incoming audio bits get fed directly to the sigma delta converters in some way. Yes, I've tried to query Cirrus for the analog<->digital latency of the...
by robiwan
Sat Aug 26, 2017 5:23 pm
Forum: Stereo soundcard for the Raspberry Pi
Topic: Lowest possible latency
Replies: 42
Views: 20456

Re: Lowest possible latency

I have not anyway. Looking at the I2S spec of the RPi, it should be possible to get really low latency by lowering the FIFO IRQ threshold of the I2S subsystem, but I have no idea if it is possible to config the current I2S driver for this.

Btw, which USB unit are you using for the 8 frame setup ?
by robiwan
Sat Jul 29, 2017 11:45 pm
Forum: Stereo soundcard for the Raspberry Pi
Topic: Audio injector zero kickstarter is live !
Replies: 22
Views: 7260

Re: Audio injector zero kickstarter is live !

The TI ones are really good too :)
by robiwan
Thu Jul 27, 2017 6:07 am
Forum: Stereo soundcard for the Raspberry Pi
Topic: Audio injector zero kickstarter is live !
Replies: 22
Views: 7260

Re: Audio injector zero kickstarter is live !

Fascinating! Hope you get your project going, seems very interesting indeed.
by robiwan
Thu Jul 27, 2017 2:00 am
Forum: Stereo soundcard for the Raspberry Pi
Topic: Audio injector zero kickstarter is live !
Replies: 22
Views: 7260

Re: Audio injector zero kickstarter is live !

Duncan, what is the main purpose of the bat detector ? Well I see the obvious one: Detecting bats! But one thing that would be interesting is to downshift frequencies into the audible range to be able to "hear" the bats.
by robiwan
Wed Jul 26, 2017 5:38 pm
Forum: Stereo soundcard for the Raspberry Pi
Topic: Lowest possible latency
Replies: 42
Views: 20456

Re: Lowest possible latency

Matt, I've measured the latency in/out to about 2.5 ms, so a part of that must be the analog <-> I2S latencies. I've tried to find info about that in the Wolfson datasheets but could not find anything. Do you have the possibility to short circuit I2S so that you can measure the ADC -> I2S -> DAC pat...