Search found 20 matches
- Sun Sep 24, 2017 2:13 am
- Forum: Octo Sound Card for the Pi
- Topic: Some measurements...
- Replies: 8
- Views: 4891
Re: Some measurements...
This is the noise spectrum, with the Micstasy gain at +18dB, so that a full-scale output produces a full-scale input to within maybe +/-2dB of error. I wonder what causes this... Could it be fixed with a more stable power supply? I'm using a five-way USB charger capable of delivering 2.5A on each ou...
- Sun Sep 24, 2017 2:05 am
- Forum: Octo Sound Card for the Pi
- Topic: Some measurements...
- Replies: 8
- Views: 4891
Re: Some measurements...
So I'm trying to quantify the noise floor by doing the following: I play an 1kHz sine wave through all eight Octo outs at -1.0dBFS into the eight Micstasy inputs. When I set them to +18dB gain, I get just about -1.0dbFS of peak value out of the AD converters. With this gain, I'm starting jnoisemeter...
- Sun Sep 24, 2017 12:40 am
- Forum: Octo Sound Card for the Pi
- Topic: JACK, DC signals, pinouts.
- Replies: 7
- Views: 2719
Re: JACK, DC signals, pinouts.
Hmm. The kernel driver thinks the card has 8 ins: static int audioinjector_octo_startup(struct snd_pcm_substream *substream) { struct snd_soc_pcm_runtime *rtd = substream->private_data; rtd->cpu_dai->driver->playback.channels_min = 8; rtd->cpu_dai->driver->playback.channels_max = 8; rtd->cpu_dai->dr...
- Sun Sep 24, 2017 12:00 am
- Forum: Octo Sound Card for the Pi
- Topic: Some measurements...
- Replies: 8
- Views: 4891
Re: Some measurements...
Having read about an Octo user who is using his in an analog synth context, I do understand the benefits of going down to DC... it's just that in everyday music use, DC coupling tends to cause quite a few problems if you're unaware of it, but hey, I take back my remark now that I've heard of a useca...
- Sat Sep 23, 2017 11:53 pm
- Forum: Octo Sound Card for the Pi
- Topic: Some measurements...
- Replies: 8
- Views: 4891
Re: Some measurements...
Here is a recording of output channels 5-8 playing digital silence. The noise peaks correspond to me running "ps aux" on the command line via an SSH session. You will notice that the noise level of channel 7 is also attenuated, not just the signal. Channels 1-4 look identical to 5,6 and 8. The wavef...
- Sat Sep 23, 2017 11:39 pm
- Forum: Octo Sound Card for the Pi
- Topic: JACK, DC signals, pinouts.
- Replies: 7
- Views: 2719
Re: JACK, DC signals, pinouts.
Using jack2 here without issues, and also a network audio connection with zita-njbridge (not netjack). All well, except somehow the card gets opened with 8 inputs rather than 6. Still investigating.
- Sat Sep 23, 2017 11:28 pm
- Forum: Octo Sound Card for the Pi
- Topic: sound quality
- Replies: 5
- Views: 2166
noise levels and high sample rates
Hi everyone, just a quick heads up: if you measure noise "by the book", you integrate across the entire spectrum. That means an excellent 192k device will have _four_times_ the noise of an excellent 48k device. If you want to read the same value always, you will have to use a bandpass from, say, 20 ...
- Sat Sep 23, 2017 10:43 pm
- Forum: Octo Sound Card for the Pi
- Topic: Purpose of P2 jumper on bottom of the board
- Replies: 3
- Views: 2078
Re: Purpose of P2 jumper on bottom of the board
Bump! I'd like to know, too!
- Sat Sep 23, 2017 10:39 pm
- Forum: Octo Sound Card for the Pi
- Topic: Some measurements...
- Replies: 8
- Views: 4891
Some measurements...
Hi Matt, first of all, congrats for pulling this off - I still have no clue how you are piping this many channels through a single I²S bus! I ordered two RCA Octos from Amazon UK and I'm now measuring them. For "consumer" sound, they are pretty ok, but for professional use, there appear to be number...
- Sat Sep 23, 2017 7:35 am
- Forum: Octo Sound Card for the Pi
- Topic: Octo Sound Card attenuated output
- Replies: 7
- Views: 3916
Re: Octo Sound Card attenuated output
Same here. Channel 7 is about 11 dB down. Just running some measurements, will report back later.