Octo out order issue

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Octo out order issue

Post by pierlox » Sun Sep 24, 2017 8:30 pm


I'm quite a beginner on raspi and just purchased an octo card to work on a simple 8 out synth in Pure Data. Sorry if my explanations aren't very clear…

Because I will not use inputs on this project, I thought I might unplug the 6 inputs (to improve compacity). So, I did some tests with the input board plugged and unplugged, using a PD patch with 8 audio outputs (using the [dac~ 1 2 3 4 5 6 7 8] object) and I found some strange results (please see scheme attached) :

• Without the 6 inputs board :
— the order of outputs seems logical but the audio signals of 5 and 6 outputs are mixed on both outs (5 and 6)
— the out n°8 has a lower audio signal and some audible distorsion

• With the 6 inputs board plugged :
— order seem tricky : 3-4-5-6-7-8-1-2
— there is the same trouble with mix on 5 and 6 outputs (the physical ones) and low vol/disto on n°8 (now outputting signal of channel 2)

Am I doing anything wrong ?! Is that possible there is a physical mis-soldering on the 5 and 6 outs ? Any idea that might help me ?

Kind regards,
octo-outs.jpg (139.74 KiB) Viewed 2021 times

Posts: 9
Joined: Tue May 02, 2017 8:38 pm

Re: Octo out order issue

Post by tha-poke » Sun Oct 01, 2017 3:53 am

I was having major issues with pure data reordering outputs every time i restarted it or the pi, I sorted it by using jack and starting the jack server at boot, then loading pd with a separate script which connects pd to the Octo outputs.

Are you using alsa or jack? I couldn’t figure out how to sort this using just the alsa driver.

Posts: 4
Joined: Sat Sep 23, 2017 2:18 am
Location: France

Re: Octo out order issue

Post by pierlox » Mon Oct 02, 2017 1:22 am

Thanks Tha-Poke for your reply!
Yes I try to do it using only ALSA, but as you said Jack seems to be more than helpful. So I'll go this way.
But concerning the mix of 5-6 outs I guess it's more an hardware issue and Jack won't help.

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Joined: Sat Jul 23, 2016 11:39 pm

Re: Octo out order issue

Post by flatmax » Mon Oct 02, 2017 8:47 pm

Hi there,
I haven't noticed mixing between channels 5 and 6 - interesting !

What is your software setup - PD I see. Can you tell me if PD opens both input and output at the same time ? Or does it open one then the other much later ?

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