Great product ...

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phorton
Posts: 1
Joined: Wed Jul 24, 2019 9:10 am

Great product ...

Post by phorton » Wed Jul 24, 2019 9:36 am

Hey there Matt,

Great product. Very quiet. I am working on a vGuitar thing https://hackaday.io/project/165696-rpi- ... guitar-rig

The octo and/or stereo AudioInjector cards figure prominently into my plans. It's kind of a looper combined with a guitar synth and effects. The audio input is important, and there aren't a ton of options for well built rPi shields with input, much less with multi-channel inputs. The AudioInjector Stereo and Octo are two such cards, and generally I plan to allow either in my system. I can see a smaller box with the wm8731, and a bigger box with the octo card.

Imagine looping your voice, with your guitar, with a synthesizer (Fishman FTP), in layers, sequentially or in parallel, ..... I'd even like to hook it up to a remote android display device (on the mic stand) displaying lyrics and structure in a "chordpro" (songbook) application. You pick a song and it knows the structure and general layout for the patches, loops, etc, while not unduly boxing you into a rigid structure. I don't use click tracks or sequencers on stage, so it has to figure out the tempo from the sound .. maybe even slowing the (audio) loop down or speeding it up on the fly. Very complicated :-)

Anyways, I wonder where to order the balanced IO cards, as your proven circuits would provide a good starting point for what I'm thinking about. It's too early to firm up the specs, but I kind of envision a 6 channel input mixer of sorts, maybe with 4 channels with pre-amps, and two with just line-ins (a stereo pair). I've ordered a bunch of different opamps (NE5532', OPA2134's), several existing inexpensive pre-amp "modules" based on them, and even a few of the expensive, completely integrated pre-amp ICs ... like the PGA2500IDB. I have a ton to learn about it, so I'm not quite ready to ask any questions yet. I will be experimenting with my first home built pre-amps in the next weeks. It will be a while before I have enough confidence to (risk) plug one into an actual octo card. I'm just now learning about differential versus single ended signals :-)

However, if you, or anybody, has created schematics for any other kinds of things that safely connect to the Octo sound card (and I know at least one user is making some kind of breakout boards, but I can't seem to find the post, you know which one I'm talking about?), or if you have any suggestions for a newbie to move towards, or away from, specific kinds of analog circuits, given your proven experience, that'd be great to know too.

Otherwise, just a quick "shout out" to let you (and everyone) know that I'm here and to thank you once again for your fine work.

Thanks,
- Patrick

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