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How to wire the balanced breakouts

Posted: Tue Jul 25, 2017 9:55 am
by flatmax
If you have purchased/received the balanced breakouts, then wiring them up is simple once you know, but seems like a jigsaw puzzle at first.

Here is a connection diagram :
octo.balanced.connectionDiagram.forum.jpg
Audio Injector Octo balanced breakouts connection diagram
octo.balanced.connectionDiagram.forum.jpg (221.91 KiB) Viewed 5199 times
Key thing is to make sure the preamp is plugged correctly into the Octo sound card. The mechanical holes should line up perfectly. The 8 outputs are on the left side, the 6 inputs are on the right side.

There is no phantom power provided on the input side (some condenser microphones require phantom power).

NOTE: you can wire up without the preamp if you want to do field recording with only the 5V supply, however you will have to be careful and reduce the gains of the ADCs and DACs from full scale to get linear recordings without clipping.

Matt

Re: How to wire the balanced breakouts

Posted: Tue Jul 25, 2017 10:08 am
by flatmax
For field recording, you can remove the preamp, however your dynamic range will be reduced.
In this case, the balanced breakouts can draw their power directly from the 5V output from the Pi's power supply. This means you only need to power the Pi and the balanced breakouts will be powered as well.

To use this setup, you will have to reduce your ADC and DAC gains from full scale to make sure you get a linear signal.
octo.balanced.connectionDiagram.fieldRecording.forum.jpg
Audio Injector octo balanced field recording connection diagram.
octo.balanced.connectionDiagram.fieldRecording.forum.jpg (201.58 KiB) Viewed 5197 times
If you will be using microphones which require phantom power, you will need to power them yourself. Dynamic microphones typically don't require external phantom power.

Matt

Re: How to wire the balanced breakouts

Posted: Sat Sep 23, 2017 1:31 pm
by waldo
Hey, new guy with question. I don't have a board in hand yet.

Can I assume that I could wire balanced i/o directly to the hat pins? Reason being that I want xlr and no preamp. So I would wire xlr jacks to a header to plug straight into the hat pins.

If so, can you point me to the pinout?

cheers,

waldo

Re: How to wire the balanced breakouts

Posted: Thu Sep 28, 2017 3:19 pm
by flatmax
Hi there,

Yes you can do this.
Have a look at the pdf of the schematic here :
https://github.com/flatmax/AudioInjector.Octo.balanced

The pdf gives all of the pin inputs to the balanced header. You can work out the sound card pin headers from this.

Matt

Re: How to wire the balanced breakouts

Posted: Mon Oct 02, 2017 9:59 pm
by MedicationTime
Hi,

there's no mention of max current for preamp's voltage supply. Anything in particular ?

Thanks !

Re: How to wire the balanced breakouts

Posted: Wed Oct 04, 2017 7:07 am
by flatmax
I think it pulls around 0.3 amps.

Matt

Re: How to wire the balanced breakouts

Posted: Sun Jan 14, 2018 12:42 pm
by Ivan
Where can we buy the preamp board and the balanced breakout boards?

Re: How to wire the balanced breakouts

Posted: Tue Jan 23, 2018 5:21 am
by flatmax
We have run out of stock for the balanced boards. There is low demand so we will not manufacture any more.

Matt