Help routing external audio in

I bet this is very easy but I can’t make it work and I have searched on the wiki and here in the forum.

The goal is simple: send audio from a synth to the Zynthian, process the audio with effects, and enjoy that wet audio.

The synth is connected to a mixer. There I have an insert cable connected to Zynthian’s audio in left and audio out left. This setup works as expected when I plug a Maschine.

In the Zynthian I have an audio chain with GxTubeDelay (could be anything, I’m still testing and happy to hear anything). In Audio Options I have selected Mono (didn’t work without this selected either). Audio capture already had both system capture 1 and 2 selected. Audio output has the mixer selected. I play the synth, no audio sounds.

Something that I find intriguing is that I need to define a midi channel to create an audio chain. What is the relation? Anyway, I select a channel where I have a keyboard controller connected. I play the synth and the keyboard, just in case the audio signal is only captured when midi is being received. Nothing.

I don’t know what else to try. Can you help me, please?

Which audio card are you using? The Audio Injector required alsamixer settings to be adjusted to get it to work, and the settings can be doing this.
It sounds like everything is correct, but if you aren’t seeing audio kicking on the zynthian mixer there can be issues upstream till you get to the audio in sockets.

It’s worth looking in the Audio Levels menu in the Main zynthian menu ( it’s under SYSTEM). This is where the audio in and out devices are configured and that would be a good place to start checking.

Yes this is a hangover from older days, but it is relvant because this is the route that allows the very powerful Zynthian MIDI infrastructure to control parameters on the audio channels you’ve made.
the zynthian allows you to easily put the GxTubeDelay PArameters onto an externally connected foot pedal ( with a zynaptik AtoD input ) and store that all as a snapshot to be loaded just before the dramatic guitar solo…

Ah, indeed. Thank you!

ADC Left Input Left was “No Select”. It took me a while to even realize that there was a second page, and how to get there.

I need to figure out what are these VINL2 etc options but some of them do bring audio, finally. There is a hiss too, and who know what is producing it (many candidates), but I’ll investigate all this later. Time for a break now. Thank you again!

This explanation was useful.

Solved. When I was looking for the problem I saw that in Audio Levels, ADC Left and Right were apparently very low. I pump them up. Turns out that the default 9 value is more than enough. This makes the hiss basically go away. Good.

Ok, “pedal mode” works now. Time to explore effects. :slight_smile:

There are certain rules about quite what I am required to do at this point…

Frankly it’s long and tedious without emojis and is explained here…

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Hi @icaria36! I’m glad you managed to get audio through your Zynthian.

The audio input options (ADC Left/Right Input) control how the differential inputs are configured:

  • No Select - disconnect input
  • VINL1[SE] - single ended (unbalanced) input, tip & sleeve
  • VINL2[SE] - single ended (unbalanced) input, ring & sleeve
  • VINL2[SE] + VINL1[SE] - single ended (unbalanced) input, tip+ring & sleeve (mono mix of tip&ring)
  • [VIN1P,VIN1M][DIFF] - differential (balanced) input, tip, ring & sleeve

(The same for the right channel, e.g. VINR1[SE], etc.)

If you are using single ended / unbalanced inputs (TS) then the first option is normal. If you are using differential / balanced inputs (TSR) then the last option is required. I like the third option that allows an unbalanced, stereo input to be connected to a single Zynthian input. That stereo source is mixed to mono in the soundcard hardware and appears as a mono source to the zynthian chain(s).

Regarding a MIDI channel used for audio only channels, @wyleu’s description is not quite right. We currently use the channel number to identify both MIDI channel and audio mixer strip. This is a simple / pragmatic way to introduce the mixer without changing the whole infrastructure. It has been mentioned many times before that we don’t really need this tight binding of MIDI & audio channels and I am currently working on changing the architecture to separate them. MIDI Continuous Control commands are filtered and processed by Zynthian before they reach any chain. This allows you to map any CC on any MIDI channel to any parameter on any chain. There is not a constraint that the CC for a chain must be the same MIDI channel as that chain.

Getting audio input levels set correctly is an important part or setting up any audio system. You want to set the mixer fader to unity gain (about -10dB from fully open) and adjust the input gain (sometimes called, “trim”) so that maximum audio input peaks to a level that is approx. -10dBfs, i.e. 10dB below full scale deflection. This gives you 10dB of headroom. Depending on the type or audio signal you may be able to get away with higher or lower headroom but that is where I tend to start. (Audio engineers may call this process, “lining up”.) If the signal has too much gain then it may overload the input stage, distorting the signal causing clipping. Too little gain and the signal to noise ratio (SNR) is poor resulting in unwanted noise (hum / hiss) on the signal. The analogue audio circuitry in the Zynthian soundcard (and Hifiberry cards) overloads quite nicely, giving a warm, analogue distortion that is quite forgiving on instruments such as guitar. Indeed I have driven the input into overload for effect.

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