Audio I/O (formerly Audio Interface II) . No visual feedback from the LEDs

Hello forum.
the LEDs on my Audio I/O (formerly Audio Interface II) don’t work anymore.
I don’t get any visual feedback thru LEDs when i´m switching on the power of my eurorack (which should be), or when i´m sending audio thru the module. The LEDs are just off while the other functions are working. I already pushed the CAL-button on the back of the module, but the LEDs still won’t work.

Is there something else I could try?

Thankful for every helpful hint,

Hi Kwad,

Please reach out to

Has anything changed in your case recently that may have caused the problem?

As in they used to work but then no longer do?

I recently ordered a 3u Audio Interface II (or whatever it is now called) and had the same reaction that you are describing on first use. The sound was coming through fine, but the LEDs were all off. I figured that they weren’t working, then I hit the inputs with a spike in the audio, basically just cranking up the signal that was feeding it, and I managed to get a little activity on the LEDs.

You may want to try that, just unplug the outputs and send a hot signal to the inputs and see if you get any lights.

On a related note - is this something that the CAL button will help me calibrate away? If I can comfortably hear the audio on the PC interface that this module is feeding, I would hope for at least one LED to show that there is signal.

If you turn all of the knobs CCW and hold the rear CAL button while you power on the module this should automatically calibrate the LEDs. Afterwards you can press the CAL button to toggle between two display modes: Line and Dot.

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Awesome! Perfect thanks for the tip!

I’m guessing this was information that I could and should have just gotten from the manual. The shame!

So I finally got around to attempting this calibration procedure and… Turns out I do not have the button in the back at all. There’s no mention of it in the manual either. But I watched the video on the product page and it shows the back of the module very briefly, and it is definitely different than mine. Even the power header is in a different spot.

The print on the bottom / exposed PCB reads “Audio Interface II MAIN rev003”.

The video on the product page is from 2017 and it shows the button. I just ordered this module from your website a couple of months ago, albeit from the blemished section. Is rev003 an older or newer model than the 2017 version that features the button? The front panels appear to be identical.

Anyway, I do have 4 trimmers available to tweak, but I assume those are for adjusting the gain amounts of the knobs, right? Any other way to calibrate the LED response on the rev003 version?


Hi @chronomod,

Yes the Legacy Audio Interfaces in the B-Stock section are an older revision before the CAL button was added, so you don’t have the auto-calibration or the LED display options.

You do still have our usual 2-year warranty so if you feel the LED behaviour is faulty you should reach out to

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Eh, the audio sounds good, and the LEDs work, it’s just the minimum threshold for them to show activity is higher than I would prefer. Considering that some output modules don’t have LEDs at all, and some only have a clipping LED, I’m not sure this is worth the trouble of sending in for service.

Thanks for the reply!