Linux - Record level of USB Audio Interface?

Hello and sorry this is very basic but apart from Alsamixer, which doesn’t change audio levels on the Audio Interface I’m trying to change, I can’t find much info.

Basically I have a Yamaha THR30 desktop amp which includes an USB audio interface. It’s all working fine, recognised by Linux when connected and Ardour I can record the audio. My only problem is that the levels I’m recording are really low so I’m trying to change the recorded level. I assume that’s a Linux issue so been searching, but like I say apart from Alsamixer I can’t find much, and nothing that actually changes the level.

For reference when I play a guitar on the interface with the tracked armed to record when I look at the “editor mixer” strip then the guitar is showing up with a peak signal of -39dB. If I record and add the apparent maximum 6dB of gain it’s still very faint at maximum output volume.

The user manual at the Yamaha site is completely worthless.
What does the “guitar output” level control affect? Does that only increase the amp output volume, or does it also increase the level sent to the USB interface?

Since Yamaha do not provide a block diagram showing the gain structure and where the USB interface fits into the signal flow, you will just have to play around with the gain, master, and guitar out controls to see how they interact with acoustic volume and USB signal level.

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Oops I had the Volume of the THR30 Max’d but only one of the three. :frowning:

Thanks a million for that help. There’s three “Volume” controls in the guitar signal path, “gain”, “Master” and “Guitar”. That last one is kind of a master master, which I had max’d. From playing about with it the USB Audio out level is coming from the first two, “gain” and “master” and both have to be Max’d to get anything usable.

Looks a lot like I’ll not be using the THR30 as an audio interface.

Thanks again for your help. I’ll play around with it and see if I can’t get it to a passable level.