Audio Crunching using an Audio Interface

Rocky Linux Help & Support
1

Hey Guys, not an audio engineer by any means, more of a hobbyist so bear with me :slight_smile:

I have a Focusrite Scarlett Solo USB 3rd Gen and I have been struggling for days to get rid of this weird audio crunching. This only happens when running my headphones through the audio interface, not when my headphones are running straight from the motherboard.

Would really appreciate any help with this.

Here is my pw-top for context

Note* “Chromium” is the Tidal streaming application

I 29 0 0 0.0us 0.0us ??? ??? 0 Dummy-Driver
S 30 0 0 — — — — 0 Freewheel-Driver
S 54 0 0 — — — — 0 Midi-Bridge
S 57 0 0 — — — — 0 bluez_midi.server
R 60 1024 48000 207.6us 11.7us 0.01 0.00 0 S32LE 2 48000 alsa_output.usb-Focusrite_Scarlett_Solo_USB_Y78CGBC19D1555-00
R 74 1024 48000 95.7us 27.7us 0.00 0.00 0 F32LE 2 48000 + Chromium
S 61 0 0 — — — — 0 alsa_input.usb-Focusrite_Scarlett_Solo_USB_Y78CGBC19D1555-00.

2

This needs a bit more clarity. You mean your headphones have a 3.5mm stereo jack (or 1/4") and you are plugging them into the headphone socket of the Scarlett?

But when you plug them directly into the computer sound card, they sound good?

More clarity needed “crunching”, do you mean like crackling, or do you mean distortion, or something else?

As I understand it, you can use the Scarlett without a computer, you can inject audio into the line in socket, and then hear it on the headphones, if so, do you get the same issue (without the computer)?

3

Ok, some more clarity.

So I’m using the Beyer-dynamic DT 770 Pro 80 Ohm headphones with a screw on 6.35mm Stereo jack adapter, into the audio interface.

When plugged into the motherboard I screw off the 6.35 and use the 3.5mm Stereo jack.

Directly into the motherboard the audio is fine.

The audio “crunching” is fuzzy/sandy sounds on all audio playback, especially on higher frequency sounds like symbols etc.

The audio interface sounds perfectly fine when I boot into windows, and when I inject audio straight into the interface (Guitar) it also sounds fine.

Let me know if I can provide any other specs and details that might help.

Thanks!

4

Found this with a google search:

So perhaps your problem is caused by the fact they aren’t getting enough power? Have you tried normal everyday headphones connected to your computer to compare? (like the ones you get with a phone, or others you may have purchased previously that aren’t as “professional”)

5

These headphones work perfectly fine without enough power, I run them on my phone with aux and on my laptop (windows) Also when plugged into the motherboard they don’t get the extra power but sound perfectly fine. All that happens when they don’t get enough power is they lose a bit of punch but not audio quality.

The audio issues happen when I plug them into to the Scarlett Solo USB (Which does provide the power needed to make use of the 80 Ohm headphones). This device acts like an amp for the headphones.

Ive been using this setup for years on windows without any issues, only ran into this once I’ve started using Rocky Linux.

6

Specs indicate headphones can be 33 to 300 ohms.

Other things to check.

Are you relying on power from USB, or do you have the Scarlett plugged into a mains adapter. USB power might be too low.

From the above, it sounds like the issue is the USB interface, does not affect analog out, and works without compter.

Try connecting “line out” from motherboard into “line in” of the Scarlett, e.g. using 3.5mm jacks. Does it work, does it sound good / bad?

7

I would suggest booting one of the Fedora Live CD’s to check/test everything since Fedora has much newer packages, kernel etc. Rocky like most Enterprise Linux is better for servers than desktops. Sure you can use it as a desktop, but it’s not ideal for every situation.

Testing the Fedora Live CD will at least show if there are any differences when using a newer kernel with newer modules/drivers for the hardware. And since it’s a Live CD no need to install to test. You can boot from a USB stick prepared from the ISO image.

8

Just to check:

Is Windows running on the exact same machine (hardware) as Rocky, or on a different device?

9

Yes, exact same hardware (dual boot)

10

Did you have to install any drivers on a) Windows, b) Rocky to get it to work, or does it work without needing drivers?

11

Windows will most likely have the latest drivers available and would explain why it works. Rocky doesn’t and won’t support all hardware by default, and thus for the latest and greatest drivers you would need something more up-to-date like Fedora. Did you test with the Fedora Live CD like I already mentioned?

Another alternative is using kernel-lt or kernel-ml from elrepo in Rocky which would be a newer kernel and a more broader range of hardware support as well as updated kernel modules/drivers.

12

You’re dealing with an impedance mismatch between Scarlett at <1 Ohm and the headphones at 80 Ohms. The Scarlett is designed for 8 Ohm phones (low-voltage/high-current) and your 80 Ohm phones for high-voltage low-current vacuum tube amps such as your guitar amp.

You could muck around trying to find a matching transformer but I would just go for the Sony MDR 7506 Professional Headphones. They are used by studio sound engineers and are priced around $100.