tptptp

Update: Took my Helix to an authorised repairer. Diagnosis: headphone pot needs replacement. The tech also noticed that the main output level was unusually low. While I was there, we confirmed this was so, by comparing mine to another Helix that was in for service. The cause is failure of coupling capacitors. Apparently, these have a given life-span that can be reduced by exposure to heat. My Helix is 10 years old, which depending on your point of view, may or may not be a long time. I will say that my now ancient HD 500 and DT 25 are both still functioning well. It's taken too long to get these issues resolved -- and the Helix is still with the tech -- but I'm happy that a resolution is in sight.

One of the three sets of headphones I tried has a 1/4" jack -- no adapter in play.

Update: Still having an issue with the headphone out. I was fooled into thinking that the issue was resolved because of the behaviour of phones output. If the phone output dial is set to just below 9 o'clock, the left and right channels are balanced and sound ok. And here's the unexpected behaviour: If the the output dial is turned all the was anti-clockwise (about 7 o'clock) then the left channel has no output, as expected, but the right continues to have some output, albeit reduced in volume. If the output dial is then turned clockwise, to about 2 or 3 o'clock, the left channel's output increases normally without distortion, but the right channel's output increases at a lesser rate and sounds distorted and crackly. Confirmed this behaviour with 3 headphones. Ideally, there's solution, but I can live it if I limit myself to using the headphones with the output set just below 9 o'clock.

Compressed air worked for me. I was skeptical. It's been a few days and it's still ok. Simply pulled the headphone volume knob up and off the pot. There's a small hole to the left of the pot shaft where it emerges from the panel. Shot the compressed air in there and bingo! Have to think that the hole could be the source of the trouble. Should I put some tape over it to prevent debris passing through? Can't think of a downside?

Been struggling with a similar issue for a couple of days. Turns out the issue was the Helix global settings -> USB in 1/2 destination. Had it set to XLR, but nothing connected to the XLR outputs. Changed it to multi and I started hearing output in my headphones.

Agreed. The lack of Linux support is disappointing. I'm really enjoying my Helix. It's a huge step up from the HD500. I got excited when I read that the Helix would be USB 2.0 class compliant. Unfortunately, under Ubuntu Studio it appears as a USB device but that's all. It's not seen by ALSA and Jack fails to connect. I don't mind booting into Windows to use the Helix Edit app, but come on Line 6, I'd really like to record direct from the Helix in Ubuntu. At present, I have to run the S/PDIF output into my existing USB 1.0 compliant sound card. I can understand that Linux is not a priority. If that's the case, how about providing the open source community with the information required to write our own driver?