I do have this high frequency white noise almost type of hiss, like you showed here: https://on.soundcloud.com/mMAUi
It’s much more manageable than the crackling issue that was happening before so it’s not the biggest deal for me.
My levels are:
-5db HP level
-6db MultiOut
This is from a very cheap basic pair of headphones, it’s also happening on my more expensive ones. It doesn’t end up coming through the recording so just headphone drama again lol.
Thanks for checking and yea, only coming through the headphones.
FWIW, i did have the crackling before and got Sweetwater to send me a new QC which didn’t have crackling. I had a reddit post on that along with some recordings, it was pretty annoying.
same here, sounds like white noise, and can be eliminated by lowering HP level. I wonder does this happen again for your replaced unit from SW?
Unfortunately i didnt notice this on the previous QC as the crackling issue was way more annoying. It’s likely that it did it too, but i dont know.
Thanks a lot!! May I ask if you only plugin your guitar and headphone in, for the replaced device now, and set the HP level at 0dB, would you notice the white noise (maybe referred to as ‘ground noise’ or ‘hiss’)?
Even without a guitar plugged in and an empty preset, at 0 volume and 0dB the hiss is very pronounced. I need tonset it to -12dB to make it fairly quiet
Thank you mate, this is very helpful! I appreciate it a lot for your information! I thought this is unit specific problem due to maybe electronic components, and I might have to replace it for a new one. But now it seems this is universal. I’d try using Cioks power supply and connect QC to ‘grounded’ device to see if it solves. Thanks again!
I actually use a grounded power supply because without that it hummed a lot, but this occurs even at 0 volume and at a different frequency range.
Update: got my Curx for my DC7, and tried it on QC. issue doesn’t eliminate. I contacted support of QC, they said it’s all about impedance. End of story : ).
I use a headphone amplifier all the time and have zero noise problems. Also allows me to attenuate the headphone signal while leaving the QC output level at 0 dB full tilt.
For those that didn’t read my post an a similar topic.
I bought a QC in April 2022 and had the same issue. Email support and this is what they said.
“ For this, the solution we are exploring involves using a floating power supply , specially engineered to reduce the pickup/ground interference issue when using QC just with headphones, while minimizing the likelihood of ground loops when using the unit in conjunction with external devices.
Our preliminary tests are very promising and we are waiting for sample approval to proceed with sourcing.”
I asked for an update in over a year later and got this from support in August 2023.
“ Hi Alan,
Thanks for getting back to us. We can happily say that the we are working with a company who have delivered us a suitable prototype of the alternative power supply you mention. is still relevant and prog
Unfortunately I don’t have an exact date when these will become available for you, but we have your details for this, and you will be among the first to know.”
It’s now coming up on 2 years.
Same here. I also told them multiple times to address this and other common issues like this publicly. But they just don’t.
The weird thing I don’t understand is they say it needs to be grounded to work, however I also use my MacBook not plugged in (so not grounded) with my guitar using irig hd cheap interface and a set of headphones. Using Neural DSP Soldano plugin there is no noise.
How can they make the plugins work with no ground but not the QC? There must be a software reason the unplugged laptop works but the QC doesn’t.
I bought one of these and the AC is 3 prong grounded. QC is VERY quiet with this power supply!!!
I will not accept an aftermarket solution for a device that costs as much as it does.
“Coming Soon” 
Did you try turning the strip input gain to 0. Set master volume dial to 100 and then adjust the output gain on the strip to desired level. I just got my unit but after reading other posts about unwanted distortion the solution was setting 0 input Gain.
I can confirm I have no noise at the headphone output, all is normal.
I tried 3 different ohm headphones. 35, 250 and 80.
35 ohm was too loud and distorted. (felt mismatched with my other levels for say via interface into Garage Band, or with studio monitors).
250 ohm was way too quiet and sounded very trebly.
80 ohm seems to be the sweet spot for me.
I did noticed was still getting more gain/distortion through the headphones (80 ohm DT770) vs studio monitors (JLB 305). When looking at the headphone out level in the I/O panel, I noticed the headphone level going in the red, but the multi out level was not (I have my levels set to be near -10 db on the output level meter). Headphone level was going to like -5, -4 db on the headphone level meter.
Oddly, adjusting the HP level doesn’t lower the Level. It lowers the volume the bars still went into the red. No change. There was still a roughly 6db different between the headphone level bars and multi-out level bars.
Then noticed (and don’t know if by default … can’t remember if I adjusted)… the Multi Out knob was at +6 db. Turning that down reduced the headphone level bars, but kept the Multi Out level bars the same. Don’t know if this is a bug or working as intended and I’m not understanding it correctly.
In any case, I have my headphone output settings as HP LEVEL -6.0 db, MULTI OUT -2.5 db. Seems to work well with the 80 ohm DT770. Although still feels like the headphones get a hotter signal than the studio monitors (which I have as mono out from OUT 3).