I have a different hum problem, tied to the headphone output. Even at 0 volume and with the QC grounded, i’m getting a bunch of white noise/hum: Reddit - Dive into anything
I contacted neural and they basically said it’s normal, use higher impedence headphones or turn the headphone volume down by 12dB.
Is this normal for other people here? Do you get pretty loud high-frequency hum at 0 volume with nothing but the headphones and some form of extra grounding plugged in?
The quad is super quiet and I use quite a bit of gain on top of that a dirt pedal in front of it. No issues. Btw the Kemper was really quiet because I never used it. The feel was not there. The sound needed help with external pedals and the ui was very tiny. The rig manager was a nightmare. Constant tweaking. I don’t want to be tied to a pc. The quad has the best UI imo the best feel and sound other than the real thing. I play and don’t tweak for hrs. I plug it into return fx of my amp and use a real guitar cab. Sounds great. The problem seems to be people’s headphones, cables, user error. If it’s not u neural will treat you better than any company I’ve dealt with besides Dave Friedman who replies to every email. Don’t give up and no offense.
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I’ve seen a number of posts from folks complaining about hiss and or hum when using the QC with headphones and no grounded gear connected. I’ve also heard mention that this can be related to the impedance of the headphones being used.
I pulled out every different model headphone in my studio and tested the QC with no grounded equipment connected.
Here are the phones I tested;
ATH-M50 38 ohms
ATH-M50x 38 ohms
ATH-M40fs 60 ohms
Sennheiser HD280 64 ohms
Sony MDR 7 55 ohm (from 1970s)
Samsung ear buds ?? ohms
I found no added hum or hiss with any of them. I recall some headphones from the dark ages that were rated at 8 to 16 ohms but don’t recall any modern phones in this load range. What is the impedance of the set you’re using?
I tried Audeze LCD-XC, Etymotic ER4 and then some HyperX gaming headset. Its also captured just fine using a usb audio interface, which is how i got the spectrum graphs in my reddit post.
I assume the ER4s are IEMs, not familiar with Audeze. do you know the impedance rating of either of these?
Based on the specs, the LCD-XCs are 20 Ohm, the E4Rs are 45 and the hyperX are 60Ohm. They all sound roughly the same noise-wise, like this https://on.soundcloud.com/mMAUi
20 ohms is low but 60 ohms is in a pretty normal range. So, once you connect a piece of grounded equipment, the noise goes away?
No, this hiss is constant and happens even with volume at 0, both grounded and ungrounded, with no guitar plugged in, blank preset, etc.
That’s not the way mine behaves. I can hear a minute bit of hiss but it’s barely audible if I’m listening for it and certainly not noticable while playing…but then my ears are likely older and more abused than yours. 
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Just got mine a few weeks ago. No hiss at all, running through a PS170 power amp in to cab
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Huh, so at 0 volume its dead quiet for you on headphones? Did you make any changes to the mixer/global eq for the headphones?
Pretty much. What little hiss there is has to be at least 100db below signal peak. I have the phones out assigned to the volume control but it seems to have no effect on the hiss level, even at 100%, which makes the guitar too loud for me to monitor comfortably, it’s quite hiss-free. Even boosting the top end with global EQ seems to add no hiss. I noticed the internal HP Level does effect hiss. I have the HP Level at 0db. If I boost it, hiss becomes quite audible. If I set the volume control all the way up and set the HP Level at -10db, it’s plenty loud (for me) and I can hear absolutely no hiss. You might try that.
I gave it a whirl, it still hisses, just a different type of hiss. At -10dB it’s relatively quiet but at around 80 volume its starting to hiss again. I suppose that’s more normal though, as the other devices I’ve tried also made some hiss.
Huh, wierd. With it set the way I discribed, I can hear no hiss at all. Very frustrating, I’m sure. Are you using a noise gate at the front end of your preset(s)?
Ok, with the settings you mentioned and a blank preset its nice and quiet. I guess a noise gate would fix this hiss as well, but has no effect on the volume at 0 case.
Have you tried comparing the hiss at whatever volume level, to actually playing something through it?
I bet when you have the volume up loud enough to hear hiss, that playing something through the unit will blow your eardrums.
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I’m glad that you are hiss-free when reducing the HP level and, you’re right, a noise gate would not alter hiss that’s introduced by the output circuitry or headphone amp. All electronics create noise. Sometimes it’s just a matter of experimenting to find the quietest settings.
Haven’t read all the comments, but I got rid of a lot of hiss when I used a power strip with mains filter like this one: https://www.amazon.de/-/en/Power-strip-surge-protection-experience-white-black/dp/B07SPDLNXX
Yep, a lot of noise can get ‘injected’ in any kind of audio device through dirty / noisy power 
It’s always worth a try to add some kind of power filter to your setup before blaming the affected device. But be aware of cheap filters that dont really do much, there are a lot available out there.
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I have found this to be true. Right at input level at +9.3, something changes. And then adding a gain block with -9.3, the hiss is gone. Seems like @M_NDSP would know about this. ?
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