Major intermittent crackling through all outputs and presets

CorOS Version: 2.00.20

Describe your issue:
Intermittent crackling on and off sometimes a lot some times few and far between. Changed cables, locations, power and presets occurs on all outputs.

Steps to reproduce your issue:
Its been impossible to recreate

I expected this to happen:
when i use the QC I expect it to work

I have tried the following things:

  • I have tried different cables
  • I have tried different presets and settings
  • I have tried different locations

Are you using PC or MAC? If PC, have you downloaded/installed the current QC ASIO driver? The next steps would be to adjust your sample size until you no longer hear crackling etc., assuming this is occurring while using as USB audio interface?

THis is happening on my quad cortex no computer involved

What outputs are you using? What monitors are you using? Have you tried alternate monitors? Are you experiencing while using headphones? Are you using the OEM power supply? If not, make sure you are providing at least 12v @ 2A etc. Have you backed up and reset the QC? Worst case, email and they will get you resolved quickly.

As OP stated “on all presets and all outputs” - that simply might be a faulty device. Things like that may happen.

Definitely contact support, and try to replace that device.

I had this problem and I found this post on facebook with a tip that came from Neural Dsp support which solved the problem for me:

  1. Turn off the unit
  2. Disconnect all the cables
  3. Wait 30 seconds, connect only the PSU cable, and turn it on again
  4. On the loading/splash screen, press and hold the “A” and “H” stomps
  5. Select “Reset Settings”
  6. Check if the problem persists.

Hi sorry for the long explanation of crackle coming back tonight but you may want to log and search for bugs. Tech question at end. Unit is fully up to date. I changed power supplies, even added a power conditioner to my line and reset multiple times. I gigged all weeked a total of 7 hours of performance time and no crackles did experience a large n loud pop burst twice through the channel using xlr and running my vocal ( change cables between pops, so not a cable issue). Got home and used it all week with no pops or crackles. Just had a rehearsal and had crackles right away. I had to unplug all cables and reset twice to get crackles to leave but they did and didn’t return all night (2 hours of rehearsal). In a facebook group I’m in , someone else had the same crackling problem and it seemed to them it was from receiving midi signals. I send midi signals from an RC 600 loop pedal, and I actually never experienced this prior but I used it as a midi controller for months before having crackle issues. . Any suggestions or insight as to if midi could be triggering a problem and causing it to crackle? Midi feedback causing a cpu crackle? I don’t know but the QC is the hub of my whole world and life without it would be like using a horse n buggy to travel instead of a car.

I had this exact same issue. Sporadic crackle through all outputs. Sometimes a week or so between appearances of the issue. The quality of the power (from the wall) made no difference. Stock power supply vs kioks made no difference. I worked though troubleshooting with support, but eventually had to send the unit in. In the end, it was replaced due to a faulty component.

I had this issue yesterday. Extreme volume jump, crackle, pops and zapping noises.
I tried rebooting several times, no avail.
I updated to 2.02 a week ago, haven’t moved to 2.03 yet.
I’ll try the reset settings method. I did that a while back for a different issue.
I just got it the QC in January. It is my main ride for gigs, both electric and acoustic. Great unit but…….
I’m not feeling like putting a whole lot of time into this to troubleshoot, email, support, all that.

I, too have been having this problem for a couple months. Have reported to support via email but have kind of gotten the run around, asking me to try things I’ve already tried. ( Different cables, different inputs, resets, ground lifts, presets, etc, etc). The most frustrating part is that it is intermittent. Sometimes unit works fine, and sometimes it does this. Has happened to me on about 5 separate occasions. I like the unit, but I just can’t trust it right now. Have been using an HX stomp for gigs. Not happy. More footage of QC problem - YouTube

Same problem here for one week, somebody have a solution ? Exactly the same crackling as in the youtube video

There are, as many users are probably already aware of, multiple issues that can cause noise. Ranging from dirty power, defective cables, and poor gain staging in a preset, to defective hardware. Just wanted to put this one out there as I remember it causing all manner of mysterious crackling, hissing, and assorted noises for me when I first got my QC - make sure not to have the input level on the I/O page cranked up too high for your guitar. This absolutely introduces all kinds of noise when set improperly. The noise becomes particularly bad as the S/N ratio gets low as the notes trails off. Turning down the input level on the I/O page cleaned things up immediately for me.

Btw, the reason I had it set too high initially was all the guidance on the forum to get the meter to touch the line towards the far end of the meter on the hardest hit chords/notes. To do that, at least on my QC, requires me to crank the input level up many decibels with anything except a guitar with very hot pickups. Don’t know if I have a hardware issue on my QC (I have tried swapping out guitars and cables) or if that is other QC owners’ experience as well. I have resigned myself to not getting up to that mark per other users’ advice. To do so requires me to set the input level at +12db or higher and that starts to cause noise issues.

Anyone else seeing this behavior on the input meter - where it tends to sit extremely low on the meter when set to 0db?

I had the same problem 2 months ago which almost made me sell the QC again. We had an upcoming gig and I was in the rehearsal room with my band. We are a cover band in which I play acoustic and electric guitar through the QC on Input 1 and 2.
On output 1 I send the acoustic to the PA. On Output 3 and 4, the guitar then runs stereo to the PA with effects, etc. Suddenly there were always crackling noises which I did not have before. First I thought of a defective cable, then a dead battery on the guitar. I changed all the cables to the PA and in the end I no longer knew what the problem was, because the crackling was gone.

Then the gig came and I was honestly a bit nervous, because we were booked for 4 hours and had almost 60 songs on the setlist. And by the third song the crackling was back. I had to play the whole gig without effects and only with the acoustic guitar directly into the PA. That night it was clear to me that I would sell the QC immediately.

One day after the gig, I played through all the presets again at home on the PC. Here I simply connected the QC via XLR to my interface and played via Ableton Live. Suddenly I noticed that the input level of Ableton was completely overdriven. I then looked into the I/O settings on the QC and adjusted the input and output level and suddenly everything was fine again. I don’t understand why this happened out of nowhere, I didn’t change any guitar or anything in the presets and have had the QC for a few months now and played several gigs with it. Anyway, the last point where I would have looked was the level meter because before that everything was always fine and I had not changed anything.

A bad feeling remains anyway. I will eventually look for a backup like a HX Stomp or similar.


I had the same issue a month ago, after contacting support and following all indications for troubleshooting without success, I had to send my QC for “inspection”. It was repaired in a week. I have to say that my experience with Neural DSP support was GREAT, answering to my mails in less than 2 hours always. My QC is finally fixed without any costs (under warranty). I asked support about the work done to my unit and their answer was “The board that hosts the inputs and outputs was confirmed defective so the whole board has been replaced.”

I encourage you to contact support team before your warranty expires.

Also the support team should investigate this issue as there might be a correlation between this problem and the QC serial number (defective batch?)



Perfect, thanks for the input. Unfortunately I encounter the same problems again after a few weeks of having none. Will contact NDSP Support.

My issue has been a sudden output jump (probably about 10-15 db I would guess). It happened to me on at least 3 or 4 occasions, all within a couple weeks.
I contacted support, they sent a call tag to send it in for service. At the same time I did a factory reset again, why not. The problem hasn’t returned. I’ve played it at about 5 gigs with no issues.
I have a backup with me because I still don’t really trust it, which is unfortunate. I
I do want to send it to them but I may wait until I don’t need it too much.
I really like and need the QC at this point. I’ve been primarily using it as my acoustic rig. It’s been a game changer for me in that mode.

I just started having this issue on a gig last Saturday…Pulling my hair out to figure out the problem. I guess I’ll need to contact support…


I have shared this video with support, but it seems to be the same issue…

My QC was randomly cutting out with an IR recently. Plus the latency on my patches has been unbearable. Haven’t even hit 50% on the usage.

Then it just wouldn’t boot today. Crazy how buggy these things are. Didn’t expect Line 6 to be a somewhat reliable company compared to the fancy boutique one.

The amps definitely sound better than Kemper and Helix. I’ve owned the other units for much longer with no issue. QC didn’t even last two months without breaking.

This issue as per the videos and descriptions above, was very quickly resolved for me, by contacting support. It had to be returned to the factory. My issue they informed me was caused by a faulty connector board. The only way to resolve this issue, is to contact support. Of course your issue may be a differnt cause, but the connector board is what my issue turned out to be. Multiple times of factory restting the unit, connector lead changes, etc etc made no difference. Save yourself a lot of time and contact support is my advice. A big “Thank You” to Neural support for sorting it out in a prompt manner, it is very much appreciated.


First of all, I have to say that NDSP’s support is unbelievably good. They contacted me immediately, and after a brief discussion about what exactly the problem is, and a short Video which showed the problem, I already got the UPS pickup label and an appointment for a free repair. Tomorrow the device should come back and apparently a defective connector board was to blame for my problem. Never enjoyed such a good and fast customer service, and at the same time comes the update 2.1.0. Am really excited.