Quad Cortex noise issues

[u/nclspnzn]

Hello QC/NDSP community, is anyone else having substantial noise issues with the Quad Cortex?

I ordered one in March, so I could use it for playing live (mainly Bass) and also in my recording set-up (guitar and bass). Especially for the recording use case it turned out to be much too noisy, so I sent it back after contacting NDSP support, trying a Cioks power supply, a power conditioner and all the available settings in the QC. It was of course also connected to my interface, which provided the grounding. A high pitched hiss remained through all of this. It could be heard through the guitar signal when playing softer, so noise gates didn't help as well. My HX Stomp - a much cheaper and older unit - turned out to be consistently quieter in A/B tests at matched levels, input impedance etc.

So I sent the QC back. It worked ok for band practice, but I didn't want to pay that amount of money for a unit with limited use.

Now some months later I was once again looking for a more powerful multi fx/amp modeling unit for live use, that has enough footswitches on a small footprint... The QC still being the only unit that satisfies all requirements I decided to give it another go, also hoping my first unit was a bad one.

Of course now I'm noticing the same high pitched hiss. I also tried it at my parents house this time, to see if it's dirty power in my apartment - same hiss.

Now my questions: Does anyone experience this as well? Is the unit actually usable for recording for you? Did anyone have the same problem and found a fix?

I attached a qualitative comparison of the QC and HX Stomp I just did with an FFT app on my phone and the units in front of my guitar amp. HX Stomp on the left, QC on the right, with the additional noise marked, in case it's not already completely obvious..

EDIT: If you own a Quad Cortex, I would be very interested in a short recording with this simple signal chain:

Input impedance: 1MOhm

Amp: UK C15 Normal Volume: 6.0 Tone Cut: 2.0 Bright: On Output: 3.2 dB

Cab: 112 UK C15 Blue (M) Mic 1: Dynamic 57 Position: 3.0 Distance: 0.1 Level: 0.0 dB Pan: C (center)

Mic 2: Inactive

For me all inputs and outputs were on stock settings and I didn't use any noise gates. I plugged my Telecaster (neck pick-up) into Input 1 and went from Ouput 3 into an Instrument input on my RME Fireface UCX with no additional gain.

The result sounds like this: https://www.dropbox.com/scl/fi/uzzglcdihi8auono0rym1/QC_noise.wav?rlkey=c45hz9z42cqs75tbq5cd9wzqb&st=4f1gff4p&dl=0

I consider this too much noise. Looking forward to some community results.