One of the reasons I bought the Qu over competing mixers was the quality and quietness of the preamps. I have done a few remote recordings with it and have been very pleased with the virtually nonexistant noise floor via the XLR channels. I have a pair of ECM8000s I may use from time to time in a pinch (usually for room mics), but in the past noise has been an issue with these mics. With the QU I have found they are far more quiet than my previous remote rig. I have not found an explanation for this beyond the quietness and quality of the pres. I was marveling last night at the cleanness and clarity I was experiencing when using a sampler connected to the mixer with an old pair of HOSA 1/4in cables I should have thrown away years ago. I was noticing when playing large arpeggios with the pedal down on a piano sample (On a Korg Kronos) I would eventually hear the cumulative noise on the SAMPLES(!) but there was never the faintest whisper of hiss from the mixer.
I feel your client has either poorly performed his tests, had something else noisy in the signal chain, or had a defective unit.
I feel the order of likelihood is from first to last in that list.
Their method of testing seems odd. I generally keep channels with nothing in them muted or at least turned down. 😉
