What does impure sound, sound like ?
Naughty.
When I started off around 15 years ago in the music hobby, my equipment was not great. There was tons of noise and jitter in my stereo system. I remember then that I appreciated equalizing more back then. Today I have world-class electronics with ultra low noise power supplies and a Mutec Rer.10 SE-120 clock for the lowest possible jitter. Also, todays headphones are just so so improved over what was available 15 years ago. I even have an isolation transformer which reduces noise by 165dcb which I did not have until a few years ago. With todays components which filter out so so much noise and minimize jitter to such low levels, equalizing to my ears (not technical proof) degrades sound and harms ultimate transparency even if the headphones have an inaccurate FR graph. Perhaps I do not know how to equalize properly???
Just sharing my point of view in my experience. To each his own....
I'm curious whether you would say this for any form of EQ or just for digital EQ. Also how are you Integrating the REF10 (I think that's what you mean) into your system? I have the original REF10 (not the SE120 version you have), and used it for a bit with a MUTEC MC-3+ USB feeding my DAC. While it seemed to have a positive effect on sound stage depth, I also had a slight harshness in my system that I found fatiguing. As it turns out, the MC-3+ USB is only bit perfect with SPDIF in (not USB) and the internal clock. Otherwise it resamples the signal (without changing the sample rate), which shows up as ringing artifacts. Not using the REF10 fixed that, though I'd love to find a way to put it to use again.
But the point is if you use an MC-3+ USB with the USB input, an external clock, a digital EQ before it and an oversampling DAC, you're chaining four digital filters that are all just an approximation of what might be ideal. Maybe a fifth one if your OS is resampling the contents as well, though you have probably taken care of that. I would imagine this can cause lots of problems. I should try to record the resampled output, feed it back in, repeat, to see whether it gets worse and worse with each iteration, that would be interesting.
I have also heard that digital EQ can cause group delay and other issues. And I suppose an analog equalizer has similar issues, using the same kind of parts that a crossover has, thus messing with the phase.
I'm far from an expert on EQ, but it's definitely clear that some issues are acknowledged (FIR is a keyword here).
So in general, if I can get away without EQ, I prefer it, even just as a practical matter. I had a need for more bass with the ATH-M50x, but my phone at the time didn't have enough power, and lowered everything other than the bass when I tried to boost it, making it not loud enough. Trying to EQ the headphones on my work laptop with virtual sound cards led to crashes and other bugs where suddenly the sound became choppy. That's why I got my first headphone amp, the Sound Blaster E5, with built-in EQ. That was also able to crash the Mac, and required special drivers/apps to use. And it's a bit annoying for commuting.
Other dongle DACs can cause issues when you use them with USB Audio Player Pro and then want to listen to a YouTube video. I have unintentionally entertained other people on the subway this way, when the video was played through the phone's speakers instead.
With the Focal Listen, the bass was good as is and it was more efficient - no more need for EQ.
Recently I tested the SMSL AD18, a super cheap integrated speaker amp / do-it-all. With my old Yamaha satellites, playing music was just a bit too spicy, so lowering the treble by just 1 dB helped. Conversely, the NHT C1 was a bit too dark and benefited from a +1 dB treble boost. I admit it was nice to have that option readily available. It did seem to impact resolution, but the unpleasant frequency response was more annoying.
But that's the complete story of my need for EQ. If I wanted to EQ my main system, I wouldn't use the Lokius - it's not balanced end to end, which worries me, but it also doesn't have a remote, making it far less interesting for speaker use.
I'd be more tempted to use an all digital DSP between my TOSLINK switch and the MC-3+ USB (so it works for all my sources), but the miniDSP ones that I looked at only work at 96 kHz internally, making them less optimal for the occasional 192 kHz material. I could adjust them from the couch via USB, though.
I gave my parents a nanoDIGI as a dialog enhancer when they watch TV. I suspect better speakers wouldn't need that, but they were grateful.
So a setup in which I don't need to EQ is definitely a welcome simplification, but I have not fully closed that chapter.
