Headphones

This is probably the best answer to this specific kind of question: https://www.youtube.com/watch?v=a3moaaOpYZM&t=39s

I've found that a dedicated amp or dac or amp/dac really improves the sound on all of my headphones. Amp making more of a difference than a dac to me. But, I do not own Beyer's so can't say anything 100%. On my first pair of headphones that I bought for better sound quality, I noticed about the same amount of improvement between having the new headphones and then adding in an amp along with the new headphones, which surprised me.

Before someone comes in here telling you an Apple dongle will do the job, yes, a DAC and amp will vastly improve your listening experience.

If you want something inexpensive I'd go for the JDS labs atom amp+ and dac+ 2. If you have a larger budget and want even better sound, consider a schitt magnius/modi Multibit stack. These are far from the only options but they're two of the most straightforward combos for a first time buyer.

Going out on a downvote limb here but I would say yes an amp and DAC will improve the sound. The 1990 is a pretty efficient / sensitive headphone so you may be able to make it work with an Apple dongle but I would recommend something with a bit more juice (could be a dongle too).

Not likely to, no. It might, depending on how distorted the GoXLR's head-out is, but pretty much any clean source will do the trick.

You might get some people telling you how much sources affect the sound; It's pure punk. Modern amps and DACs are very good, and they all do the job they're designed to.

Unless you're looking for esoteric stuff like R2R or Tubes, expect to hear nothing different. Unless you really expect it, then placebo and expectation bias will kick in to change things up. Hell, even a 0.5 dB volume difference can make you prefer one over the other.

TL;DR, if you have a good clean source, which is very easy to get these days, expect it to sound the same as all the other good clean sources.

yes

Unless you need more volume with headroom or there’s noise in the signal from an inadequate existing DAC (there isn’t) it won’t make a difference. They’re designed to be audibly transparent, just about every modern amp or DAC is so if they did do anything to the sound, it would be a flaw more than any sort of improvement.

EQ will make a difference - try that first

There are way too many of these posts

Imo, in general, the biggest lift in quality you'll ever get will come from avoiding an analog link between the source and the amplifier, and not having the noise-filters intended to handle that applied to the output. I'm not sure how the Goxlr works, but think it's a mixing thing for multiple inputs? So it probably has some filters, a range limit, and a pre-amp that will shear off the edges a bit, and put a generally clean sound out. That probably also applies if you're running usb input for the playback as well.

If you compare that to having some usb-c put to a pre-amp or a dac that has minimal range enough to drive the speakers (200Ohm?). And that also does nothing to the output other than convert it. Or, you have an hdmi-input to an amplifier that just amplifies. Then you'll hear a difference very quickly.

It won't be huge. But having a pass-through analog cable to an amp really requires you to add a few filters and tune the input to not get kind of crappy sound, regardless of setup. A mixing board needs to do certain things to the signal on the way. While just tuning the output at the end of a converted digital signal is sort of impossible to get wrong.

So that's - I think at least partially - why this stuff is somewhat controversial. Because it is the case that with tuning options and mixing possibilities, you can make a lot of things sound significantly less bad if you mix it well. Like one of the sound-tuning wizards I knew that mixed for the local bands - he always managed to do.. something, either live or on the recordings that would salvage what was absolute crap to begin with. And it was really impressive. But he would never claim or say that anything of what he did was somehow getting the best sound that could be reproduced. He made that point a few times, that he was pulling filters to bring out certain things to produce a particular sound-picture that would work on the speakers, not that he was somehow drawing on the knobs and getting some magical state where all the waves mathematically align and becomes perfection.

So being able to remove that part of the equation with the analog inputs and the balancing - and preferably also the noise-filters that are in there to avoid amplifying the noise from mixed inputs - is kind of where it's at, imo.

I just use a FiiO KA3 dongle amp because it feels better to use the balanced port on my headphones, but the even the 660S2 will sound fine out of almost any headphone jack.