I can run the single ended kph40s and my balanced Goldplanar GL2000s at the same time ā and damn theyāre close. If anything the kph40s have higher resolution than the GL2000s.
Not sure if thatās a compliment to the kph40s or a knock on Goldplanar 
Listening to mine a bit that I got today. So far, the kph40 is the worst sounding pair Iāve heard out of koss so far. It sounds cheap and not like their other stuff. But that said, the kph30 needed some break in so Iāll try these our for a bit before giving actual impressions.
Wow, and I know youāre feeding it some top end gear too.
Iām going to let mine burn in for a week or two before I try any critical listening with my desktop rig and comparing them against my 30iās.
They are not perfect out of the box, but I like them so far.
Iām only using my BTR5 right now. The RNHP is out on loan but Iāll use my Vali 2+ or mz2 later. You get in your face with some details but it doesnāt resonate how I hoped.
I will say, for $40 it sounds amazing. But the fan favorite koss stuff on the the BTR5 sounds better so far. For reference, the kph30 took some break in in my experience and the porta pros I have sound great with the yaxi pads.
Now the goodā¦ The kph40 is so light and holds better. So if you want put on roller skates and get those old school walk man vibes, these are great. The comfort is outstanding.
So far the bass feels a bit less precise and something in the 4k-5k range is strange. Nothing bad but maybe itās me trying to hope these match the Zeos hype.
Maybe itās time I try these out with the Hugo 2 and see what happens.
Good news, the kph40 sounds better on the Chord Hugo 2 over the BTR5. Not sure if that means anything to anyone but the headphones definitely sound like they may need 24 hours of break in or brain burn in.
I recall Zeos saying they do scale well so that result does not surprise me. That is why I am looking forward to trying them with my desktop setup after some burn in.
Just need a Chord Hugo 2 haha clearly need an m scaler too lol.
Would make for a great kph40 meme.
Verdict after night 1. Kph40ās are the worst sounding headphones of the Koss I own to date. Still a bargain at $40 USD compared to skull candy. Super comfortable, but I like porta pro, 75, and 30i better. Why? Better instrument separation resolution.
The kph40 is super comfy but letās see how it sounds with the USB C utility wire. If that does not fix things, it looks like itās time to get another Porta Pro and put on Yaxi pads.
Even if they sound bad, at least you can salvage the headband and repurpose it.
So basically, youāre saying its the āworst student in the gifted classā? 
have you had a chance to get the Utility porta pros?
First comment: I wouldnāt say itās a gifted class. Donāt put these headphones on a pedestal.
Second: I have the regular porta proās and I think I prefer them for phone calls due to the mic placement with the BTR5.
The USB-C cable came in today soā¦ I FINALLY HAVE A HEADPHONE JACK AGAIN!!! Sort of.
Just got the kph40 in, straight out of the box I find them to be rather muffled sounding. Running off of a questyle m12 dongle for now. Will give them a try on the desktop gear later today, and try some burn in.
The USB-C cable for the KPH40. Itās as good for buttons and operation as Zeos says. Howeverā¦ it doesnāt sound as good as the BTR by a mile or 20. Butā¦ I think it sounds better than some of the headphone jacks Iāve heard on many phones and laptops so that is something.
It may suck but Iām glad to have a nice inline feeling āheadphone jackā feeling again. The DFC is too bulky to be used and the microphone works well enough in a pinch.
But as far as sound quality, everything sounds less intimate and even more vague. But I can say if you miss some sound signatures of cassette decks, this dongle + KPH40 brings that sound signature (I think) and without the hiss.
Happy listening! When you say muffled you mean like the Porta Pros? 
I would say itās quite noticeably worse than the Porta pro.
I also have the GL2000s and Iām going to have to disagree and say they are far and away superior to the KPH 40s. Iām running a Liquid Spark DAC and a Singxer SA-1, so can also drive them both at the same time. For $40, the 40s are for sure amazing and put a smile on my face when listening. But the GL2000s (only mod is Brainwavs gel pads) have so much better soundstage, imaging, literally everything other than maybe sound quality (the KPH 40s are a tad more muffled in the mids though imo), it isnāt even really a fair comparison.
I do also have a pair of modded 30iās to compare them to, but Iām going to let these 40s burn in a bit more before I do that.
These just showed up today.
Even over the first hour of listening Iāve noticed some significant break-in (Iāve heard enough change that I suspect thereās going to be quite a bit of part-to-part variation in sound until thereās enough break-in). So Iām not going to comment too much on sound, other than to say my observations are generally in line with @DagoRed - least favorite of the Koss lineup, and something odd in the ~5k range.
Something very noticeable is with regard to the USB-C DAC cable. Playing from the Qobuz app sounds 'meh. Not horrible, but nothing really great. Switching over to UAPP app is an entirely different story. Depth, detail, tonality, all much better (the ~5k issue is tamed as well, making me wonder about DSP). The sound is closer to what Iām hearing on my desktop setup (Jot2/BF2 and G111/Revolution). The flavor of those setups comes through for sure, so not an apples-to-apples comparison. But with the USB-C DAC cable, running on UAPP, itās respectable - on par with the ddhifi TC35b running from UAPP. From the stock Qobuz app it sounds much worse than the TC35b. It must need the ābit-perfectā magic 
The addition of the in-line controls / microphone make it a nice āside gradeā to the TC35b.
Got my set yesterday as well. Break in is for sure a thing with these.
I thought they sounded decent after a night of playing music through them.
My verdict is still out on the sound, but I think for $40 they arenāt bad.
