Please read this article, it contains details of how balanced connections differ from unbalanced ones, and there is also a description of the 4.4 connector https://www.headphonesty.com/2019/05/balanced-vs-unbalanced-audio-connections/

4-pole connector, because a balanced connection requires 2 contacts (positive and negative contact for each channel) and 3 contacts for an unbalanced connection, because 2 negative contacts are combined into one contact - a common ground

You need to look for a cable specifically for Fostex t60rp headphones, because different headphones may have different cable pinouts. I can advise you to cut off the 3.5 connector in your defective cable and solder a new one in accordance with the Fostex pinout (in the messages above I attached...

Fostex T50RP mk4 support balanced connection out of the box. For a balanced connection you need a balanced cable (pinout is the same as for T60RP). The headphones come standard with 1 unbalanced cable: φ3.5 mm (4-pole) ⇔ φ 3.5 mm (3-pole) stereo phone cable (2 m) x 1, φ3.5 mm → φ6.3 mm stereo...

updated model on the way!

Yes, you are right, I was wrong about this ess chip. I have an M15 and it does not support a microphone. As far as I know, the new M15i is practically no different from the M15

it doesn't have an ADC, so the M12/M15 doesn't support a microphone

Using a dimming film, I finally made the LEDs not so bright, so the M15 became pleasant to listen to at night before falling asleep. Previously, these were blinding lights in the dark

I decided to make a balanced 4.4 cable for my Fostex T60RP. I took the pinout from the manual that came with the headphones. I soldered the cable, and it converts the audio signal to mono - this is interesting. Where did I (or someone at Fostex) make a mistake? I downloaded the PDF manual from...

My modifications for the convenience of the Questyle M15. I bought a darkening clear film and covered the screen with it because the LEDs are too bright. I made a new cable because I can, because I wanted to check whether the cable makes a change in the sound (I didn’t find any effect) and I...

I checked some information and I think it's HR3020 polyurethane foam

does anybody knows the markings (density/hardness) of baffle foam?

a balanced output will typically have about a 2x more power, as + and - are amplified. you have the opposite in your answer, SE output is much more powerful than balanced

are you sure about that?

Is it safe to connect 2 headphones at the same time to k7 (bal and se outputs)? I did not find this in the instructions, but it was forbidden to do this in the FiiO ka3 instructions.