As your TV has optical out, you might try a optical to USB converter: https://hifimediy.com/product/hifime-ur23-spdif-optical-to-usb-converter/

Measurements can be found here: https://www.audiosciencereview.com/forum/index.php?threads/rme-babyface-pro-fs-portable-interface-review.12313/

Interpreting your “highest possible” as “highest quality”.

If I have to choose between a lossy format and a lossless format e.g. $5 for the MP3 and $10 for the FLAC, I choose the lossless version simply to future proof my collection and to avoid even the tiniest possible artifacts inherent to lossy compression (Fraunhofer & Co never claimed MP3 to be 100% transparant all of the time).

If I have to choose between CD quality (16/44.1) ar $10 or Hires (24/96) at $20, I choose CD quality simple because I don’t hear the difference.

If I have a download in 24/176 or 24/192, I always inspect the content using a spectrum analyzer. Often there are all kind of artifacts like high amount of quantization noise, some gear injecting a spike at 88 kHz, etc. I downsample them to 88 resp. 96 to get rid of the garbage https://www.thewelltemperedcomputer.com/SW/AudioTools/Spectrum.htm

Latency is a combination of hard and software.

Robert Triggs did some measurements: https://www.soundguys.com/android-bluetooth-latency-22732/

On older smartphone latency runs as high as 500 ms, on newer models it dropped to 40 ms and lower.

Indeed it take two to tango. Your phone might have APTX-LL (low latency), if your buds don’t have it, it cannot be used.

True gaming headsets often come with their own dongle. They use their own protocol to circumnavigate the latency of Bluetooth. Likewise the gear used in live sound https://www.shure.com/en-GB/performance-production/louder/digital-wireless-latency-explained

Bit more detail about Bluetooth: https://www.thewelltemperedcomputer.com/HW/Bluetooth.htm

Found this: https://drop.com/buy/drop-hifiman-he-x4-planar-magnetic-headphones

Sensitivity: 91 dB

Impedance: 25 ohms

Not very sensitive so might need a bit more power than the PC can deliver. Of cours, try it first before buying a headphone amp.

Very low impedance. Important is the damping factor (impedance headphone / impedance headphone out). 8 is considered a minimum. It might very well be that your receiver doesn’t have separate headphone amp. This means the headphone out is derived from the power amp but tuned down by a couple of resistors. Hence the headphone out might have a high output impedance resulting in a bloated bass due to insufficient damping.

Technically it is very easy, get a 3.5 to 2x RCA to connect a PC to a receiver.

Another route is a external USB DAC/amp. This might improve on both the DAC and the amp in the PC. Today one can get pretty good solutions at decent price levels: https://www.audiosciencereview.com/forum/index.php?threads/tempotec-sonata-bhd-pro-portable-dac-amp-review.47929/

Perhaps stating the obvious

• Experiment before you buy. If possible, do a unsighted test because we are prone to hear what we believe.
• Buy only from vendors with a decent return policy
• Check if there are measurements (ASR is a good source) as more expensive is not necessarily better.
• At 66 you have age related hearing loss but audio is most of all mid range so you still hear a hell of a lot.

Android by default is programed to output 44.1 khz

Really?

Android resamples everything to 48 kHz. There are media players bypassing this default. You also need a USB DAC.

Android 14 comes with an option to override this default but again you must have both the software and the hardware to utilize this.

https://www.thewelltemperedcomputer.com/SW/Android/AndroidMediaPlayers.htm

A demping ratio of 8 to 10 is considered a minimum.

According to https://pioneer.hr/controller-combo-dj-system/1199-ddj-flx4.html the headphone out is 10 Ohm so a headphone with a 80 Ohm impedance is a minimum (or you accept a bloated bass).

Shouldn’t be to hard to Google the materials used, isn’t it?

Just to get you started: https://www.upsbatterycenter.com/blog/metals-used-batteries/

What is wrong with recycling?

Only in the app by the manufacturer. You might EQ on the source.

It is very simple, SBC is like MP3, it is lossy compression and the lower the bit rate the more information has to be discarded. Software compensating effectively for severe lossy compression don’t exist as far as I know.

Obvious you are listening to AAC so lossy.

If you use a browser to listen to Apple Music, this is the best you can get.

There seems to be an app for Win 11 allowing you to listen to lossless

https://www.audiosciencereview.com/forum/index.php?threads/apple-music-lossless-is-finally-coming-to-windows-11.40922/

Wonder how you have established this 90 dB.

Anyway, if this is the correct number the answer is no. Would have been a very shitty product if it can’t cope with this modest level.

Simply play some music. If you don’t hear a thing, yes you fried them, likewise if it is distorted.

Most amps today have a ruler flat frequency response and distortion products at vanishing low levels. So as long as you don’t drive them into clipping, they will sound the same or better formulated: they don’t have a sound of their own so nothing audible that set them apart.

However, the interaction between the impedance of the amp and the impedance headphone might make an audible difference. If the amp has a impedance of 10 Ohm and you combine it with a headphone having a impedance of 30, you have a damping ration of 3. Way to low and will result in a bloated bass.

Combine at with a 300 Ohm headphone and you have a damping ration of 10, a value considered sufficient.

However the biggest difference is simply us. Most of the time we don’t test properly. We simply listen with our eyes. We see that impressive piece of audio gear, we have read raving reviews, it has a eyewatering price tag so it must be good. And indeed, what we believe, we will hear. Most of these perceived differences are a product of our perception. Not to be mistaken for properties of a product.

Compare the specs: https://www.fiio.com/k7_parameters

You will notice that balanced / normal are almost identical in distortion, impedance etc. except for power, there the balanced almost doubles.

It is called masking. A bird is whistling and a trains rolls by. You simply won’t hear the bird as its sound is masked by the train.

The same applies to a lot of consumer gear. It often comes with a V-shape frequency response as people love a thundering bass and a brilliant treble but it comes at he expense of the midrange. It is masked by the bass and the midrange is exactly the place where all acoustic instruments live.

The 6xx is reasonably neutral, keep it that way!

Exclusive!

Just get a media player supporting wasapi/exclusive like Musicbee or Foobar.

I don’t want to hear a email notifications when listening to a string quartet!

I want to play all recordings I have at their native sample rate. No need to have it resampled to the system default as dictated by the shared mode setting.

Is shared mode bad? No, if you have a 24 or 32 data path to your DAC you won’t notice the difference (except for the email notifications). However, if you play recordings with a level close to 0 dBFS and resample, there might be audible distortion. This can be cured by using a EQ offering a pre-amp function.

https://www.thewelltemperedcomputer.com/SW/Windows/SRC.htm

Have you tried the Sennheiser Smart Control App?

As it is an older gaming headset (low latency) I don’t think it supports Bluetooth at all but has its own proprietary tansmission protocol.

As the transmitter has various inputs, connect a Bluetooth receiver to e.g. the Toslink input and pair it with your phone

If the source you are listening to has a analog output as well you can try guitar and source both in to a mixer, mixer output into a Bluetooth transmitter