LG Sound Sync to DAC for wired headphone connectivity

[Nullen]

I recently purhased an LG 43” Smart TV (Model 43LJ550M).  I’m trying to figure out a way to do optical audio out to 3.5 mm, so that I can use my wired headphones to listen to my TV in my tiny studio apartment in NY without disturbing my neighbors.  

I tried a DAC (Digital Audio Converter) that was capable of converting 5.1 digital to 2.0 analogue with a mini jack female and RCA females that also had what I thought was a volume control, but apparently was merely a line leveler for the RCAs. 

I first set the TV’s audio to standard “Optical Out” (unfortunately this model did not have a PCM option) and tried an RCA male to 3.5 female cord (headphone plugged into the 3.5) to connect through the RCAs, but the levels were way too low—even with the line level knob on the DAC all the way up—and the TV remote’s volume control did nothing. So next I tried plugging directly into the mini jack port on the DAC and the sound level was ok (about medium, I’d say), but again, TV remote’s volume control didn’t work, so I couldn’t increase (or decrease) the volume.

Evidently the only way to get the TV remote’s volume control to work is to use the LG Sound Sync (Optical) audio out function and have an LG Sound Sync compatible device, but I can’t find a DAC that specifies such compatibility and everything on the net regarding Sound Sync is just all about pairing bluetooth wireless, which I do not want (latency).

I’m trying to save money, otherwise I’d drop a couple hundred on a Sennheiser RF setup. 

So, I either need some sort of DAC with a volume amplifier or an LG Sound Sync compatible DAC so that the remote’s volume control will work. Headphones with volume amps would be great too, of course, but so far the only ones I’ve found are even more expensive than the Senn RF.

One would think that it would be a simple matter and/or that LG would be aware of the issue and have a list of compatible products to solve it, but if so, I can’t find it.  

Please help. Thanks.