Use 5.1 with my PC

[Simonliii]

So I've got this motherboard (MSI Z77A-G43) and this home theater setup (Samsung HT-BD1250) I got from my aunt & uncle. I've been using it as 2.1 for about a year now but thought it was time to get 5.1 working.

There are images of all the HTBD1250s outputs / inputs in the link and it supposedly supports onboard decoding for Dolby TrueHD and DTS-HD Master Audio.

I'm not sure what this means, but i was wondering if it would work with my motherboards outputs, or if I would have to buy something and in that case, what?

[Naeaes]

Looks like your only option is optical over Toslink. Sadly your motherboard doesn't have it but you could add a sound card that does have it: https://www.amazon.com/ASUS-XONAR-Headphone-Audio-Card/dp/B003ZXDOL6 

[Simonliii]

1 hour ago, Naeaes said:

Looks like your only option is optical over Toslink. Sadly your motherboard doesn't have it but you could add a sound card that does have it: https://www.amazon.com/ASUS-XONAR-Headphone-Audio-Card/dp/B003ZXDOL6 

Okay, but I need my soundcard to have an output ompedance lower than 7 Ohms, and I read that one has around 10 Ohms. Do you know of any soundcards that have the optical over Toslink and a low output impedance for my headphones?

[Naeaes]

14 minutes ago, Simonliii said:

Okay, but I need my soundcard to have an output ompedance lower than 7 Ohms, and I read that one has around 10 Ohms. Do you know of any soundcards that have the optical over Toslink and a low output impedance for my headphones?

Umm. Either you have some very weird setups or you have things reversed. The smaller the impedance of the headphones is, the crappier they are. I find it hard to believe they even make 7 Ohm headphones. Anyway, so long as your sound card can handle higher impedance, it's fine. Just don't turn the volume all the way up. And Xonar DG has got to be able to drive higher than 10 Ohms. I found nothing conclusive but there were mentions of 150 Ohms on other forums. 

[Simonliii]

Nonono, the output impedance of your source should be <1/8th of the headphones impedance. So the output impedance from the sound card would have to be <7Ohms since my headphones are 50Ohms. I copy pasted an explanation to this here.

Spoiler

Simplified Electrical Engineering explanation:

There are two principals at work here:

The first is the fact that impedance isn't just resistance, it's reactance too. Reactance basically describes how much capacitance and inductance a component or system has. More to the point, reactance acts like resistance for AC signals. Obviously, headphones have a LOT of reactance, since they're almost always just coils of wire (apologies to all the electrostatic and planar magnetic fans).

Remember how I said that reactance acted like resistance for AC signals? Well how MUCH it effects that AC signal changes depends on the frequency of the AC. Capacitive elements tend to allow higher frequencies to pass more easily, while inductive elements allow lower frequencies to pass more easily.

The second principal is the fact that the amount of power transferred from a source (amp) to a load (headphones) depends on how closely their impedances match. The Maximum Power Transfer Theorem states that maximum power transfer is achieved when the impedance match exactly. For headphones, power means either heat or noise. Mostly noise, though.

You should be able to see where this is going. As the impedance of the headphones changes with frequency, the amount of power transferred to those headphones changes. Obviously that's going to have a huge effect on frequency response, as certain frequencies will transfer more energy than others.

The problem gets worse the closer the impedances are to matching. If you have a 1Ω amp and a headphone that varies in impedance from 600Ω to 700Ω, the difference in efficiency across that impedance/frequency range is very small. If you have a 10Ω amp and a headphone that varies in impedance from 20Ω to 30Ω, suddenly the difference is HUGE.

Ideally, you want the impedance of your headphones to be as different from the impedance of your amp as possible. Usually that means having a very low output impedance on your amp and high impedance on your headphones.

Since the output impedance on my motherboard is >7Ohms my HD558 get a bassboost which makes them sound "boomy" compared to when I use them with my phone. Therefore I need a soundcard with an output impedance of <7Ohms.