How connect amp with pc: Toslink or USB DAC?

[vincik]

Hi, i want to buy a stereo amp, which i want to connect with pc. One of those: https://www.audioholics.com/amplifier-reviews/yamaha-a-s301-501-701-801-integrated-amplifier-preview . First three differs with power and all have optical input. The fourth one, the most expensive one, has also USB input and USB DAC function.
 
1.What are pros and cons of USB vs Toslink connection? Which one is better?
2.What device does digital to analoge conversion when i play pcm through toslink? Soundcard or amplifier? And how much can quality of that soundcard/amp impact sound quality?

 

[PleasantSounds]

In all the stated cases conversion to analog would take place in the amp - they all must have onboard DACs. Toslink carries digital signal, so it has to be converted to analog by the receiver. The difference between USB and Toslink is an additional bus controller chip needed by USB, plus data clocking and buffering. In case of Toslink connection data is buffered on the sender side (your PC).
 
USB DAC may be able to handle higher data rates, as the official Toslink standard goes only up to 96 kHz, though some devices offer also 192 kHz. But in practice anything above 48 kHz is an overkill, as many players are be able to downsample higher data rates without noticeable impact on sound.
 
Toslink has the advantage of maintaining galvanic isolation between your PC and the amp - this way you don't have a risk of experiencing ground loops. Plus, you could still take advantage of the DSP capabilities of your soundcard, for example virtual surround sound.

 

[vincik]

thank you for reply. one more question: do stereo amplifiers (not receivers) with optical input have all DACs? Im a bit confused now. There is only written that it supports TV and bluray players and no mention about pc support or if it has any DAC.

 

[PleasantSounds]

They all do. Digital input always requires a DAC if the output is analog. Manufacturers of consumer goods rarely mention DACs in the specs as this only confuses most of the users. 
All these devices use the same S/PDIF protocol, so there's no reason why it shouldn't work. In fact one of my old DACs which was connected to my PC using Toslink is now used with a TV - again using the same Toslink. 

 

[ProtegeManiac]

  thank you for reply. one more question: do stereo amplifiers (not receivers) with optical input have all DACs? Im a bit confused now. There is only written that it supports TV and bluray players and no mention about pc support or if it has any DAC.

 
DAC is Digital to Analogue Converter. Optical only transmits digital. The reason why it doesn't mention PC support is because they're too lazy to have to write there that it requires one with optical output, something that anyone who knows audio would know anyway (or ask a forum about).