I would like to buy a sound card so that I can play samples on my Yamaha YDP-181 using Kontakt. As I understand it, I should have ASIO as well as optical connections. Can anyone suggest which sound card I should buy or give any other helpful hints. Thanks.

If you're using a Mac, its sound card is probably all you need (and no ASIO is needed).

If you're using a PC, its sound card might be adequate, but you'll need ASIO software.

If the latter does not work well, only then will you need a replacement sound card.

Optical connections have no place here because everything is digital, right up to the analog output to the amp/speakers.

Note: on a PC, you have ASIO4ALL which enable a ASIO mode with sound cards which doesn't have its ASIO driver. (We can also use WASAPI mode with some softwares like Reaper)

A Xonar DG or Xonar DGX will do just fine, those have native Asio. Or use Asio4All without a soundcard.

First thing, I think one of the issues the Yamaha YDP-181 has no USB to host.

You can either buy a Midi to USB adapter and connect your piano to a USB on the PC, a quick check would seem to suggest this one for the yamaha,

http://www.amazon.co.uk/Yamaha-SUX1...8-1&keywords=ux16+usb-midi+interface

or perhaps any one of the cheaper ones would do, check the manual for your piano. Others will be able to comment on a decent cheaper adapter if one exists, I have no experience using such adapters.

The adapter approach is a good option if you feel your current onboard soundcard is good enough and may be your cheapest route since there is a good chance you will find that it is good enough if your PC is you fairly typical i3 - i7 machine these days.

Alternatively, you could buy an external USB audio interface with MIDI inputs, a fairly decent cheap option that is well regarded would be the focusrite 2i2 which has MIDI

http://www.amazon.co.uk/Focusrite-S...8947&sr=8-1&keywords=scarlet+2i2

another route: Internal PCI soundcard which has MIDI input, but those can get really costly.

With both you'd need a midi cable to connect the piano to the MIDI inputs of the interface/soundcard, but that type of cable should cost hardly anything.

edit:

http://www.sonicsense.com/media/documents/yama/ydp181_en_om_a1.pdf

page 52 has the relevant info.