Not sure what you mean. The switcher allows you to "connect" four each devices to your single optical input on your soundbar. The soundbar can decode Dolby Digital or DTS Digital Surround.
Without the switcher, you will only be able to connect and decode one device at a time. Please explain what you mean by "sound converting".
Experience with the following gear: Cambridge Audio 640R; Cabmridge Audio 752BD; Rotel RCD-1072; Pioneer BDP-05FD; Emotiva UPA-7; Sherbourn PT-7020A; Manley Labs Stingray Integrated; Totem Acoustics Rainmaker Center; Totem Acoustics Hawks; Totem Acoustics Tribe I and II; Totem Acoustics Mask In-Ceiling; Adams Audio MK3 Pencil; Onkyo PR-SC5530; JL Audio Fathom and Dominion; Integra RDA-7; Lexicon LX-5; Arcam Muse; Sonos