使用Ruby SDK从Soundcloud下载歌曲

I am trying to download a track from Soundcloud using the ruby sdk (soundcloud 0.2.0 gem) with an app. I have registered the app on soundcloud and the client_secret is correct. I know this because I can see my profile info and tracks using the app. Now when I try to download a track using the following code I am trying to download a track from Soundcloud