Cable Radio Deal: Digital Cable Radio, a company that provides compact-disc-quality music to subscribers through local cable television systems, said it has received an equity investment from Time Warner Cable and a joint venture of Sony Software Corp. and Warner Music Group. Digital Cable said its new partners have agreed to provide additional capital that will enable the Hatboro, Pa., company to increase its programming and international distribution. Time Warner Cable is the nation's second-largest cable TV operator. Digital Cable's approximately 50,000 home subscribers receive 28 channels of commercial-free, CD-quality music ranging from soft rock to classical and country. Subscribers pay about $10 to have the music broadcast through their home stereos. Digital Cable already has financial backing from several other major cable operators.