Citrix Systems, makers of GotoMeeting, GotoWebinar and other video conferencing services has quietly acquired high definition voice conference provider Vapps for $26.6 million in cash. The details of the acquisition were released with Citrix’s November 14th SEC filings. Vapps had been a pioneer in the field of “HD” voice conferencing services, and has partnered with Skype, Adobe, Yahoo and MSN among other services providing high quality audio conferencing.

Vapps HD conferencing is audio that is sent on the 16 KHz “wideband” codec. This is twice the standard 8 KHz that most VoIP encoding (roughly what you’d get on a PSTN call) provides. Vapps services supports up to 500 callers on the line and provides a monthly flat rate service that encourages all day, continuous use. Vapps customers reportedly use roughly half a billion minutes per year.

Citrix will likely integrate Vapps technology into it’s current suite of collaboration services. In addition to the $26.6 million in cash, Vapps also has the usual “if they meet certain goals” incentives at a not-so-usual $4.4 million price tag. According to both companies, Vapps and Citrix have been negotiating the deal for “several months.”

Vapps had been financed solely by Azure Capital Partners, who will see a 3.6 times return on it’s initial VC investment that it staked only 18 months ago. Much shorter than the duration most VCs have to wait to see any it at all a return on their investment.