April sales of Mac seem ahead of street expectations according to Piper Jaffray analyst Gene Munster who quotes data from research firm NPD.

The data from NPD shows that Mac sales grew 39% year-over-year with the street consensus resting on 19% growth for the June quarter.

Munster also goes onto to discuss iPad cannibalisation which he believes is having a stronger effect on the sale of iPods rather than Macs. iPod unit sales are predicted by NPD to be down 17% year-over-year for April.

“Given the ASP and margin profile of the iPad, we see this as a net positive for Apple’s business,” Munster writes. “We believe in the long run Mac cannibalization will exist, but will be minimal.”