BY DAVE SMALLEY

You're in Def Leppard. Your band has written some of the most popular rock songs of all time--tunes like "Photograph," "Rock of Ages," "Foolin'" and "Bringin' on the Heartbreak," to name just a few.

Your album sales--including "Hysteria" and "Pyromania"--are among the best-selling rock albums of all time, with more than 65 million copies sold.

And then the market changes. Grunge and then hip-hop start to dominate the charts, and the rise of file-sharing means that it's all the more difficult for any artist, in any genre, to sell in the numbers of previous eras.

What do you do? If you're in Def Leppard, you respect the music and keep on rockin'.

"There's a real strong ambition in the band," guitarist Vivian Campbell told Weekender in a recent phone interview.

"There's a desire within Def Leppard to be one of the great British bands. We're always striving to write the best songs we could write. 'Cause that's what it's about. It's not about getting the supermodel or getting in the tabloids. It's about writing a [expletive] great song--something that's going to endure."

The candor from Campbell is refreshing, and might even be surprising to those who just remember the band from more lighthearted hits like "Pour Some Sugar on Me."

But the band's most recent album, "Songs from the Sparkle Lounge," deals with some more adult topics--while still maintaining the trademark Leppard wall-of-guitar sound and singer Joe Elliott's signature vocals.

"The lyrics have changed because the perspectives have changed," said Campbell. "Most of us are parents now. 'Songs from the Sparkle Lounge' is a very strong example, because lyrically it's very diverse and very different from any other Def Leppard record."

Some of the topics include the loss of a father, and a tribute to deceased Leppard guitarist Steve Clark (whose spot Campbell filled nearly two decades ago, after having worked with performers like Ronnie James Dio and Whitesnake during the '80s).

Still, don't think you'll get hit with a lot of heavy new stuff that you might not know at Def Leppard's show on Sunday at Nissan Pavilion. The band knows better than to mess with success.