LOS ANGELES — On his first day of work at “America’s Got Talent” yesterday, a kinder, gentler Howard Stern was confronted with his worst nightmare — a Stern impersonator who has been following the shock jock around New York for years.

At a taping of auditions in LA — the first of the season — Stern was unpredictably compassionate with the young hopefuls — letting them down easy and offering words of encouragement.

But he was not amused when comic Stewart Brodian came out on stage to audition for the show.

“How many times have I told you, you have got to get some [better] material,” Stern told him. “It is not enough to look like me.”

Clearly, the 1,500-seat theater where the show was taped was filled with fans of the shock jock, eager to see what he would be like as a judge on a family show like “Talent.”

The applause that greeted him when he took his seat at the judge’s table yesterday afternoon was easily two or three times louder than when the other judges, Sharon Osbourne and Howie Mandel, were introduced.

“I have been fired by NBC many times,” he told the crowd. “What the heck . . . One more time? I say I don’t make it through the first show.”

And the fans did not have long to wait.

Stern — dressed all in black with a charcoal grey scarf and tinted glasses — buzzed the first act of the day, a high-school marching band, within the first 30 seconds.

Stern was hired last fall — at a reported salary of $15 million — when Piers Morgan stepped down to devote more time to his nightly CNN show.

The show, owned by Simon Cowell, was bombarded with protests from parent groups that complained that Stern would carry his raunchy radio talk on to the top-rated summer TV show and ruin it for family viewing.

True to his promise, Stern buzzed most of the children who performed at the first taping. (He doesn’t believe kids should be allowed on the show.)

At one point during the auditions Stern pleaded with Mandel to vote against a 6-year-old dancer.

“The worst nightmare of this show is to tell any 6-year-old, ‘I gave you the X’,” he told the little girl.

It didn’t work, and the little girl went through to the second round in Las Vegas.

When a 14-year-old singer from San Diego came on stage, he asked her before she started to sing: “Will you be OK if we tell you it is not your time?”

The girl said she would be OK, but she was good enough for the judges — including Stern — to send to Vegas.

“He is definitely polished up and much nicer,” said one audience member.

“People who love Howard are going to enjoy him. But people who think he is going to be a monster on the show will probably be disappointed.”

Stern even tried to let down the bad acts (like the marching band) by sharing tidbits about himself.

“I played clarinet in high school,” he said sweetly.

He was harsh on one act — a pair of comedians — whom he called “a colossal waste of time.”

Stern agreed to go to LA for the first round of auditions even though he is famously phobic about flying.

He is expected to take part in only a handful of auditions around the country before the show moves to New York permanently for the live portion of the competition, when viewers get to vote.