“Well, this is interesting,” said Robert Plant, late in his set Thursday night at the Hard Rock Live in Hollywood. “I feel alive ... like we split the atom.”

Plant and his Band of Joy didn’t make any scientific discoveries during their mostly stirring 90-minute performance, but the closing numbers did test the limits of their road crew’s engineering skills—and even prompted the former Led Zeppelin front man to drop a few apologetic f-bombs.

That’s because the speaker system blew a gasket in the middle of “Please Read the Letter,” the song that Plant recorded as a duet with Alison Krauss on the Grammy Award-winning “Raising Sand.” Much to the group’s credit, the band plowed through the number, encouraged by a less-than-capacity crowd that rose to its feet in support. At one point, Plant was even moving sound monitors in mid-song, like a roadie. From there, Plant, never one to chat up an audience in concert, took the microphone and ad-libbed.

“My mother told me to never be profane,” Plant said. “But I believe this occasion calls for it. The PA is f---ed up. We’ll have to use British intuition to fix it. ... This is what it was like in 1969—you couldn’t hear a f---ing thing!”

When you could hear the Band of Joy, it was something to behold. A few critics describe Plant as a chameleon for traveling down experimental roads in his post-Zeppelin solo career. But if anything, this second incarnation of Band of Joy (Plant also fronted a group by this name in the late 1960s that included future Zeppelin drummer John Bonham) is Plant being true to his roots, the music that not only inspired him as a youth but found its way into many of the blues-based riffs that drove Zeppelin.

Band of Joy, featuring country guitar great Buddy Miller and backup vocalist Patty Griffin (who won a Grammy this year for Best Traditional Gospel Album, “Downtown Church), seamlessly blends bluegrass grit and hardened blues with Plant’s soulful, unmistakable voice to produce the tightest sounding group of his entire solo career.

The group opened with a foot-stomping, bluesy version of the Zeppelin classic “Black Dog,” followed by a searing take on “Down to the Sea” (from Plant’s solo effort, “Fate of Nations”) and the hard-driving “Angel Dance” from the Band of Joy’s album by the same name.

Plant carefully selects the Zeppelin tunes that will receive Band of Joy treatment, and more often than not his choices are right on the money, infusing timeless rock classics with a country edge thanks to Miller’s signature guitar work as well as the occasional lap steel guitar or banjo from Darrell Scott. “Black Country Woman”—from the Zep epic “Physical Graffiti”—perfectly played into Band of Joy’s wheelhouse, with just enough of a naughty nod from Plant to send a few Baby Boomers into front-row delirium (“Hey, hey, mama, why you treat me mean ... But that’s alright, I know your sister, too.”)

Highlights included “House of Cards,” Band of Joy’s soaring cover of the Richard Thompson song; the dreamy treatment of the Plant solo hit “I’m in the Mood,” which he worked as a duet with Griffin; and the Zep classic “Ramble On,” which closed the opening set and had the crowd in full throat on the chorus.

In addition to the equipment malfunction, the biggest disappointment was the encore. The group had been playing three songs, but Thursday night produced one more Zep offering—“Gallows Pole”—and then a quick exit from the stage. Maybe the speaker issues had finally rattled the man who once gave us “Now and Zen.” Then again, when hasn’t Robert Plant left a crowd wanting more.