"I'll be with you in a minute," said John Kass as I entered Go Johnny Go—his small, crowded White Bear Lake record store. "I have go give these people the bad news."

Kass stepped outside and spoke to a couple who had just brought a batch of records in for him to appraise. "I can give you two dollars for the lot," he said. One of the would-be sellers made a remark I didn't catch, and then I heard Kass respond, "Yeah, but do you know how many editions of every Beatles album there are?"

When Kass came back into the shop, he traded a few words with Joey Franklin, one of his co-founders of Dead Media—a Minneapolis shop that Kass is stepping away from since Franklin and the other proprietors are having such success with their own programming.

"I'm borrowing this for the road," said Franklin, holding up an MC5 cassette.

"That's one of the best albums of all time!" called Kass as Franklin waved and walked out. Then, Kass had one more person to talk with—a person he introduced as Jim, "my best customer." Jim, too, traded a few words with Kass and headed on his way.

"I'll probably see you tomorrow," Jim said as he left.

I was there because Kass had caught my attention—along with the attention of many others, worldwide—with an eBay listing that offered 200,000 records for sale. Bids for the lot went up to $19,000, but the auction ended without Kass's undisclosed reserve having been met. He didn't want to give too close an estimate of the trove's value, but "it's six figures—I'll just say that."

Among those who inquired about the sale was the man who's actually pictured in the auction listing. No, that's not Kass standing in a gigantic warehouse—it's Zero Freitas, pithily identified in a New York Times headline as "the Brazilian bus magnate who's buying up all the world's vinyl records."

A Freitas representative contacted Kass, but he wasn't ready to pay Kass's price, despite the fact that Kass arrived at the value thusly: "I take the market price, and then I cut it in half. Then I cut that in half, and I cut it in half again. One-eighth of the inventory's value. Of course, it's still a good chunk of change." Also, Kass acknowledges, buying and sorting the collection "would be a lot of work."

The records are stored in the basement of Kass's White Bear Lake shop—a vast subterranean space where he took occupancy 20 years ago. "I had 90,000 records then," remembers Kass. "Now, I have 625,000."

Some of that stock resides at Kass's other retail locations—Dead Media, Hi-Fi Hair—but about half a million records, CDs, tapes, eight-tracks, reel-to-reels, and other recordings in obscure formats (I spotted at least one laserdisc) are stored in White Bear Lake, where Kass finds his collection growing at a rapid rate.

"This is just the past hour," Kass told me, sweeping his arm over several boxes. "White Bear Lake has the highest average age among the 110 municipalities in the seven-county metro area." Whether they're members of the Silent Generation or the Baby Boom, White Bear Lake residents are ready to downsize—and "they don't just have their own Neil Diamond records. They also have their kids' Metallica CDs and Smiths tapes."

Kass knows that the owners of his space are looking to sell, and that whether the space is preserved and renovated—a former livery stable, it's been owned by the same family for the past century—or cleared to make room for a Starbucks, the time is coming when Kass is going to have to clear out. With that knowledge, and even more incoming stock than seven employees have time to process, Kass is currently looking to move a couple hundred thousand records that have been culled, but not sorted.

"My inventory is a cross-section from Archie Shepp to the Beatles to Billy Joel," explained Kass. "I've pulled all the bullshit. What's left is either common records in stone mint condition, collectibles, and a whole lot of limited-edition, private-press...who knows what."

Kass is a longtime veteran of the local music scene; he's worked as a DJ, he's run record labels, and for over a decade he worked in sales for Warner Records. Walking through the vast basement storehouse is a fascinating experience. Boxes are stacked high, full of LPs and singles and eight-tracks—many preserved in their original wrapping, time capsules from an earlier era that are waiting to be rediscovered.

Though Kass, like any collector, prizes rarities, he says that much of his stock in trade is what's known as "chud": records that were produced in substantial quantity. Chud records have value for fans of the music, but won't command astronomical prices.

Some treasures are just too hard to let go of. "If I get a Velvet Underground record and a Neil Diamond record," Kass confesses, "I'll keep the Velvet Underground, and sell the Neil Diamond." Still, Kass emphasizes, all 200,000 of the records he's offering are sellable—to the right buyer.