Oswald’s Mill is a four-story, 10,000-square-foot house-mill in scenic Lehigh County, Pennsylvania. Brawny German immigrants used to grind flour here between massive millstones. Built around 1800, it’s now the only known house-mill left in the country. All these things about the mill—its immense size, secluded setting, and historic significance—appealed to Weiss. So he bought the place and electrified it. As it happens, those 2-foot-thick stone walls make it the perfect lab for developing audio products.

Weiss’ record collection is big. Conservative count: 12,000. His go-to reference discs for setting up a turntable system are Será Una Noche and La Segunda, both produced by Santiago Vazquez and Todd Garfinkle. In the jazz stacks, “Mood Indigo” from the reissue of Masterpieces by Ellington, paired with “a good mono cartridge,” gets a lot of play. Those giant horns, an OMA signature, are designed to work with Weiss’ low-wattage triode tube amps.

The hefty black contraption attached to the back of that gorgeous walnut horn is the RCA MI-1428B, a magnificent piece of engineering that went out of production in 1939. It was the best field coil driver of its era. Some connoisseurs think it’s still the best. Weiss cornered the market on these beauties long ago; studying them is part of OMA’s R&D. Inside that silver thing that looks like a perforated coffee can is a tiny flame in a quartz cell heated to 1,000 degrees Celsius. This is mad scientist tech from the 1930s: a tweeter with zero mass, just the thing for transmitting high-frequency sound waves.

A couple of Weiss’ personally modified record players. The Technics SP-10 MKIII direct-drive turntable on the left rests on a vibration-smothering, 210-pound slate plinth (quarried and cut locally). The Gates CB-100 on the right is a 16-inch transcription turntable. In the 1940s, live radio shows were recorded on 16-inch acetates, and stations around the country needed a turntable big enough to play those discs. On the lower shelf is one of Weiss’ dual-chassis phono preamps.

This juicy piece of OMA circuitry is the crossover network hooked up to The Mill's testbed system. "We use this network as a reference when designing new products and testing components," explains Weiss. "When we change a component in our sound system, we go in here and add, remove or change things -- caps, resistors, inductors -- as necessary. It's like tweaking a recipe."

Long before Quentin Tarantino needed special film projectors for The Hateful Eight, Walt Disney needed special amplifiers to screen Fantasia in theaters. This is an original 1940 RCA system used in one of those venues. It has 5four separate amplifiers, one for each sound channel. Touch the wrong leads and you’ll get zapped with 1,500 volts of DC juice. These beasts were locked in cages to safe-guard projectionists, but Weiss prefers to keep his triode amps under glass.

Just your average collection of vintage RCA amplifiers. “It blows my mind that these machines still work,” Weiss says. “I hook them up to a Variac, slowly bring up the voltage, and they start to glow—it’s like magic.” A Variac is essential when working with old electronics; it prevents voltage spikes and surges that can fry your gear.

Weiss has a collection of vintage horn speakers in his attic.

The exposed electrical system at The Mill is called knob and tube, otherwise known as "K&T." This early 2-wire system (no ground) is the same technology that Thomas Edison and Nikola Tesla used in their labs to conduct experiments. Why the old school K&T wiring? Weiss: "Because there isn't any drywall to hide wires behind and it's incredibly cool looking." Before you start start nailing ceramic knobs in the ceiling, consult the National Electrical Code.

"Flotsam and jetsam," Weiss said of this collection. That's a highly-collectable RCA "On Air" studio sign. The vibrant red letters have faded over the decades.

These mammoth speakers are the kind of horns that used to pump sound through cavernous movie palaces in the 1930s. Each one weighs 250 pounds, has 18 cells, and a 300Hz cutoff frequency. Part of RCA's Shearer 2-way commercial sound system, these beasts can still project a movie soundtrack to the cheap seats at Radio City Music Hall with ease.

The three boxes that look like sci-fi B-movie props are Klangfilm cinema and studio amplifiers (Germany; 1950s). The console on the left is a vintage Ampex R2R tape machine, pulled from a record executive's office (only playback; no record heads). Weiss: "Simple, elegant industrial design can be traced from the Bauhaus to these machines, then to Dieter Rams at Braun and Joni Ives at Apple."