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Alex Rosner

Alex RosnerAlex Rosner
  • Alex Rosner
  • Website: - or Google "Alex Rosner"
  • Legacy: Inventory of the Stereo DJ Mixer - used by millions of DJ's since - Influenced customization of BOZAK mixer to work for Club DJs in 70's.
  • Contact: Rosner Custom Sound, New York, USA

Alex Rosner began his love affair with sound in the golden age of hi-fi - and by the early '70s had pioneered the first stereo sound system in clubs, the first pair of tweeter arrays and crossover. You're likely to hear his name mentioned in connection with the success of legendary New York clubs such as David Mancuso's The Loft; but you might not know he radically changed the world of DJing when he came up with the prototype for another new gadget - a friendly little mixer with cueing system called Rosie. Alex Rosner has plenty of tricks for people interested in clear, loin-vibrating sound reproduction - but when we say, "That’s magic", he says, "That's just ordinary basic principles."

Alex Rosner - Rosie DJ Mixer

1971, The First DJ mixer is designed for the Haven Club by Alex Rosner, and nicknamed “Rosie” for its inventor and red color. A one-off stereo design for in-house use by their resident DJ, Francis Grasso, recognized as the Godfather of the modern performing DJ.


"There was a guy named Louis Bozak, who made mono mixers for broadcast uses and public address systems use. And it seemed to me that one of those mixers that he had - which had ten in and two out, to go to two zones - was a perfect vehicle, which, with some modification, you could make a stereo mixer. So I said to him one day: "What’s really needed out here is a stereo mixer because stereo is the way to go." I had read the technical papers from Bell laboratories about [stereo]. That early 'cocktail party' effect. I knew that stereo would be a good thing to have in clubs. And up until then, I made my own little stereo mixer using two headphone amplifiers for the cueing system and a sliding fader – a very, very primitive device. My technician painted it red, so they called it Rosie, because it was rose red. And when I met Bozak I said: "I do not want to manufacture these things, but I think you, as a manufacturer of equipment, can make a stereo mixer." And he said: "OK!"

Alex Rosner - Rosie DJ MixerHe made the original mixer and he sends it to me for testing. He said: "Test it for ruggedness; I don't know what to do." So I took a bottle of Coca Cola and I poured it on the mixer. That was my reliability test, I thought that was a realistic test, little knowing that DJs probably don't drink Coca Cola's. But I felt that Coca Cola was corrosive because I knew when I put it on my car battery, it dissolves the corrosion at the battery terminal. So I felt that had some effect. When I poured the Coca Cola in the mixer fader it had no effect. So I got back to Bozak and I said: "You got it, that's it, it's reliable!" Then the CMA 10-2 was born, that was a standard of the industry."

The rest, as they say, is history.  Thank you Alex.

About Us

DJ Pro Audio™ (the ORIGINAL) has been operating since 1992, incorporated in 1995, and opened it's first retail store in 1998 in New York City's trendy St. Marks Place (aka 8th Street) block.  Voted best record shop in 1998 and 1999 by Village Voice and NY Free Press.  Today, we no longer operate retail locations, and have instead opted to join the digital revolution managing multiple online properties dedicated to the DJ Industry.  We've been a proud SPONSOR of DMC USA, Roc Raida's (RIP) GONG DJ Battle Show, and up and coming DJ Battles like the AIRPLAY DJ BATTLE - where it's about rockin the party with the gear we love and proudly support.  Don't be fooled by web sites with similar names, claiming to be the original.  There's only ONE.

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