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Radio Wrangler · 28th Sep 2019, 2:30 pm

Not sure of the 807, but studer/revox used a milled series of slots in the bell of the Papst outer rotor capstan motor, along with a variable reluctance sensor to read the passage of the slots. The permanent magnet in the sensor applies a little force to the bell which varies as the slots pass and this creates a quiet characteristic whine. Different pitch for different tape speeds.

At mains freq, it could be from a motor winding or the pinch wheel engagement solenoid.

David

28th Sep 2019, 2:30 pm	#2
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,902	Re: Studer Motor hum Not sure of the 807, but studer/revox used a milled series of slots in the bell of the Papst outer rotor capstan motor, along with a variable reluctance sensor to read the passage of the slots. The permanent magnet in the sensor applies a little force to the bell which varies as the slots pass and this creates a quiet characteristic whine. Different pitch for different tape speeds. At mains freq, it could be from a motor winding or the pinch wheel engagement solenoid. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done