Record Changer - Operation

Operation

The purely mechanical mechanisms of record changers were often very complex. Changers typically had an extended central spindle that the records were stacked on, and an extra arm designed to hold the stack steady. Some units had feelers that could detect the size of each record (standard sizes 7", 10", or 12") and position the tone arm accordingly. Some, including the changer pictured, used a variable size sensor which allowed sizes other than the three standard sizes to be played. (Note that the pictured Dual 1003 has four sizes loaded, and records sizes can be mixed in any order.) The more basic models required the record diameter to be set manually, and hence did not allow records of different sizes to be stacked together. The following devices were the most popular (with examples):

Three size sensors:

• Size selector knob - no size intermix (BSR 1968 to 1973)
• Size and speed selector knob - no size intermix, some types can't be played automatically (Garrard after 1969)
• Rising feelers in or alongside turntable - no size intermix, but automatic sensing of size (PE after 1970)
• Falling record sensor - random intermix - sizes mixed in any order (BSR before 1968)
• Rising and falling record sensors - Intermix 10" and 12" records, 7" played separately (V-M 1950 to 1970)
• Unplayed stack sensor - Arranged intermix - large records before small (Webster Chicago 1950 to 1953)
• Unplayed stack arm tip sensor - Arranged intermix (Collaro/Magnavox after 1967)

Variable size sensors:

• Pickup arm scan of unplayed stack - Arranged intermix, odd sizes (Collaro/Magnavox 1954 to 1967)
• Pickup arm scan of lowered record - Random intermix, odd sizes (PE 1957 to 1969)
• Arm tip feeler wheels (feel only top record on turntable) - Random intermix, odd sizes (Dual 1003, 1004, 1005, 1006)
• Arm top feeler Wheels (feel only bottom record on stack) - Random intermix, odd sizes (Miracord 9 and 90)
• Pickup arm scan of separated record - Random intermix, odd sizes (Thorens TD-224)

Record changers were met with disdain by audiophiles because of the perceived compromise in fidelity resulting from changes in tone arm angle with the height of the stack, and concerns about changers' seemingly rough treatment of discs, particularly slight but cumulative damage to the spindle hole, as the records were effectively dropped from a height of a few inches onto the record platter. Additionally there is some sliding and rubbing of the discs which scratches the record labels, due to the dropped disc not immediately accelerating to the rotational speed of the spindle or discs below it. Most of these fears are unfounded in changers made after 1953. More advanced changers, such as the TD-224 model from Thorens, and the ADC Accutrac+6, went some way towards addressing these problems.