LA Audio Electronic SPX20 Operation Manual page 6

Pin 2 = Hot (+)
Fig 2.6.3: Pin arrangement for XLR inputs on the SPX20
Pin 1
Pin 2
Pin 3
For unbalanced operation join pins 1 and 3 and connect to Screen (signal
ground) and use pin 2 as Hot (signal +).
Input 1 also has a pair of front panel inserts on TRS jacks which are wired
as follows -
Fig 2.6.3: Pin arrangement TRS jack inserts on Input 1
Tip
Ring
Sleeve Screen
For unbalanced operation join Ring and sleeve and connect to screen
(signal ground) and use Tip as Hot (signal +).
Plugging a mono jack into these inserts effectively unbalances the
connection.
Fig 2.6.4: Mono jack pin arrangement
Tip
Sleeve Screen (signal ground)
PUSH
Pin 3 = Cold (-)
Screen Signal ground
Hot
Cold
Sleeve Ring
Screen Cold (-)
Hot
Cold
Signal ground
Sleeve
Screen
Hot (signal +)
Page 6
Pin 1 = Screen
Signal +
Signal -
Tip
Hot (+)
Signal +
Signal -
Tip
Hot (+)