Weinschel model 6038

poles for 0.25, 0.5, 1, 2, 4, 8, 16, and 32 (8 total poles)
ground is common

relays rated at 12vdc
contacts close at 6.7v, 8mA
draw reaches14mA at 12v
contacts release at 1.8v

using largest 5 poles, total draw is 70mA

UDN2981 is rated at 
pins 1-8 are inputs 1-8
pin 9 is VCC (50v max)
pin 10 is GND
pins 11-18 are outputs 1-8
has clamp diode, but does NOT have pull-down
output voltage 5-50v, switched from VCC
max sum of continuous current across all poles at 15v is 115mA
max sum of continuous current across 5 poles at 15v is 200mA

Arduino running A/V switcher draws 12-17mA at 0, and 50mA at 31.
100mA regulator gets warm but will probably survive it.
Turning off the bar graph indicator would keep draw at 17mA.