NEXT
Click on picture
to enlarge
Parts
Mic gain and frequency response of an Ampex recorder or mixer can be measured using the attenuator circuit illustrated on page 5-1 of the MX-10 / MX-35 manual. When fed with a 1 Volt signal from an audio oscillator, this circuit will apply 1 mV (-60dB) to the mic input at 200 Ohms impedance.
This construction is modeled after the design actually used at Ampex.
Pomona double banana plug, Mouser 565-MDP-0
200k Ohms 1/2 Watt 1% resistor, Mouser 273-200K
200 Ohms 1/2 Watt 1% resistor, Mouser 273-200
6 foot length of 2 conductor shielded mic cable
#6 x 3/8" nylon spacer, hardware store
#6 x 3/8" self tapping sheet metal screw, hardware store
2 - 3/4" #4 brass machine screws, nuts and flat washers, hardware store
3 - #4 internal tooth solder lugs, Mouser 534-7311
Devcon 5 Minute Epoxy
Mic Input Attenuator For Measuring Gain and Response