Introduction
The G.R.A.S. RA0075 is a coupler for testing earphones. It uses a 1” microphone.
The RA0075 complies with the requirements of:
ANSI S 3.7 American National Standard for Testing Earphones.
It is also part of the 43AF Artificial Ear.
Components
The RA0075 comprises the following components:
RA0075 NBS 9-A Coupler
GR0572 Stop Collar (to maintain consistent coupler-volume)
The RA0075 is delivered as shown in Fig. 1. It uses a 1” pressure condenser microphone with
preamplifier. An exploded view of its user-serviceable components together with a suitable pre-
amplifier and adapter, and microphone is shown in Fig. 2.
Preamplifiers
It can use either a 1” preamplifier or ½” preamplifier with an adapter. The example in Fig. 2
shows:
26AK
G.R.A.S. ½” Preamplifier
RA0073 G.R.A.S. ½” - to 1” Adapter
Microphones
It uses primarily a 1” pressure condenser microphone (of the type WS1P) with the normal protec-
tion grid replaced by a special coupler-adapter ring (shown below). It can also be used with protec-
tion grid.
40EN 1” Pressure Condenser Microphone
fitted with
RA0074 Coupler-adapter ring
Fig. 1.
NBS 9A Coupler RA0075 as delivered
4
LI0078 – 28 September 2017
