Martin Audio – MA900 Amplifier
E
NGLISH
6
5.1.1
The DIP-switch
D iffe re n t ga ins a nd fu nctio n ca n b e selecte d for ch an ne l A a n d B, b y
a pp ro priate setting of th e DIP switch . Se le cting th e ma xim um ga in o f the
a mp lifie r is alwa ys a tra de o ff be tw e en n oise an d h ea dro om . A low g a in
a mp lifie r am p lifies le ss of the no ise o f th e p re ced in g e qu ip m en t (m ixe r,
cro ssove r, e q ua lize r e tc.). A h igh er in pu t level is the n req u ired to a tta in full
p ow er o u tp ut, so th e h ea d ro om w ill b e d ecre a se d o n mixe r o r cro ssove r
o utpu ts. In a n actively d rive n syste m the re is u sua lly a d ed ica te d lou dsp ea ke r
p ro ce sso r or co ntro lle r, fo r th e lou d sp ea ke r system . So m e lo u dspe ake r
m an ufacturers recom m en d a spe cific g a in for th e a mp lifie rs fo r use w ith the ir
con trollers.
T he re a re eig ht p osition s o f ga in, se le ctab le fro m 20 dB , to 4 1d B in 3d B ste ps.
T he d ifferen t settin gs fo r th e D IP -sw itch es are liste d in th e tab le be lo w . Th e three sw itch e s to th e ve ry le ft are for
cha nn el B, a n d th e three to the ve ry righ t a re fo r ch an n el A . T he tw o sw itche s in th e m id dle sele ct the op era ting m o de
o f th e a mp lifie r, S tereo or L in k /Bridg e A+ B .
5.1.2
Sensitivity
Sensitivity is the input level in volts (rms.) or dBu (referred to 0.775Vrms) that is
required to obtain full output power. As the output power varies with the load
impedance, 4 ohms is usually taken as the reference. The table below gives input
volts rms Versus gain for full output power @ 1% t.h.d, 1Khz sinewave 4 Ohm load.
5.1.3
Options
A s th e D IP -switch is recessed , A security sticke r can b e p la ce d a cro ss the ba y to preve nt u n au th orize d tam pe rin g
o nce th e g ain h as b e en se t. A no the r o ptio n is to re mo ve th e D IP -switch . T his sh o uld o nly be ca rried o ut by q u alifie d
service pe rso nn el! T his corre sp o nd s to all switch es set to “O FF ”, i.e. 3 2 dB g ain a nd stereo mo de .
5.2
Link switch
T he L in k switch loca te d o n th e rea r p an el (the ce ntra l D IP -sw itch ) is fo r cha ng ing th e op era ting mo de o f the am plifier
( sectio n 5.3 ).
5.3
Operating modes
5.3.1
Stereo mode
In this configuration, both channels operate independently of each other. This is used
for all 2-channel operations, eg Bi amp and stereo. Stereo mode is selected by
placing the two central switches in the “OFF” position (Down). The attenuators on the
front panel control the respective channel levels.
Never connect either output terminal to ground or in parallel. The recommended
minimum nominal impedance, for stereo or tandem operation, is 2 ohms per channel.
Gain dB
20
23
26
29
32
35
38
41
Input dBu
+13.3
+10.3
+7.3
+4.7
+ 1.7
-1.3
- 4.3
- 7.3
Input V rms
3.58
2.53
1.79
1.27
0.90
0.64
0.45
0.33
All material © 2007. Martin Audio Ltd. Subject to change without notice.
