Martin Audio – MA2.8s Amplifier
ENGLISH
6
5 R E A R PA N E L FE A T UR E S
5 .1 G a i n s w i t c h
T he g ain switch loca te d o n th e rea r p an el (the ce ntra l D IP -sw itch ) cha ng e s th e g ain/inp ut se nsitivity o f the am plifier.
T his ca n b e u se fu l w he n u sing lo w or high n o mina l inp ut sign a ls. Mo st pro fe ssio n al m ixing co nsole s op era te a t a
n om in al le ve l o f +4 to + 6 d Bu ; th e 3 2d B g ain p osition e nsu re s the re is p le n ty o f fad er mo ve me n t ava ilab le . F or se mi
p ro fe ssion al mixing de sks o pe ra tin g a t a no m in al le ve l o f 0d B o r -1 0 dB th e high e r ga in se tting s o f th e a mp lifie r ca n b e
u se d.
T he D IP -sw itch
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 . Mo st 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.
5.1.1 G ain
T he re a re eig ht p osition s o f ga in se lecta ble , fro m 20 dB to 4 1 dB in 3 dB step s. T h e diffe re nt se tting s fo r the DIP-
switche s a re listed in th e ta ble b elo w. T he th re e switch es to the ve ry le ft a re fo r cha nn el B, a n d th e three to the ve ry
rig ht a re fo r cha nn e l A. Th e tw o switch es in the midd le se le ct th e o pe ra tin g mo d e of th e am p lifie r, S te reo o r L in k
/Brid ge A+ B.
5.1.2 S en sitiv ity
S en sitivity is th e level in volts (rms) or d Bu (re ferre d to 0.7 75 Vrm s) tha t is req uire d to
o btain full o utpu t p ow er. A s th e o utp ut p ow e r va rie s with th e loa d imp ed a nce, u sua lly 4
o hm s is usua lly take n as th e re feren ce. B eca use the M A2 .8s is e qu ip p ed w ith a n M LS -
switch the re are nu m erou s varia tio ns of o utp ut p o we r ve rsu s sen sitivity versu s loa d
imp ed an ce.
W e re co m me nd ca lcula ting th e se n sitivity if th is is n ece ssary.
A s a gu ide th e ta ble b elo w give s the in pu t level in volts rms versus g a in for fu ll po we r
o utpu t @1% thd 1 KH z sin e w ave, ML S switche s in p ositio n 0 dB
G ain dB 2 0 2 3 2 6 2 93 23 53 84 1
Inp ut d Bu + 21 .6 + 18 .6 + 15 .6 + 12 .6 + 9 .6 + 6 .6 + 3 .6 + 0 .6
Inp ut V rms 9 .4 0 6 . 6 5 4 . 7 0 3 . 3 4 2 . 3 6 1 . 6 7 1 . 1 8 0 . 8 4
5.1.3 O ptio ns
A s th e D IP -sw itch is rece ssed , a sticke r ca n b e p la ce d a cross the cu t ou t to pre ve nt un au th o rize d tam pe rin g. An othe r
o ptio n is to re mo ve th e D IP -switch . T his sh o uld o nly be do ne by a uth orize d se rv ice p e rs on ne l T his co rre sp o nd s
to all switch es set to “o ff ”, i.e . 3 2d B ga in an d ste re o m od e .
5 .2 L in k s w i t c h
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
(se e be low , section 5.3).
All material © 2007. Martin Audio Ltd. Subject to change without notice.
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