Protection Features; Output Limiter; Thermal Protection; Vhf Protection - Martin Audio MA1400 Manual

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CONTENTS
9

PROTECTION FEATURES

E ach MA R TIN A UD IO M A series a mp lifie r h as m a ny a d va nced prote ctio n fea tu res, th a t will prote ct b o th the am plifier
a nd the lo ud spe akers con n ecte d to it, sho uld a fa ult co n ditio n arise . Un d er n orm al u se th ese fea tures a re in a ud ib le .
A ll p ro tectio n circu its o pe ra te in de p en de ntly.
9.1.1
A n ou tp u t lim iter is includ ed to a vo id am plifier clip pin g. W h en a n a mp lifie r is se ve rely ove rd riven , its o utp ut w ave fo rm
is clip p ed (its p ea ks are squ are d off) –red u cing th e cre st fa ctor. In extre me ca se s, th e wa veform can a p proa ch th at of
a squ are w ave . An a m plifier is n orma lly cap a ble o f prod u cing fa r mo re po w er u nd e r th e se con d itio n s th an its n orma l
u nd isto rte d rated o u tp ut po we r.
T he lim ite r w orks b y m on ito ring th e o utpu t a nd co mp arin g the distortio n p ro du ce d b etw ee n th e inp u t an d o utpu t o f th e
a mp lifie r. If the d istortio n excee ds 1% TH D for a n y re aso n (vo ltag e o r cu rre nt clip pin g), th e lim ite r re d uces th e in p ut
sig na l p ro po rtion ally. N o te tha t, if th e sig na l is disto rted or clip pe d b efore it re a ch es th e am p lifier, the clip limite r w ill n ot
b e activated .
U nd er n o rm al op eration th e clip limiter is ina ud ible. T h e lim iter ca n be tu rn ed "O n" or "Off" by pressin g th e releva nt clip
lim it sw itch .(3 p ag e 5 )
S om e ma n ufacturers o f lo u dspe ake r pro ce ssors d o n ot reco mm en d the u se of clip limite rs in a m plifiers, a s it can
e ffect the tracking of th e proce ssor's limiters.
If th e a mp lifie r is be in g u se d w itho u t an y e xtern al lim iting , M artin A ud io re co m me nd le avin g the clip limite rs sw itche d
"ON " (b u tton de pressed ).
9.1.2
W he n th e a mp lifie r is drive n ve ry ha rd in to a lo w imp ed a nce loa d, th e co o ling fa ns w ill run at h igh spe e d. If the se
o pe ra tin g co n dition s con tin ue , the P rotect ind ica to r(s) will illu min ate ind icating th at the am plifier is a bo u t to g o into
the rm al sh utd ow n.
A fter five se co nd s the a m plifie r w ill g o in to th e rm al p rotect b y mu tin g the inp u t sig na l. A fte r 1 5-20 se co nd s the
a mp lifie r will ha ve co ole d do wn en ou g h fo r the a m plifie r to com e ou t o f shu td ow n a nd op erate a s n orma l. If th e lo ad
con ditio ns re ma in u n ch an g ed the th erm al p ro tectio n will be re - initia te d . Th erm al p rotectio n occurs wh e n th e h ea tsin k
tem pe ra ture rea ch es 90
9.1.3
If a signal of more than 12kHz, at full power is detected for more than five seconds, the VHF protection mutes the
input signal. (This is indicated on the front panel (4) by the protect LED ). After five seconds the outputs will un-
mute and return to normal operation, unless the output signal has remained unchanged, in which case the VHF
protection will re-initiate.
9.1.4
All MARTIN AUDIO MA Series amplifiers are completely short circuit protected. The protection circuit permits very
high peak currents, but still holds the output devices within the safe operating area. If a sh o rt circuit is ma intaine d ,
the cha n ne l a ffecte d w ill e ve ntu ally go into a th erma l p ro te ct cycle u ntil th e sho rt circuit h as be en re mo ve d .
9.1.5
If the AC mains voltage is outside the operational window (over or under voltage), the power supply will
automatically shut down. When the mains voltage is above the minimum start voltage and below its maximum
operating voltage the amplifier will restart.
The two green "ON" LED's indicate when the power supply is operating correctly.
9.1.6
T he re a re tw o typ es of D C p ro te ction :
•
•
All material © 2007. Martin Audio Ltd. Subject to change without notice.
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Output Limiter

Thermal protection

°
C .

VHF protection

Short circuit protection

AC mains voltage protection

DC protection

F uses o n the su pp ly bran che s of ea ch ch an ne l.
D C crow b ar p rotectio n th a t sh orts th e o utpu t if m ore th a n 10 vo lts D C is be in g d etected o n the o u tp uts. Bo th
the se circuits co me in to effe ct on ce a DC le ve l is de te cte d o n eith e r ch a nn el.
Martin Audio – MA1400 Amplifier
13
GUIDES