MXR M-150 Preamp Manual

8/12/2019 MXR M-150 Preamp Manual

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I ~ I a O D U I I O ~

The MXR SYs t e m Pr eam p I I ha s be en de s i gned to p rov i de th eu lt imt e in comprehen s i ve s te reo s ~ s t e cont ro l whil e a i n a i ne xcept i onal s on i c in te r i t t The S ~ t e Pre a P of f ers the homea udio e n th us i a s t con t r o l capa b i l t s a nd s ig na l - ro ut ing f l e;{ i b l t Yp r e v i o u s l ~ re s t r i c t ed to lecordinS n ~ n e e r using sop J i s t ica te dmixins conso l e s

The SYs t e m Pr e amp I I se r ves as th e c en t r a l con tro l un i t in ahi sh - Qua l i t y componen t s y s t e m. I t a l lows t he use r t o r ou te tw oinde penden t s i sna l s ou r c es simu lta neous l y to a moni t or ou tpu t t apedeck or powe r amp and speake r s . A Mix con t ro l c a n bl en d t he t wos i sn a l s and pro v ide s th e mean s to accomp l i sh p ro fe s s i ona l - so undingf ad e s be tw e en progr a m se l ec t io ns . A sepa ra t e mon t or c ha nne l ope r a t i ns wi t hou t a f f e c t i n s the ma in c ha nne l f e a tu r e s i t s own Se l ec ta nd Le ve l c on t r ol s . A ve r s a t l e in s t rumen t i np u t e nab le s th e s i Sna lfrom a n e l ec t ron ic in s t r umen t o r a mi c rOPh on e to b e b lended wi t hproSr a m ma t e r i a l . Th e cont ro l s a nd f e a tu r e s a r e u s e r or ien t e dof fe r in s except io na l f l e xi b i l i ty a nd ease of u s e .

Like a l l MXR p r oduc t s t he SYs t em Pre amp I I re f l e c t s t he l a t e s tadvan c e s in Amer ic a n a udio te c hno l ogy . Thi s in nova t iv e preamp l i f ie rha s be en de s i gne d wit h i ma s in a t on t o provide th e u l t im a t e i nf le xib l e cont ro l f o r th e c r ea t i ve a udio enth us i a s t .To e nsure p ro pe r ope r a t ion we re c omm e nd t ha t YOU f i r s t r e ad th i s

manua l to f amil i a r i z e you r s e l f wt h t he SYs t em Pre amp I I t scon t ro l s and t he i r funct ion s and app l ca t ions . No t e t ha t when a c t ua llab e l s a re re f e r e nc ed th e Y wil l be ind i c a t ed by a l l c api t a l l e t t e r s e . s . the LANCE c on t r o l . The ircut De s c r i pt ion sec t i o n i sinclud ed fo r te chn ica l r e f erence .


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lU Sl uLLAIIO U

The MXR SYs t e m P r e amp I I c an be e a s i ly in c o r p o r a t ed in to anycom po nen t s t8 re o s ~ s t e m he comp lex i ty o f th e in s t a l l a t i on de pends o nth e us er s i n d i v idua l 5us t e m and how n o f th e pre s f e a tur e s a reu t i l i z e d. The SYs t e m Pr eamp I I i s t he c en t r a l c on t r ol un i t in th es t e r e o sYst e m th r oush whi c h a s i Sna l source s a r e r out ed befo re be inSout pu t to t he powe r a mpl i f i e r a nd sp e ake r s . A typ ica l connec t io ns e t up i s s hown i n F i gu r e 1 . Ha nv vr i a t i o ns are poss i b l e

Con s i de r a b l e f r e e d om i s a f f o r d e d the us e r in de t e rm i n i ns t heopt i mu m phys i c a l lo c a t i on o f t he SYs tem Pre amp I I . Howe ve r , i t i sr e c omme nded th a t t h e p re a mp not be p la ce d ne a r within app r o x i ma t e l Yf ou r i nch es o f a ~ POw e r t r an sforme r s uc h a s th a t f ound in apower a to p revent hum f rom be i ng in duc e d i n t he sen s i t i v e phonopr e amp se c t ion s The pre amp mau be rack o u n t wi t h optio na lrack ount e rs

Al l c on n e c t io ns t o t he SYs t e m Pre a mp I I with th e exc e p t ion o ft he G pos t discuss ed be l ow and t he f ront-p an e l INSTRUMENT a ndhe adphone J a ck s a re made with s ta nda r d R A-t ype phono p l us s . ThePHONO input s a c c e p t a low- l e ve l s i sna l and a r e de s i Sned to be us e dwith a ny madne t ic phono c a r t r id Se . A Sroun d wi r e from th e tu r n t ab leshou l d be c onne cted to th e r e a r - pane l GN pos t to pr eve n t hum. Thefron t - p anel I NSTRUMENT J ac k acc e p ts a va r i a bl e - l e ve l in pu t s iS na lth r ouSh a s t a ndard t wo- conduc to r mon o phone p l us . Th i s i npu t i sde s i Sned t o be u s ed wi t h a va r i e ty of mono Phoni c sou rces such as amicrophone or e le c t r i c a l l y-amp l i f i e d mus ic a l i ns t rumen t . A othe ri nput s a ccep t h i s h - l e ve l s iS n a l s . Th e TUNER i np u t may be us e d wi th awi de var ie ty of s iS na l s ou r c es , inc l ud in S t uners , a ux i l i a r y t a pede c ks , t e l e v i s ion and v ide o t a pe record e r so und , and a uxi l i a ry phonopr e amps .

The Ja ck s l abeled TAPE 1 and TAPE 2 a re in te nded fo r u s e witht a pe decks whi le th e Ja c ks l ab e l ed LOO P 1 a nd LOOP 2 a re in t ende d fo ruse with ex t erna l s i sn a l proc e s s or s . The se ass iS nmen t s e f l e x ib l e ,howe ver . Si Sna l p r ocesso rs , a s we l l a s t a pe decks , may be us ed in thet ape loops . Theo re t i c a l l y the p r ocesso r loo ps may a l s o be use d fo rta pinS but we r ecomme nd th a t t he i r use be lim i t ed to t h e i r des i sna tedfunct ion to s i mp l ifY opera t on o f th e SYs t em P re a mp I I . Thedes i Sna t ion s IN a nd OUT a r e de f i ne d with r e s p e c t t o th e SYs t em Pream pI I . In othe r words , IN i mpl i es th a t the J ac k e e i ~ e a s iS na l fom a ne xt ern al source tape deck o r s i sna l pro c e s so r a nd OUT impl i e s th a tthe J ack seods a siSn a l to a n ex t e r n a l un i t . Note th a t th e s iS na ll eve l a t th e TAPE and LOOP OUT J acks i s not a f f e c t ed by thef ron t -pane l VOLUME or LEVEL con t ro l .

The output a t the MAIN OUT Jac ks wil l d r ive any bas i c powerampl i f ie r wi th a n in put impeda nc e S rea te r th an 600 ohms . Thi s ou tputi s con t r o l l e d bY the MAIN f ron t - pa ne l con t r o l s . Th e ou t pu t a t both th efro n t - panel head phone Ja c k and the rea r-p ane l MONITOR OUT J ack s i scon t ro l l ed by th e MONI TOR f r o n t -p a ne l con t r o l s . The he a dphone J ac k maybe us e d with bo th low and hi sh impedance h e adphone s . The MONITOR OUTJ a c ks provi de th e Marne s i s n a l as th e headphone J a c k withou t th e ex t r a


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buf fe r ins n e c e s s r ~ to dr ive headphones The MONITOR OUT Jacks m ~ beused with a separa te power ampl i f ier and speakersNorth American vers ions of the ~ s t e m Preamp provide an convenience o u t l e t on the rear panel This o u t l e t i s unswitched and i sideal fo r use with a tu rn tab le which i s u s u l l ~ b es t c on tr ol le d b ~ i t sown on o f f swi tch The t o t a l power consumption of n ~ deviceCsconnected to th i s o u t l e t should not exceed the maximum power r a t in s o f600 wattsThe ~ s t e m Preamp I I operates from a power source of between 110and 125 vo l t s AC 50 60 Hz Mode l s manufactured fo r use outs ide theUnited Sta tes have been modified to c o m p l ~ with the reau irede lec t r i ca l spec i f ica t ion s fo r the c o u n t r ~ of des t ina t ion


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O ~ R ~ I I O

The c on t r o l s p r o v ide d on th e MXR S ~ s t e m Preamp I I re de s i dnedfo r ma x i mum e r t i l i t a nd s t ra i gh t fo rward oper a t i o n . Although th eS s t Preamp I I a ~ have ma u have more con t rol s than uo u reac cus t om e d t o s ee i n g on a p r eamp, don t f e e l i n tim i da t e d . A l i tt et me sp en t exp er i mcntind wi th the con t r ol s w be we l l wor th t heef f o r t . The s l i gh t i nc reas e in o m p l e x i t ~ ~ i a new r e a lm o fcon t r ol a nd s ig n a l - ro u t ing l e x i b i l i t ~ Th e f o l l owi ng d i s cuss i oneXPla i ns t he fu nc t ion o f e h con t ro l .

POWERThe s wi tc h l abe l ed POWER turn s th e Sus t e m P reamp l I on or o f f .Before turn in g on th e pre amp , f i r s t tu rn the VOLUME con t r ol f u l lcounter c l ockwi s e . Th e r e i s a few second e l a ~ a f te r powe r i s a pp l i e dbefore th e un t i s ac t ve. This pro te c t s the r e s t of t he s ~ s t e m f r om

p o t e n t i a l l ~ damagin g turn-on trans i e n t s .

INSTRUMENT Inpu t and Leve l ControlThe J ac k and a s s o c i a te d leve l c on t r o l l a b e l e d I NSTR ENT ar e fo ruse with a monoPhon ic source . The mono inp u t s i dn a l i s r ou t ed to bo t hth e l e f t and r i dh t c ha nne l s . The le vel con t ro l determines th e ga in o fan in te rn a l ampl i f i e r which c a n pro v id e e n oug h ga i n u p t o 30 dB ) t o

i f ~ a low- l e ve l s ou r ce suc h a s a mi c r OPhone o r e l e c t r i c a l l ~amplif i e d mus i c a l in s t rumen t e .g . an e l ectr i c gu i ta r ) to normals te reo s ~ l in e le vel s . Th i s fea tu r e a long with th e MIX con t ro ld e sc r ib ed below ) al lows ~ o t o a ~ o r s i ng in a c c ompan i ment tof a vo r i t e songs. The INSTRUMENT input c an a l so be used wi thhighe r - l eve l monOPhonic source s th e aud io ou tpu t o f a video t aperecorder , fo r i n s t ance with lower s e t t i ngs o f t he lev e l con t ro l . Whenusing th e INSTRUMENT inpu t , ad jus t the le ve l c on tro l so th a t th ein s t rument l eve l i s about th e same as th e l eve l from the o ther in putsources . Turning the con t ro l clockwise inc re a s e s the l eve l .

A and B SOUR E Selec t ionThe S ~ s t e m Preamp I I m a be v iewed a s two separa te preamps i n one

un i t with versa t i l e l ink in g funct io ns . Because o f i t s dual na tu re , th eS ~ s t e m Preamp I I al lows a minimum o f two s i gna l s to be processed androuted i n d e p e n d e n t l ~ There r two ma in s t e r eo input buses , A and B,and two output s e c t i on s , M IN and MONITOR d iscu s sed be low . Thecont ro l s l abe led A and B SOURCE allow two sep ar a te s t e r eo i npu ts igna l s to be n d e p e n d e n s e l ec t e d f rom amond th e INSTRUMENT mono ,TAPE 2 , TAPE TUNER, PHONO 2, or PHONO 1 i npu t s .


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Subson i c F i l t e r r -Pu sh i n g t h i s b u t t on i n enabl e s a su bs on i c low-cut filt e r whichwo r k s in c on j unc t i o n with t h e PHONO 1 c i r c u i t r ~ The s ubso n i c f i l t e rr emove s i n au d i b l e w c ~ informa t i o n c aused ton e a r mre sonance e f f e c t s t u r n t ab l e rum b l e , e v e r ~ wa rped r ecord s , a nda co u s t i c feedb ack. Th i s subso n i c i nforma t i on has no mus i c a l cont e n t

a nd wa s t e s amp lif i e r powe r acc en t u a t es sp e a ke r non - l i n ea r i ti e s , a ndcou l d po t e nti a l l y c au s e s pea ke r d amage . Fi gur e 2 shows t h e re s pon s e o ft h e SYs t em Pr e a mp I I with t he su bs on i c filt e r a c t i v a t ed and l sowithou t filt e r i n g . The s ubso n i c filt e r i s d es i gned t o hav e a ver ys ha rp ro l l o f f be l ow 20 Hz a nd v e r ~ little e f f e c t a bove t h i s f r G u e n c ~The PHONO 2 c i r c u i t r ~ i n c o r p o r a t e s a s i m i l a r subsonic f i l t e rwhich i s a w a ~ s a c t i v a t e d .

MIX Con t r o lThe S ~ s t e m P reamp s f e a t u r e s i n c l u d e a mi xin g s e c t ion which

b l ends a po r t i on o f t h e s e l e c t e d A a nd B s i gna l s t o ge th er t o form at h i r d sign a l bus . The MIX con t r o l ad jus t s t he r a t i o o f two s i g na l s .Whe n t u r n e d f u l l ~ coun t e rc lockwi s e t o A o n l ~ t h e A s i g na l i s p r e s e n ton t h e mi x bu s . As t h e MIX con t r o l i s r o t a t ed clockwi s e t h e A s i gna lleve l decrea s e s as t h e B s i g na l l e ve l i n c r ea s e s . In t h e c e n t e rpos i t i on t h e A a nd B s i g na l s a r e eGua l i n l e v e l . When t h e c o n t r ol i sr o t a t ed f u l l y clockwise t o B, onl y t h e B s i g n a l i s p r ese nt on t h e mi xbus.

Tl and T2 RECORD ASSIGN Swi t c h e sThe S ~ s t e m Preamp I I provides v e r ~ complete and us e f u l , ifsomewha t unor thodox, t a p ing f a c i l i t i e s . The outpu t t o t h e r e ar - p an elJac ks l abel ed TAPE lOUT a nd T PE 2 OUT i s a c t i v a t e d b ~ dep r e s s i n g t h eTl o r T2 RE ORD ASSIGN bu t t o n , r e s p e c t v e l ~ Tl and T2 m a ~ bo t h bes e l e c t e d a t t h e same time . The t a p e ou tpu t s i g n a l a l w a ~ s comes

d i r e c t l ~ f r om t h e mi x bus . T h e r e f o r e , ~ o u can record i n p u t s ou rc e Ainpu t source B, o r a n ~ p r o p o r t i o n o f t h e two , dependin g on t h ep o s i t i o n o f t h e MIX c o n t r o l . With e i t h e r RE ORD ASSIGN b u t t o n i n t h eout p o s i t i o n , t h e c o r r e s ponding o u t p u t Jacks a r e d i s c o n n e c t e d .

Note t h a t t h e S ~ s t e m Preamp I I does not have t h e normalt ape -mon i t o r i n g a nd c o d i r e c t i o n s wi t c he s . I n s te ad t h e r e a r e moregenera l and us e f u l f a c i l it i e s . For example, t o monitor t h e ou tp u ts igna l from e i t h e r o f two t ape dec ks , s m p ~ choose t h e approp r i a t epos i t i o n , Tl o r T2, on e i t h e r t h e M IN o r t h e MONITOR SELECT swi tchdi scussed below . To c o p ~ from on t a p e deck t o ano t h e r , s e l e c t t h edeck t o be copied from with e i t h e r t h e A o r B SOUR E s e l e c t con t r o l ,makE s u r e t h e MIX c o n t r o l i s i n t h e app r o p r i a t e pos i t i o n , and push t h eRE ORD ASSIGN b u t t o n c o r respondin g t o t h e deck t o be recorded on. Youd o n t have t o w o r r ~ about i n a d v e r t e n t l ~ c r e a t i n g a feedback p a t h b ~t r ~ i n g t o record onto a t a pe deck s e l e c t e d a s an i n p u t s o u r c e as i t u a t i o n whi c h c an e a s i l occur with m a k e- sh if t p atc hi ng c on n ec tio n swith l e s s versa t i l e pre amps s i n c e t h e S ~ s t e m Preamp I I d i s c o n n e c t s


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the t ape in pu t s whe n th e co r r e s ponding RECORD ASSIGN but ton i s pu sh ed .

LOOP 1 and LOOP 2 SwitchesIn a dd it io n to t he t wo tape loo ps , th e SYs t em Prea mp I I h a s t wo

in e pend ent pro e s so r l o op s f o r ex t rn l i ~ n a pro sso rs s u h se oua l i ze rs and d yn ami c - r ange expande rs . Ea c h l oo p ha s two assoc ia te dswi tches . Pu sh i ng t he LOOP 1 I N/OUT bu t t on in i n se r t s th e s ig nalpro c e s so r connec t e d i n LOOP 1 i n to th e s ig na l pa t h . Wi th th e button inthe out pos t i on, the l oo p i s bypa s se d. The LOOP 2 I N/OUT s wi t chse rv e s th e same f unc t io n fo r LOOP 2 .

The s pec i f i c lo ca t ion o f each lo op i n t h e s ig na l pa th i sdete r mined bY the tw o o t he r a s s oc i a t e d s wi t c hes . Pushi ng th e LOOP 1A/M IN but ton i n A pos i t ion p la ce s th e LOOP 1 p rocess o r d i rec t lya f t e r the A SOURCE se l e c t con t r o l a nd befo re th e mi x in g sec t io n .Pu s h in g t he bu tton aga i n r e tu rn s i t t o th e out MAIN posi t on andpl ace s t he proc e s so r a f t e r th e M I N SELECT con t r o l a nd be fore t he LMand RM s wtc hes , BALNCE cont r o l , a n d VOLUME cont r o l . In t h i spos i t i on th e LOOP 1 p rocessor af fec t s on ly t he M I N ou tpu t . Pu sh in gth e LOOP 2 B/ MIX bu t t on in B pos ti on p l aces t he LOOP 2 p rocesso rd ir ec t l y a f te r th e B SOURCE se l e c t con t ro l and be f o r e th e mi x in gse c t ion . Pu shin g t h e b ut t o n a ga in r e tu rn s i t to th e ou t MI X pos i t ionand p l ace s t he proc e s s o r in t he mi x bu s a f te r t h e MIX con t r o l andbe f or e th e M IN and MONIT OR SELECT con t r o l s a nd a l s o be f or e t h e T1 a ndT2 RE ORD ASSIGN s wi t ches . Re f e r to t h e b lo ck di a gr am, Fi gu r e 8 i nthe Ci rc u i t De s c r i p t i on s ec t ion fo r a grap h ic r e pr e s en t a t i o n o f t h ea l te rn a te l oca t i on s of th e tw o p rocessor l o op s in t he s ig na l path s o fth e SYs t em Pr e amp I I .

Left /R i gh t Mono, S t e re o / Rev e rse Swi t c h i ngThe two s wi tc hes l ab e l ed M Le f t Mono and RM Righ t Mono

con tro l th e r ou t ing o f t h e l e f t and r i gh t cha nne l s ig na l s . Wit h bothbu t t ons in the out pos i t i on norma l STEREO ope r a t i on i s ob t a ine d .Pus h i n g Ju s t th e LM but to n in r o u te s th e le f t ch anne l i n p u s i gna l t oboth l e f t a nd r i gh t ou t pu t c han ne ls . The RM s witc h p e r f orms a s imi l a rfunct ion f or the r i gh t ch annel in pu t s i gna l . With bo t h bu t tons in th el e f t and r i gh t cha nne ls a re in t erch ange d f o r V op e r a t ion . Noteth a t summed-ch annel mono opera t i on le f t pl us r i ght i s not po s s ib l ewithout e x t ern a l c i r cu i t y . The LM and RM swi tche s a f f e c t both th eM IN and MONITOR ou tput s e c t i ons .


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O ~ Cuteut CootolsAs men t ioned previou s l Y th e SYs t em Pre amp I I has two independen t

outpu t sec t o n s Th e MAIN outpu t sec t i o n incorpora t e s th e BALANCE a ndVOLUME con t ro l s found on more convent iona l pr e amps as we l l a s a unioueSELECT con t ro l . Th e s e con t r o l s hav e no e f fe c t o n the MONITOR outpu ts e c t i o n The MAIN output sec t ion i s norma l ly u s ed to dr iv e a pow e r ampand speake r s .MAIN SELECT Cont ro l

The con t r o l l abe l ed MAIN SELECT a l lows th e MAIN outpu t to bese l ec t ed from among s o u r ce A s o u r c e B a var i ab l e MIX o f the twosources th e TI inpu t o r the T2 inpu t .

BALANCE Cont r o lI t i s impor tan t fo r re a l i s t i c s t e re o ima g in g t h a t th e ap p a r en t

s ound lev e l from b l th sp eakers b e e o ua l Th e BALANCE con t ro l a l lo wsthe stener to ad jus t th e r e l a t iv e l eve l s of t h e l e f t a n d r ig h tchannels to compens a t e fo r ac t ua l l eve l d i f f e r en c e s or changes in s tenin g pos i t i o n The BALANCE con t rol i s de s i gned so t h a t the p r op e rove ra l l vol um e i s ma i n t a ine d a t a l l pos i t i o n s o f the con t ro l withou tth e need to ad jus t the VOLUME con t ro l .

VOLUME ControlThe VOLUME con t ro l provides cont inous ly va r i a b l e adju stmen t o f

the MAIN outpu t s i gnal l eve l in conju nc t ion with the GAIN s wi t c hd iscu s sed below> The con t ro l c i rcu i t ry i s con f i gured s uch th a t th econ t ro l d ir ec tly a ff ec t s gain r a th e r th an a t tenu a t ing a h i gh -g a ins iSna l . This a l lows th e optimum dynamic ranSe to be ob t a in ed with a l ls e t t i n s s of th e con t ro l . The VULUME con t ro l i s spec i a l l y s e l ec t ed fo rt rackinS accuracy between the two ch anne l s .

GAIN SwitchThe GAIN swi tch works in conjunct ion with the VOLUME con t ro l .With th e bu tton in the out LOW pos i t i on th e maximum s e t t i ng of the

VOLUME con t ro l wil l prov ide uni ty Sa i n ou tpu t l eve l eoua l to inpu tlevel> a t th e outpu t o f th e p r e amp fo r l i ne - l ev e l inpu t s i Sna l s .Push ins the but ton i n se l e c t s the HIGH pos i t ion which prov id es anadd i t iona l 2 0 dB of s a i n The SYs t em Pre amp I I wil l dr ive most poweramps to normal l i s te ninS l eve l s with th e GAIN swi tch in the LOWpos i t ion . I t i s recommended t ha t th e s wi t c h be l e f t in t h i s pos i t ionwhen poss ib l e to ensure th e lowes t poss i b l e noi se . The HIGH Sainpos i t ion maY be u sed in those occas iona l in s tan ces where a Srea t e routput l eve l i s needed


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~ O N O R OUtEUt o o t ~ o l sThe MONITOR outpu t s ec ti on i nc or po ra te s i t s own SELECT and LEVELcon t ro l . These con t ro l s have no e f f e c t on th e M IN output sec t ion . The

MONlTOR output s ec t ion m a ~ be used to dr ive a pa i r of headphones or asepara te power amp and speakers or both.

MONITOR SELECT ControlThe MONITOR SELECT con t ro l fu nc t io ns in a manner id e n t i c a l tot ha t of the M IN SELECT c o n t ro l al lowing se lec t ion among B, MIX

T OR T2.

MONITOR L V L ControlThe MONITOR LEVEL con t ro l func t ions in a manner i de n t i c a l to th e

VOLUM con t ro l providing c o n t i n o u s l ~ var i able adjustm en t o f theMONITOR outpu t s i gna l l e ve l .

Headphone Jack f r ont-pan e l s te r e o phone Jack i s provid ed fo r monitor ing or

pr iva te stenin g with headphones. The LEVEL con t ro l var i es the s ig n a lleve l a t t h i s outpu t as well a s a t the MONITOR OUT Jac ks on the r ea rpanel . The headphone output i s i so la ted from th e r ea r pane l output s b ~i t s own amp l i f i e r capabl e of providing a p p r o x i m a t e l ~ 150 m i l l iw a t t swhich i s s u f f i c i e n t to d rive most headphones both low and highimpedance to ad eau a te l i s t e n ing l eve l s . Plugging headphones in doesnot disconnec t e i t he r th e M IN or MONITOR outpu t s on the r ea r pane l .


12/21

g e e L I I I D ~ S

The f o l l o w i n g diagram s and n o te s p r e sen t in a p ic to r i a l f a s h i o n afe w o f th e m a n ~ pos s i b l e appl ica t ions o f t h e S ~ s t e m P re amp I I t ha twe ve th o u g h t of . T h e ~ are de s i g n e d to demons t r a t e th e us e o f th eS ~ s t e m P re amp I I s u n i au e fea tures and to s t i mul a te ~ o u r thinkin g a sto how can bes t u t i l i z e thes e f e a t u r e s i n own s ~ s t experimen t wi t h t h e a n ~ ~ s t e m con f i g u ra t io n s a nd contro l s e t t i ng sposs ib le un t i l o u f ind th e a r ra ngement bes t s u i t e d to ~ o u rreauiremen ts . The S ~ s t e m P reamp I I c an n o t be harmed b ~ comb i na t i o no f c o n t r o l s e t t i n gs


13/21

POWER

s y s t m p r mp n

,OWC IN

o= EVEIlSET EI lEOlM RM o0 0BAL NCE

OUT MilLOOP 2

e1R\t.::7\

MA N YOLUMESELECT0 r n

OUT ANLOOP 1

N A@OMIX

s,., T2DO

RECORO ASSI GN

A-----SOURCE-----s - TAPE 1- TUNE lPHON02PHONQoIJIlSTFlUMENTo[MXR

FIGURE 3

OBJECTIVES: Lis ten to expanded an d eaua l i zed in pu t from PHONO 1Record s i s na l from ?HONO 1 o r PHONO 2 on t apeMonitor PHOND 1 , PHONO 2, o r r eco rd in s with headphones

CONTROL SETTINGS: Refer to the diasram above. The f o l lowins comments a ls o p e rt ai n:The s i snal to be re corded i s as signed to th e T1 tape loopWith th e MIX cont ro l a t A, th e A SOURCE s e l e c t i o n (PHONO 2 be recordedAt B, th e B SOURCE se lec t ion PHONO 1 be recordedPushins the LOOP 1 IN /OUT bu t ton i n en abl e s th e e x pande rPushing th e LOOP 2 IN /OUT b utto n in en abl es the eQua l i z e rThe MAIN ou tpu t i s expanded ( LOOP 1 A/MAIN button in MAIN pos i t i onI f th e button were in the A pos i t i on , th e PHONO 2 s i s n a l would be e xpanded before being recorded>The PHONO 1 s i gna l i s eQualized before be ing recorded (L OOP 2 B/MIX button in B pos i t i onI f th e b utt on were in th e MIX pos i t i on , e i t h e r PHONO 1 o r PHONO 2 o r va r i a b l e mix would eQualizedWith th e HONITOR SELECT co n t r o l a t A, th e PHONO 2 s i s na l be mo n i t o r e d with head phonesAt B, th e PHONO 1 s i sna l be nlonitoredAt T l, the s i gnal be ins recorded be moni tored assumins a th ree -head deck i s used>

CONNECTIONS: Turn tab le 1 to PHONO 1 i nput sTurn tab le 2 to PHONO 2 i nput sExpander in LOOP 1EQua l i z e r in LOOP 2Tape deck. to TAF E 1 JacksMAIN OUT Jacks to power amp l i f i e r and speaker sHeadphones to f ront -pane l Jack


14/21

sys te lT l prea lT lp IIMONITORSELECT L V L0 C) .oe 2

OWER

HICH

O .GAINo=TEREOlM RMCUTLOOP 2

MA N VOLUMESELECTLY

OUT INLOOP 1

MIX

AG. ,0 0U O

RECORD ASSIGN

A SO URCE BO 0TAPETUtlERP O N 0P ON0INSTRUMENTo[MXR]

4

OBJECTIVES: Listen to eaualized input ro PHONO i mixed with su i t a rRecord mixed s i g n a l on t apeMonitor PHONO 1 with headphonesCONTROL SETTINGS: f r to th e d iag ram above . The following comments also per ta in :

S et the INSTRUMENT le ve l c on tr ol f or adeauate su i ta r levelThe MIX cont ro l s e l ec t s th e propor t ion su i t a r o r PHONQ 1 (A = s u i t a r D = PHONO 1The PHONO 1 s i ~ n l i s eaua l i zed before being mi xe d (LOOP 2 B/MIX but ton in B po s i t i o n )The s ig na l to be recorded i s assigned to th e T1 t ap e loopTo monitor th e r e c o r d i n ~ s e t th e MONITOR SELECT c o n tro l to the Tl pos i t ion

CONNECTIONS Guitar t o f ron t p anel INSTRUMENT JackTu rn tab le to PHONQ 1 i nput sE a ua li ze r i n LOOP 2Ta pe de ck in TAPE 1 loopMAIN OUT Jacks to power ampl i f i e r an d sp eak er sHeadphones t o f ro n t pa ne l Jack


15/21

POWER

M ON TORSELECT lEVEL0 to 0os y s t em p r e amp n

cewCo=rrsecLM AM o

BALANCE

OUT l ,.l OOP 2

,

AIN VOLUMESELECT0

OUT . . . ..l OOP 10 0

MIX

66RECORD ASSIGN

A-----sOuRce-----B

o 0TAPE- TUNERPHQ 0 PH )NQ - - -INSTRUJ fENToo[MXR]

F IG UR E 5

OBJECTIVES: Operate two separate s tereo 5wstemsLis ten to eaua l i zed PHONO 1 in room 1Li s t en to e xe a rrded PHONO 2 in ro om 2Record s i ~ n l f ro m PHONO 1 o r PHONO 2 on tapeMonitor PHONO 2 with headphone sCONTROL SETTINGS: Refer to th e d ia sr am above . The fol lowins comments also per ta in :

The VOLUME control determines th e leve l in room 1The MONITOR LEVEL control determines the level in room 2The s i ~ n l to be recorded i s as s isned to the T2 tape loopThe MIX control determines the s i s n ~ l to be recorded.To monitor the recordins, s et e it he r SELECT c on tr ol t o the T2 posi t ion

CONNECTIONS Turntable 1 to PHONO 1 inputsTurn t able 2 to PHO 2 inputsE au al iz er i n LOOP 1Expander in LOOP 2Tap e deck in TAPE 2 loopMAIN OUT Jack to powe r m p l i ~ i r and speakers t room 1MONITOR OUT Jacks to p o ~ r m p l i ~ i r an d speakers fo r room 2Headphones t o f ron t- p ane l Jack


16/21

POWER

sys te fT l preafT lp n

HIe;

coGAIN=.M RMo0 0BALANCE

OIJT IILOOP 2

M A N VOLUMESELECT0

OUT ... 'UNLOOP 1

MIX

n 1'2 IN0 0 0 0

RECORD ASSI GN

A SOURCE----- .

oO I N S ~ ~ 0TAPE- TWlEPHON0 2- - - PHONO 1- - -oo[MXR]

FIGURE 6

OBJECTIVES: Listen to Quad 4 channel tape deckP r o c e s s f r on t an d r ea r s i ~ nONTROL SETTINGS: Refer to th e diagr am above The fol lowing comments a ls o p e rt a in :

The VOLUME con t r o l de t e r mi n es the f ro n t s igna l l e velThe MONITOR LEVEL control determines th e r r s i snal levelThe MIX contro l be us ed to bl end a por t ion of th e s isna l in with th e front s i sna l or v ic e v er saTurn th e ap prop r ia t e SELECT cont ro l to t he MIX pos i t ionWith t h i s conf i s ura t ion c anno t r e c o r dPushins e i t h e r RE ORD ASSIG N bu t ton in wil l disconnec t th e c o r r e s p o n d TAPE i nput Th i s preven ts an un des i r able f e edback l oop from created

CONNECTIONS: Tap e deck f ron t o u t p u to TAPE 1 i nput sde c k r r ou t pu t s to TAPE 2 in pu tsF ront s ig n a l proc e ssor in LOO? 1Rear s i snal processor in LOOP 2M IN OUT Jacks to power amp l i f i e r and s peakers fo r f r on t s i ~ n a lMONITOR OUT Jacks to power ampl i f ie r an d speakers for rear i ~ n a l


17/21

s y s t em p r e amp II MONIT RSELECT LEVE L0 t ) . .oe 2OW RowGA IN

oREYEASE5T [ I>EOLM RM o0 0BALANCE

'O UT ... :1LOOP 2

,0 0

M INI VQlUMESELECT0,t t.

'OUT ANlO OP 1

oMIX

rT n0 0

RECORD ASSIGN

A - - - S O U RCE----- .O 0- TAPE 1- TUflPHo rl0 2- - P1 0 lO 1- - -oT R U Po[MXFI]

F IGURE 7

OBJECTIVES: Mix music in D.J . s t ~ l eBl en d r e c o r d t o r e c o r d , r e c o r d t o t a p e , o r t a p e t o t a p eA microph on e I'l ay a l s o be u ue d a s on e o f t h e so u r c e s t o blend t o or from Th e micr o phone ma y be u se d whil e t h e o t h e r so u r c e i s b ei n s c ue d u p )Moni tor s o u r c e be i n s cued UP w i t h he ad phonesEQual ize t he o ut pu t s i gn a lONTROL SETTINGS: f r t o th e diagram above. The following cOR,ments also p e r t a i n :

Se t t he I NSTRUM ENT l ev el c on tr o l f o r ad e Qua t e microph one l e v e lS e t t h e A SOURCE c on tr ol t o t h e s o u r c e t o be blended fromS e t t h e B SOURCE c o n t r o l t o t h e s o u r c e t o be b l en d ed t oTu rn t h e MIX c o n t r o l clockw i s e f r onl A t o b l e n d o r - f a d eR ) from s o u r c e A t o s o u r c e B

CONNECTIONS: Micro phone t o f r o n t - p a n e l INSTRUMENT J a c kTu r n t a b l e 1 t o PHONO 1 i n p u t sT u r n t a b l e 2 t o PHONO 2 i n p u t sEaua l i z e r i n LOOP 1Ta pe k 1 i n TAPE 1 loopTape d ec k 2 i n TAPE 2 loopMAIN OUT J a cks t o pow e r a mp l i f i e r an d s p e a k e r sHeadphon e s t o f ro nt - p a n e l J a c k


18/21

CIRCULI E S R I ~ I I O ~The c i r c u i t r y o f t h e MXR SYstem Preamp I I i n c o r p o r a t e s t h e l a t e s tadvan c e s i n au d i o i n t e g r a t ed c i r c u i t t e c h n o l o g y . The p r i m a r y d e s i gng o a l was t o p r ov i d e c o n t r o l f l e x i b i l i t y w i t h o u t a l t e r i n g t h e s i g na l i nany u n d e s i r a b l e way. Low d i s t o r t i o n , wide b a n d w i d t h , v e r y lo w n o i s e ,

a n d , mos t im p o r t a n t l Y , s o n i c c l a r i t y a r e p r i ma r y a c h i evem e n t s o f t h ed e s i g n. The pha s e i n t e g r i t y o f t h e s i g n a l i s m a i n t a i n ed a t a l l t i m e s .A l l s i gn a l p a t h s , from a nY i n p u t t o any o u t p u t , a r e n o n - i n v e r t i n g i npha s e ) . The c i r c u i t r y i s c o n s t r u c t e d u s i n g a d o u b l e - s i d e d ,m i l i t a r y - g r ad e , g l a s s epo xy p r i n t e d c i r c u i t PC ) bo a r d . C ar e fu l d es ig nand l a y o u t o f t h e PC bo a r d m i n i m i z e s c r o s s t a l k and o p t i m i z es pu l s ere s pon s e , and s ub s t a n t i a l ground p l a n e p r o v i de s s h i e l d i n g f r om s t r aYf i e l d s . The f o l l o w i n g d i s cu s s i o n h i g h l i g h t s t h o s e ch a r a c t e r i s t i c s o ft h e i n t e rn a l c i r c u i t r y n o t a l r e ad y m e n t i o n e d . R e f e r t o t h e b l o ckd i a g r a m, F i g u r e 8 , s howin g how e ac h s t aS e i s i n t e r c o n n e c t e d .

The phono p r e amp s e c t i o n r e p r e s e n t s on e o f t h e most c r u c i a l a r e a si n th p de s i gn o f a h i gh - au a l itY p r e amp. The RIA A ea u a l i z a t i o n networki s e s p e c i a l l Y c r t i c a l . T h i s c i r c u i t ac c u ra t e l y com pen s a t e s f o r t h eeau a l i z a t i o n t h a t i s i n t r o d u c ed d u r i n g t h e c u t t i n g o f a r e c o rd byp r o v i d i n g an ex a c t co mp l eme n t t o t h e r e c o r d i n g e a u a l i z a t i o n . G r e a tc a r e was a l s o t ak en d u r i n g t h e d e s i gn s t a ge t o en s u r e r e p rodu c t i o n o ft h e verY lo w an d h i gh f r e a u e n c i e s be Yond t h e l i m i t s o f th e RIAAs t a n d a r d . The phono s e ct i o n a l s o p r o v i d e s 40 dB o f g a i n a t 1 kHz)w i t h Very low no i s e . The s e ch a r a c t e r i s t i c s al l o w almo s t anY phonoc a r t r i d g e to be u s e d w i t h t h e SYs t em Preamp I I w i t h e x c e l l e n t r e s u l t s .

The r e s i s t i v e l o a d i n g o f t h e phono c a r t r i d g e i s f a c t o r Y s e t t o v a l u e o f 47 k oh ms + / - 5 ) i n k e e p i n g w i t h t h e recommendation s o fmost c a r t r i d ge ma n u f a c t u r e r s . Th e c a p a c i t i v e l o a d i n g i s s e t a t 2 0 0p i c o f a r ad s pf ) . T h i s va l u e r e p r e s e n t s a compromi s e between d i f f e r e n tmanuf a c t u r e r s recommend ed l o ad c a p a c i t a n c e a nd t h e t ype and l e n g t h o fc a b l e c o n n e c t i n g t h e phono c a r t r i d g e t o t h e p r e amp. The p h o n o - l o a d i n gc a p a c i t o r s may be c h a nged bY t h e u s e r de s i r e d . The fo l l o w in gr e l a t i o n s h i p maY be u s e d t o d e t e r m i n e t h e optimum v a l u e o f preamp l o a dc a p a c i t a n c e


19/21

INPUTS B SELECTS MIX AMP MAIN SECTION MONITOR SECTION

: , ,f

, ,INSTRUMENT , UPLIFIER ..........: +

PMOH01 RIA = . . . ..... . -.. ... :SOUR E t MONITORPHONO MAIN SELECT :ELETORS : SELECT ..... .. .... ::

ru MEI : ............... ....... . ..TAPE2 I rz : ..... ............. .. ........

l 4LM RM S T l ~ O R E V+ iE OR ASSGN

BALANCE I LEVEL AMP+ I . ... I VOI.l,IMEAMP:

lOOP SWl TCHABU: PO fT1ONe OOP SWJTCHABLE POSITIONRECORDOUT

igur 8

M N OUT HEAOPWONEOU


20/21

A n o t h e r potent ia l s o u r c e of unwa n t e d 10w- f r e a u e n c Y informat ion ,b e s i d e s t ha t from the t u rn t able to n earm ca r t r idSe c o m b i n a t i o n i shum from the in t ernal powe r s upp l y . The powe r s u p p l y i n th e SYs t en.Preamp I I i s ex t r emelY w e l l f i l t e r e d and d ec o u P l e d from th e se ns i t i v ephono p re amp sec tio ns to e l imina te hum.The INSTRUM NT i npu t ha s i t s own S a i n s t aSe whose h ish inpu t

imped ance p r e ven t s a ny adv e r s e lo adins e f f e c t s on th e s ou r c e . Thef ron t - p a ne l leve l con t ro l va r i e s th e S a i n from uni ty to 30 dB.The SYstem Preamp II s mixinS c i r cu it ry i s fu l ly buff e r e d top r e v e n t anY unint en t iona l 1 0 a d i n S o r c ro s s t a lk be t w e en t he A a nd Bs isn a l bu s es . Al so , th e c i rcu i t ry i s de s i S n ed s o t ha t when th e MIXc o n t r o l i s fu l l y a t A or B th e s i S na l from th e o th e r bus will n o t b ep r e s e n t a t th e mi x o u tpu t .The M IN o u t put VOLUME c o n t r o l i s i n th e f e edb a c k l oop of a n.o pe r a t i o na l amp l i f i e r and th e r e fo r e d ir ec tlY c on tr ol s the S a i n of theamp l i f i e r . The MONITOR ou t p u t L VEL c on t r o l i s conf iSured to p ro v i d e

va r i ab l e a t t e nua t i on of th e s i Sn a l from p r e c e ed i n S s t a s es . Also th e NI TOR LEV L con t r o l doe s n o t in c o r p o ra te swi tch -se lec tab le s a in .

The h ea dphone o u t p u t i s bu f f e re d from th e mon i t o r p r e a mp ou tpu tsbY its cwn a m p l i f i e r , t h u s e l i mi n a t i nd loadin d o f the mon i to r ou t pu tsbY l o w n headp hon e s . The SYs t em P re a mp I I ha s a n outputimpedan c e ma in o u t put s of a p p r ox i ma t e l y 60 0 ohms whic h wil l al l o w itt o dr ive any power ampl i f i e r w i t h an i npu t i mped an c e o f 600 ohms orS re a t e r .

S p e c i a l m u t i n c i rcu i t ry in the SYstem P re amp I I e l imina testurn-o n a nd turn -o f f t r an s i en t s . F E T s F ie ld -Effec t T r an s i s t o r s ,con t ro l l ed bY a tim e-de l a y c i r cu i t s h u n t th e s i d n a l output s s a fe l y toSround un t i l a l l on-of f t r ans ien t s hav e occurred . Th i s met hod to t a l lye l iminates the e f fec t s of i n - l i ne re l ay c o n tac ts or ac t ive swi tches onth e s iS nal d urin s operat ion . Add i t io na l l y , I o n s - t e r m r e l i a b i l i t y i sSrea t ly e n h a n c e d compared w i t h des i Sns us ins re l ays .


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Input Level

Output LevelImpedance

Impedance

OutputNoise

Response

Phono 1 ,2Line

Phono 1 ,2LineMa inMonitor

Phono 1,2Line

Phono 1Phono 2Line

grea t e r than 120 mv peak 1 kHzgrea t e r than 1 vo l t peak 20 kHz+16.9 dBV 7 vo l t s rms 20 Hz - 20 kHz+16.9 dBV 7 vo l t s rms 20 Hz - 20 kHz47 k ohms100 k ohmsapprox. 600 ohmsapp r-ox , 600 hR S150 in to 200 ohmsbe t t e r than 88 dB below 10 mv inputA weigh tedbe t t e r than 90 dB below 1 vo l t inpu t20 Hz - 20 kHzle ss than .0057- a t 0 dBV 20 Hz - 20 k

a n ~ in pu t to outpu t )l e s s than .0057- a t 0 dBV60 Hz /7 kHz, 4:120 Hz - 20 kHz, +/-0 .25 dB a t 0 dBV3 dB down a t 5 Hz and 80 kHz30 Hz - 20 kHz, +/-0 .25 dB a t 0 dBV3 dB down a t 20 Hz and 80 kHz10 Hz - 40 kHz, +/-0 .25 dB a t 0 dBV3 dB down a t 10 Hz and 100 kHz

F i l t e r Response Phono 1 -1 dB a t 23 Hz, -3 dB a t 19 Hz,-29 dB a t 5 Hz

Separa t ionReauirements

Phono 1,2LineIn s t .

Domestic:Fore ign :

40 dB kHzo dB/20 dB max. se lec tab leo dB - 30 dB v ia f ron t -pane l cont ro lbe t t e r than 60 dB a n ~ input110 - 125 vo l t s AC, 50 - 60 Hz,80 ma, 10 wat t s220 - 250 vo l t s AC, 50 - 60 Hz,40 ma, 10 wat t s

50COSPII812

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MXR M-150 Preamp Manual