Neve BA712, BA713 User Manual

BA712/713 INFORMATION

GENERAL

2S1!!/!!? ^l3 **? ﬁXGd to*ether to form a sandwich assembly at the top

artl L ? t I BSUX e - -The y 3eleC t ^ M ? l i f V t h e mi c r o p h one, l ine,or tape inputs up to the nominal -lOdBu level used prefade

SefS!«M.S8? refulat?a the *0wer suPPlieB f°r the whole channel module,RF ﬁlters each input, and has a phase inversion facility.

USER CONTROLS

r«?/LTn-/T^inPUt Selection» Phase, Mic gain (20dB to 80dB in 6dB steps)

G a i n T r i m ( O d B + 1 0 d B c o n t i n u o u s l y v a r i a b l e ) . s t e p s ; .

DETAIL

SEE ET1020T (Circuit Diagram) AND EB2036U

(Channel module block diagram)

™^S?er-left7h^d *?* °f EB2°36U 8hOWS the ^or Actions of the BA712/713 VS^SS^ 1Q relatl0n to the rest of the channel strip. The circuit diagram

n e x i s t T r i p ? W S " ° t h * * • " ( e n Cl ° S e d i n ^ - - d o t t e d l l ^ ) ^ P S t i £ S 2 M 0 t l a |

inrth! SnJ?e0tiiO^ vCtren connectors on the PCB are shown as "tie lines"

in the bottom left-hand table, if they do not involve any circuitry.

BRIEF DESCRIPTION

" Vo ^ c ^ a f t h f t o ? ^ U r- * f T S ? e ) " e r e C e i ve d f r o m * * c o n ne c t o r s

ninnPh°°e °f UB,.,*ifUr °utputs «e-selected by SI ("LINE") on BA712 the ? S : d S S W l T ^ h ^ t h S ± ^ ' ^ ^ c i " u i t i n s i s t i n g o f R V l ,

HA, and R2 on BA713 (which gives an attenuation of OdB to -20dB with -lOdB

£1 UltrrTl f0li°Wed by IC1C °n M712 (vhich S-es lOdB of Sin).Trim (from IClc) or Tape outputs are selected by S3 ("TAPE") which is mechanically interlocked with SI to give the following:-

^TnrJ.'LINf ^ "TAPE" ^P^sed • Mic selected » 5 J S » ° n ! y P r e 8 S e d : L i n e s e l e c t e d

TA P E " o n l y p r e s s e d . T a p e s e l e c t e d LINE' and "TAPE" both pressed (interlock defeated)

: Tape selected

ampli^ie^ialW h i c h 8 - d i T tly t 0 * V, ? E A SP ^ d t0 a p h a s e inverting ™«i™ V ' ? * aXso connected to SI*. With "PHASE" impressed the

T h e B A 7 1 2 / 7 % n ° n ' < T t ° f ^ ^ * " * * * t h e ° U t p U t " ^ ^ m^i J2 mi? °f P2 +!1^al 1S takeQ fr°m Sk and i3 CalledJ "CHANNEL TO

JESS i JSSi % &£ h e Tape l n p ut " ^ i fier ( iCl a ) is a l s o s e n t t o the

^ mS)7 FILTERS SWITCH'T) tod to the console track meters <"*"

MICROPHONE INPUT AMPLIFIER

Thi s c onsi sts of a lOdB s t ep- u p t ran s form er (Tl on BA 7 12) fo l lowe d b y a n or.

i n v e r t i n g am p l i ﬁ e r ( I C 1 on B A 7 1 3 ) wit h s w it ch e d g a i n . The t r a ns fo r m e r in p u t is b ala nce d and ﬂoating an d has ph antom po wer a ppl ied f rom a +U 8V su ppl y

via two 1 % h i g h s t a b ility resist o r s R l and R2 o n B A 7 12. I n put i mpedanc e is 1K2 + 10# fro m U O Hz to 1 5kHz . I C 1 i s a h i g h p erfo r manc e o p e rati o nal amp l iﬁer wit h D .C. op e rat i ng con diti ons se t b y R 3 a nd RU, an d A.C . g ain set b y t he

swi t ched pot e ntio m eter ch a in form e d b y t he 11 - pos i tion SI, RP 1 , a nd RP2, all on BA713. RP1 and RP2 each contain precision 6.1% ratio-matched resistors

e n s u r i n g ac c u r ate a n d r e l i abl e g a i n s e t t i n g s. S I s e l e cts w h at p r o por t i o n o f

the output sign a l is fed back to the o p a m p f r o m t h e R P 1 /2 r e sistor stri n g and thus set s the gai n be t w een OdB and 60dB . Ta k ing into acc o u nt t he t rans f o rmer

volt a g e g a in and the subs e q uent lOdB gai n in the cha n n el s trip, the mic r o phone amp liﬁe r h as a gain ra nge of +20 t o + 80dB .

LINE AND TAPE INPUT AMPLIFIERS

Th e s e a r e elect r o n i c a l l y b al a n c e d i n p u t a m p l i ﬁ e r ( i C la a n d d o n B A 7 1 2) w i t h t r a n s i e n t oy e r v o l ta g e p r o t e c t i o n pr o v i d e d by f o u r d i o d e s on e a c h . G ai n i s

-lOdB^to bring the level down to that required prefade in the channel strip

The L ine i n put h as a n a l t e r n ative -ll+dB gain settin g selec t e d by a D I L swit on t he P C b o ard ( S2 o n B A 712). Preci s i o n 0 . 1# r a tio-ma t c h ed r e sisto r pack s

RP1, 2, 3 on BA712 are used to assure the performance of these ampliﬁers.

POWER REGULATORS

Integrated three-term i n a l devic e s (IC2, 3 o n B A 7 1 2 ) a r e used to r e g u l a te t h e raw +22V input power to +18V at up to 500mA for the BA712/713 assembly and

the rest of the channel strip. C17 and 18 ensure stability, D9, 10 prevent

r e v e r s e d o u t pu t p o l a r i t i e s u n d e r fault c o n d i t i o n s , R l 8 , 19 a n d C 1 5, 1 6 improve noi s e p erfo r manc e . I C2 and 3 are hea t -sun k o nto the XLR br a cket .

D.C. SUPPLIES

BA 712/7 13 r uns fro m +22V unregul ated po wer, a nd also uses +U8V r egula ted pow er for p hant om poweri ng mic rop hon es.

TEST POINTS

Test po i nts are pr o vide d a s f ollo w s o n BA71 2 :

TP1 Regulated +18V T P 2 O V r e f e r e n c e

TP3 Regulated -18V T P l * "TA P E O U T P U T " s i g n a l T P 5 M a i n " C H ANN E L " o u t p u t s i g n a l

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