Neve BA714, BA715 User Manual

I jw U U U I i x / , i

Bkllk/115 INFORMATION

(Includes BATlU/A & BAT15/A information)

GENERAL - (See figure l)

BA71U and BA715 together form a sandwich assembly and are mounted in the upper
part of channe l or r«v modules. A single l6 way flying flatcable co nnector

connects BA71U to BA712. BA71H/715 make up two independant 12dB/octave high

pass and low pass filters with variable corner frequencies, which can be switched I

into the Channel or the Mixdown signal paths.
An electronic switch selects the input for the Mixdown path according to the
console mode. This switch is not present in the /A variant.

USER CONTROLS

"CH" button

: out - filters in mixdown path

in - fi l te r s i n c h a n n e l pa t h

f ~ " b u t t o n

: out - high pass filter bypassed

in - h i g h p as s fi l t er i n pa t h

""> " button

: out - low pass filter bypassed

in - l o w pas s fi lt e r in p a t h

"25Hz - 250Hz" control

: Varies high pass filter co rner freque ncy

over this range.

"3kHz - 15kHz" control

: Varies low pass fil ter corner frequency

over this range.

DETAIL

BA71U/715
See ET10213

[circuit diagram), EB2036U (channel module block diagram), and

figure 1.

There are two signal paths through the filters assembly, known as the Channel
and the Mixdown paths. The input to the Channel path comes from the main

(mic, line, or tape) output of the BA712/713 assembly. Mixdown path input is

selected by the electronic switch (see below) to be the Tape output from BA712/713

when the console is in "TRACK" or "MIX" modes, and the channel Post-Insertion

signal from the BA740/7U1 Group Control assembly when in "DIRECT" mode.

SI on BA715 is the "CH" button and puts both high and lowpass filters into
the channel path when pressed. When not pressed both filters are in the
mixdown path.
The highpass filter (see below) is on BA715 and is either selected or bypassed

by SI on BA71U, the "_/— " button. BA71U also carries the lowpass filter (see
below) and S2, the " ~ " button, which either selects the lowpass output
or bypasses it. One pole of each switch is used to switch LED's mounted

remotely on BA7U0.
The two outputs from the BA71U/715 assembly, "CHANNEL FROM FILTERS" and

MIXDOWN FROM FILTERS" go to the insertion switches on the BA7U0/7U1 Group

Control assembly via the BA712/713 assembly.

1.

r

BA71U/A and BA715/A

Refer to ET10213/A (circuit diagram), EB20386 (rev strip block diagram), e
figure 2.

Th is va rian t of the filt ers assembly lacks the el ectr onic switch, and is used

in Rev modules where the Rev Return output from the BA752/753 assembly is

permanently connected to the Mixdown path input of the filters.
The channel signal path is then used for either the Rev Send or the Delay

Insertion signals depending upon the setting of the "INS" buttons on BA752.

In all o t h e r respects the /A fi l t e r a s sembly variant is id e n t i c a l to the
normal one as described above.

ELECTRONIC SWITCH

This is an electronic changeover switch on the Bkjlh card which selects either
the Tape output from the BA712/713 assembly or the Channel Post-Insertion

signal from the BA7U0/7U1 Group Control assembly to be the Mixdown path
input for the filte rs. TR1 and TR2 are the actual switching elements, the

one corresponding to the desired input being turned on (low resistance)
and the other one being turned off (high res istance). These tran sistors both

fe ed into a virt ual-e arth amplifi er IC3, whose outpu t is inverted by ICl d
in order to maintain phase integrity. ICld output is thus the Mixdown path

i n p u t f o r t h e fi l t e r s .

D5, D6,f RT, R9, and IC2 on BA7lU control the states of TR1 and TR2 according
to the MODE SELECT" control voltage which is produced by the BA720 card.

When in "TRACK" or "MIX" modes (+18V or OV control voltages) the input to IC2d

is pulled up to OV by RT, TR2 gate is thus held at -12V (TR2 off) and TR1

gate is held at OV (TR1 on). In "DIRECT" mode the control voltage is -18V

which pulls down IC2d input to -12V and reverses the states of TR1 and TR2.

HIGHPASS FILTER

The highpass filter circuits are all on the BA715 card and comprise IClb,c
and d. IClb is a n o n - i n v e r t i n g buffer driving the filter proper w h i c h i s
based upon the maximally flat sallen-key circuit below:

^V\A-

IN

Highpass out

2C

>
^

OV

Ov

f- 3d6 =

zk~rcIT~

RV1 on BA715 is used to vary both Rs in the above circuit together and thus
varies the -3dB frequency from 25Hz to 250Hz.

LOWPASS FILTER

The lowpass filter circuits are all on the BA71U card and comprise' ICla and b

IC la is a non- inve rtin g buffer drivi ng the filte r proper which is based upo n

the maxi m a l l y fl a t s allen-key circuit below:

2C

hJ

AAA

R

AAA

R

Ov o-

-3d8

f

RV1 on BA71^ is used to vary both Rs in the above circuit together and thus

varies the -3dB frequency from 3kHz to.15kHz.

LEVELS

All input and output levels are nominally -lOdBu.

D.C. SUPPLIES

BA71U/715 and its /A variant run from +18V regulated supplies provided by the
BA712/713 or the BA752/753 (for the /AT assemblies.

1

ZirRCJT

Lowpass out

-o Ov

C

TEST POINTS

Test points are provided as follows on BA71U:

TP1 Channel path input signal "CH TO FILTERS"
TP2 Channel path output signal "CH FROM FILTERS"

TP3 Mixdown path output signal "MIXDOWN FROM FILTERS"
TPU "CH POST INSERTION" input to electronic switch

TP 5 "TAPE 0/P TO FILTERS" inpu t to electroni c switch
TP 6 M i xd o wn p a th i n put s i gn a l af t er e l e ct r on i c sw i t ch

TP7 OV
TP+18V +18V regulated supply

TP-18V -18V regulated supply

3.

BA7H- a*d 3A7I5

P(6UR£ 1

Channel to Filters

rpiuT ERS IN

1 THIS PATH

▶ , IF

I <«cH'

I p «* 5S E D

CHANNEL FROM FIUER5

r "I

hk;hpass

filter

^

L

TA.PE OJP To
FiutwS

p

CMAMUfrL. PotfT.

lt4fl**7ToN

rt

i

L. Jl iu»**m I L|J—^

■ ^ F I L T E R

("FTLrws IN

I This P*XH

JF

I - C H " 1

Ml X D O W M FR ot t F I LTE R S

MoDC 5£Lf&r

EL^ITTRONIC

SWITCH

BA7I4-/A and 3AH5/A

Figure 2

Channel to Filters

r

HKJHPAiS

FiuTfR

L

Rev 0/p ra Ftt-TE*s

I ^ L T E M t N n

1 T H l t P A T H ,

- ▶ .IF L

1 - C H ' I

I PR ESS ED

7\~

LOWPASS

Filter

_V_

fFTLrER5 IN
I 1mi3 BATH

». IF ,L

I m C M * 1

Ln^T P«E3^0a |

Channel from fh-thks

n

i^-~

Mix d ow m f rom F i lt e r s

c