Inovonics DYNEX User manual

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\
INSTRUCTION
MANUAL
MODEL
241
11
0YNEX
11
NOISE
SUPPRESSOR
July,
1976
1630
DELL
AVE
.,
CA
MP
~EI.L
,
CALIF
9!:i008
(408)
374
-8300
• I

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TABLE
OF
CONTENTS
I.
GENERAL
INFORMATION
AND
SPECIFICATIONS
3
II.
INSTALLATION
.
6
III.
OPER
AT
ION
ANO
FUNCTIO
NAL
DESCRIPTION
7
IV.
CIRC
UI
T
DESCRIPTION
13
v.
ALIGl~MENT
AND
CALI
BRATION
15
111
ustrati
ons
1-1
DYNEX
Noise
Suppression
Characteristics
4
1-2
Broadband
Expansion Transfer Function 5
3-~}
3-2
Dynamics
of
DYNEX
Rumble
Suppression 9
3-~}
Dyna
m
ics
of
DYNEX
Hiss Suppression
10
3-4
3-5
Dyn
am
ics
of
Wideband
Noise Suppression
11
-2-

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I.
GENERAL
INFORMATION
T
he
Inovonics
DYNEX
is
a program-
controlled
fi
lter/expander
offering
a si
mple
yet
effective
means
of
suppressing a
certain
amount
of
the
residual background noise
present
in
most
audio transmission
and
re
-
cording/reproducing systems.
DYNEX
is
a single-ended device,
rather
than a
full
comple
men
tary
com-
pression/
expansion :ioise Reduction System, but should not be confused
with a
si
mple
noise "gate,
11
or
program-actuated s\-.,itch.
In
its
oper-
ation,
DYNEX
first
introduces a fixed
amount
of
either
frequency-selective
or
bro
adband
signal
loss,
and
then
linearl
y re-expands program gain
to
a
flat,
unity value
when
energy in the suppressed
band
exceeds a
selected
threshold value.
DYNEX
uses include:
Reduction
of
surface noise
or
rumble
in
disc
playback equipment.
Suppression
of
r-~gne
tic
asperity
noise
(tape
hiss)
in
tape
or
fil
m
reproducing systems.
Quieting
of
optic
al film sound channels.
Improving
S/N
in
interface
between
low
grade
te
lephone
line
and
broadcast
facilities
.
Among
the features
of
DYNEX
are
:
Choic
e
of
operating
modes
for
selective
suppression
of
low
frequency,
mechanical nois
es,
higher
order
system
noise,
or
a combination
of
both,
and
restorc~ion
of
pro
gram
dynamic
range
by
linear
broadband
expansion.
Variable Thresho
~d
adjustment
to
permit
optimum
selection
of
the
point
of
which
re-expansion begins.
Visual
indicatic
~
of
Threshold coincidence
and
ful l expansion.
Avail
ability
i
nt
var
iety
of
versions
for
professional
or
semi-pro
require
ment
s.
-3-

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DYNEX SPECIFICATIONS
Frequency Response: ±0.5dB, 20Hz - 20kHz
Output Noise Level: below -85dBm
Distortion: be l ow 0.1% THO up to +lOdBm output
below 0.3% THO up to +23dB m output
(Clipping level above
+24dBm)
Noise Sup pression Chara cteristics:
RUMBLE: Choice of two LF rolloff curves (Fig. 1-1; A & B) with
restoration to flat response when low frequency energy
exceeds
preset Threshold.
HISS: Choice of two HF "shelving" curves (Fig. 1-1; C & D) with
restoration to flat response when high frequency energy
exceeds
preset Threshold.
WIDEBAND NOISE: LF + HF rolloff characteristic (Fig. 1-1; E) with
restoratio n to flat res pon se when energy in suppressed
band exceeds · preset Threshold.
LINEA R EXPAND: lOd B of broadba nd program attenuation with linear
re-expansion to unity gain beginning at Threshold (Fig. 1- 2).
+5 ,----, - --,--,-,......,....--,--,-~--r---,----,-·r- ,-.--,-..,.........-,---,,---~ ---r-- --:--r- --:----:-r- rr---r--,
!i I I I I ! I
20
so
100 200
500 lk 2k
5k
] 0 1<
Fig. 1-1
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Input:
+10
O
dB
.-10
0
u
T -20
p
u
T -
30
-
40
-
50
V
-50
l7
V
,/
•
'./I
,V
I,
'
✓
V
1
..
/
I
lOdB
/
I(
-b
/ ,v
/ V I
/
~
~7
hreshold
I l
/
-
40
-30 -20 -10
OdB
+10
I NP UT
Fi
g. 1-2
lOOK
unbalanced (transformer
optional)
for
nominal
studio
line
levels
of
+4
or
+
8dBm
. -
03
version accepts unbalanced inpu
ts
betw
een -10
and
OdBm
.
Output:
Feed
s
600
ohm
lines
or bridging
inputs
at
no
mina
l
lin
e lev
els
.
Clipping level in excess of
+24dB
m.
Power
Requ
ir
ement
:
105
-
130VAC
(230V
available)
,
50/60Hz;
O
.l
A.
Size
and
~/eight:
1-7/8
'' X
8-1/2"
X
6-
1/
2";
4
lb
s.
- 5-

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-
II.
INSTALLATIO
N
Upon
rec
eipt
of
the
equi
pment
, inspect
at
once
for
shipping d
amage
.
Should
any
such d
amage
be
observed, notify the
carri
er
immediately;
if
not,
proceed as
outlined
be
low.
It
is
suggested
that
the
original
sh
ip-
ping carton
and
ma
terials
be
ret
ained should future
re-shi
pmen
t
become
nece
ssary.
Mounting
Th
e Inovonics
DYNEX
is
in a compact
"half-r
c:ck''
package. Opti
ona
l
mounting hardware
permi
ts
eit
he
r a
single
unit
or
a p
air
of
units
to
be
mounted
in a standard 19-inch
eq
uip
men
t rack.
Alternat
ely,
the
DYNEX
can
be
cu
sto
m
-fi
tted
by
t
he
user to a
partic
u
lar
~ounting
situation.
l!!/Out Connection
-00,
-01
an
d
-02
op
tion
units
have
a
scre~-t
erm
inal
barri
er
strip
for
input
and
output
con
ne
ction
.
The
"se
r:i
-pro" -03 v
ers
ion i s
outfitted
with
RCA
-
ty
pe
"phono" connectors for lov!er l
ev
el,
vr,bcl -
anced
li
ne
s.
·
Lin
e
Con
side
ratio
ns
-00, -
01
and
-
02
unit
s
are
meant
to
i
nterface
with n
omirial
stucifo
l i
ne
levels
of
+4
or
+8dBm
.
No
output
line
termination
is
neces-
sary, as t
he
1
01-.,
sou1·
ce i
m!)edance
of
the
un
it
obviates
any
shift
in
charac
teristics,
whet
he
r
or
not
the
output
is
terminated in EJJ
ohms
.
Should
the
equipment
1'
:h
ich feeds
the
DYND
'.
i·equ
ire
output
lo
cc'ing ,
an
external
600
oh
mres
ist
ors
-hould
be
co
nn2c
ted
across the ir:p!.Jt
termina
ls;
othenvise the input
is
"bridgi
ng
•·.
Th
e "se
mi
-pro" -
03
version
OYNEX
is
desig
ned
to
int
erface
1·1it
h
li
ne
level s
of
-10
to
O
dBm
(u
nb
alanced) as
co
m~on
1y encountered in
les
s
professional
or
con
sume
r grade equipment .
-6-
I

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II
I.
OPER
A
TI
Otl
AND
F
UNCTIONAL
OESCRl
PTION
Every
day
use
of
the
DYNEX
is
meant
to
be
a simple,
strai
ghtforward oper-
ation,
and
all
panel
controls
are
marked
with
least
con
f
using,
best
des-
cripti
ons
of
their
funct
io
ns
.
As
unnec
essary
as
it
thus
ma
y
seem
to
give
detailed
operating
instruc
tion
s,
a
basic
understanding
of
audio
noise
and
methods
for
its
re
duct
i
on
is
i
mpo
rta
n
t,
as
is
awareness
of
the various
limitations
of
the
DYNEX
an
d simil
ar
noise
-
suppressing
devices.
Noise Reduction Syste
rns
Background noise in audio reproduci
ng
systems has always been a
source
of
annoyance
to
all
but casual
listeners
. Over
the
years
,
adv
ances
in
the
art
hav
e i
mpro
ved
the
sign
al -
to
-
noise
ratio
of
the
various
trans
~iss
ion
or
re
cording methods,
generally
as
the
second-
orde;· effcc~
cf~
change
i~
ma
teri~ls
and proced~res.
Contributions
hav
e been
either
dramatic,
as
in the changeover from
shellac
to
vinyl
pressings,
or
less
evident
on
the
li
stener
level,
as
in
im-
prover.ient
in
magnetic oxide
formu
l
ations
.
With
appreciable
improvements
in
other
aspects
of
audio reproduction
quality
, noise
h~s
re
m:5.ined
a
single,
seemingly
increasing
irritatio
n.
Recently,
therefore,
special
steps
have been taken
in
a
specifi
c
atte
m
pt
to
substantially
reduce residual
noise
.
Noise Reductior. Systems \'thich
empl
oy
complementary dynamic range
compression
an
d re-expansion have
been
utilized
·
in
telep
i,one
and
oth
er
co
m;nun
ic
i~ions equip
me
nt
for
several decades . This
same
tech-
nique has only
recently
been applied
to
high
quality
audio
repro-
duction,
hm
·1ever, most
notably
the
O0lby
and
db
x Noise Reduction
SystE:ms
. These systems
are
very
effective
in
improving
S/1~,
as
the
audio signal
is
''encoded"
prior
to
introduction
of
the
major
noise
co
r-;poil
ent,
an
d "decoded"
to
recover
the
audio
less
noise
.
in
those
riu;:ierot:s
cases
when
a
co
mplementary
syst
em
is
no
t e
mp
loyed
or
when
~oise
is
subs
equently
introduced, t
hat
class
of
device gen-
erally
rE:feiT".:d
to
as a "Prn9ram
-Co
ntrolled
Filter"
or
"Single-Ended
Nois<.?
Reduce1~
11
can be used
to
suppress s
omP
of
the
residual
noise
vlit.lr
ne!J1
igi
blc-
effect
on
the
legiti
mo.t
e
progrcim
materia
l.
Again,
the
concE:pt
is
not
a
nev,
one. Devices
of
this
type
enjoyed n
brief
popuhrity
during
the
la
te
Forti
es
and
early
Fifties
1..,.hen
consumer
audio
sy~tr
m
i€-::l-:nology
fel
l out
of
step
with
that
\·
!hich
was
em-
bodied in professional
gear.
F
or
effect
i
vci1~
ss
in
operc:~tion, "Single-
Ended"
devices depend
to
a
lar
g~
degr~e
u~on
the steady-
state
nDtur~
of
residual
noise;
for
as
-
7-

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program material
is
made
up
of
harmonically-
related
components with
si
milarly
varying dynamics,
the
greatest
distraction
and
annoyance
comes
from
the
o~niprese
nt
residual
elements which
are
related
to
t
he
program
neither
in harmonic nor
dyna
m
ic
qualities.
DYNEX
Operation
Since noise
is
fairly
well
masked
by
higher energy program
material,
it
is
possible to suppress
that
noise
to
so
me
degree
by
reducing
syst
em
gain
at
low
program
levels
,
either
on
a broadband
basis
or
in
those
portio
~s
of
the
spectrum
which
contain
insignificant
pro-
gram
energy,
and
then
restoring
gain
to
full
value
or
flat
response
when
program
a~
p
litude
increases
suffici
ently
to
mask
noise.
It
is
by
this
mechanism
that
the
DYNEX
and
similar
devices operate.
Rumble
Suppression
Figs. 3-1
and
3-2 graph
the
t1.,io
DYNEX
lm·,
frequency
suppression/res-
tor
ation
chara
cter
istics.
Th
ese
are
effective
in reducing
AC
line
hum,
turntable
ru~ble,
studio
air
co
nditioner
noises
and
other
low
pitch,
mechanically-generated disturbances. Restoration
to
flat
response occurrs only
when
low
frequen
cy
program energy
incre
ases
suffi
ciently
ab~ve
the
noise level
to
provide
mask
in
g.
The
THRESHOLD
control
facilitates
setting
the
unit's
restoration
sensitivity
to
discr
iminate bet~een
residual
noise
and
legitimate
program.
Since
the
ear
is
not
particularly
pitch-discriminating
in
the
low
frequ
enc
y range, noise in
thi~
par·~
of
the spectrum ·is
easily
1o'1askeJ
by
even
a
sma
11
a
::".o
unt
of
1
eg
it
imate
101•1
freque
ncy
program
co
mponent.
The
re-expansion
ratio
in
the
Rumble
Suppression
modes
can thus afford
to
be
'
quite
ste
e?,
restoring
response
fully
to
flat
once Threshold has
been
exceeded.
Hiss
Supp_r
ession
Two
Hiss Suppre
ss
ion
characteristics
are provided,
and
are
graphed
in Figs. 3-3
and
3-4. This
mode
is
particularly
effe
ct
ive in
re-
ducing
the
apparent
level
of
tape
hiss,
record surface
effects,
op-
tical
sound
trac
~ noise
and
higher-order
electronic
annoyances.
As
in the case
of
P.
·
_;
r.
ble Suppression, the t
1.,rc
Hiss
Suppr~
ss
ion
modes
reduce gain
at
higher frequen
cies
,
and
re-expand
to
f l
at
res
ponse
when
high frequ~~cy program energy
is
present in
sufficient
magnitude
to
mask
noise.
-8
-

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3 -1, RUMBLE - 12d 8
Fig.
2 RUM 13 LE - Fig. 3- -,
-9 -
13d8

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12dl3

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+30~---.,----,-,-,--,--r-r--r-r----.--r--r--r--r-r-.-,,-lrr--r---r - ....,. --y-Tl -,- -r- TTr - ,-7
l------i - · --+--+-r-1-"1 ·· - - -~--i - - - ¼----+-1--l ·--+- Tt-- -1---+- --+---1----t l -t--,-, -+-t- -------t---;
+20 1-----1 r------i---r- >- f- --1--+-+--11--1 -+ ++ -H-i--f --t -t- - · t---t--r-
1
-i-n-i-r--r-
:
+10L - l------l - -+ -+-+-l--+-+--+-+-- -+---+ ·-+-+-+iH-t---1 r--t---t-----i------t
1
-r --t - rr~ -r _7
I ,1 - I i Od B in
Cdsl----!~-i,-.J-.J.-"4,-l-f--~
1-,---!--""'r"'-r~'"T'""'+t------:~'i--"'t--,----r,
-;-~r--r--1
! I i : I ' I I Ii
Fig. 3-5, tJID ESA:W 1lO ISE
Since an additional degree of high frequency program e~ ergy is re -
quired to ma sk hiss than lo w frequency energy to mas k rumb le, the
re-expansion ratio for the HISS - 12dB s ~p pressi on ~ o~ e is a ~e re
gentle, linear function wh ic h restores response fully to flat only
after high frequency energy is well above the Thresh o'i::i va lue (Fig.
3-4).
\.Ji de band tloi se Su ppr ession
This DYNEX mode, graphed in Fig. 3-5, is m ost effecti ve in "problem"
noise
situations, such as noisy l ocation-re cording or ~roadcest
environm
ents, sal vaging of ea rly , noisy p ho nograph r ec~ rds and
brod
dcast or recording of voice-channel te lephone or s~~ rtwave
radio co mmu nications li nks . {\s sho1·m in Fia. 3- 5, t hi s ~ode e ill -
ploys LF rolloff, HF reduction and hrotdb and atte nuat~2n, v1 it h
restoration of circuit gain t o a flat, un ity va l ue be~~nn ing as
energy
in the suppressed area excee ds t he Threshold le ve l.
-11-
I
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Broadhand Expansion
In this fourth DY!ffX operating mode, broadband gain is reduced by
a fixed lOdB, and linearly re-expanded to unity beginning at the
Threshold setting. Although the Broadband Exp ansion mo de is useful
in the suppression
of many forms of no i se, the primary utility of
this mode is the restoration of dyna mic range to previously compres -
sed
program materia l. The expansion curve is shoi :n under DY i ~EX
Specifications in Fig. 1-2.
Pa nel Indicators
A red LED indicator signals Threshold coincidence, visually indi-
cating that the DYNEX is active in restoring gai n to a unity, flat
value. A green FULL E XPANSION indicator li ghts when gain is fully
restored .
DYNEX Operation - SUGGESTED INITIAL CONTROL SETTINGS
Select either a frequency- selective suppression mode for specific
noises, or the LI NEAR EXPAND mode for restoration of program dynamics.
Use only the degree of·frequency-selective suppression necessary to
reduce annoyance to a tolerable level .
Set the
THRESHOLD control at a point which will cause the associ-
ated red LED to remain on fairly constantly when program material
is present, but not advanced to the point th at will cause the
indicator to light solely on noise in the absence of legitimate
progi·am . The green LED indic ates FULL EXPAt6IO';, and may or may
not flash on program pea ks, depending on the dyn~mic range of the
input program . The P RESET position of th e THRESHOLD control is
a generally acceptable Threshold settin g for most operatior,s.
-12-

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..,.
IV. CIRCUIT DESCRIPTION
Re ferr in g to the DYNEX schematic, input signals are first fed to a ur.ity-
ga in buffer a1np 1 ifi er, IC4. The 1 ow output i r.1peda nce of IC4 drives the
five low and high frequency p re- emphas is networks associat ed wi th t he
frequency- se l ective noise suppression modes . These networks co ~prise
Cl/R2, RUMBLE-12dB; C2/R3, RUMBLE-18dB; C3/ R4, HISS-6dB; C4/R5, HISS -12d3;
R6, 41, 42 , 43/CS , 19, BROADBAND NOISE . Mode sw i tch S1 selects the pre-
emphasized
output of these various networks, or , in the case of LJ :;~ ~R
EXPA ND, a flat signal via Rl . ·
T
he signal selected by S1 is fed to the variab l e ga i n sta ge consi s~ ing
of IC2 and its associ ated co mpone nts, incl uding the two FET's, QI znd 2.
Th is circuit configuration, known as the Santana Circuit, utilizes FET
Ql as an act ive variable resistor across the inverting input of op2ra t-
ional ampl i fier IC2 . A si m ilar "du mm y" FET, Q2, across the non-i nver ti ng
ampli fier input, serves to cancel the channel non-l in ear it i es of Ql and
permit gain control at audio sign al levels which would ordinarily be
above the norma l , low distortion work in g range of the FET's.
IC3 is a sum ming and output amp l ifier stage . The associ ated tr ansistors,
Q4 and 5, are current ga i n stages to provide adequate outp ut fo r lo~
impedance loads
and long c ab les. These stag es are protected fro ~ cJtput
short-circuits by diodes CR5 and 6.
In its fu nction as a summing ampl i fier, IC 3 receives signals both fro m
t
he variable gain stage , through R23, and directly fro m t he input bJff er
a mp lifi er, through R24 . With the variable gain stage , I C2, at r~xi~u~
attenuation, the DYNEX is a flat, unity -gain ampl ifier 1•1itl1 the ou:::, •Jt
sign al id entica l to what is being fed to the input. With IC2 at Gin i-
mu m at tenuation (unity-gain, i nverting), the pre-emphasized or fl2t signal
selected by S1 is fed out-of-phase wi th the buffered input sig n2l to IC3,
and
the DYNEX output assu mes a l ow and/or high frequency rol loff, or bro5d-
band atten u ated character i stic . It is thus between these two extre ~~s ,
or wi thin the active operat ing region of IC2, that the DYN EX f~~ ct ions to
reduce residual noise.
As descr i bed in Section III, one of two expansi on ratios is sel e cted
to restore flat , unity ga i n, depending on t he suppression mode se lec-
ted . These characte1· istics are generated by sa rr. pl ing eith er t he inpu t
or the output signal of the vai·iable gain sta ~e to derive the DC con-
t rol volta ge to reduce the gain of th at sta ge . \ ·! hen the output si;r.a1
is sa mp led, as is the case of th e LINEAR EXP AND and HISS-12dB or ~:DE-
BAND NOISE mo de s, re- exp,rnsion is a gentle, lin ear function . Ot:-ier
modes d er iv e control by·sampling tl1e input si gnal , generati ng a steeper
curve. T he optimum re-expansion r atio is det ermined when the sup~res-
sion mode is selected .
-13-

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The selected signal is fed through the front panel TH RESHOLD control,
R44 to amplifier ICl . Transis tor Q3 yields a differential output to
permit full wave rectification by diodes CR2 and 3. Th e cathodes of
these two diodes are set to the Ql pinchoff voltage by Rl?, and rec-
tified qontrol volt age drives this point positive to reduce gain of
IC2. R21 and C6 filter the rectified control signal, with R22 also
selectiv ely switched in to extend the time constant in the RUMBL E modes.
I '
IC5, a dual op - amp, is connected as a differential co mpara tor, sampling
the DC control signal and il lum inating ei tt,er the THRES HOLD (coincidence)·
for FULL EXPANSION panel ind icato rs as required.
The 18-volt bipolar power supply com prises rectifier diodes CR B-11,
filter capacitors C15 and 16, and regula tor IC's 6 and 7.
-1 4-
I I

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V. ALIGNMENT AND CALIBRATION
Equip ment Required
VOL T-OH/·\'.'iETER
AUDIO OSCILLATOR -H.P. 200 CD or equiv.
AC VOLTMETER -H.P. 400 E or equiv.
Procedure
NOTE: All alignment steps are done in the LINEAR EXPAND mode, and
'r'1ith the DYNEX
II
IN".
A. Power Supply Check
Apply primary power to the DYNEX and check that both supplies
are \·lithin 1 volt of 18 volts. Pins 7 and 4 of any type 748 IC
are convenient monitor points.
B. Variable Gain Staqe Bal~nce
1.
Ground the gate of QI with a clip lead to chassis. The bare
jumper wire marked
TEST, and located behind the Threshold
control is a convenient connection to Ql's gate.
2. Apply a nominal line level signal of 500Hz to the DYNEX input
and monitor
the output of IC2 with the AC voltmeter. A con-
venient monitor point is the end of R23 nearest IC2.
3. Adjust R8 for minimum reading (null).
4. Re mo ve the ground le ad .
C. FET Pi nchoff Adjustment
1. Rotate the THRESH O LD control fully counterclockwise, but _r:i_ot
into its PRESET position.
2. Apply a SOOHz signal to the DYtffX input at a level roughly
30dB below nominal lin e level, and monitor the unit's output
with the AC voltm eter .
3. Rotate
R17 slowly clockwise from full CCW, setting it for a
l/4dB output increase from minimum.
-15-

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D. Indicator Calibrat i on
1. Apply a 500Hz signal to the DYNEX input at a level approx-
imately
30dB below nominal line level . Monitor the unit's
output with the AC volt m eter.
2. Adv ance the front panel THRESHOLD control slowly clockwise
from the
full CCW position. At some point the DYNEX output
will begin to increase. Adjust
the THRESH OLD control for
an increase of ldB . At this THRESHOLD setting, adjust R33
so that the red LED just comes on . Make sure that when the
TH RESHOLD control is rota ted counterclockwise the LED turns
off and the monitored outp ut drops by ldB .
3. Increase the
oscillator amplitude to no minal line level .
4. Rotate the
THRES H OLD contro l ful ly clockwise and note the
monitored output reading; then slowly
turn . t he control
cou nterc lockwise until the sig na l dr ops lcJB from -~he max -
imu mvalue. At this point adjust R34 so that the green LED
just co mes on. Check that the green indicator turns off as
the T
HRESHOLD co nt rol is rotated further counterclockwise
and the monitored signal level drops .
This
Coir , pletes Calibrat i on .
-16-

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COMPONENTS
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CAPAC
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TOR,
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35V
II
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