Symetrix 564E User manual

Quad Expander/Gate
Operating Manual
mm
Version 1^0
Mav 1^991
.• .'.'0
c1991 Symetrix, Inc.
4211 24th Ave. West Seattle, WA 98199 USA Telephone 206*282*2555 Fax 206>283<5504

Table of Coot
Section Page
1. Introduction 1
1.1 Product Description 1
1.2 Control of Dynamic Range with Expanders and Gates 1
1.3 Threshold 1
1.4 Expanders and Ratio 2
1.5 Gates and Range 2
1.6 Frequency Conscious Gating 2
2. Using the 564E 3
2.1 Block Diagram 3
2.2 Installation 4
2.3 Signal Levels 4
2.4 Front Panel Controls and Switches 5
2.5 Rear Panel Connections 6
3. Fast First Time Setup 8
3.1 Connections 8
3.2 Switch Settings 8
3.3 Rotary Control Settings 8
3.4 Meter Readings 8
4. Applications 9
4.1 Introduction 9
4.2 Noise Elimination 10
4.3 Tightening Up Drums 1
1
4.4 Preventing False Triggering 12
4.5 Console Sub-Outs 13
4.6 Effects Returns 14
4.7 Vocal Monitors 15
5. Troubleshooting 16
6. Specifications 17
7. Appendix—Hipass &Lopass Filter Roll-Off 18
8. Service Information 19
9. Limited Warranty 20
10. 564E PCB Layout and Schematics 21

INTRODUCTION
Tliank you ior pUR'h;isinf> ihc Symclrix 5(mE. Tlif Ibllowinj; intbniwtion in this imniuil
may help you achieve optimum pertbnnance from your Quad Expander (>ale Entcessor.
The S(hE Quad Expander Gale has lieen desijjned to the hijjhesi pn)fessional slan-
dards for use in fixed or mobile sound systems. The use of anify>ed .steel chassis,
tlouhle sided printed circuit boards, toroidal power transfomier. and industrial grade
eleciro/mechanical components ihrougltout the SChE enable the prcKluct to provide
years of ilependable .serx’ice in any and all profes.sional audit) applications.
'X'hile the sb tE is easy to install and u.se it will greatly lienelil the u.ser to lake the lime
nece.ssarx' to read this entire manual. However, if you're going to jump right in and
start using the ^(hE wiihttui reading the manual plea.se. just take aminute to run
through the East First Time .Set I'E -Section
Any comments on our products or this manual aa- more than welcome.
1-ach of the four ciianneis may lx- iiulividually operaietl in GATE or EXPander moile.
balanced or unbalancet.1 signals may lx- applied to the XI.E .style input connectors. To
further expand the %iE's functional [X)s.sibilities, acontrol l<H>p (send and reiurni is
included for ilevices like delay lines and graphic equali/ers (for enhancement of
fix'(|uency .sensitive operation). This allows .special enecis and manipulation of prob-
lem audio sources,
Wide range frt>m panel control allows extensive signal manipulation to .solve problems
found in both .studio and live environments. With all controls Ix-ing fully variable, the
level of perfonttance you are able to extract from the S() lE de[x-n<.ls eniia-ly on your
understanding of these controls. E»)r this reason, the following pages include atutorial
.section to aid in understanding the various functions available from the A(>iE.
1.1
Product
Description
when ^lealing with audio signals, the term •dynamic range' de.scrilx's actual level
changes, or the range over which signals fluctuate. The dynamic range of the human
voice, from awhisper to a shout is well over l(K)<.lb. So amientphone will convert the
sound pressure of avoice going fn)m awhisper to ashout into an ekvlrical output
signal with adynamic range of well over lOOdH.
Expansion and gating are both vlerived from the same signal puR'essing family of gain
reduction. The heart of this pnx'ess is based on amplifier circuitrv' in which the gain is
dependent on the signal level pas.sing through it. These ampliflers are known as VC^A's
(Voltage Controlled Amplifier), by changing the gain, based on signal conditions, the
dynamic range of that signal can lx- automatic-ally altered.
1.2
Control of
Dynamic
Range with
Expanders and
Gates
The threshold is the level at which adynamic range pnHes.sor's activity begins. In
operation, the dynamic range proces.sor's sen.sing circuitrv' constantly 'looks' at the
incoming signal and compares it to arelerc-nce level, which is called the threshold
iroini. Kemember. expanders and gates respond only when signals at the input aa'
lower than the defined threshold.
1.3
Threshoid

1.4
Expanders
&Ratio
Adownward expander may lx- ihouglii of a.s adevice whicli causes auiomalic gain
reduction Moiv some definable signal level. In oilier words, an expander can he
l(K)ked upon as the 'opposite' of acompre.s.sor limiler.
r.xpanders typically operate at low ratios. Al.so, it is im|iortant to keep in mind that the
ratio of an expander is the numix-r of dll's of decrea.se in input level compared to the
numher of dB’s of decrease in the output signal. At 1:,^. klB of decrease Iheiow
threshold) at the input causes a.V.IIJ decrease at the output.
1.5
Gates &
Range
Gates can lx- thought of as high niiio (around 1:20) expantlers. They are iniendetl to
sluil out undesired signals that fail Ix-low ihreslmkl. I'.se the Kh^' input to create
special elfects. (See General Applications in Section t).
1.6
Frequency
Conscious
Gating
The KhY l.ISTKN. IIII’ASS and I.OI'ASS controls together provide afeature whicli is
commonly referred to as "ITei|uency Gon.scious Gating". Fxpanders and gati's ai'i' built
from two basic circuit elements: ( 1 ) the Voltage Conimlled Ampliller IVCAI Im h
causes the actual changes in the audio level and (2) the Cainlrol Loop whii his iiasi-
cally alittle analog computer that lotiks' at the incoming amlio, the luser's lotiiml
panel sc-ttings, ami then tells' the VGA what to do.
In afret|uency con.scious expander or gale, laipass and Ilipass controls Lin- .idiled to
the Control Uxip in order to re.slricl the range of fret|uencies fed to the an.ilog u>nv
puter. Uy doing .so the expander or gtile can lx- told to lx- very .selective .iIhhii whicli
.sounds it is triggered by. The.se signals are .sometimes referred to its Kl-V sign.ils
which is just another n;ime for trigger. Hence, the front panel switch whuii .illnws you
to listen to the.se signals is lalx-Iled 'KHV LIS TI-'N'.
l-'or exampk-—Let’s s;iy afull tlrum kit is being recordetl. Amicrophone li.i' Ken
ptisitioned above the head of atl<Hir tom. Achannel of tlie S6 tl'. has been inserteil into
the console input channel for that microphone. The ^(hK is set in gate nuHle hnthe
purj-xise of removing leakage from acymbal which is in close proximiiv ti <tin ll> mr
tom. Keen with the directional mic positioned to reject a.s much cymiiLil as (sisMble the
S(mK gate 'opens' when the drummer strikes either the lltxir tom or cynib.il 1in-
engineer now pushes the S(hK's KHY LISTHN switch allowing him to lisu-ti a.ilu-
CON'I'KOL LOOP audio. (This is \OT the gated signal—just the audio Ih-imu ted iu the
analog computer!) He tunes the HIPASS and I.OPASS controls until the oml'.il i' iiiiK-il
out and he Is hearing primarily the tlmir tom. This is now the signal the an.ilog lom-
puter will use to decide when to turn the gale on ami oif after the KH')' I.IS'I'IK sw itch
is relea.sed to nonnal position.
2
um

nuoN
2. USING THE 564E
2.1 Block
Diagram
This functional block
diagram illusirates the signal
How into, inside of, and out
of the 564E The levels and
impedance at the INPUTS
and OUTPUTS are designed
to match all common line
level systems. All conneaors
arelocatedon the rear panel,
all switches andcontrols arc
located on the front panel.
In the blodc diagram, control
and switch names arc
enclosed with abox.
3

2.2
Installation
2.3
Signal Levels
Tlic is designed for mounting in astandard 19" rack and recjiiircs only one rack
space (lU). The 564Es INPUTs. OlTIUTs. and CONTROL LOOFs should he wired to
apaicli hay for ease of operation. Asugge.sied arrangement for unbalanced operation
witli amono paichixiy is shmvn Ik-Iow. If the 564F. is used with apatchbay, the
connections from the control Uk>p must go to normalled jacks.
Top row
toulpuls)
'normalized' to
bottom row
(Inpulsi.
The is designed to tv used po-sl-preamp. at aplace in the system where the
signals haw already Iven amplified to line levels. 'Line level' is ageneric lemi that's
been used at one lime or another to descritv signals ranging anywhere Irom
tOdHV to +2()dHV. As aix-siill there's really no way for us to predict wlial the actual
operating levels in your .sy.siem will Iv. The ftOdH range of the %I's THKK.SHOl.l)
control allows you to make it work will) awide range of line level input signals.
Miemphone and guitars, for example, are not line level and should not he plugged
directly into the Doing so will not damage the unit, Init will result in excessive
noise.
The overall level in any signal chain is determined to alarge extent hy the transient
content of the program material. Tninsienis are ver\ .sliort duration signals. Peak
reading LED type meters will usually resjxmd to transients, lull VT meters are de.signeil
to indicate average levels ami thea'fore will not respond to transients. As aresult,
transients are long gone Ivloa- aVI meter can a-spond.
Drums, and [vreussive insirumenis like piano or hanjo. generate the kitul ol veiy large
transients which aa* not sliown hy a\'l 'meter. Signals from these instruments may
trigger the sf>iE when llie I'l IRI'SI lOLD control is set at +10 even though your \'l
meter says ilie level never g<vs alxive O'. (If precise metering ol'shori transient peaks
is neccessaiy for your needs. Symeirix" digital SX20tI’recision Audio Meter will meet
the most demanding situations.) On the oilier hand, instruments like violins do not
ereale large transients, so the eorrelalion Ivtween llie VT meter abiding and the
indicatetl tlia’.shold appears to Iv more accurate.

2.4 FRONT PANEL CONTROLS &SWITCHES
r.
r.
Xj
•r.
C
V
c.
c
c
c
r.
•r.
\r.
<
r.
sc
SC
c
f-
i7
<
•/.
c
sc
c.
5
d)
GATE/EXPAND
-
Deleniiinos
whether
the
5
(hK
operates
as
either
an
expander
lci<x;kwise)
or
a
jtale
lcoiinter-c!<Kkwise).
'I'he
expander
ratio
is
increased
as
the
control
is
rotated
ckK'kwise.
The
gate
range
is
increased
as
ilte
control
is
rotated
counter-clockwise.

1
6
®
CONTROL
LOOP
-
This
connc’clor
is
unusual,
and
should
lx.-
.siudicd
tartTully.
Rear
panel
space
con.sirainis
require
ihe
use
of
a
single
1
R.S
(tip-rin>{-
sleeve)
connector
for
both
the
in
out
SIDIiCHAIN
access
to
the
VGA's
contr*)l
l<K)p.
and
for
e.xiernal
('key')
input
signals.
This
jack
accepts
1
4"
3-
conduclor
(stereo
type)
plugs
(Sxvitchcnift
“292
or
equixalent).

2.5 REAR PANEL CONNECTIONS
c
tj
cu
£i
D—
V2
2-5
c
fau
V
>J;
A
C
V. r?
^-z
•i £
c
c
c
'S.
P
2.S ^
e. V5
£
'D c=
I
^i^
rs «
I
i= s
“SC V
5-7 2
ii ^
•SPo
e^o
$CO m
wCO
r**
Q
w
>:
w/
L/
P“
78-2
I5
e°^
^©-
In
situations
where
the
56-*E
drives
an
unbalanced
h>ad
pin
3
must
be
grounded.
The
balanced
output
source
impedance
of
the
564F.
is
200U.
The
minimum
load
impedance
is
600U.

1
3. FAST FIRS
3.1
Connections
I'olkjw ihis .sequcncL- lo gci (he %-4F: up and nmninj>:
INPUT •Conned lo ihe ouipui of the si>>nal source to Iv processc-tl.
OUTPUT -Conned lo ihe input of the Idllowinj; device.
CONTROL LOOP (OPTIONAL) •Connect lo and Irom external proce.ssinn (l-.Q, key
driver audio trucks), etc.
The I.KD meter on each channel will n«il lijjhl when the GATH HXP conirol is centered.
34The meler i.s pcnik reading and will accur.ilely track the atlenuaiion of the VCA (voltajje
Meter Reaclinns eomrolled amplifier). Mower RK1.KASK limes will kcvp the lllelerin^ i.HD's li>>hled
"longer Ivcausc’ they inick ihe control voltage as it's applied to the VCA.
Note
Although the 564E's meter wilt not showany activity when the GATE/EXP
control is In it's center position, we do not recommend this control
position as a method of bypassing GATE/EXP action. Small amounts of
gain reduction (less than 2dB) may occur with no indication on the meter.
Use the Bypass switch to bring the signal out of the 564E circuitry.