Drawmer THREE-SUM User manual

DRAWMER
THREE-SUM
Multi-Band Interface
OPERATOR’S MANUAL
CONTENTS
Warranty
SafetyConsideration
Chapter 1 - Introduction
Introduction
Installation
AudioConnections
PowerConnection
Chapter 2 - Control Description
ControlDescription
Chapter 3 - Operation
Operation
Chapter 4 - General Information
Ifafaultdevelops
ContactingDrawmer
Specification
Block Diagram
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2DRAWMERTHREE-SUM OPERATOR’S MANUAL
Drawmer Electronics Ltd., warrants the Drawmer Three-Sum
Multi-Band Interface to conform substantially to the
specifications of this manual for a period of one year from the
original date of purchase when used in accordance with the
specifications detailed in this manual. In the case of a valid
warrantyclaim, yoursoleandexclusiveremedyandDrawmer’s
entireliabilityunderanytheory ofliabilitywillbeto,atDrawmer’s
discretion, repair or replace the product without charge, or, if
notpossible, torefundthepurchasepricetoyou. Thiswarranty
is not transferable. It applies only to the original purchaser of
theproduct.
For warranty service please call your local Drawmer dealer.
Alternatively call Drawmer Electronics Ltd. at +44 (0)1709
527574. Then ship the defective product, with transportation
andinsurancecharges pre-paid, toDrawmerElectronics Ltd.,
ColemanStreet, Parkgate,Rotherham,S62 6ELUK. Writethe
RA number in large letters in a prominent position on the
shippingbox. Encloseyour name,address,telephonenumber,
copy of the original sales invoice and a detailed description of
theproblem.Drawmer will not accept responsibilityforloss or
damage during transit.
This warranty is void if the product has been damaged by
misuse, modification or unauthorised repair.
THIS WARRANTY IS IN LIEU OF ALL WARRANTIES,
WHETHERORALORWRITTEN,EXPRESSED,IMPLIEDOR
STATUTORY.DRAWMER MAKESNOOTHER WARRANTY
EITHER EXPRESS OR IMPLIED, INCLUDING, WITHOUT
LIMITATION, ANY IMPLIED WARRANTIES OF
MERCHANTABILITY,FITNESSFORAPARTICULARPURPOSE,
OR NON-INFRINGEMENT. PURCHASER’S SOLE AND
EXCLUSIVEREMEDY UNDERTHISWARRANTYSHALLBE
REPAIR ORREPLACEMENTASSPECIFIEDHEREIN.
IN NO EVENT WILL DRAWMER ELECTRONICS LTD. BE
LIABLEFORANYDIRECT,INDIRECT,SPECIAL,INCIDENTAL
ORCONSEQUENTIALDAMAGESRESULTINGFROMANY
DEFECT IN THE PRODUCT, INCLUDING LOST PROFITS,
DAMAGETOPROPERTY,AND,TOTHEEXTENTPERMITTED
BY LAW, DAMAGE FOR PERSONAL INJURY, EVEN IF
DRAWMERHASBEEN ADVISEDOF THE POSSIBILITYOF
SUCHDAMAGES.
Somestatesand specific countries do notallowthe exclusion
of implied warranties or limitations on how long an implied
warranty may last, so the above limitations may not apply to
you. This warranty gives you specific legal rights. You may
haveadditionalrights thatvary from stateto state,andcountry
tocountry.
In the interests of product development, Drawmer reserve the right to modify or
improve specifications of this product at any time, without prior notice.
ONE YEAR LIMITED WARRANTY
COPYRIGHT
This manual is copyrighted © 2005 by Drawmer Electronics Ltd. With all rights reserved. Under copyright
laws, no part of this publication may be reproduced, transmitted, stored in a retrieval system or translated
into any language in any form by any means, mechanical, optical, electronic, recording, or otherwise, with-
out the written permission of Drawmer Electronics Ltd.
DRAWMER
Three-Sum
Multi-Band Interface
SAFETY CONSIDERATIONS
CAUTION-MAINSFUSE
TO REDUCE THE RISK OF FIRE
REPLACE THE MAINS FUSE ONLY WITH
A FUSE THAT CONFORMS TO IEC127-2.
250 VOLT WORKING, TIME DELAY TYPE
AND BODY SIZE OF 20mm x 5mm.
THEMAINS INPUTFUSE MUSTBE
RATED AT 230V=T80mA and 115V=T160mA.
CAUTION-MAINSCABLE
DO NOTATTEMPT TO CHANGE
OR TAMPER WITH THE
SUPPLIEDMAINS CABLE.
CAUTION-SERVICING
DO NOT PERFORM ANY SERVICING.
REFERALL SERVICING TOQUALIFIED
SERVICE PERSONNEL.
WARNING
TO REDUCE THE RISK OF FIRE OR
ELECTRIC SHOCK DO NOT EXPOSE
THISEQUIPMENT TO RAINOR MOISTURE.

3
DRAWMERTHREE-SUM OPERATOR’S MANUAL
DRAWMER
THREE-SUM
MULTI-BAND INTERFACE
The benefits of multi-band processing, with the ability to
applydifferentparameters todifferentsectionsofthe audio
bandwidthhave beenapparenttosoundengineersforquite
some time.
However,‘lockingin’your audio toanyone specific multi-
band unit can vastly reduce the creative options. The
desired combination of processing to deal with low
frequencyenergy, thevocalmidrangeandhighfrequency
detailand enhancement is not necessarilyavailablefrom
anyonemanufacturer.
The new Drawmer THREE-SUM opens up a whole new
setof options allowingtheengineer to splittheaudio into
twoorthreebandsandapply hisorherownsonicsignature
toeach part oftheaudio bandwidth.
CHAPTER 1
INTRODUCTION
The THREE-SUM employs a high quality signal path
culminatingina variablethreshold,brickwall limitersection
with bypass facility. To ensure transparency the limiter
designis ‘two stage’,applyingdifferent processing to the
H.F. content of the material. In applications where the
dynamicsof the material needtoberetained to create an
open sound, the limiter is essential for catching peaks.
TheTHREE-SUM has been designed foruseinhigh-end
masteringandgeneralrecordingapplications,alternatively,
itcantransformaproject studio, equipped onlywith‘single
band’processors, into a serious multi-band facility.
The Key Features are as follows:
• Continuously Variable Band Splitting
• Switchable Mute & Bypass On Each Band
• Variable Threshold, Two Stage Brick Wall Limiter Section
•TwoOrThreeBand Operation
• VU Metering With +10dB Re-Scale Mode For Hot Output Levels
•VariableInput& Output Levels
•Individual Band Or Multi-BandProcessing
• High Quality, Minimal Signal Path With Balanced XLR Inputs/Outputs
Applications:
• Mastering • Stereo Sweetening • Bass Tracks • Drum Tracks • Voice Smoothing
• Use More Creatively - Single Band Distortion / Reverb / Delay

4DRAWMERTHREE-SUM OPERATOR’S MANUAL
The THREE-SUM is designed for standard 19" rack
mountingandoccupies1Uofrackspace.Avoidmounting
theunitdirectlyabove power amplifiers or power supplies
that radiate significant amounts of heat. Always connect
the mains earth to the unit. Fibre or plastic washers may
be used to prevent the front panel becoming marked by
the mounting bolts.
INSTALLATION
AUDIO CONNECTIONS
Theinputsandoutputsareelectronically balanced on conventionally wired XLRs (pin 1 screen, pin 2 hot,pin3coldand
XLR shell is connected to chassis). The operating level is nominally +4dBu. Balanced use is recommended.
•Interference:
If the unit is to be used where it maybe exposed to
highlevelsofdisturbancesuchasfoundcloseto a TV
or radio transmitter, we advise that the unit is oper-
ated in a balanced configuration. The screens of the
signalcablesshouldbeconnectedtothechassiscon-
nectionontheXLRconnectorasopposedtoconnect-
ing to pin1. The Three-Sum conforms to the EMC
standards.
•Ground Loops:
If ground loop problems are encountered, never dis-
connect the mains earth, but instead, try disconnect-
ingthesignalscreenononeend of each of the cables
connecting the outputs of the Three-Sum to the
patchbay. If suchmeasuresare necessary,balanced
operationisrecommended.
fig.1 TYPICAL THREE-SUM SETUP

5
DRAWMERTHREE-SUM OPERATOR’S MANUAL
TheThree-Sum unit will be supplied with a power cable suitablefordomesticpoweroutletsinyourcountry.Foryourown
safety, it isimportantthatyouusethis cable to connect tothemainssupplyearth.Thecablemustnot be tampered with
ormodified.
Thepowersupplysockethasanintegral fuse drawer con-
tainingthepowerfuseofthesamevalue,tosuitthemains
voltage for which the unit has been supplied. Removal of
the drawer is only possible with the power cord removed.
Thefuseshouldneverblowundernormaloperation.Ifthe
fuse is suspected of having blown, then a fault will have
occurredandthis fault condition should be inspected bya
qualifiedserviceengineer.Whenreplacingthe fuse,always
comply with the Safety Instructions.
Iftheunitis to beusedwithamainsinputoperating voltage
differentto that for whichtheunit is supplied, thefollowing
procedure must be carried out by a technically competent
person,(seefollowingdiagrams)
fig.2 THREE-SUM REAR CONNECTOR WIRING
POWER CONNECTION
Fuse
fig.4 The Voltage Selector Switch
fig.3 The Location of the Fuse
Voltage
Selector
Switch
1: Disconnect the unit from the mains.
2: Using a number 1 size pozidrive screwdriver,
remove the eleven self -tapping screws that retain
thetopcover.Onescrew is located in the top centre
of the front panel (next to the “PEAK LEVEL” text);
six screws are located on the top cover; and two
screws on either side.
3:Insidetheunitslidethevoltagechange-overswitch
(SW8) until the correct (or nearest) mains input
voltage is visible on the switch actuator.
(seefig.4)
4:Inthefusedrawchangethefusetosuitthefollowing
values:
For230 Voltoperationalterthefusetoasimilartype
ratedat T80mA.
For115Voltoperation alter the fuse to asimilartype
ratedatT160mA.

6DRAWMERTHREE-SUM OPERATOR’S MANUAL
CONTROL DESCRIPTION
Input Level Trim: -10dB - +10dB
Typically,theInputTrimlevel controlisusedtomatchtheoutputofthe preceding
device to the input needs of the three compressors that the signal will pass
through.Alter the “Meter Input/Output Switch” to "input" to see the effect of the
input trim on the signal level to the three compressors.
On an optimal signal the 0dB provides optimum headroom and signal-to-noise
ratio.If the input trimis set too lowlittlecompression will occur (and,raising the
overalloutputlevelofthesignalwillamplifythenoisefloor).Alternatively,increasing
theinputtrimcontrol pushes morelevelintothecompressorsand therefore more
compressionoccurs.
Low Split Frequency: 18Hz - 1.6kHz
Sets the frequency point at which the split between low and mid bands occurs.
High Split Frequency: 530Hz - 42kHz
Setsthefrequency point at which thesplitbetweenmidand high bands occurs.
THREEBAND
Switches:
Low: is the signal below that set by the Low Split Frequency;
Mid: is the signal between that set by the two Split Frequency controls;
High: is the signal above that set by the High Split Frequency control.
Across all three bands
Mute:
Inthe“MUTE”positionthesignalforthatparticularbandis effectively turned off.
Any combination of mute is available - to hear only the signal of the low band
mute the mid and high bands etc.
Bypass:
In the “BYPASS” position the signal for the low, mid, or high band is allowed to
pass through to the summing stage without being output to a compressor.
Usinga combination of muteandbypassswitches for the variousbandsallows
the operator to hear and monitor only the frequencies that are required and so
tunethe low andhighfrequency settings.
Output Gain: -10dB - +10dB
Afterthethreebands havereturnedtotheThree-Sumthe signalissummedback
to a single stereo band. If at this point the signal is too low or so high that
eccessivelimitingoccursthen itwouldbedifficulttoadjusts allthreegaincontrols
ofeachcompressorwhilstmaintainingthelow/mid/highbalance,forthisreason
asingleOUTPUTGAINcontrolhasbeenincorporated.
Adjust so that the limiter works only on signal peaks.
CHAPTER 2

7
DRAWMERTHREE-SUM OPERATOR’S MANUAL
Limiter
The signal culminates in a variable threshold, brick wall limiter. The limiter can
be bypassed completely using this switch in the OUT position. When in bypass
the unit will sum the three bands back to a full band stereo signal but then no
further processing is applied (the VCA is also bypassed). This is ideal for the
purists who would prefer to keep the signal path as simple as possible, but it
doesmeanthesignallevelwill have to managed by themselves elsewhere.
Peak Level 0dB - +16dB
Sets an absolute limit to the level that the output signal will not be permitted to
exceed. This limiter is very fast acting enabling it to control any peaks without
audible distortion.The Output Gain control should be used to ensure that the
peaklimiteroperatesonlyrarelyifatall,ifitistobeusedpurelyforpeakprotection.
Alternatively, itmaybedeliberatelydriveninto limitingtoproducecreativeeffects.
G.R. Meter -1, -3, -6, -10dB
VU Meter
A moving coil VU meter monitors either the level of the output or input signal.
Because the meter has VU characteristics, it closely reflects what is actually
being heard, though will not respond quickly enough to register short signal
peaks.
Meter Options:
VU+10dB / VU
A two-position switch adjusts the meters to show either normal output level or
VU +10dB mode, which re-scales the meter for users working at ‘hot’ output
levels.Inother words, with the switchatVU+10dBthe VU meter reads 0dB but
the actual level is +10dB.
Input / Output
A two-position switch adjusts the meters to show either input or output level.
Intheinputpositionthesignallevel is derivedaftertheinputgain, butpreceeding
the split into its three bands. This always monitors the full band of the audio
signal;
Intheoutputpositon the signal levelcomesafterthethreebandsignalhas been
summedandpassedthroughtheoutputgain and limiter.Ifanyofthe bands have
been muted or bypassed this is also reflected in the meter.

8DRAWMERTHREE-SUM OPERATOR’S MANUAL
Most conventional compressors work by processing the
full-band of the music, where the whole of the signal is
compressedusing the samecontrols,however,this is by
nomeansperfect.Aproblemoccurswhereby when apeak
occurs, such as the beat of a kick drum, all of the signal
is effectively "turned down" by the compressor, including
thevocals, guitar,hi-hatsetc. eventhoughthesemay not
needcompressing.Inaddition,whenprocessingcomplex
mixes using a conventional compressor, you can easily
reachthepoint wheregainpumpingbecomes audible,with
high-energy, low-frequency sounds affecting the gain of
thewholemix. Multi-band compressors were designed to
avoidtheseproblems, by treating different sections of the
frequencyspectrumindependently.
TheDrawmerThree-Sumhasbeen designed to allow the
audioto splitintothreeseparatefrequencybandsbymeans
ofacrossovercircuit,eachbandthenbeing treated with a
separatecompressorand,at the output,thevariousbands
areagaincombinedtoprovideafull-rangesignal.Inaddition,
unlikeconventionalthree bandcompressors,theDrawmer
Three-Sum allows the three signals to be sent to three
independentcompressors,eachgiving their own unique
flavour to the music - some warmer at bottom end
compression,othersprovidingan enhanced top end. The
control is entirely with the operator.
TheDrawmerThree-Sum, where eachband'scompressor
canbeadjusted separately,isavery versatileandpowerful
tool. For instance, the perceived amount of bass can be
increased by setting a higher ratio or lower threshold for
the bass band than in the mid and high bands. Similarly,
ifyoufeel themidfrequenciesof themixarelacking, simply
turnupthe outputlevelofthemid-band compressor-using
more compression in the mid-band can often help lift out
thevocals. Likewise, compress thetop end a littleharder
to give it more brightness or enhancement. If the gain
reductionofeach bandiscontrolledbyadjusting themake-
up gain knobs on each of the three
compressorsthen the overall levelsof
signal peaks will not increase but the
sound will be much more impressive.
However, no matter how much care is
taken,itisquitepossibleto fully control
thesignal in each band butstillendup
with a signal that is too high in level
when the bands are combined.
Therefore an output gain control has
beenprovidedontheThree-Sumtotrim
the whole stereo signal, followed by a fast acting limiter
that will catch any overshoots. To ensure transparency
the limiter design is ‘two stage’, applying different
processing to the H.F. content of the material. In
applications where the dynamics of the material need to
be retained to create an open sound, set the output gain
so that the limiter only activates on fast signal peaks.
Setting up the Cross-Over Points.
Which cross-over frequencies should be used? This
invariably depends on the material being processed, the
settings of a mix will be very different from that of a full
drumkit,howeverthegeneralruleofthumbisthatinmost
circumstancesthecross-overpointsneedto
besetinsuch a way as to separate themain
bassand treble sounds fromthemid-range.
Keeping in mind that instruments have
harmonics that can extend over several
octaves, the goal is to try to partition your
mixinto bands. Playyourmix, and mute the
bandsnotrequired.Nowyou canhearexactly
which frequencies are contained in each
band, and can tune in to the signal.
On a full mix the kick drums and bass instruments will be
mainly in the low band while the mid band should be set
wideenoughtoaccommodatethefullvocalrange,except
forperhaps the highest harmonicsand breath noises -
OPERATION CHAPTER 3

9
DRAWMERTHREE-SUM OPERATOR’S MANUAL
UsingMulti-BandCompression onSingleInstruments.
TheDrawmerThree-Sumcanbeusedtoverygoodeffect
during the recording stages. Because the signal is split
into three each band can be compressed and modified
much more precisely to add bass, or enhanced top end
brightnessofasingleinstrument,suchasapianoordrum
kit. Obviously, all instruments are different and require
different settings. As before a good starting point is to
mute the unwanted bands and to tune into the required
frequencies using the "Low Split Frequency" and "High
Split Frequency" controls. This ensures that the overall
sonal quality of the instrument is compressed, but the
unwantednoises,such as rumble from traffic, or amplifier
hiss etc. are not. On vocals multi-band compressors can
be used to alter the timbre. Compressing the lower band
willprovideamuch thicker voice giving it presence, whilst
compressingthetopbandwillimproveair and give a more
sweet sound to what was a quite dull voice. Remember,
any gain should be controlled by the three individual
compresses before being summed by the Three-Sum.
Subtlety is the key.
Other Uses.
TheDrawmerThree-Sumhasprimarilybeendesignedfor
use as a three band compressor, however, the fact that it
uses external compressors after splitting the signal into
its three bands opens up endless other uses. The signal
neednotpassto acompressor,tryusingittoadddistortion
or reverb to only the bass of a guitar or other instrument.
Imaginehavingaleadguitarwithoverdrivenbottomstrings,
but a clear crisp tone to the top strings.
setting a crossover point in the middle of the vocal range
can completely mess up the vocal sound. In general it's
best to set the low crossover point below the vocal
frequencyrange(about150Hzto250Hz) and set the high
crossover point between 5kHz and 8kHz (but no lower
3kHz) to catch the brightness of an acoustic guitar or
cymbals etc, and embellish the feeling of detail and air,
creating an effect similar to that of using an enhancer.
Inall cases listen totheaudio and try todetermine where
the signal is lacking, the different ranges covered by the
variousinstrumentsand sounds and adjust the crossover
points accordingly. However, try to be subtle, remember
that the more make-up gain you apply, the more you will
be bringing up the background noise — tape hiss etc.
Careful selection of crossover points and ratio/threshold
settings can help to subdue any adverse effects, but
remember,over processingisalwaysdamagingtoapiece
of music.

10 DRAWMERTHREE-SUM OPERATOR’S MANUAL
IF A FAULT DEVELOPS
For warranty service please call Drawmer Electronics Ltd. or
their nearest authorised service facility, giving full details of
the difficulty.
A list of all main dealers can be found on the Drawmer
webpages.
On receipt of this information, service or shipping instructions
will be forwarded to you.
No equipment should be returned under the warranty without
prior consent from Drawmer or their authorised representative.
For service claims under the warranty agreement a service
Returns Authorisation (RA) number will be issued.
Write this RA number in large letters in a prominent position
on the shipping box. Enclose your name, address, telephone
number, copy of the original sales invoice and a detailed
description of the problem.
Authorised returns should be prepaid and must be insured.
All Drawmer products are packaged in specially designed
containersfor protection. Ifthe unitis to bereturned, theoriginal
container must be used. If this container is not available, then
the equipment should be packaged in substantial shock-proof
material, capable of withstanding the handling for the transit.
CONTACTING DRAWMER
Drawmer Electronics Ltd., will be pleased to answer all
application questions to enhance your usage of this
equipment. Please address correspondence to:
Drawmer (Technical Help line)
Coleman Street
Parkgate
Rotherham
S62 6EL
UK
Alternatively contact us by E-mail on :
[e-mail]
Further information on all Drawmer dealers, Authorised service
departments and other contact information can be obtained
from our web pages on:
http://www.drawmer.com
GENERAL INFORMATION
CHAPTER 4
INPUT IMPEDANCE
Input Impedance 20k Ohms
Maximum Input Level +20dBu
OUTPUT
Output Impedance 50 Ohms
Maximum Output Level +21dBu
BANDWIDTH <20Hz to 20kHz +/- <.5dB
<17Hz to 28kHz -1dB
<10Hz to 47kHz -3dB
CROSSTALK better than 63dB @ 10kHz
THREE-SUM MULTI-BAND INTERFACE
DATA SPECIFICATION
It is the responsibility of the installer to ensure that the continuous power rating of the speakers is not exceeded, as Drawmer
Electronics Ltd will not accept any responsibitlity for speaker damage caused by incorrect settings.
THD & Noise -85dB
POWER REQUIREMENTS
230Volt or 115V at 50-60hZ, 13VA
FUSE RATING
T80mA for 230Volt, T160mAfor 115Volt
Conforming to IEC 127-2
FUSE TYPE
20mm x 5mm, Class 3 Slo-Blo, 250Volt working
CASE SIZE
482mm (W) x 44mm (H) x 200mm (D)
WEIGHT 4Kgs