Drawmer 1968 MKII User manual

DRAWMER
Dual Channel
Vacuum Tube Compressor
OPERATOR’S MANUAL
CONTENTS
Warranty
SafetyConsideration
Chapter 1 - Introduction
Introduction
Installation
AudioConnections
PowerConnection
Chapter 2 - Control Description
ControlDescription
TheQuickSetupProcedure
Chapter 3 - General Information
Ifafaultdevelops
ContactingDrawmer
Specification
Block Diagram
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2DRAWMER 1968MkII OPERATOR’S MANUAL
Drawmer Electronics Ltd., warrants the Drawmer 1968 MkII
Dual Channel Vacuum Tube Compressor 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 warranty claim, your sole and exclusive
remedyandDrawmer’sentireliabilityunderanytheoryofliability
willbeto,atDrawmer’sdiscretion,repairorreplacethe product
withoutcharge,or, if notpossible,to refund thepurchase price
to you. This warranty is not transferable. It applies only to the
original purchaser of the product.
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
andinsurance charges pre-paid,to Drawmer ElectronicsLtd.,
ColemanStreet,Parkgate,Rotherham,S62 6EL UK. Writethe
RA number in large letters in a prominent position on the
shippingbox.Encloseyourname,address,telephonenumber,
copy of the original sales invoice and a detailed description of
theproblem. Drawmerwill not accept responsibility for loss 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,
WHETHERORAL OR WRITTEN, 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 UNDER THIS WARRANTY SHALL BE
REPAIRORREPLACEMENTASSPECIFIEDHEREIN.
IN NO EVENT WILL DRAWMER ELECTRONICS LTD. BE
LIABLEFORANYDIRECT,INDIRECT,SPECIAL,INCIDENTAL
ORCONSEQUENTIALDAMAGESRESULTING FROMANY
DEFECT IN THE PRODUCT, INCLUDING LOST PROFITS,
DAMAGETOPROPERTY,AND,TOTHEEXTENTPERMITTED
BY LAW, DAMAGE FOR PERSONAL INJURY, EVEN IF
DRAWMERHASBEEN ADVISED OFTHEPOSSIBILITY OF
SUCHDAMAGES.
Somestates andspecific countries do not allow the 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 that varyfromstate to 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 82011 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
1968 MkII
DualChannel
VacuumTubeCompressor
SAFETY CONSIDERATIONS
CAUTION-MAINSFUSE
TO REDUCE THE RISK OF FIRE
REPLACETHE MAINS FUSE ONLYWITH
AFUSE THATCONFORMS TO IEC127-2.
250 VOLTWORKING, TIME DELAY TYPE
AND BODY SIZE OF 20mm x 5mm.
THEMAINS INPUT FUSEMUST BE
RATED AT 230V=T160mA and 115V=T315mA.
CAUTION-MAINSCABLE
DO NOTATTEMPT TO CHANGE
OR TAMPER WITH THE
SUPPLIEDMAINS CABLE.
CAUTION-SERVICING
DO NOT PERFORM ANY SERVICING.
REFERALL SERVICINGTO QUALIFIED
SERVICE PERSONNEL.
WARNING
TO REDUCE THE RISK OF FIRE OR
ELECTRIC SHOCK DO NOT EXPOSE
THISEQUIPMENT TORAIN ORMOISTURE.

3
DRAWMER 1968MkII OPERATOR’S MANUAL
DRAWMER
1968 MkII
DUAL CHANNEL VACUUM TUBE COMPRESSOR
The 1968 MkII is a 1U Tube/FET dual channel / ‘stereo
bus’ compressor which by design delivers a transparent
‘open’sound even during periodsofheavy compression.
TheoriginalDrawmer 1960 used a tube stage at the front
of the compressor, whilst the 1968 MkII utilisies a J-FET
(FieldEffectTransistor)gainreductioncircuitthat operates
fasterthanan opto-isolator.Thecompressor usesa12AX7
tube makeup gain amplifier where you can add, with the
Output Gain control, up to 20 dB of additional gain.
The need for a ratio control has been removed as the
compressoroperates on the softkneeprinciple where the
onsetofcompression is progressive.
The 1968 MkII expands attack times to six choices: 2, 9,
15, 25, 30 and 50 ms. Release times come in three fixed
times(100ms,500 ms and 1 second) and three program-
dependent choices--200 ms to 2 sec, 500 ms to 5 sec
and 1 to 10 seconds--all program-dependent and
automatic.
The1968MkIIprovidesfullsidechainaccessforconnecting
CHAPTER 1
INTRODUCTION
anexternalequalizerforvocalstressing or de-essing.
Featured on both channels is a switchable ‘BIG’ and
‘BIGGER’ mode which applies less processing to the
fundamental low frequency but still disciplines the upward
associated harmonics which if untamed can result in a
‘boomy’ or ‘boxy’ sound. The result - a solid bottom end
withenhanced sub-bassanda smoother,wider frequency
response overall. This lets the operator use more
compression on an overall mix with less pumping action
caused by a kick and/or bass instrument.
The outputs of Channels 1 and 2 are monitored on two
yellowilluminated VU meters - with a redwarningglow to
signify ‘approaching clipping’. A three-position switch
adjuststhe metersto showeithernormal outputlevel, gain
reduction or VU +10dB mode, which re-scales the meter
for users working at ‘hot’ output levels.
Anoutput switch selectsnormal compressor output,hard-
wired bypass and sidechain listen.
Thekey features are as follows:
•2 ChannelTube/FETCompressor
•2 soft-knee compressors with variable threshold, attack, release and output gain
•Switchable BIG and BIGGER control on each channel
•Dual mono or true stereo link operation
• Side chain access and side chain listen facility
•VUmeteringofgainreduction and output levels
• Switchable +10dB mode on VU re-scales the meter for users working at ‘hot’ output levels.
•VUredwarningglowtosignify‘approachingclipping’
• Balanced +4dB XLR in/outs

4DRAWMER 1968MkII OPERATOR’S MANUAL
The1968 MkII isdesigned for standard19"rack mounting
and occupies 1U of rack space. Avoid mounting the unit
directly above power amplifiers or power supplies that
radiate significant amounts of heat and 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. Because the tube circuitry generates
more heat than an equivalent solid-state design, it is
advisabletoleavespaceabovetheunittoallowtheheatto
dissipate.
INSTALLATION
AUDIO CONNECTIONS
Theinputs and outputs areelectronicallybalanced on conventionallywiredXLRs (pin 1 screen,pin2 hot, pin 3cold and
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
highlevels of disturbance suchas found close toaTV
or radio transmitter, we advise that the unit is oper-
ated in a balanced configuration. The screens of the
signalcables shouldbeconnected tothechassis con-
nectionon the XLRconnector as opposedtoconnect-
ingtopin1.The 1968MkII conformsto theEMC stand-
ards.
•GroundLoops:
If ground loop problems are encountered, never dis-
connect the mains earth, but instead, try disconnect-
ingthe signal screen onone end of eachofthe cables
connecting the outputs of the 1968 MkII to the
patchbay. If such measures are necessary,balanced
operationis recommended.
fig.1 1968 MkII WIRING
Thesidechainfeatureonthe 1968 MkII is part of the compressor feedback stage and would normally be connected to
anormalisedorsemi-normalised pair of patchbay contacts. This would allow the user to insert additional EQ for some
de-essing,orfrequency consciouscompression.Theside-chainaccesspointisunbalanced,connectionisviastereo
1/4" jacks, the wiring convention being: ring is signal send, tip is signal return and sleeve ground.

5
DRAWMER 1968MkII OPERATOR’S MANUAL
The1968 MkII unit will be suppliedwitha power cable suitablefordomestic power outletsinyourcountry.For yourown
safety, it is importantthatyou use this cable to connect to the mainssupplyearth.The cable must not be tamperedwith
ormodified.
The power supply socket has an integral fuse drawer containing the power fuse of the same value, to suit the mains
voltageforwhich the unit has been supplied. Removalofthedrawer is only possible with the power cordremoved.The
fuseshould never blow undernormaloperation. If the fuseissuspected of having blown, then afault will have occurred
andthis faultconditionshould beinspected by aqualified serviceengineer.When replacing thefuse, alwayscomplywith
the Safety Instructions.
If the unit is to be used with a mains input operating
voltagedifferentto that for which the unit issupplied,the
following procedure must be carried out by a technically
competentperson, (seefollowingdiagrams)
POWER CONNECTION
1: Disconnect the unit from the mains.
2: Using a number 1 size pozidrive screwdriver,
removethesevenself-tapping screwsthat retainthe
topcover.Twoscrewsarefoundalongeach side;two
alongthe top edgeatthe rear; andtheupper central
screwonthe front facia panel.
3: Slide the voltage change-over switch (SW8) until
thecorrect (ornearest)mains input voltageis visible
on the switch actuator.
(seefig.2)
For conversion to 115Volt AC (previously set to
230VoltAC).....
4a: Exchange the 160mA fuse below the mains
socket for a similar type rated at 315mA
For conversion to 230Volt AC (previously set to
115VoltAC).....
4b: Exchange the 315mA fuse below the mains
socket for a similar type rated at 160mA
In all cases:
5: Replace the top cover using the seven screws.
6: Re-connect to mains power source. Fuse
fig.2 The Voltage Selector Switch
fig.3 The Location of the Fuse

6DRAWMER 1968MkII OPERATOR’S MANUAL
CONTROL DESCRIPTION
Threshold: Determinestheinputlevelabove whichgain reductionwill beapplied andmaybe
setintherange-30dBtoinfinity. Because the compression system is based on
the Soft Knee principle, the onset of compression is progressive, so no Ratio
control is necessary.
Big: Makes the compressor side chain less sensitive to low bass frequencies, so
reducingthe ducking effect caused by bass energyandeffectively boosting the
bass output, the ‘Bigger’ option more so.
Attack: SixswitchableAttack settings are provided giving various settings.Theactual
attacktime is further modified by the release setting chosen
AttackTimes: 12 ms
28 msec
315 msec
425 msec
530 msec
650 msec
Release: Therearethree fixed Release times and a further threewhichare programme
dependent.Switchsettings 1 through to 3 provide progressively increasing
release times, while positions 4, 5 and 6 cause the release times to vary in a
manner which automatically adapts to the dynamics of the incoming signal, as
detailedbelow.
Release Times 1100 ms (Fixed)
2500 msec (Fixed)
31 sec (Fixed)
4Semi-Auto 200 ms to 2 sec Signal dependent
5Semi-Auto 500 ms to 5 sec signal dependent
6Automatic 1 sec to 10 sec signal dependent
CHAPTER 2

7
DRAWMER 1968MkII OPERATOR’S MANUAL
Initially, set theAttack selector to 3 (a Medium position) and set Release to
6(Programme Dependent).
Set the Mode switch to Normal and the Meter switch to GR.
Withprogrammematerialplaying, adjusttheThresholdcontroluntilthedesired
amount of gain reduction registers on the meters.
Use the Output Gain control to restore any level lost due to compression.
If necessary, change the Attack and Release settings to suit the material.
THE QUICK SETUP PROCEDURE
Usethefollowingproceduretosetupthecompressor.
Output:(Gain) The Output level may be amplified, or attenuated by upto20dBtocompensate
forlevel changes caused by compression.
VU Meter A moving coil VU meter monitors either the level of the output signal or the
amountofgain reductiontakingplace.BecausethemeterhasVU characteristics,
it closely reflects what is actually being heard, though will not respond quickly
enough to register short signal peaks.
VU +10dB/VU / GR A three-position switch adjusts the meters to show either normal output level,
gainreductionor VU +10dB mode, which re-scales themeterforusers working
at‘hot’ output levels. In otherwords,with the switch atVU+10dB - when the VU
meter reads 0dB the actual level is +10dB.
Side Chain/Norm/Bypass S/C Listen routesthe side-chainsignal directly totheoutput allowingtheeffects
of any additional side-chain processing, such as equalisation, to be monitored.
Normal mode, the signal is passed through the compressor.
Bypass takes the compressor and the vacuum tubes out of circuit path; the
output signal is taken from the channel input point.
Stereo Link ThismakesChannel 1 controls the stereo master and disablesthecompressor
stage of channel 2 when the unit is used for processing a stereo signal. Since
thesame gain reduction isappliedto both audio channelsno image shifting can
occur.
•
•
•
•
•

8DRAWMER 1968MkII OPERATOR’S MANUAL
IF AFAULT 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
containersforprotection. If the unit isto be returned, the original
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 3
INPUT IMPEDANCE
Input Impedance 20k Ohms
Maximum Input Level +20dBu
OUTPUT
Output Impedance 50 Ohms
Maximum Output Level +21dBu
BANDWIDTH <17Hz to 28kHz -1dB
<10Hz to 47kHz -3dB
UNITY GAIN NOISE
22Hz - 22kHz (RMS) -85dB
CROSSTALK better than 70dB @ 10kHz
better than 100dB @ 1kHz
1968 MkII DUAL CHANNEL VACUUM TUBE COMPRESSOR
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.
DISTORTION (THD & Noise) 1kHz
Line Input with BYPASS selected <0.01%
Line Input with NORMAL selected <0.35%
POWER REQUIREMENTS
230Volt or 115V at 50-60hZ, 13VA
FUSE RATING
160mA for 230Volt, 315mA for 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 225mm (D)
WEIGHT 4Kgs

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DRAWMER 1968MkII OPERATOR’S MANUAL
BLOCKDIAGRAM
1968mkII ver 04 B 26/03/13

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DRAWMER 1968MkII OPERATOR’S MANUAL