Drawmer 1961 Manuel utilisateur

1961

VACUUM TUBE EQUALISER

OPERATORS MANUAL

CONTENTS

SAFETY CONSIDERATIONS page 1

POWER CONNECTION page 2

INSTALLATION page 2

FUSES page 3

INTRODUCTION page 4

APPLICATIONS page 5

CONTROL DESCRIPTIONS page 5

OPERATION page 7

IF A FAULT DEVELOPS page 10

CONTACTING DRAWMER page 10

TECHNICAL SPECIFICATION page 11

BLOCK DIAGRAM page 12

reserved. Under copyright laws, this manual may not be duplicated in whole or in

part without the written consent of Drawmer.

ONE YEAR LIMITED WARRANTY

Drawmer Electronics Ltd., warrants the Drawmer 1961 audio processor 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 remedy and Drawmer’s entire liability under any theory of

liability will be to, at Drawmer’s discretion, repair or replace the product without

charge, or, if not possible, to refund the purchase 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 and insurance charges pre-paid, to Drawmer

Electronics Ltd., Coleman Street, Parkgate, Rotherham, S62 6EL UK. Write the

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. Drawmer will 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, WHETHER ORAL OR

WRITTEN, EXPRESSED, IMPLIED OR STATUTORY. DRAWMER MAKES NO

OTHER WARRANTY EITHER EXPRESS OR IMPLIED, INCLUDING, WITHOUT

LIMITATION, ANY IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS

FOR A PARTICULAR PURPOSE, OR NON-INFRINGEMENT. PURCHASER’S

SOLE AND EXCLUSIVE REMEDY UNDER THIS WARRANTY SHALL BE REPAIR

OR REPLACEMENT AS SPECIFIED HEREIN.

IN NO EVENT WILL DRAWMER ELECTRONICS LTD. BE LIABLE FOR ANY

DIRECT, INDIRECT, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES

RESULTING FROM ANY DEFECT IN THE PRODUCT, INCLUDING LOST

PROFITS, DAMAGE TO PROPERTY, AND, TO THE EXTENT PERMITTED BY

LAW, DAMAGE FOR PERSONAL INJURY, EVEN IF DRAWMER HAS BEEN

ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.

Some states and specific 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 have additional rights that vary from state to state, and country to country.

In the interests of product development, Drawmer reserve the right to modify or

improve specifications of this product at any time, without prior notice.

1961 OPERATORS’ MANUAL 1

DRAWMER 1961

VACUUM TUBE EQUALISER

SAFETY CONSIDERATIONS

CAUTION - MAINS FUSE

TO REDUCE THE RISK OF FIRE REPLACE THE MAINS FUSE ONLY WITH A

FUSE THAT CONFORMS TO IEC 127-2. 250 VOLT WORKING, TIME DELAY

TYPE WITH A BODY SIZE OF 20mm x 5mm.

THE MAINS INPUT FUSE MUST BE RATED AT 250mA WHERE THE MAINS

INPUT VOLTAGE SWITCH IS SET TO 230 VOLTS AC. AND 500mA WHERE

THE MAINS INPUT VOLTAGE IS 115 VOLTS AC.

THE REAR PANEL H.T. FUSE MUST ALWAYS BE RATED AT 50mA,

IRRESPECTIVE OF THE MAINS VOLTAGE SETTING.

CAUTION - MAINS CABLE

DO NOT ATTEMPT TO CHANGE OR TAMPER WITH THE SUPPLIED MAINS

CABLE.

CAUTION - SERVICING

DO NOT PERFORM ANY SERVICING. REFER ALL SERVICING TO

QUALIFIED SERVICE PERSONNEL.

WARNING

TO REDUCE THE RISK OF FIRE OR ELECTRIC SHOCK DO NOT EXPOSE

THIS EQUIPMENT TO RAIN OR MOISTURE.

1961 OPERATORS’ MANUAL2

POWER CONNECTION

The unit will have been supplied with a power cable suitable for domestic power

outlets in your country. For your own safety it is important that you use this cable.

The unit should always be connected to the mains supply earth using this cable.

If for some reason the unit is to be used at a mains input operating voltage which is

different to that as supplied, the following procedure must be carried out. (See

following diagram)

1: Disconnect the unit from the mains.

2: Using a number 1 size pozidrive screwdriver, remove the two self-tapping

screws holding the voltage selection switch cover plate on the rear panel.

3: Remove the cover plate and slide the switch fully to its opposite end.

4: Rotate the cover plate one half turn, (180E) and refit the two screws.

5: Fit a correctly rated fuse for the selected operation voltage.

6: Reconnect to mains power source.

INSTALLATION

The 1961 is designed for standard 19" rack mounting and occupies 2U of rack space.

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, we recommend space be left above the unit to allow

the heat to dissipate.

!Care should be taken in the choice of positioning. The unit should not be

mounted where other equipment obstructs the normal air flow. The unit should

not be situated near any heat source, such as a radiator, stove or a high

power amplifier that would generate heat.

!The appliance should not be operated near any water or in a location where

moisture might be present.

!Always connect the mains earth to the unit.

If the 1961 is to be continuously moved from one location to another, we suggest

using additional support in the rack at the rear of the unit.

1961 OPERATORS’ MANUAL 3

FUSES

The mains fuse should be a class 3, 250 Volt, Time delay type, with a body size of

20mm x 5mm, at the correct rating for the mains input voltage. It is very important

that this fuse complies with IEC127-2. Remember that, in the unlikely event of the

unit developing a fault, it is normal for the mains fuse to blow and the unit must be

serviced by a qualified service technician.

For added protection the 1961 is also fitted with silicon re-setable fuses. Under

certain conditions, - eg. intermittent mains power, faulty mains cable - these fuses

will 'trip', effectively removing power from the internal circuitry. If this should happen,

the silicon fuses will automatically reset after switching off the unit for 15 to 30

seconds and then switching back on again. The fuses will probably never trip.

Occasionally the fuses might trip repetitively due to an internal fault, in which case

the unit will need attention from a service technician before the silicon fuses will

reset.

AUDIO CONNECTIONS

The inputs and outputs are electronically balanced XLRs where pin 1 is screen, pin 2

hot, pin 3 cold and the XLR shell is connected to chassis. The operating level is

nominally +4dBu. Balanced use is recommended. The 1961 fully conforms to the

EMC standards, if you propose to use the unit where it maybe exposed to high levels

of disturbance such as found close to TV and radio transmitters we suggest that the

screen of the signal cable is connected to the chassis connection on the XLR type

connector.

A further connection point is provided in the form of the Audio Insert jack on the rear

panel. This is a stereo jack socket wired such that the Ring carries the input to the

1961 and the Tip carries the output. When a plug is inserted, the XLR input for that

channel is disconnected. The Audio Insert point may be connected directly to the

side-chain access point of a Drawmer 1960 using a stereo jack cable wired with

screened cable where the tip connects to the tip; ring connects to ring and the screen

is connected at both ends. Alternatively, the same type of stereo jack lead may be

used to connect the 1961 Audio Inserts to the +4dBU Signal Insert point of the 1960

allowing the two units to be used in series. In this latter configuration, only the

balanced audio connections of the 1960 are used; the 1961 is connected only via its

Audio insert points.

If earth loop problems are encountered, do not disconnect the mains earth. Try

disconnecting the signal screen on one of the cables connecting the outputs of the

1961 to the patchbay. If such measures are necessary, balanced operation is

recommended.

1961 OPERATORS’ MANUAL4

INTRODUCTION

The Drawmer 1961 is a hybrid, vacuum tube/semi-conductor, dual-channel equaliser

designed to combine the tonal qualities of classic tube circuitry with the low noise

and high reliability associated with contemporary circuit design.

A simple linking facility is included which allows the 1961 to be used in conjunction

with the Drawmer 1960 tube compressor/preamplifier where it may be used either in

the side-chain ( for de-essing, de-popping and so forth ) or in the main signal path for

conventional equalisation.

In addition to tube circuitry being used in each of the four main equaliser bands, a

further tube amplifier is included in the output stage which may be deliberately

overdriven to achieve the warm, detailed sound of vintage classic tube designs.

The filters are based around a specialist adaptation of the gyrator 'virtual inductor'

circuit which faithfully recreates the essential characteristics of a vintage LC

(coil/capacitor) network without incurring the penalties of noise, instability or

susceptibility to magnetic interference. Rather than employ a continuously variable

resistor as a means of frequency control, the 1961 utilises the same rotary 'step'

switching system used in vintage designs. This enables the component values for

each frequency band to be optimised for uncompromising performance across the

entire audio spectrum and also makes setting up more accurate, especially when

treating stereo signals.

The 1961 has numerous applications in studio recording, live sound, location

recording, post-production and as part of a musician's rack system. It has the benefit

of being both simple and intuitive to use and shares the traditional Drawmer styling

adopted for the rest of the product range.

In addition to the four parametric equaliser sections in each channel, the 1961

incorporates both high and low pass, 12 dB per octave shelving filters providing the

user with a very precise means of controlling the cutoff frequency at both ends of the

audio spectrum. All filter bands, including the high and low-pass filters, have

independent Bypass controls and a further Master Bypass switch is provided which

switches the entire equaliser out of circuit making A/B comparison straightforward.

There are six, dual-stage tubes in the audio signal path with low noise microcircuits

used in the input and output balancing stages as well in certain other noise-critical

areas of the design. The input stages feature extremely low noise, balanced input

circuitry which may be switched on the rear panel to accept either -10dBV or +4dBU

signals while a five-section, three-colour LED meter monitors the input signal level (

whether it is fed from the input XLR or the 1960 Insert linking jack ). An Input gain

control provides up to 20dB of further gain and a red peak overload LED warns when

clipping is imminent; a yellow soft-clipping LED shows that the tube circuitry is being

driven to the level where it is producing musically useful harmonic distortion.

1961 OPERATORS’ MANUAL 5

APPLICATIONS

Further to its obvious applications as a general studio equaliser, the 1961 is also

particularly effective as a post-production or mastering tool when used to treat

complete stereo mixes, especially when used in conjunction with the 1960 tube

compressor. Even before EQ is applied, the output tube circuitry may be mildly

overdriven in order to add warmth and depth to the sound, while at the same time,

emphasising mid-range and high-frequency detail. When used in the side-chain of

the 1960 or other suitable compressor, the 1961 provides extremely precise control

of de-essing or de-popping.

CONTROL DESCRIPTION

Both channels of the 1961 are identical and may be used independently, or together

to process a stereo signal. Because the filters use switched frequency controls, it is

easier to set up both channels in an identical manner when processing a stereo

signal such as a completed mix. From left to right, the front panel controls are as

follows:

Input Enables the input gain to be varied over the range -20 to +20 dB.

A five-segment LED meter shows the input level over the range

-10 to +10dB, measured after the input stage but before the

equaliser sections. The optimum setting is when the amber LED

is normally illuminated and the +5dB LED lights occasionally.

High-Pass: This is a continually variable 12dB per octave shelving, high-

pass filter which may be adjusted over the range 15Hz to 500Hz.

In: This Bypass switch, when pushed in will illuminate the red LED,

indicating that the High - Pass is in circuit.

PARAMETRIC FILTERS:

The four filter sections marked Bass, Low-Mid, High-Mid and

Treble constitute a fully parametric equaliser, capable of

providing up to 18dB of cut or boost at the selected frequency as

set by the rotary Hz switch. The six switchable frequencies have

been chosen to correspond to key musical areas in the relevant

area of the musical spectrum. The bandwidth or Q of the filter is

determined by the Octave control which is continuously variable.

This control is calibrated in octaves making it easier to assess

its likely effect in a musical context. Each filter section follows

the same basic layout:

1961 OPERATORS’ MANUAL6

Hz: Frequency selector switch. Available frequencies are:

Frequency

Switch

1st

position

2nd

position

3rd

position

4th

position

5th

position

6th

position

Bass 20Hz 32Hz 50Hz 80Hz 125Hz 200Hz

Low-Mid 100Hz 160Hz 250Hz 400Hz 650Hz 1kHz

High-Mid 500Hz 800Hz 1.2kHz 2kHz 3.2Khz 5kHz

Treble 2.5kHz 4kHz 6kHz 10kHz 15kHz 25kHz

Octave: Filter bandwidth (or 'Q') control. Variable between 0.3 and 3

octaves.

Cut/Boost: Filter cut or boost control providing ±18dB of control.

In: Each filter section has an associated Bypass switch. When the

switch is pushed in, the red LED below will illuminate, indicating

that the equaliser is in circuit.

Low-Pass: This is a continually variable 12dB per octave shelving, low -

pass filter which may be adjusted over the range 2.5kHz to

56kHz.

In: This Bypass switch, when pushed in will illuminate the red LED,

indicating that the Low - Pass is in circuit.

Out: This acts as a Master Bypass switch. If the switch is depressed,

the associated Out LED illuminates. This indicates that all the

equaliser sections, including the high and low-pass filters, are

out of circuit. This Master Bypass switch also bypasses the tube

section of the output stage; if it is desired to use the tube output

stage without equalisation, the EQ Master Bypass should be left

In circuit and all the individual Bypasses should be switched Out

of circuit. When the Master Bypass switch is set to Out, the

individual equaliser status LEDs are extinguished.

1961 OPERATORS’ MANUAL 7

O/L (LED): This Overload red LED illuminates when the tube output stage

is being driven into audible distortion. This may be used as a

creative effect and will not damage the 1961.

Soft (LED): This yellow LED illuminates when the tube output stage is being

driven into 'soft clipping'. This is the area that produces the

classic tube sound, and though a small amount of harmonic

distortion is being added, the result can often sound cleaner and

more detailed than before treatment. This is due to a psycho

acoustic phenomenon whereby the human hearing system

translates musically related, high frequency harmonics as

additional high frequency detail and low frequency, second-

harmonic distortion as an increase in bass projection. Again, this

effect can be fine-tuned by ear, using the Input level control to

set the precise amount of harmonic distortion.

Power: Power switch. A red status LED beneath the switch shows that

the unit is powered up.

OPERATION

The unit should be connected in-line with the signal to be processed either directly or

via suitable insert points. The 1961 may also be linked directly to the Side-Chain

access connector (or to the Audio Insert points) of a Drawmer 1960 tube compressor

via the stereo Audio insert jacks on the 1961 rear panel. This requires only a

standard (tip-wired-to-tip and ring-wired-to-ring) screened stereo jack lead.

For mono operation, each channel of the 1961 may be considered as completely

independent and set up accordingly. For use with stereo signals such as complete

mixes or submixes, both sets of channel controls should be set to the same position

unless there is a specific reason for not doing so.

Setting up is best approached, initially, by switching In one filter section at a time.

Setting the Cut/Boost control to maximum Boost, and then switching through the

available frequencies is the simplest way of identifying the area of the spectrum that

requires attention. Once this has been located, the Cut/Boost control may be set to

produce the required amount of Cut or Boost. The Octave control may then be

adjusted, by listening to the Input signal and rotating the control to the desired

setting: An extreme anticlockwise setting produces the narrowest filter characteristic

which is ideal for 'notching out' troublesome frequencies. However, when the

equaliser is being used in Boost mode, a low Octave setting may produce a honky or

peaky sound unless used in moderation. Medium to wide Octave settings, combined

with modest degrees of Boost, produce the most musical results when it is required

to emphasize a particular range of frequencies. Narrower Octave settings can be

used to emphasize specific instruments such as bass drums or hi-hats, but care must

be taken not to use so much Boost so as to create an unnatural sound - unless this

is the intention! If large amounts of Boost are applied using one or more equaliser

sections, there is a possibility that the signal will be amplified to a point where there

is a danger of clipping. If this occurs, monitor the output O/L and Soft LEDs, and

adjust the Input gain accordingly.

1961 OPERATORS’ MANUAL8

Note that a small amount of deliberately added tube distortion can produce the

flattering effect associated with vintage tube equipment.

The major feature when using the 1961 is that you can control the amount of

enhancement using the Input level control, rather than having to accept what the

equipment gives you! Driving the input until the yellow Soft LED comes on generally

produces the most pleasing result, but this will vary depending on the material being

processed and on the taste of the user. If the red O/L LED flashes, the unit is at, or

very near, clipping. It is possible to add subtle amounts of tube distortion by leaving

the master bypass switch set to In and the individual filter bypass switches set to out.

This leaves only the output tube in circuit. More dramatic colouration may be added

when switching in the individual equalisers; the more EQ Boost applied, the greater

the degree of tube colouration added by the equaliser stage.

Though the 1961 has a very quiet signal path, applying large amounts of high

frequency Boost will emphasise tape hiss and other background noises, especially

during pauses and quiet passages where there is no other sound to mask it. For this

reason, it is unwise to use unnecessary amounts of high end Boost, especially in

areas of the spectrum where there is little or no signal to work on. In the case of

instruments with a limited bandwidth, the noise performance can be improved by

using the Low - Pass filter to 'trim' away the unused top end of the audio spectrum.

The filter frequency should be lowered slowly while monitoring its effect on the

material being processed, so as not to apply filtering and too low a frequency.

Examples of where this may be beneficial are when working on miked electric guitar

sounds or some of the older electric pianos, both of which produce negligible

amounts of energy above 5kHz. Similarly, the High - Pass filter may be used to

remove unwanted bottom end from a sound, for example, the hum from an electric

guitar track or the boxiness from a close-miked acoustic guitar.

Hints on Useful Equalisation Frequencies

!Mains hum in the UK and Europe has a fundamental frequency at 50Hz

and harmonics at 50Hz intervals stretching up throughout the audio

spectrum. By filtering at 50Hz and 100Hz using the narrowest Octave

setting, it is often possible to significantly reduce the perceived level of

hum without unduly affecting the wanted signal. On signals containing

no very low frequencies, the High-Pass filter may also be used. Its

frequency should be set by experimentation so that it is tuned as high

as possible without affecting the bass end of the wanted signal.

!Kick Drums: Rock kick drums often benefit from a slight boost at 80Hz

which produces a tight, punchy sound. However, a deeper sound, more

suited to dance music production, can be achieved by boosting the

bass at 32Hz or 50Hz using a medium Octave setting and

simultaneously applying cut at 160Hz to prevent the mid-range from

becoming too boxy (or honky).

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