Chiswick Reach Stereo Valve User manual

Studio
Manual
version 2.0
chiswick reach
stereo valve compressor

Contents
1.Introductionpage 3
2.Installation &
Connections page 4
3.Controls page 7
4.Driving the
Compressor page 9
5.Maintenance page 11
6.Troubleshooting page 14
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1. Introduction
The Chiswick Reach Compressor is a high quality, all valve,
hand built studio tool. Developed as the result of over sixty five
man years experience working with professional valve rec-
ording equipment, we believe you will find it an invaluable
tool in your production arsenal.
It is important however that some fundamental differences
between solid state and valve equipment are appreciated,
so please READ THIS MANUAL!
The primary reason for using valve equipment is the quality
of the sound that is obtained, and the forgiving nature of this
technology on the signal. As with all matters involving the
subjectivity of the senses when quality is the issue; the
Thermionic -Vs- Solid State debate with its theories, sceptics
and believers, will continue.
We Believe.
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2. Installation &
Connections
2.1 Installation
Important! Serious consideration should be paid to the
positioning of the compressor. All electronic equipment
produces heat, and valve devices produce lots of it! In rack
bays it is advisable to site towards the top of the rack frame
and ensure that there is adequate air flow round the unit.
We advise that a 1U vent panel is installed above the unit in
racks containing large amounts of equipment, or those racks
that are very enclosed. Vent panels are available from most
rack manufacturers and professional audio equipment
stockists. In extreme cases fan cooling of the rack should be
considered; although most sound engineers dislike fans due to
the noise produced. The penalties of badly vented equipment
will be premature ageing of the components, lowered valve
life and loss of performance. This will be a slow process and
will not be noticed initially but can occur. Heat can also
adversely affect other equipment too…
…you have been warned!
We would suggest that some form of rear support be used
- preferably a racking tray - to support the weight (11.2kg) of
the unit, arising mainly from the input & output transformers.
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2.2 Connections
All connections to the compressor are on the rear chassis,
together with the two fuse holders.
Signal connectors are XLR type and are wired to the following
convention:
• Pin 1 Ground. Pin 2 Hot. Pin 3 Cold.
• Input and output are wired floating balanced.
• Signal ground is floating with respect to chassis.
Mains power input connector is a European standard IEC 3 pin
socket centre pin ground.
WARNING!
~ MAINS POWER GROUND MUST BE CONNECTED ~
It is also advisable to ground the chassis in the rack installation
if this method of mounting is used.
All European models are equipped for use with 240/220 volt
supplies only. Dual voltage available by special request.
Export models for the U.S.A. and Canada are fitted with
240/120 volt transformers and are dispatched wired for
120 volt AC mains supplies.
rear view
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Input Level (Right Channel)
Input Level (Left Channel) Indicator
Stereo Link
ThresholdRelease
Output
Attack
Bypass
Threshold
Input Atten.
Attack Release
Power Panel Meter
Output Bypass
Input Atten.
3. Controls
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3.Controls
To understand the function of the controls in this equipment,
we will follow the signal path from input to output and
examine each control’s effect on the signal as we progress.
Bypass: After the signal enters the compressor, the first control
in the path is the Bypass switch. Operating to the ‘down’
position removes the output from the compressor and connects
the output socket directly to the input socket. The input is still
receiving signal, enabling rough setup adjustments to be made.
Be warned that it is possible the output level will be higher than
the input level, depending on the other control settings. This will
become apparent when re-inserting the compressor but the
Output control can be used to adjust for this.
Input Atten: When operated in the down position this gives
a 10dB reduction of the input signal before the Input control
and input transformer. This is useful in allowing the Input
control to be operated at sensible mid settings when using
high level sources and avoiding possible high level transient
signals saturating the input transformer.
Input Control: Quite obviously this controls the signal level
into the compressor and as previously mentioned is before the
input transformer. As rotary potentiometers are notorious for
having tracking errors at the extremes of rotation it is
advisable to operate the control away from these extremes if
possible, especially when using the compressor in the stereo
mode. The input controls are factory matched to minimise
these effects.
Threshold: This controls the sensitivity of the compression
circuitry and sets the level at which compression begins
relative to the input signal. Advancing the control clockwise
causes the onset of compression to occur at lower signal
levels and the output level will fall.
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Attack: Controls the speed at which compression takes effect.
Advancing the control clockwise speeds up the attack time so that
the compressor controls signals faster, allowing less of the initial
transient through controlled. Turning the knob to the Thump
position operates a switch that changes the way that the control
circuit behaves and can be useful as a production effect on
certain programme material.
Release: Varies the time taken for the compressor to recover full
amplification when the signal falls below the compression
threshold. Advancing the control clockwise speeds this process up.
The release time is variable between 2.5 seconds and 0.25
seconds.
Output: This is a balanced switched attenuator connected
between the output transformer and the output socket. Attenuation
is variable in 4dB steps between -8dB and +4dB.
Panel Meter: This is an electronically biased meter that directly
indicates the amount of gain reduction in dBs that the compressor
is achieving. For adjustment of the ‘zero’ position see the
Maintenance section.
Meter Presets: Located in the centre of the panel below the
Power and Stereo Link switches. Top preset adjusts the right hand
meter, bottom preset the left hand meter.
Stereo Link: In the ‘down’ position this switch connects the
control circuits in both compressor channels together. this function
is useful when treating a stereo signal and avoids “image
wandering” by applying equal gain reduction to both channels.
Power: Operating the switch to the down position allows mains
AC power to flow, linking the wonderful thermionic devices
together with the Indicator neon. Slowly electrons start to get very
excited, the panel meters rise to the ‘0’ position and the com-
pressor is ready for use. Provided the mains power is plugged in
or a fuse has not blown, of course! (see Maintenance section).
Indicator: Located in the Chiswick Reach logo on the front panel -
should glow orange! The logo is a stylised map of the very spot on
the banks of the river Thames where the compressor was conceived.
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4. Driving the
Compressor
Depending on the requirement for using compression, circum-
stances will dictate the settings. For example in a mastering or
copying requirement:- light compression may be required with
‘stereo linking’ to take care of any slight over-peaking of the
programme material. On the other hand, in a track laying
session extreme compression is often applied to instruments.
In a production sense the rule is:- there are no rules!
As a guide however, here are some settings we have found
useful in the studio:-
Drums
Snare...................Input Atten. ............To taste
Input Level..............To taste
Threshold................6
Attack.....................’Fast’ - tune to taste
Release...................’Fast’
Output Atten. ..........Use to reduce Output level
Kick.....................Input Atten. ............To taste
Input Level..............To taste
Threshold............... 4 - 5
Attack....................’Slow’ - to taste
Release..................’Fast’
Output Atten. ..........If required
Overheads..........Input Atten. ............To taste
Input Level..............Set after other adjustments to
obtain 2 - 4 dBs gain reduction
Threshold................7+
Attack.....................’Fast’ - tune to taste
Release...................’Fast’ - tune to taste
Output Atten. .........Use to reduce Output level
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Light...................Input Atten. .............To taste
Stereo Input Level..............To taste
Master Threshold................7
Mix Attack.....................’Med Fast’ - ‘Fast’
Release..................Set to taste i.e. Lively sound set ‘Fast’ -
Dense sound set ‘Slow’
Output Atten. .........As required
~ Match both levels of both channels
before switching stereo link in ~
Heavy................Input Atten. ............To taste
Guitar Input Level...............To taste
Threshold................5
Attack.....................5
Release...................10
Output Atten. .........Use to reduce Output level
Bass...................Input Atten. ............To taste
Guitar Input Level..............To taste
Threshold...............5
Attack....................4
Release..................9 - 10
Output Atten. ........ In as required
Big rich..............Input Atten. ............To taste
‘Hammond’ Input Level..............To taste
Threshold................6
Attack....................’Thump’
Release.................. 9-10
Output Atten. .........Use to reduce Output level
Vocals
‘Light’................Input Atten. ............To taste
Input Level..............To taste
Threshold............... 6 - 7
Attack....................’Fast’ - ‘Medium’
Release..................Breathy = Fast. Smooth = 9-10
Output Atten. .........If required
‘Heavy’..............Input Atten. ...........Out
Input Level..............4 - 5
Threshold...............4 - 6
Attack....................Fast
Release...................Medium Fast.
Output Atten. .........Reduce as required
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5. Maintenance
First, a WARNING! POTENTIALLY LETHAL VOLTAGES
ARE PRESENT INSIDE THIS EQUIPMENT! REPAIR
WORK SHOULD BE CARRIED OUT ONLY BY
QUALIFIED PERSONNEL. Valve technologies by their very
nature use high voltages, the high tension rail in the unit has
over 300 volts DC present in use. Even after disconnection
from the mains these voltages will persist for a period of time
while the safety discharge resistors dissipate the charge.
Before removing any covers allow at least five minutes for
these voltages to subside. Always check with voltmeter or
insulated shorting stick that the H.T. capacitors are
discharged before touching any part of the circuitry.
5.1 Valves
In normal use we hope this unit will prove trouble free, but
unlike solid state equipment (which also goes wrong from
time to time!), valves slowly age in use and this will change
their operating parameters. From time to time valves will
require replacement and it is important to note that the
valves in this unit are all SELECTED AND MATCHED on
test in the unit to obtain optimum performance. If a problem
is suspected with any valve, substitution from the other
channel can be used to prove the fault; BUT before making
any such move, the valves should be marked beforehand
and replaced in the original position to retain best
performance. After replacement of any valve the unit should
be checked and if required realigned for best distortion,
gain and tracking match with the other channel. It is ad-
visable to obtain several possible replacement valves since
parameters vary from manufacturer and batch to batch;
ideally, replace with the same make as installed in the unit.
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5.2 Meter Alignment
Under no circumstances use the meter mechanical
adjustments on the meter front to correct readings.
The electronically ‘zero biased’ meter settings will require
periodic re-adjustment. The metering circuit is necessarily very
sensitive, change from the ‘zero’ position is quite normal and
is not a cause for concern. The causes are normally slight
changes in valve performance due to ageing or variations in
the mains supply voltage.
5.3 Meter Adjustment
Procedure:
1. Turn power on, wait for five minutes for the unit to warm up.
2. While waiting, make tea or other refreshing beverage.
3. With no signals present at the input, ensure Input Level
controls are turned right down.
4. Set Threshold to ‘zero’, Attack to ‘Fast’, Release to ‘Slow’.
5. Ensure Stereo Link switch is in ‘up’ position (no linking).
6. Use a trimming tool or small instrument screwdriver turn the
appropriate multiturn preset located on the front panel below
the Power and Stereo Link switches until the meter needle
is at the ‘0’ position on the scale.
7. Repeat procedure to other channel.
8. Drink tea or other beverage.
5.4 Distortion Trim
Always get this done if a signal valve has been changed.
This procedure should be carried out by qualified personnel only.
Test Equipment required:
Low distortion Audio signal generator.
Distortion Analyzer or Meter Trimming tool.
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5.4 Distortion Trim continued…
Procedure:
Connect generator to input of compressor.
Connect Analyzer or distortion meter to output.
Ensure the compressor has warmed up for at least five minutes.
Set generator for 1 Khz and +4dBm output.
Set Threshold to 5.
Set Attack to ‘Fast’, Release to ‘Slow’.
Adjust Input Level control to obtain 2 dB of gain reduction.
Ensure Stereo Link switch is in the ‘up’ position (no linking).
Adjust the presets with a trimming tool or instrument screwdriver
shaft which are inside the hole in the black plastic nuts (one for
each channel) located on the valve deck, for minimum distortion.
Note: If using an analyzer which displays harmonic analysis
adjust for minimum odd order distortion.
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6.Trouble Shooting
O.K. we know… It’s the last day of the mix sessions……the
killer track’s just come together……the compressor’s failed, it’s
use is essential and you’re NO technician; ……you hunt the
manual out, skimming through, frantic for a clue .…only to find
the damn manual is waiting for you …… Gees!
BEFORE PROCEEDING READ THE WARNING AT THE
BEGINNING OF THE SECTION ON MAINTENANCE.
6.1 Check List
• Problem Affects BOTH channels.
Is the power getting in? Check by moving the power lead
to another bit of gear, does it power that? Yes? - Proceed.
No ? - Replace plug fuse, or replace power lead.
Is the panel INDICATOR glowing orange? Yes? - Power is get-
ting in. Proceed. No? - Mains fuse back panel (1 amp) blown,
replace with correct fuse. Mains switch not on or faulty. Neon
indicator faulty in which case are the valves glowing orange?
No? - Mains transformer fault possibly, seek technical advice.
Valves are glowing……meters reading ‘0’ ? Yes? - Proceed.
Meters moving in time to the music. Proceed. Meter reading
below 25, H.T. fuse (125ma Anti-surge) blown? - Replace.
Fuse OK. Rectifier valve (GZ34) faulty? Is it glowing?
No? - Valve heater fault, or transformer heater supply faulty.
It all glows, and HT fuse is OK, both channels are out. Check
that signal is getting to the compressor by plugging the input
and output signal leads together, not that either?…Check the
settings, then……seek technical advice.
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6.2 Check List
• Problem affects ONE Channel.
Meter reading ‘0’ - check that the signal is getting to the compressor
by plugging the input and output signal leads together, OK? Check
the Bypass switch. Controls set correctly? All valves on this channel
glowing? Fault on Bypass switch or 12AT7/ECC81 output valve
fault, EB91 side chain rectifier valve fault, fault on output transformer
circuit or output attenuator switch……seek technical advice.
Meter reading below 25; - H.T. fault or 6BQ7 control valve fault.
No? - Oh well…you’ve covered most checks…seek technical advice.
Chiswick Reach Ltd ~ Stereo Valve Compressor
Tel: [phone] Fax: [phone] Mobile: [phone]
E- mail: [email protected] or [email protected]
Extra copies of this manual; new Chiswick Reach products info and the latest
reviewscan be found on the Web at: http://www.chiswickreach.co.uk
For more background we recommend the following reading:-
‘Tubes -v- Transistors - Is There an Audible Difference?’ ‘Zen and the Art of Motorcycle Maintenance’
Russell O.Hamm ~ AES Journal Vol 21 No. 4TH May 1973 Robert M. Pirsig ~ ISBN 0552 101664
‘Stu io Manual’ esign by [e-mail] ~ Tel/Fax: [phone]
Printed on 100 gsm ‘Conqueror’ recycled paper ~ please recycle your waste. © Chiswick Reach Ltd. 2000
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