Thermionic Culture The Phoenix Operating Manual

THERMIONIC

CULTURE

TPHE HOENIX

valve compressor

OPERATING MANUAL

WARNING

Please read this operating manual thoroughly before using
the equipment.

To reduce the risk of electric shock, it is essential that the
unit is disconnected from the mains supply before any of the
covers are removed.

Please also note that the power supply capacitors within this
unit can remain charged even after the mains supply has
been disconnected. It is essential that these capacitors are
discharged after the mains supply has been disconnected
and the covers have been removed.

©Thermionic Culture Ltd, January 1999 1

CONTENTS

Section Page
1 Introduction 3

2 Controls & Operation 4

2.1 Output trim 4

2.2 Gain 4

2.3 Attack 4

2.4 Release 4

2.5 Threshold 5

2.6 Bypass 5

2.7 Link 5

2.8 Pre-sets 6

2.9 Meters 6

3 Servicing & Maintenance 7

3.1 Valves 7

3.2 Operating voltage / Fuses 7

4 Specification 8

©Thermionic Culture Ltd, January 1999 2

1 Introduction

The Phoenix is a stereo compressor which can be used as a
pair of mono compressors. It has a ‘soft knee’ or ‘variable
mu’ characteristic in that the compression ratio increases
with the amount of compression being used. Initial
compression is 1.2:1 increasing to 5:1 at 15dB compression.

©Thermionic Culture Ltd, January 1999 3

2 Controls & operation

2.1 Output Trim Control

This control is used to trim the output levels when
compressing a stereo mix. Its function occurs after the
electronics and therefore reduces the maximum output
level (MOL) and noise.

For operation at line level (+4dBV), this control is best
left at around 7. For -10dBV operation it should be set
to 2.

2.2 Gain Control

For line level and medium compression, this control
should be set, typically, to between 3 and 5.

2.3 Attack Control

The attack control varies the rate at which the
compressor starts to react. Attack rates of between
4ms (fully anti-clockwise) and 120ms (fully clockwise)
can be achieved. This control is typically set to 3 for
normal operation. Slow attack rates make the
compressor less efficient, but can be effective for
percussion.

2.4 Release Control

The release control varies the rate at which the
compressor ‘lets go’ of the input signal. Release varies
from 60ms (fully anti-clockwise) to 2.2s (fully
clockwise), typically. Faster release times can give
rise to low frequency distortion. A typical setting for
normal operation of the release control is 3.

©Thermionic Culture Ltd, January 1999 4

N.B. The compressor will become inefficient if very
slow attack and very fast release times are used.
However, this can be used to advantage if ‘thumping’
bass effects are required.

2.5 Threshold Control

The threshold control is used to adjust the amount of
compression in conjunction with the input level. With
the control in the fully clockwise position, there will be
no compression. Turning the control anti-clockwise
increases the amount of compression.

2.6 Bypass

This control totally bypasses the compressors, by
linking the inputs to the outputs.

2.7 Link

Links the two compressors for compressing a stereo
track. All controls are still in use, so both channels
should be set to around the same setting. Ideally, a
1kHz tone should be used to setup the levels so that
both channels’ inputs and outputs are equal. In
practice, this is not always necessary.

In another application, the link control can be used to
allow one compressor to control the other in a mono
application. For example, to increase the high end
compression, use the channel 1 compressor as the
signal path and feed an equalised version of the same
signal with additional top lift into channel 2. Turn off
the compression to channel 1 by turning the threshold
control fully clockwise. The opposite applies to

©Thermionic Culture Ltd, January 1999 5

channel 2. Channel 2 controls channel 1 when link is
in.

2.8 Pre-sets

There are four pre-sets on the compressor chassis.
The two just behind the front panel controls are to
adjust for minimum low frequency distortion. They are
set up with an oscilloscope for minimum distortion and
phase shift at 40Hz. These pre-sets should not be
adjusted, unless the valves are changed.

The two pre-sets behind the meters are used to adjust
the zero points of the meters. They can be adjusted
with a long thin screwdriver, without removing the top
cover of the compressor. Zero readings will vary a little
with mains voltage and valve ageing. The zero setting
is not critical, but both must be the same if
compressing a stereo track.

2.9 Meters

The Phoenix can operate much faster than the meters
will read.

The meter scales should be used as a guide. Actual
compression will vary slightly with individual valves
and the meters may not be accurate at high readings.

©Thermionic Culture Ltd, January 1999 6

3 Servicing & Maintenance

3.1 Valves

All valves are selected to ensure that the unit gives
optimum performance. Input valves are always
matched when the unit is calibrated to ensure
consistent performance across both channels.

Although Thermionic Culture Ltd guarantees the
valves for twelve months, they can last for up to
twenty years.

Spares can be obtained in matched pairs from
Thermionic Culture Ltd.

3.2 Operating voltage / Fuses

The Phoenix Valve Compressor is factory set to
operate from a 230V 50/60Hz AC mains supply It can
be set to operate from 115V AC by sliding the voltage
selector switch on the rear panel to the ‘115V’
position.

NOTE: If the mains supply voltage is reduced to 115V,
then the mains fuse MUST be increased to 1.6A in
accordance with the following table:

Operating Voltage Fuse Rating

115V T1.6A 20mm type
230V T800mA 20mm type

©Thermionic Culture Ltd, January 1999 7

4 Specification

Max. o/p level (MOL): +19dB into 600Ω
+24dB into 10kΩ

Max gain: 30dB.

THD (at no compression): better than 0.09% @ 1kHz

0.1% @ 100Hz

Noise, IEC weighted: 95dB below MOL.

Input impedance: 15kΩ.

Frequency response: <1dB variation over range of
12Hz to 56kHz.

Attack time: 0.004s to 0.12s

Release time: 0.06s to 2.2s

Output impedance: 600Ω

Distortion will increase with compression, typically 0.2% &

0.25% at 1kHz & 100Hz with 8dB compression.

VALVE COMPLEMENT (2 ea):

Input/Compression: 6BQ7A (equiv. CV5365) or
PCC85 (equiv. 9AQ8) in units
with ‘P’ suffix to serial number.
NB. These must be accurately
matched.

Output: 12AT7 (equiv. ECC81, CV4024,
33A/101K etc.).

Side chain detector: 6AL5 (equiv. EB91, CV4007,

CV4025).

©Thermionic Culture Ltd, January 1999 8

Thermionic Culture Ltd. 83 Collins Meadow, Harlow, Essex, CM19 4EL, UK

©Thermionic Culture Ltd., January 1999. Printed in UK.

Tel: [phone] Fax: [phone]