Thermionic Culture The Purple Bustard User manual
e rple Busrd
Thermionic Culture Ltd, April 2018 1
WARNING
For your personal safety, please read this operating manual
and warning thoroughly before using the equipment.
This unit must be installed in such a manner that operator
access to the mains plug is maintained. Where the product is
to be rack mounted, this may be achieved by having access to
the disconnection device for the whole rack.
To reduce the risk of electric shock, it is essential that the unit
is disconnected from the mains supply before removing the
cover.
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.
In the event that this unit has been dropped or has suffered an
impact, an electrical safety test must be carried out before
reconnection to the mains supply.
This equipment is not intended for use in explosion hazard
environments. It must be used and stored in studio conditions,
such that the ambient relative humidity does not exceed 80%,
nor is the temperature to be allowed to drop to a level, which
would cause dew point to be reached.
It is not advisable to operate this equipment if all valves are not
in place and working, as voltages will rise and components
may overheat and fail.
Thermionic Culture Ltd, April 2018 2
CONTENTS
Section Page
1 Introduction 3
2 Controls 4
2.1 Channels 1 to 12 4
2.2 Channels 13 to 16 4
2.3 Attitude 4
2.4 Air 4
2.5 Output Level 4
3 The Eyes 5
4 Inputs and Outputs 6
5 Servicing and Maintenance 7
5.1 Valves 7
5.2 Operating Voltage / Fuse 7
6 Specification 8
Thermionic Culture Ltd, April 2018 3
1 Introduction
The Purple Bustard is a compact version of the Fat Bustard
summing mixer. It has more inputs – there are 16 in all. These
come in on semi floating XLR’s and are switched in as required.
The last 4 (Channels 13 – 16) can be switched to centre.
There is no individual level control over any input. The only
controls are ‘Attitude’, ‘Air’ and Output Levels.
We have provided some simple but unique indication of level at
the stereo output by using multicoloured LEDs in the eyes of
The Purple Bustard icon.
Output levels are on XLRs – unbalanced.
A ‘balancing box containing 2 Sowter 1:1 transformers can be
supplied.
The Purple Bustard can easily drive a DAW to full level without
saturation, or it can be plugged into the aux inputs on a Fat
Bustard to give 28 input channels.
Thermionic Culture Ltd, April 2018 4
2 Controls
U2.1 Channels 1 to 12
These channels come as fixed gain stereo pairs. Each pair
of channels has an on/off switch. The switch cuts the
signal from the mix bus when off and the signal is present
at unity gain, (at attitude setting 1) when the switch is on.
U2.2 Channels 13 to 16
These are as 2.1 Channels but have a mono switch which
switches to centre each pair of channels.
U2.3 Attitude
This control is a clone from the Fat Bustard and provides
exactly the same 2nd harmonics as are found in it’s big
brother.
Ranging from 0.01% to 5+% it’s a very useful tool to add
‘character’ to a mix.
Frequency response is a little restricted at high ‘Attitude
levels so the sound is more ‘valvey’.
2.4 Air
The ‘Air’ control provides a boost of higher frequencies
( above 7 kHz ) and it peaks at around 30kHz – well above
the range of human hearing. Because the sound of valves
is soft rather than hard solid state the use of this can create
a lovely velvety sheen to the mix.,
U2.5 Output Level
These controls vary the signal level going to each output
level. They are indented pots for easy recall. Set to zero
the input on any 2 channels will equal the output with
Attitude at 1 and Output |Levels at 0 dB.
As the Attitude is increased the gain will increase by up to
12dB, so levels will have to be reduced.
Thermionic Culture Ltd, April 2018 5
3 The Eyes
The multicoloured LEDs situated in the eyes of The Purple
Bustard icon, provide a simple indication of level at the stereo
output before the output level pots. The ranges shown are:
Yellow for signal present
Green for optimal signal level (0 dBu to +10 dBu)
Red for high signal level (+10 dBu upwards)
Obviously, the higher the signal level goes, the more likely it is
that there will be distortion and the associated second
harmonics found in triode valve output stages at high levels.
However, we have chosen not to make this a serious feature of
The Purple Bustard due to our choice of output valves. The
Purple Bustard stays remarkably distortion free provided that
the input stages are not overloaded.
For cleanest results, keep the Output Level controls high,
unless you are adding extra attitude.
Thermionic Culture Ltd, April 2018 6
4 Inputs & Outputs
All audio connectors are standard XLR type.
The Purple Bustard, as the Fat Bustard, works on an
unbalanced system.
The 16 input connectors are wired Pin 1 Earth, Pin 2 Signal
('hot') and Pin 3 Signal negative ('cold'). Pins 1 & 3 are
connected by a small resistor, which means that The Purple
Bustard will accept outputs from electronically balanced sources
(certain DAWs) without quality deterioration, as well as
unbalanced and transformer balanced sources.
The output XLRs are wired Pin 2 Signal, pins 1 & 3 shorted to
Earth.
Thermionic Culture Ltd, April 2018 7
5 Servicing & Maintenance
The unit comes with a 12 month warranty covering all parts,
including valves. It is essential that it is returned to our factory or to
the dealer from which it was purchased for repairs to be carried out
otherwise the warranty is invalidated. There is, however, one
important exception to this rule:
U5.1 Valves
It is safe for the user to change the valves, but the unit must
not be operated without all valves plugged in. If a fault
occurs, it may be a valve, so unplug the mains, remove the
top cover, and wait for the valves to cool down a little. DO
NOT touch any part of the circuit board.
The two input valves are in screening cans on the left side of
the unit (looking from the front). The 2 Output Valves are a
little to the right of centre and do not have screening cans.
You can swap the valves from side to side to isolate a fault.
For optimum results, if valves are replaced, replace them in
pairs. DO NOT MIX INPUTS WITH OUTPUTS.
Valve complement:
Input - 2 x 5965;
Output - 2 x 6189 / 13D5 / ECC82 /12AU7
U5.2 Operating voltage / Fuse
The Purple Bustard is switch selectable to operate from either
230V or 115V 50/60Hz AC mains supply.
NOTE: Mains fuses may be replaced in accordance with the
following table:
Operating Voltage Fuse Rating
115V T1A 20mm type
230V T0.5A 20mm type
Thermionic Culture Ltd, April 2018 8
6 Specification
Input impedance: 10k
Output impedance: 250. Load impedance should be 2k
or greater.
Distortion and MOL specs are for a load of 10k
Distortion: <0.025% @ +4dBu
(THD, unweighted,
30kHz filter)
Maximum o/p level: +25dBu
(MOL @ 1% distortion)
The following specs are for Attitude 1 setting: -
Noise (30kHz filter): < - 82dBu
Frequency response
+/- 1dB: 12Hz to 55kHz
Phase shift @10kHz: 5% (18°)
Crosstalk: 1kHz < - 60dB
10kHz < - 50dB
Power consumption 35 watts
Weight 5.3 kg
THESE SPECIFICATIONS CAN BE SUBJECT TO CHANGE
Thermionic Culture Ltd., Harlow, Essex, UK
Tel: +44 (0)1279 414770 email: [email protected]
Thermionic Culture Ltd, April 2018. Printed in UK.
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