Thermionic Culture THE FAT BUSTARD II 12 User Manual

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.

The Fat Bustard gets hot! Please ensure that adequate
ventilation is provided and that the ventilation slots are not
obstructed. When rack mounting this equipment, mount it at
the top of the rack, or if there is equipment above it, leave an
air gap of 1U ( 1.75”) for heat to escape. A fan may be
required to provide sufficient airflow. Failure to observe these
precautions may result in damage occurring to the equipment
above and/or to the Fat Bustard.

©Thermionic Culture Ltd, May 2011 1

CONTENTS

Section Page
1 Introduction 3

2 Controls 4

2.1 Attitude 4

2.2 EQ section 4

2.3 Stereo width section 5

2.4 Stereo spread 5

2.5 Bandwidth 5

2.6 Bass to centre 6

2.7 Balance 6

2.8 Output level 6

2.9 Monitor 6

3 Installation Hints 7

3.1 Installation 7

3.2 Power 7

3.3 Inputs 7

3.4 Outputs 7

3.5 Audio Connections 7

3.6 Tips 8

4 Operational Hints 9
5 Inputs and Outputs 10
6 Servicing and Maintenance 11

6.1 Valves 11

6.2 Operating voltage / Fuse 11

7 Specification 12

© Thermionic Culture Ltd, May 2011 2

1 Introduction

The Fat Bustard is a passive input summing mixer that has all
valve summing and output stages. There are 12 input channels
and 2 auxiliary inputs. Included in the output stage are facilities
for stereo EQ, gain, distortion and also control of the stereo /
mono balance over different frequencies. These features are all
tried & tested and are felt to be useful and unique to what the
Fat Bustard offers and what it can be used to achieve.

The Fat Bustard owes its sound largely to the unusual choice of
valves used. The summing / EQ amplifier uses 5965 valves,
only used in audio applications by Fairchild before now. These
excellent valves give smoothness and fatness to the sound. The
output amplifier uses 6SN7 valves. These large output valves
give a huge amount of headroom and a tough punchy
character. The stereo width is controlled by a 12AU7 valve
giving a wide spectrum to the sound.

The Fat Bustard has been left with unbalanced inputs and
output as standard because, after much experimentation, the
sound of the unit was preferred this way.

© Thermionic Culture Ltd, May 2011 3

2 Controls

2.1 Attitude

The Attitude control has the same effect as found in
Thermionic Culture’s Rooster. At low settings (1 is low,
Max is high) the distortion is kept to a minimum and the
frequency response of the unit is very flat. At higher
settings the distortion increases and the frequency
response changes, tending to become less linear at high
frequencies.
At setting 1 on the attitude control the summing amplifier is
working at unity( 0dB ) gain. As the Attitude control is
increased the gain rises to +14dB at the max setting.

2.2 EQ section

The EQ section comprises a Bass lift, Top lift, Bass cut and
Top cut.

The Bass lift and Top lift utilise Thermionic Culture’s own
varislope EQ curves where:-

The Bass lift curve starts to rise at 2kHz at low settings

and at high settings the curve peaks at 50Hz.;

The Top lift curve starts to rise at 800Hz at low settings

and then gives a peak at 10kHz at high settings.

The Bass cut is a stepped switch control. Positions 1 to 3

give a 6dB / octave High pass filter rising in frequency as
the control is increased. Then positions 4 to 6 give a
shelving filter that begins to act higher in frequency as the
control is increased. This is intended to be used with the
Bass lift control, much like classic passive valve EQ
designs whereby a bass cut that acts slightly higher than
the bass lift will give a mid cut, then a bass lift.

© Thermionic Culture Ltd, May 2011 4

The Top cut is also a stepped switch control. It acts in the

same way as the Bass cut control. Positions 1 to 3 give a
6dB / octave low pass filter that decreases in frequency as
the control is increased. Positions 4 to 6 give a shelving
filter that acts lower in frequency the more the control is
increased.

2.3 Stereo Width Section

This section of the Fat Bustard is concerned with adjusting
and tailoring the width of stereo with respect to frequency.
Some features here are very similar to those found in
Elliptical equalisers, most often found in mastering
applications. Specifically vinyl mastering and cutting.

2.4 Stereo Spread

This control can increase the apparent width of stereo at
full bandwidth, or frequencies above a selected point
ascertained by the Bandwidth control. As the Spread
control is increased the stereo width increases from normal
to very exaggerated.
There is an On/Off switch located next to the Spread
control. This takes the Spread in and out of circuit.

2.5 Bandwidth

This control is a stepped switch. At the bottom position the
spread can be increased across all frequencies. Then the
next positions give a high pass filter function to the spread
at frequencies 100Hz, 250Hz, and 3kHz respectively. This
effectively means that at maximum (3kHz) the spread
affects higher frequencies only.

2.6 Bass to centre

This control is a switched step control. At the bottom
position (Full) the stereo is unaffected. At the next position
up frequencies below 100Hz are made Mono whilst

© Thermionic Culture Ltd, May 2011 5

2.7 Balance

2.8 Output Level

2.9 Monitor

frequencies above are stereo. At the next position
frequencies below 200Hz are made Mono. At the last
position all frequencies are Mono.

This control allows a fine control over the left / right balance
of the Fat Bustard. This can be very useful in correcting
any discrepancies of outboard equipment that may be
slightly misaligned with respect to the level of the left and

right hand signals.

This control is a rotary switch that governs the final output
level of the Fat Bustard. The switch is a high quality Elma
switch and gives a smooth precise result.

This controls the level to the monitor output, which is 8 dB
lower than the main output. It is switchable (INT/EXT)
between the Fat Bustard output and an external input, and
it is intended that this can be used to compare the original
signal to the playback from the equipment used for the final
master. This is especially useful if a compressor (eg. a
Phoenix) is inserted after The Fat Bustard.

There is a pre-set adjuster near the External Input jacks
which determines the level of signal from the External
Inputs. This should ideally be set up with a tone so that INT
= EXT in level with any inserted equipment in bypass. It
requires an “electrical” type flat-bladed screwdriver.

© Thermionic Culture Ltd, May 2011 6

3 Installation Hints

3.1 Installation

The Fat Bustard is designed for 19" rack mounting and, to

repeat the warning on page 1, must have adequate

ventilation.

3.2 Power

The unit can operate from mains supplies of 220-240V AC
or 110-120V AC, 50/60Hz. Check that the voltage selector
at the back near the power inlet is set to the correct voltage
setting.

3.3 Inputs

All inputs are unbalanced but 'floating' slightly above
ground due to a small resistor. This is connected between
pins 3 & 1 of XLR sockets and between ring and sleeve of

the EXT input jacks. This is to prevent the shorting to

ground of one side of a low impedance electronically
balanced source with consequent loss of quality.

3.4 Outputs

Outputs are unbalanced with XLR main outputs having pins
1&3 shorted. The ring and sleeve on the monitor out jacks
are also shorted.

3.5 Audio Connections

Use standard balanced cables to connect to all audio
equipment, whether balanced or unbalanced. For XLRs
pins 2 & 3 are signal with pin 2 'hot'. Pin 3 is ground. On
jacks, these are standard 0.25” stereo types with the tip
'hot'. Unbalanced jacks can also be used.

© Thermionic Culture Ltd, May 2011 7

3.6 Tips

To minimise the possibility of hum loops, quality loss, or
pick up of unwanted signals, keep cables as short as
reasonably possible. This applies especially to the monitor
outputs which come out at relatively low level and higher
impedance. The power connections to the Fat Bustard and
other equipment connected to it should all come from the
same mains distribution point.

© Thermionic Culture Ltd, May 2011 8

4 Operational Hints

Try increasing the Attitude control for more aggression, punch,
warmth in the sound of a mix.

Bass drums, snare drums and vocals can all benefit from being
sent to a mono channel with pan turned off for more level. This
allows them to be high in the mix without running preceding
outboard equipment unnecessarily hot.

Try using the bass cut shelving positions together with the bass
lift for that classic Pultec style equalisation trick.

A harsh sounding mix can be enhanced by using the stereo
spread control at a frequency above the Full setting on the
bandwidth control. In effect the harsh upper frequencies of the
mono part of the mix will be softened and the stereo part of the
mix will sound more open. Also try adding treble to the mix and
the effec

t on a modern board will be to make it more 'Sixties’

due to the ‘soft’ sound of our ‘varislope’ valve eq. design.

Don’t be afraid to use the top and bottom lift EQ. There is no
extra circuitry in the signal path, so no degradation of the signal
occurs.

Drums can be made more solid by using the bass to centre
control, the low end will sound more focused and feel heavier.

The output valves will handle huge amounts of headroom, so

don’t be afraid to run the Fat Bustard hot. The needles in the

meters won’t bend if you go too far, believe me I’ve tried!!

This unit makes a great sidecar desk when mixing, if you have
the luxury, maybe put your drums through it. Or think of it as a
second mix buss.

It is advisable to mute any channels (or aux) when not in use, to
minimise noise and crosstalk.

© Thermionic Culture Ltd, May 2011 9

5 Inputs & Outputs

The 12 inputs can be connected by the 12 labelled XLR
sockets on the back of the unit.

As the front panel indicates, 8 of these inputs are pairs of
stereo inputs and 4 are mono inputs.

The stereo inputs (channels 1 to 8) have a stereo rotary fader
and a channel on/off switch.

The mono inputs (channels 9 to 12) have a mono rotary fader,
pan pot and channel on/off switch. There is also a Mono/Pan
switch for each mono channel. Set to ‘Pan’, the channel can
be panned left to right with the pan pot. Set to ‘Mono’, the
channel won’t be affected by the pan pot and will go to stereo
centre. The channel will also gain about 3dB of gain.

The 2 auxiliary inputs can be used as either a further 2 inputs
to be summed, or as the interface for the Little Bustard which
will provide the facility to extend the number of input channels
to be summed. There are 2 XLR sockets on the back of the
unit, that are used to connect the auxiliary inputs. When used
as 2 more inputs to be summed they have an on/off switch
each. Also the inputs will normally be configured as Aux 1 to
stereo left and Aux 2 to stereo right. The Aux to centre switch
sends both Aux inputs to stereo centre (mono).

The Fat Bustard has unbalanced inputs and output as
standard because, after much experimentation, the sound of
the unit was preferred this way.

© Thermionic Culture Ltd, May 2011 10

6 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:

6.1 Valves
It is quite 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 and

remove the top cover.

The two input valves are nearest the front panel and there is
one for each channel. Similarly, the two output valves are at
the rear (the large hot ones!).

You can swap the valves from side to side to isolate a fault, in
fact we recommend that you swap the two 5965 valves after
about 18 months to prolong their life.

Valve complement (spares are available from Thermionic
Culture Ltd.):

Input - 2 x 5965;
Output - 2 x 6SN7
Stereo spread 1 x 12AU7 (ECC82)

6.2 Operating voltage / Fuse

The Fat 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 T2.5A 20mm type
230V T1.25A 20mm type

© Thermionic Culture Ltd, May 2011 11

7 Specification

Input impedance: 10kΩ (dependent upon channel and

setting), unbalanced

Output impedance: 600Ω unbalanced

Monitor: 5kΩ unbalanced

Gain (ch. 1-8): 0 at Attitude 1, +11dB at max attitude

Maximum Output level: +25dBU

Distortion: (at Attitude 1) 0.015% +8dBm output
(at Attitude 3) 0.25%
(at max. attitude) ≥1% (dependent on

how hard valves are driven)

Signal to noise: at least 100dB below MOL at Att.1
(IEC weighted)

Freq. response (±1dB): 16Hz to 40kHz (at Attitude 1)

Max bass lift +10dB @ 50Hz

Max top lift: +12db @ 12kHz

Phase shift (10kHz): (at Att.1), 7% (26°)
with EQ flat (at Att. 4), 10% (36°)

Crosstalk: 59dB @ 1kHz, 44dB @ 10kHz.
(average at Att. 1 & 2) Crosstalk will increase at high attitude

settings and when stereo spread
and/or bass to centre controls are
used.

© Thermionic Culture Ltd, May 2011 12

15

The Fat Bustard - frequency response curves

10

5

0

Gain (dB)

-5

-10

-15

-20

Frequency (kHz)

Bass Lift @ Max.
Bass Lift @ 7
Bass Lift @ 2
Top Lift @ Max.
Top Lift @ 7
Top Lift @ 4
Flat
Bass Cut @ 1
Bass Cut @ 2
Bass Cut @ 3
Bass Cut @ 4
Bass Cut @ 5
Bass Cut @ 6
Top Cut @ 1
Top Cut @ 2
Top Cut @ 3
Top Cut @ 4
Top Cut @ 5
Top Cut @ 6

0010111.010.0

Thermionic Culture Ltd., Harlow, Essex, UK

Tel: [phone] Fax: [phone]

© Thermionic Culture Ltd, May 2011. Printed in UK.