TL Audio Ebony A3 User Manual

T L Audio

User Manual

Ebony Series A3 Mono Processor

TL Audio Limited, Letchworth, England.

Tel [phone], Fax [phone].

www.tlaudio.co.uk email: [e-mail]

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CONTENTS

INTRODUCTION ......................................................................................................................................... 3

WHY CLASS-A?............................................................................................................................................ 4

WHY TUBES? ................................................................................................................................................4

WHY BALANCED I/O?.................................................................................................................................. 5

BLOCK DIAGRAM......................................................................................................................................6

PRECAUTIONS ............................................................................................................................................ 7

INSTALLATION........................................................................................................................................... 8

AC Mains Supply. ....................................................................................................................................8

Mic Input. .................................................................................................................................................8

Line Input. ................................................................................................................................................ 9

Instrument Inputs.....................................................................................................................................9

Insertion Point. ........................................................................................................................................ 9

Output..................................................................................................................................................... 10

Ventilation.............................................................................................................................................. 10

OPERATION ............................................................................................................................................... 11

Input Stage. ............................................................................................................................................11

Microphone Input. .................................................................................................................................11

Line Input. ..............................................................................................................................................11

Instrument Input. ................................................................................................................................... 11

30dB Pad................................................................................................................................................12

90Hz Filter. ............................................................................................................................................12

Phantom Power. ....................................................................................................................................12

Tube Stage Drive and Peak LEDs. .......................................................................................................12

WHAT IS COMPRESSION? ...........................................................................................................................12

Overview of Compressor Operation. ...................................................................................................13

Threshold. ..............................................................................................................................................13

Attack and Release. ...............................................................................................................................14

Gain Make Up. ...................................................................................................................................... 15

Compressor On...................................................................................................................................... 15

Equalisation. .......................................................................................................................................... 15

LF Band.................................................................................................................................................. 16

Mid Band................................................................................................................................................16

HF Band. ................................................................................................................................................ 16

EQ On.....................................................................................................................................................16

EQ Pre.................................................................................................................................................... 16

Output Gain. .......................................................................................................................................... 16

Digital Output........................................................................................................................................ 17

Output Peak LED. .................................................................................................................................17

GETTING STARTED ................................................................................................................................ 18

CONNECTIONS. ...........................................................................................................................................18

IN USE ......................................................................................................................................................... 19

SPECIFICATION .......................................................................................................................................21

Mic Input:...............................................................................................................................................21

Line Input:..............................................................................................................................................21

Instrument Input: ...................................................................................................................................21

High Pass Filter: ...................................................................................................................................21

Insertion Point:...................................................................................................................................... 22

Output: ................................................................................................................................................... 22

Tube Stage: ............................................................................................................................................22

Compressor: ..........................................................................................................................................22

Equaliser:...............................................................................................................................................22

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Metering:................................................................................................................................................23

Power Requirements: ............................................................................................................................ 23

Dimensions: ...........................................................................................................................................23

SERVICE ...................................................................................................................................................... 24

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INTRODUCTION

The TL Audio Ebony Series of audio processors are a sleek looking range of discrete
Class A processors designed to heighten your audio experience; they use signal paths
constructed from discrete transistor “Class A” circuits, with switchable variable drive
tube stages, putting you in control of how ‘creamy’ or how ‘cool’ your unit sounds.
These techniques provide very high quality, uncoloured audio, with the option to add
valve warmth at the touch of a button.

Hand assembled in England to the highest standards, the Ebony uses stylish, quality
chrome knobs together with a high gloss black finish to make the exterior look just as
smooth as the circuits sound. The Ebony Series have all the features you come to
expect with TL Audio, including balanced I/O, multi input options, analogue VU
metering and intuitive, precise controls. All units are also compatible with the TL
Audio DO-2 digital SPDIF interface for easy digital connectivity with high quality
conversion. A combination of supreme quality, unrivalled sound and stylish aesthetics

- this range offers superior analogue processing to accompany a digital world.

The Ebony Series A3 Processor is a single channel unit, accepting mic, line and
instrument inputs. Processing includes gain and phase control, compression and
equalisation. A tube stage may be switched into the signal path, with variable drive
control.

The block diagram of the processor is shown in fig.1. A discrete Class A electronically
balanced mic input amplifier is used, delivering superior audio performance with very
low noise, low distortion and wide bandwidth. The mic input is suitable for low
impedance (150-600 ohm) microphones, with a gain control range of +16 to +60dB.
Front panel switches provide 48V phantom power, and 30dB pad for high output mic
applications.

The front panel mounted jack socket is suitable for a variety of sources, including
electric guitar, acoustic pickup and keyboard. The instrument input has high/low
switching, and a dedicated valve input stage.

Phase reverse and high pass filter switches are provided; affecting whichever of the
mic, line and instrument inputs are selected.

The tube stage has a variable drive control, with the signal level indicated by the
variable intensity “Drive” LED and “Peak” LED. Use of this feature typically
introduces 1% to 10% harmonic distortion, predominately second harmonic, without
changing the output level from the unit. The tube stage can be selected or bypassed as
required.

The Compressor has continuously variable threshold, ratio and gain make-up, and
switched settings for hard or soft knee and fast or slow attack and release times.

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The Equaliser has 3 bands. The HF and LF controls are shelving whilst the mid
control is a swept, peaking filter.

Comprehensive switching (via relays) allows the A3 to be configured with the
equaliser pre or post the compressor, or with the equaliser in the sidechain, for de­essing or frequency variable compressor effects.

A VU meter is provided, which can be selected to either input or output signals. It may
also be selected to display the compressor Gain Reduction. In this mode the meter
normally indicates 0dB, falling back as the signal is compressed. The amount of
compression may be read directly from the dB scale. The meter is also provided with a
“+10dB” switch, which keeps the reading on the scale when driving a high level out
(to a DAW, for example). In the +10 mode, 0VU is calibrated as +14dBu out.

Why Class-A?

Class A circuits are designed with a constant current flowing through all of the
transistors, which is sufficient to drive the peak output required from each block of the
circuit. This ensures that every transistor is kept at its optimum operating point,
minimising non-linearities due to changes in current and internal thermal effects, and
eliminating the objectionable “cross-over” distortion typical of class AB circuits.

Due to the higher steady state (or “quiescent”) currents used, the power dissipation of
class A circuits is substantially higher than can in general be handled by integrated
circuits. It is also possible to design discrete transistor circuits to operate at higher
voltage rails than are available for audio integrated circuits, adding the benefit of
greater headroom and improved dynamic range. For these reasons, there are no
integrated circuits in the audio paths of the Ebony Series.

The outstanding audio quality is reflected in the technical specification of the units,
with particularly low noise and distortion, and wide frequency response.

Why Tubes?

Valves - or “Tubes” - have long been associated with excellent audio quality,
recognised as adding “warmth” or “depth” to a signal. Driving the valves harder
results in an increasing level of mainly second harmonic distortion, which is
responsible for the characteristic overdriven valve sound.

The Ebony Series feature variable drive valve circuits, which may be switched into the
audio paths, or bypassed completely. The valve drive control varies the signal level
through the valve stage, without affecting the overall gain from input to output. It is
therefore possible to vary to the degree of harmonics added by the valve, from subtle

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warming to crunchy overdrive, with a single control. The signal level through the
valve is displayed by the variable intensity “Drive” LED and the “Peak” LED.

Where instrument inputs are present on the Ebony models, dedicated valve input
stages are used. Switchable to high or low sensititivity (and impedance), these input
stages represent the ultimate quality for the first stage of instrument amplification.

Why Balanced I/O?

Balanced I/O (Inputs and Outputs) are always preferable to unbalanced connection in
an audio system. A balanced signal consists of signal phase and non-phase
connections, which form a differential pair, independent of the ground (or earth)
connection. Noise, particularly mains hum and high frequency interference can often
be present in unbalanced systems due to small differences in ground potential or
circulating ground currents (“loops”) between units, where the signal phase (only) is
taken as an absolute value with respect to ground.

A correctly designed balanced interface should have both phase and non-phase signals
of equal magnitude (and source impedance), but should allow either of the phase and
non-phase signals to be connected to an arbitrary electrical point (e.g. ground) without
changing the differential level. Therefore, if, for instance, the non-phase signal is
shorted to ground by an unbalanced input on a piece of equipment, then the phase
signal should double in magnitude to compensate. Such an arrangement is referred to
as “floating” or “ground-free”. Balanced signals require 3 pin connectors, such as
XLR’s or TRS jack plugs, carrying the phase and non-phase signals, plus a screening
ground connection.

Naturally, the Ebony Series features balanced, ground-free signals for all line inputs
and outputs, as well as insertion points where present. The range is also compatible
with unbalanced equipment, as described above.

Please read this manual fully before installing or operating the Processor.

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BLOCK DIAGRAM

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PRECAUTIONS

The T L Audio Ebony Series units require very little installation, but like all electrical
equipment, care must be taken to ensure reliable, safe operation. The following points
should always be observed:

- All mains wiring should be installed and checked by a qualified
electrician,

- Ensure the mains operating voltage stated on the rear panel is correct
before connecting to the mains supply,

- Never operate the unit with any cover removed,

- Do not expose to rain or moisture, as this may present an electric
shock hazard,

- Replace the fuse with the correct type and rating only.

Warning: This equipment must be earthed.