TL Audio A2 User Manual

T L Audio

User Manual

Ebony Series A2 Stereo Processor

TL Audio Limited, Letchworth, England.

Tel [phone], Fax [phone].

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

1

TABLE OF CONTENTS

TABLE OF CONTENTS..............................................................................................................................1

INTRODUCTION .........................................................................................................................................2

WHY CLASS-A?............................................................................................................................................ 2

WHY TUBES? ................................................................................................................................................ 3

WHY BALANCED I/O?.................................................................................................................................. 3

THE A2 STEREO PROCESSOR. ...................................................................................................................... 4

PRECAUTIONS ............................................................................................................................................ 5

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

INSTALLATION........................................................................................................................................... 7

AC Mains Supply. .................................................................................................................................... 7

Audio Inputs. ............................................................................................................................................ 7

Outputs. ....................................................................................................................................................8

Ventilation................................................................................................................................................ 8

OPERATION. ................................................................................................................................................ 9

Input Gain stage ......................................................................................................................................9

Tube Stage Drive and Peak LEDs. ......................................................................................................... 9

WHAT IS COMPRESSION? ............................................................................................................................. 9

Overview of Compressor Operation. ...................................................................................................10

Threshold. ..............................................................................................................................................10

Attack and Release. ...............................................................................................................................11

Gain Make Up. ...................................................................................................................................... 11

Compressor On...................................................................................................................................... 12

Equalisation. .......................................................................................................................................... 12

LF Band.................................................................................................................................................. 12

Mid Band................................................................................................................................................12

HF Band. ................................................................................................................................................ 12

EQ On.....................................................................................................................................................13

EQ Pre.................................................................................................................................................... 13

EQ Side Chain ....................................................................................................................................... 13

Sidechain Operation.............................................................................................................................. 13

Output Gain. .......................................................................................................................................... 13

Digital Output........................................................................................................................................ 14

Output Peak LED. .................................................................................................................................14

GETTING STARTED ................................................................................................................................ 14

Using as an inserted dynamic effect.....................................................................................................15

Using to process your stereo mix / mastering .....................................................................................15

SPECIFICATIONS .....................................................................................................................................18

Line Inputs: ............................................................................................................................................18

Outputs:.................................................................................................................................................. 18

Tube Stage: ............................................................................................................................................18

Compressor: ..........................................................................................................................................18

Equaliser:...............................................................................................................................................19

Metering:................................................................................................................................................19

Power Requirements: ............................................................................................................................ 19

Dimensions: ...........................................................................................................................................19

SERVICE ...................................................................................................................................................... 20

2

INTRODUCTION

New from TL Audio, The Ebony Series is a sleek looking range of discrete Class A
processors designed to heighten your audio experience.

The range consists of 3 units, all of which use Discrete Class A circuitry and have an
optional tube stage with variable drive putting you in control of how ‘creamy’ or how
‘cool’ your unit sounds.

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.

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.

3

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
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.

4

The A2 Stereo Processor.

The Ebony Series A2 Processor is a dedicated stereo unit, providing gain and phase
control, compression and equalisation. A tube stage is available to each signal path,
with variable drive control. The block diagram of the unit is shown in fig.1.

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. The
compressor is stereo coupled, to ensure both A and B channels are compressed
identically, in order to preserve the stereo image.

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

Comprehensive switching (via relays) allows the A2 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 channel, and 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.

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

5

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.

6

BLOCK DIAGRAM