Vertex Aletheia dac-1 User Manual

Aletheia dac-1

A superlative quality 16-bit non-oversampling

D to A converter

Manufactured in Wales by Vertex AQ Limited

Background

Aletheia is a new brand of electronics produced by
the design team at Vertex AQ. The dac-1 is a high­end, 16 bit, non-oversampling (NOS) DAC of
superlative performance.

To understand the dac-1 we need to look first at the
development of Vertex AQ, a company that
produces a range of accessories covering mains,
cables and supports. Their USP is based on the
reduction of systematic interaction faults caused by
RFI/EMI1 and microphony. When Vertex products
are applied to a hi-fi system, significant gains are
achieved. But the design process employed for the
Vertex products always started at the electronics
inside the box. So the next logical step was to take
the 'systematic thinking' inside the box and through
every internal process, in just the same manner as
at a system level.

Over the past 3 years, the level of development in
digital and analogue processing has increased
within the company, driven by the desire to apply
the proven techniques of the Vertex approach, and
the skills and knowledge acquired through our
more general research work. This has led us to the
dac-1.

Key Design Criterion

The dac-1 employs 16 bit D to A conversion with no
oversampling in order to reduce processing
complexity. No software or hardware noise
shaping, or filtering is used to avoid break-down of
signal integrity, phase shifting and filter ringing. So
lets be clear here, the dac-1 is deliberately a very
basic DAC in processing terms, with the majority of
the design effort focussed on reducing systematic
interactions right down to a component level. But
the essence of the dac-1 development pivots
around the desire to prevent systematic
interactions around the player, down to a
component-by-component level.

There is extensive RFI suppression throughout the
design - all internal wiring is fitted with EMI
absorptive tubing, and all wiring downstream of the
mains transformer is solid-core silver. The major
components in the design (mains transformer, pre­regulator, DAC board) are housed in separate

modules, each with EM absorptive linings and
acoustic absorption. Within these modules is
extensive acoustic absorption right down to
individual components. The mains transformer and
pre-regulator are housed in separate, compliant
mounted modules, with extensive EM absorption.
The mains input has a built-in 'HiRez Jaya' shunt
filter, and input/output signal lines each have an
internal RFI/acoustic absorption module fitted, and
signal sockets are mounted on isolated sub-panels.

An ultra high-speed, dual-stage power supply
topology is used. A pre-regulator feeds 4 discrete
component second-stage regulators to separately
feed each processor supply. Each analogue output
is taken straight out of the DAC chip and converted
to a voltage signal passively, across a high quality
resistor (passive I/V) to avoid any additional active
output stages. Output capacitors are the
outstanding Mundorf Supreme (silver/gold in oil).

The balance of engineering decisions for the dac-1
is based more around time domain thinking, not
frequency domain thinking. The core processing is
simple 16 bit non oversampling with no filtering. In
our view the problems that filtering brings are
worse, in sound quality terms, than any residual
aliasing or sampling noise. The filter ringing
problem and phase shifting seems to directly affect
the musical performance quite significantly,
whereas without filters, any residual high frequency
sampling noise does not seem to do any damage
to the listening experience, much the same way
that vinyl surface noise is quickly ignored.

Our experience has shown us that the systematic
faults are far more crippling to performance than
most people imagine. The biggest issue is these
effects are closely linked to the musical
programme, breaking down the structure of the
music. We have seen these effects in the
measurement alliance2, and in essence these
systematic faults prevent the system from correctly
tracking the desired output in the time domain. In
our view the musical envelope is broken down and
re-mixed into a lower level of reality by too much
processing. So, by avoiding as much processing as
possible, and minimizing systematic faults at every
possible point within the dac-1 design, we believe
we have a DAC that outputs very closely the
intended waveform - in the time domain.

Aletheia dac-1

1

1

RFI = Radio Frequency Interference - high frequency signals carried within and around conductors

EMI = Electro Magnetic Interference - high frequency radio waves transmitted/received through the air between conductors

2

Research project between Vertex AQ, Nordost and Acuity Products. See www.vertexaq.com and click on Projects > Knowledge

Alliance.