A30 Integrated Amplifier (GBP 1399.00)
We have been selling Pure Sound for a year or so now, and have nothing but praise for the brand. Guy Sergeant, a famous name in British audio, is responsible for the design, and the units are manufactured in the Far East, possibly the best of both worlds. Appearance is, in my opinion, strictly functional, but where these designs really stand out is in sound quality versus price. Another factor which pleases me is the serviceability, something not always mentioned in reviews. I'm the Unfortunate at Walrus who gets to nurse sick equipment back to health, by the way. Don't get me wrong, Pure Sound is very reliable, but if it does go wrong, as everything will eventually, I can say it's a pleasure to service, because of the careful design and layout. So it gets my thumbs up on that score as well. Highly recommended by Walrus from whichever angle you look.
Over to Pure Sound themselves now:
| The pure sound A30 amplifier was developed to meet the demand for an affordable Class
A amplifier that would be compatible with all types of loudspeakers. The
A30 is a line level integrated design that allows for the selection of
up to 3 different source components and control of the volume by a high
quality ALPS Blue Velvet potentiometer. Class A operation was
chosen because it gives lower distortion and a more relaxing, natural sound. The amplifier uses the very robust Electro Harmonix 6550 output valves in an Ultra Linear Push Pull configuration. This arrangement gives a combination of power and clarity that is difficult to beat. The amplifier uses an Auto Bias system, which means that replacement output valves
should be fitted as matched pairs. There will be no need to reset or monitor
bias conditions. Very high quality components are used throughout including selected carbon film resistors
and SCR polypropylene capacitors. The power supply makes use of twin valve rectifiers and choke smoothing. The output can be configured for use with 4 or 8 ohm loudspeakers. The output stage can also be switched to triode-coupled configuration.
This further linearises the operation of the valves at the expense of some output power. It may be preferable with higher sensitivity loudspeakers. The A30 may also be used as a very high quality stereo power amplifier if the volume control is turned up fully. When partnered with appropriate ancillary equipment the A30 is capable of very satisfying performance. Features Class A operation 3 Line level inputs 30 Watts per Channel Output 4 and 8 ohm output taps Twin valve rectifiers Choke smoothing SCR coupling capacitors Carbon film resistors (for better sound quality) ElectroHarmonix ( Very substantial construction including cast metal transformer shrouds. |
A8000 CD Player (GBP 1059.00)
The pure sound A8000 CD
Player was developed as a high quality source to be used with the pure sound range of amplifiers. It can also be used in a wide range of other systems with great success. The A8000 is built around the SONY 213Q high precision
mechanism, renowned for both its stability and reliability. A
proprietary 24 Bit 192KHz D/A converter handles the data stream, which,
once converted, is filtered using OPA2604 Op amps. The powerful output
stage comprises a pair of 6N3 double triodes. Signal coupling here is
via MIT capacitors while the output stage power supply utilises the
German MCap capacitors. The
incoming mains supply is filtered by a choke regulated circuit which in
turn feeds 8 separate regulated supplies each of which uses Silmic and
Rubycon capacitors. These deliver power independently to various parts
of the circuitry. At switch on, the CD Player counts down for 20 seconds to allow the valve circuitry to warm and stabilise before the machine can be used.
The A8000 also offers the facility to switch the upsampling frequency from 44.1 KHz to 88.2 or 176.4 KHz. The
substantially constructed chassis includes a 10mm anodised aluminium
front panel, high quality gold plated RCA sockets for L-R and digital
outputs. The remote control is a sleek, anodised design machined
from solid aluminium. |
P10 MM Phono Stage (GBP 599.00)
(HiFi World February 2008)
The P10 phono amplifier is the latest addition to the highly acclaimed
Pure Sound product range. It is intended to meet the requirements of audio enthusiasts who still enjoy the distinctive
strengths and high quality of reproduction that can be derived from vinyl records. It
is compatible with moving magnet and high output moving coil cartridges. Low
output moving coil cartridges will require the use of an additional
step-up device or matching transformer. Full output from the P10 is sufficient to drive the line level inputs of any integrated amplifier or pre-amplifier. The
active amplification stages use double triodes in a simple anode
follower configuration. The phono equalisation is achieved using
passive components and can therefore maintain its accuracy over time
without introducing the unacceptable levels of phase shift found in
active equalisation stages. There is no negative feedback in the
circuit. The P10 features a particularly elaborate HT power supply. After
the initial rectification and smoothing, the supply is split and two
separate, heavily decoupled high voltage rails are established. These
feed each half of the output valve while further decoupling of each
rail allows the cleanest and most independent voltage rails possible to
feed each half of the input valve.
The absolute stability of this supply regardless of the demands made by the audio signal on the circuit, lends the
P10 a stability and poise which allows effortless reproduction of the most demanding source material. The valve filaments are also fed by a DC supply thereby ensuring constant operating conditions for the
amplifier. The circuit makes use of close tolerance metal film resistors, polypropylene signal coupling capacitors and selected valves.
The P10 phono amplifier meets the very strict performance criteria required of all Pure Sound products and will give excellent results with vinyl records provided that it is used with appropriate ancillary equipment. |
L300 Line Preamplifier (GBP 4799.00)
The L300 has 5 inputs and twin outputs (2 pairs single ended and 2 pairs balanced via XLR). The circuit uses output transformers and a sophisticated full valve rectified, choke smoothed, regulated power supply including a 300B triode as the series element. A Line Stage pre-amplifier needs to offer the facility to select between different sources, to provide some means of attenuating the chosen source and then deliver it in an uncorrupted form to the power amplifier. Controlling the Volume ...
In recent times, with the prevalence of digital source components, many audio enthusiasts have adopted the use of passive volume controls incorporating resistive potential dividers and even transformer based attenuators. These are volume controls where attenuation is achieved through the use of tapped transformer windings. On the face of it either of these might appear to offer the purest approach. However, it’s not so simple. Resistive attenuators are generally of quite a high impedance so as not to load the source driving them but in turn confer little drive capability themselves. In some circumstances they can sound quite transparent but it’s a commonly experienced subjective impression, that such attenuators leave the music with a lack of purpose and grip. Long connecting cables may also blunt the high frequency response, a situation which may be worsened by using a following amplifier with low input impedance. Transformer volume controls seem to address the issue of drive capability to some extent, but they have their own problems. A wide bandwidth transformer can be made such that, when using both windings in full, i.e. with no attenuation, it transfers a pretty good facsimile of the source signal. However, as attenuation is applied and the transformer has to transform more and more, difficulties start to arise. By the time significant attenuation is applied, the performance of the transformer no longer looks quite as impressive with differing patterns of resonance being visible at each step. The reproduction of timbre suffers and the sound quality realized alters slightly with each change in level. Auto-formers which attenuate by tapping off a single sided winding have actually proved to be the most transparent passive controls we have tested and yet even they seem to lack a certain something. The other issue with volume controls based on a multi position switch is a sense that the right level for listening to a piece of music can never quite be reached. If the steps of the attenuator are made close enough to suit a source with a given output or a following amplifier with a particular sensitivity, it will be wrong with another source or another amplifier. A conventional potentiometer gives a much finer range of adjustment. In the L300, source selection is via a high quality switch located near to the input sockets. The chosen source is routed to a high quality film potentiometer and from there on to the audio circuit. This consists of 2 directly coupled triode stages, the second loaded by an output transformer which steps down the amplified signal allowing it to be coupled to the power amplifier at a manageable level and via a low impedance output. The output stage of the L300 is impervious to long interconnecting cables or lower impedance power amplifier input stages. The use of output transformers also allows the option of a true balanced output configuration if desired. A low gain, low output impedance stage is in itself nothing new. Many transistor pre-amplifiers are similarly specified. However, they usually achieve it by means of excessive negative feedback which is highly detrimental to the subjective reproduction of music.
Power Supplied properly ...
The L300 also incorporates an extremely sophisticated regulated power supply to maintain constant operating conditions for the audio circuitry. It includes a valve rectifier, a choke filtered stage and then a series regulator featuring the 300B power triode as the passing tube. A very elaborate error amplifier referenced to a gas voltage reference valve allows the circuit to precisely maintain the high tension supply regardless of fluctuations in the mains supply and the varying current drawn by the audio circuit. Filament supplies are also fully regulated to further reduce the potential for noise. The L300 preserves the verve and energy in recordings that almost all pre-amplifiers and passive volume controls otherwise lose. It does this without sacrificing transparency or introducing euphonic colouration to the sound. |
