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Pure
sound A30 amplifier
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.
Why this amplifier? Why now?
With the recent interest in lower powered Single Ended triode
amplifiers has come the realization that to get the best from
these, the speakers used have to be both sensitive and quite
large to give truly satisfying results. There are also not that
many good, high sensitivity (>97 dB/W) designs available at any
price never mind at price levels the majority of music lovers
can afford. However, there are some very good loudspeakers
currently being made with sensitivities between 88 and 94 dB/W.
These are sufficiently revealing to make the virtues of simple,
high quality amplification readily apparent, although in most
cases the output of a typical single ended amplifier is
insufficient to give the scale and drama many types of music
demand.
A good amplifier with 25 -30 watts of output power is more than
enough to drive this type of loudspeaker to sensible levels even
in quite a large room. For simplicity a valve amplifier is
preferable. Recently, there has been an increase in the number
of relatively affordable valve amplifiers made in China. Many of
these are compromised by the quality of their transformers,
components, layout and because they operate in Class AB or B to
give a higher power specification. They often also use a lot of
negative feedback in an attempt to compensate for these
shortcomings with a consequential impact on clarity and low
frequency control.
The pure sound A30 operates fully in Class A up to its rated
output so it does not change character at any signal level.
There is none of the distortion caused by output devices
switching on and off and therefore no requirement for excessive
feedback to correct for it. The 6550 valves supplied are the
extremely robust Russian Electro-Harmonix variety and are quite
content with dissipating the power required to maintain Class A
operation up to 30 Watts.
The valve rectifiers used keep the high voltage power supply
clear of the noise that can be introduced by silicon rectifiers.
A substantial choke is also incorporated to keep the power
supply impedance low. The output transformers also give
extremely wide bandwidth allowing very solid low frequency
performance as well as exceptional reproduction of timbre. These
design features combined with the use of high quality passive
components, octal based input and driver triodes and an elegant
but simple internal layout results in an amplifier which sets a
new benchmark for performance, build quality and value.
Features
• Class A operation
• 3 Line level inputs
• 30 Watts per Channel Output
• 4 and 8 ohm output taps
• Twin valve rectifiers
• Choke smoothing
• ALPS potentiometer
• SCR coupling capacitors
• Carbon film resistors (for better sound quality)
• ElectroHarmonix (Russia) 6550 output tubes, 5U4G
recifiers (2), 6SN7 drivers, 6SL7 input.
• Very substantial construction including cast metal transformer
shrouds.
Price £1395.00
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P10 Phono
Amplifier
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 gain of the P10 is 40 dB (x 100). 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. ECC83 input & ECC88 output driver.
Click here for the Hi Fi
World review
Price £595.00
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