Pure Sound
http://www.puresound.info
Please contact me for current prices.
Integrated Amplifiers
A10 Integrated Class A Amplifier
The Pure Sound A10 is a new integrated amplifier, operating in Class A and delivering a warm, rich valve sound, an ideal choice for valve lovers with limited space. It features 10 Watts per channel and is intended for users of high sensitivity loudspeakers or for those seeking high performance with small speakers in a smaller environment such as a bedroom or study. The A10 accepts two line level inputs and may be switched to drive 4 or 8 ohm loudspeakers. The circuit is based around the sweet sounding 6P14 a modern equivalent to the EL84/6BQ5 family.
- Class A operation
- 3 Line level inputs
- 10 Watts per Channel Output
- 4 and 8 ohm output taps
A30 Integrated Class A Valve Amplifier
The Pure Sound A30 is a Class A integrated valve amplifier capable of delivering pure Class A operation at 30W per channel and features a spec previously unheard of at this price. It was developed to provide an affordable Class A amplifier compatible with all types of loudspeakers with excellent sound quality. Class A operation was selected because of lower distortion and a smoother, relaxing and more natural sound.
The A30 includes 3 line level inputs and comes complete with very robust Electro Harmonix 6550 output valves in an Ultra Linear Push Pull configuration, a combination of power and clarity that's hard to beat. The A30 also uses an Auto Bias system, meaning that replacement vavles should be fitted as pairs but there isn't any requirement to set or adjust bias - a task which has traditionally required on valve amps.
For flexibility, the A30 features outputs for both 4 ohm and 8 ohm speakers and is able to drive even very large speakers with ease due to its design. We have this on demonstration with a pair of floorstanding Focal 918 Profile speakers in a large room and the resulting sound is simply sublime. The A30 is the first affordable Class A valve amplifier in many years and opens up the wonderfully warm and involving sound of valves for a modest price.
- 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 n) 6550 output tubes
2A3 Integrated Class A Valve Amplifier
The Pure Sound 2A3 is an integrated Class A valve amplifier, based on 2A3 valves which create a very warm and charming amplifier. The 2A3 is one of the best sounding valves and is in production again. The Pure Sound 2A3 is an 18 watt per channel line level integrated design that accepts upto 3 different source components. Don't let the 18 watts put you off though, as the 2A3 has plenty of power on tap to drive even reasonably sized floorstanding speakers.
There are many amplifiers now making use of directly heated triodes but few which adequately address the particularly awkward issues involved in driving these devices properly. The Pure Sound 2A3 amplifier features an unusual choke loaded driver stage which allows the 6SN7 driver valves to deliver the full measure of signal to the push/pull output valves. This rather exotic configuration usually results in a tremendous depth to the tone of instruments and the Pure Sound 2A3 is no exception in this regard.
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. There are speaker terminals for both 4 ohm or 8 ohm loudspeakers. The Pure Sound 2A3 may also be used as a very high quality stereo power amplifier if the volume control is turned up fully
Pre & Power Amplifiers
L300 Line Level Pre Amplifier
The Pure Sound L300 line level pre amplifiers features 5 inputs and twin outputs (2 sets RCA and 2 sets balanced XLR), a circuit with output transformers and a sophisticated full valve rectified, choke smoothed, regulated power supply including a 300B triode as the series element. The L300 follows some significant research and development at Pure Sound, resulting in several advancements in purity of circuit design and signal transfer. By properly addressing the simple yet important aspects of design below, the L300 offers a truly high end bridge between source and power amps.
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.
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.
L10 Line Level Pre-amplifier
Following the positive response to our flagship L300 pre-amplifier, pure sound has developed the L10, a new, more affordable design which incorporates much of the thinking that makes the L300 so highly regarded. The L10 has 4 inputs, a separate passive Record In Record Out loop and two pairs of single ended outputs. The circuit uses output transformers and a sophisticated full valve rectified, twin choke smoothed power supply. It also offers remote control of the volume via a separate handset.
In the L10, source selection is via a high quality switch located near to the input sockets. The chosen source is routed to a high quality motorized, film potentiometer and from there on to the audio circuit. This consists of a single ended triode stage loaded by a custom wound wideband output transformer which steps down the amplified signal allowing it to be coupled to the power amplifier at a manageable level and as a low impedance source. The output stage of the L10 is impervious to long interconnecting cables or lower impedance power amplifier input stages.
The L10 also incorporates an extremely sophisticated power supply to maintain constant operating conditions for the audio circuitry. It includes a valve rectifier, and a twin choke filtered LCLC stage which provides a stiff, voltage rail allowing the audio circuit to operate in a calm and orderly way regardless of the demands the music makes on the amplifying stage. Filament supplies are fully regulated to further reduce the potential for noise.
P10 MM Phono Stage
The P10 phono amplifier 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.
T10 Impedance Matching Transformer
The T10 mc transformer is now available. It has been our experience that the best results are achieved when using moving coil cartridges loaded via a correctly matched transformer. The T10 contains two wide bandwidth, custom manufactured transformers with MuMetal cores. The transformers have a step up ratio of 1:36 switchable to 1:18 and therefore allow for the adjustment of cartridge loading between 36 and 144 ohms.
M845 Mono Power Amplifier
The M845 mono power amplifier is a single ended design based around the 845 power triode. Operating in Class A and giving 27 Watts of output power, it will complement a wide range of medium to high efficiency loudspeakers.
The 845 triode was originally developed by RCA in 1931 as a radio transmitting and audio amplification valve. The anode is machined from solid graphite to allow high power dissipation. It has an extremely linear transfer characteristic. In recent years, a renewed interest in this kind of valve has resulted in them being manufactured again by various factories in China.
Implementing the 845 in a sympathetic circuit which takes full advantage of its capabilities is not straightforward. The filament draws a significant amount of power and also forms a part of the signal path so energising it correctly is a critical part of the design. The valve also operates with very high voltages across it so again, a careful choice of filtering components for that high voltage supply is essential such that adequate current is available to the valve at all audio frequencies instantaneously. In the M845 this supply includes a hybrid Graetz bridge for the initial rectification and a substantial smoothing choke as part of its CLC type filter.
Although all of the elements; power supply, circuit topology & component choice have a profound effect on the overall performance of a valve amplifier, one of the most important aspects is the design & construction of the output transformer. A high primary impedance, the resultant large step down ratio and the need to maintain a high level of insulation between the windings all conspire against the transformer designer and the quest for extended bandwidth with efficient power transmission. The M845 utilises an in house designed output transformer that underwent extensive trials using a variety of core materials and winding techniques before the final configuration was chosen.
The other difficulty in using the 845 is in the design of a stage capable of cleanly delivering the voltage swing necessary at its grid to take it to full output. The M845 incorporates a driver stage based on the 6SN7 triode coupled via a custom wound, wideband, interstage transformer. The amplifier’s input stage is directly coupled to this driver meaning that there are no coupling capacitors used in the circuit at all.
The circuit also operates without any negative feedback.
The end result is an amplifier capable of reproducing the full measure of instrument tone with extraordinary dynamic contrast, energy and colour. When partnered with appropriate loudspeakers the M845 will deliver an unparalleled reproduction of all types of music.
