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Pure Sound M845 Mono Power Amplifiers

code: PS-M845
£7,499.95 (FREE UK Delivery)
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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.

Please Note: Price is for a pair of amplifiers.

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.

We endeavour to despatch same day for orders placed up to 12 noon on available stock items (items with stock message "Usually dispatched within 24 hours"). Please remember to check with us first for a physical stock check if next day delivery is important to you. Any items with stock message "Usually dispatched within 72 hours" are items that we do not hold in stock but order in from the importer or manufacturer as soon as a customer order is recieved. Occasionally these may be delayed beyond 72 hours due to importer/manufacturer stock levels but we will inform you as soon as we can if this is the case.

UK ORDERS:  We despatch the bulk of our UK mainland items on a 24 hour service – Free of Charge.  Non Mainland locations - Isle of Man, Isle of Wight, the Scilly Isles, the Scottish highlands and Islands, the Channel Islands and Northern Ireland may take a day or so longer and are not Free of Charge. Smaller items are delivered using Royal Mail recorded delivery or special delivery. Larger items are delivered using a courier service such as Interlink Express, DPD, UPS or DHL. 

INTERNATIONAL ORDERS: We offer competitive rates which can be confirmed by email. Please just ask – we will need a full delivery address and telephone number. Smaller items are delivered using Royal Mail Small Packets Airmail with International Tracked and/or Signed depending on value of item and availability of the service. Larger International shipments are sent by insured and tracked services using DPD, DHL or UPS. If there are any delays due to specific customs regulations, etc, you will be contacted by Turntableworld or by the courier with a request for any further information required. Customs duties do not apply for shipments into any EU country (for a full list please refer to the EU Country List). Customs duties can apply for countries outside of the EU. Customers in these countries are responsible for all taxes and duties incurred when the items enter their country.

COLLECT IN STORE OR HOME INSTALL:At the request of the manufacturer some items cannot be supplied by mail order but you can click and buy them and then elect to collect them from our store or arrange a home install (if applicable). Applicable items clearly state that they are Collect in store or home install. Once ordered you will receive a message prompting you to contact us by phone or email to arrange for us to deliver and install or to reserve and collect from our store at your convenience, you will also be advised of the delivery time / stock availability as not all Home install / collect in store items are held in stock. 

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