User manual MARSHALL AMPLIFIER 1974X

[. . . ] From the handwired, tag-board circuit housed in an aluminium chassis, to the exclusively re-issued and specially `aged' Celestion 20 Watt speaker, I am extremely proud of the incredible accuracy and authenticity of this re-issue. I sincerely hope that this handwired piece of Marshall history will provide you with countless hours of playing pleasure. Yours Sincerely, As Jim has already pointed out, we went to incredible lengths to achieve maximum authenticity in terms of components, circuitry, constructional methods, materials, specifications, aesthetics, signal path, performance, tonal characteristics and feel. We are delighted to report that our suppliers were equally as exacting in their tasks ­ none more so than Dagnall Transformers and Celestion Speakers. [. . . ] Celestion's proprietary `ageing' is largely achieved by the following two things: i) Matching the magnetic flux to that of our vintage references in order to duplicate the output of the older speakers. Doing this not only affected the `loudness' of the speakers but also altered the tonal balance, warming up the low end and also making the top end less aggressive ­ exactly like the originals. ii) Specially manufacturing the cone material to be more `pulpy', recreating the ageing effect and thus further softening the sound of the combo. Tone Circuit: In typical Marshall fashion, the tone network is post gain and passive. The tone circuit involves a blend of high frequency pre-emphasis and passive high frequency cut ­ the mix of which is dependant upon the setting of the Tone control on the channel being used. Components: With the obvious exception of the valves, all components used were sourced from European and American manufacturers ­ including some custom built, `double can' (a. k. a. `dual gang can' or `dual electrolytic' ­ meaning two capacitors in a common case) power supply capacitors due to the odd value used in the original ­ one of many steps taken to ensure maximum authenticity. Tag Board: This is exactly the same as the original in terms of dimensions, thickness and matrix pitch. The material used is EM42. The reason we didn't use a board with the exact same chemical composition as in the original units is because that material doesn't pass current safety legislation regarding flammability. Transformers: Because the 1974 combo was produced relatively early in Marshall's history (1966 - '68), Jim had yet to strike up his now well-known relationship with transformer manufacturers, Dagnall and Drake. As a result, both the power and mains transformers used in the original 1974s were `off-the-shelf' devices purchased from a highly regarded, general electronic component supplier. This company, whilst still in existence, does not have records of exactly who manufactured the original transformers. As you probably know, the output and mains transformers are vital components in an amplifier as they influence performance, sound and feel. Consequently, we worked extremely closely with our associates in Dagnall's R&D department in order to duplicate the original transformers in all areas. To do this we spent a great deal of time and attention studying and analysing the constructional methods and materials (e. g. : lamination grade, insulation, coil spacing, etc. ), used in both transformers so we could match everything as closely as possible and also ensure that the all-important electrical characteristics and performance were identical. With Dagnall's expert help and dedication, we've done exactly that. 2 3 Top Panel: Extra thick, gold coloured Plexiglas (actually Perspex, causing some people to refer to it as `Perplexi'!) ­ exactly as the original. Specific details pertaining to the front panel features can be found on page 5 of this manual. 1974X Top Panel Cabinet Construction: High-grade, flawless (knot-free) Baltic birch ply with fingerlocked (a. k. a. The main cabinet frame (both sides, top and bottom) plus the front baffle are constructed from 12mm ply while the back of the cabinet is 9mm ply. All edges have a 22mm radius. ENGLISH Cabinet Cosmetics: The black Levant, beading, piping and small 6" gold logo are exactly as the original. The original grey and white striped `Bluesbreaker' grille cloth (used from 1965 to 1968) is no longer available, which is a moot point due to the fact that it wouldn't satisfy current-day safety legislation regarding flammability because of its rubber content. (High Tension) voltage required by the two EL84 output valves to pass signal (and hence produce sound) is applied. In order to prolong valve life, the Standby Switch alone should also be used to turn the amplifier `on' and `off' during breaks in a performance. Also, upon full power down, always disengage the Standby Switch prior to the main Power Switch. 6. TONE CONTROL This adjusts the tonal character of the Tremolo Channel. Turning this control clockwise increases the amount of high frequencies (treble) present in the sound. 7. [. . . ] Before connecting for the first time, please ensure that your amplifier is compatible with your electricity supply. OUTPUT IMPEDANCE SELECTOR Matches the amplifier's output to the load (speaker) impedance. As is the case with any Marshall all-valve amplifier it is imperative that: a) the amplifier is connected to a load whilst in operation and b) the impedance selected on the amplifier matches the total impedance of the internal speaker and/or extension speaker cabinets. The combo's internal speaker is 15 Ohms so when it is being used by itself the Impedance Selector must be set to 16 Ohms. [. . . ]