Marshall 1974X
Marshall 1974X Overview:
Tone and Tech Talk The 1974X is an all-valve, 18 Watt, two-channel, 1x12" combo with valve driven tremolo and no negative feedback in its cathode-biased output stage. When building this handwired re-issue our goal was both obvious and simple: to make it as close as possible to the original.
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.
As you can see from its top panel layout, the 1974X is an extremely straightforward amplifier. Channel 1 (the non-tremolo channel) only boasts two, self-explanatory controls: Volume and Tone; while Channel 2, the Tremolo Channel, boasts four - namely Volume and Tone, plus Speed and Intensity for the valve driven tremolo circuit.
Like all Marshall valve amplifiers, the 1974X sounds truly majestic when turned up full - and because of its relatively low wattage this can be done at ear friendly volumes, making it a wonderful recording tool. In keeping with bigger, non-master-volume, all-valve, Marshall amplifiers such as the 1962 'Bluesbreaker' combo and the legendary 100 Watt 'Plexi' head, the 1974X's sweetly distorted, harmonically rich, thick, musical tones result from the power valves being overdriven. Our proprietary, re-issued and 'aged' 20 Watt Celestion speaker contributes to the combo's unique, punchy yet smooth sound as well. As a result, when 'cranked' the 1974X is incredibly touch-sensitive, cleaning up or, if desired, sitting right on the edge of distortion when the guitar's volume is turned down. It responds well to picking dynamics too, 'sagging' nicely when you play like you really mean it and, once again, cleaning up as you pull back on your picking attack.
There now follows some information regarding the inner workings and build of the 1974X. Valve complement: Three ECC83s (12AX7s) in the pre-amp, a EZ81 rectifier and a pair of EL84 power valves working in push-pull. All valves are of the highest quality available and go through a meticulous grading and testing process.
The way the three ECC83s (V1, V2 & V3) in the pre-amp are utilised is as follows: V1 is dedicated to Channel 1, the non-tremolo channel. As Channel 1's pre-amp has a single gain stage, each half of the valve (the ECC83 being a dual-triode) acts as a dedicated gain stage for the channel's two inputs (which are identical). V2 acts as the amplifier's phase-splitter. V3 is dedicated to Channel 2, the Tremolo channel. To be precise, one half of the ECC83 acts as the single pre-amp gain stage for the channel's two inputs (High and Low) while the other half acts as the oscillator for the amp's tremolo circuit.
Due to the fact that the EZ81 rectifier valve and also the pair of EL84 output valves attain extremely high temperatures when the amplifier is in use, their bases are made from the highest grade ceramic available.
Marshall 1974X Top Panel Features:
1. INDICATOR
This filament bulb indicator will light up when your amplifier is switched on. It will not be lit when the amplifier is switched off and/or is not receiving mains power.
2. STANDBY SWITCH
The Standby Switch is used in conjunction with the Power Switch (item 3) to 'warm up' the amplifier before use and to prolong the life of the output valves.
When powering up the amplifier always engage the Power Switch first, leaving the Standby switch on 'Standby'. This allows the application of the voltage required to heat the valves to their correct operating temperature - hence the switch's name. After approximately two minutes the valves will have reached the correct operating temperature and the Standby Switch can be engaged. Upon doing this the H.T. (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.
3. POWER SWITCH
This is the On/Off switch for mains power to the amplifier. Note: Please ensure the amplifier is switched off and unplugged from the mains electricity supply whenever it is moved.
CHANNEL 2 THE TREMOLO CHANNEL
4. TREMOLO SPEED CONTROL
This controls the speed of tremolo oscillation when this effect (which can be switched on/off via the supplied footswitch) is being used. Oscillation speed increases when the Speed control is turned clockwise and decreases when it is turned anticlockwise.
5. TREMOLO INTENSITY CONTROL
This controls the intensity or depth of the tremolo oscillation when the effect is being used. The effect depth increases when the Intensity control is turned clockwise and decreases when it is turned anticlockwise.
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. VOLUME CONTROL
This controls the volume of the Tremolo Channel. Turning it clockwise increases the volume level of the channel.
8. CHANNEL 2 INPUTS
These are the guitar inputs for the Tremolo Channel. The top one is the 'high sensitivity' input for this channel, the bottom one is the 'low sensitivity' input which is 6dB lower (i.e. half) than the 'high sensitivity' input and has a darker sound. Always use a high quality screened guitar lead.
CHANNEL 1THE NON-TREMOLO CHANNEL
9. TONE CONTROL
This controls the tonal character of Channel 1. Turning the tone control clockwise increases the amount of high frequencies (treble) present in the sound.
10. VOLUME CONTROL
This controls the volume of Channel 1. Turning it clockwise increases the volume level of the channel.
11. CHANNEL 1 INPUTS
These are the guitar inputs for this Channel and both are identical.
Marshall 1974X Rear Panel Features:
1. TREMOLO FOOTSWITCH JACK
This is where the supplied Tremolo on/off footswitch is plugged in.
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2. LOUDSPEAKER OUTPUTS
There are two parallel loudspeaker output jacks provided for connection to the internal speaker and/or an external load, i.e. speaker extension cabinet(s). When connecting speaker(s) please always ensure that the amplifier's output impedance is set correctly (item 3).
WARNING! Never use the combo without a load attached!
Always use a non-screened Marshall approved speaker lead when connecting an extension cabinet to these units.
3. 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. If an additional 16 Ohm extension speaker cabinet is used in conjunction with the internal speaker the Impedance Selector should be set to 8 Ohms.
WARNING! An extension speaker cabinet with an impedance of less than 16 Ohms should NOT be used in conjunction with the internal speaker.
The amp should be completely powered down before the Output Impedance Selector is turned. Failure to comply with any of the points raised in this section will result in damage to the amplifier.
4. MAINS FUSE
The correct value of mains fuse is specified on the rear panel of the amplifier. NEVER attempt to bypass the fuse or fit one of the incorrect value.
5. H.T. FUSE
The correct value of H.T. fuse is specified on the rear panel of the amplifier. NEVER attempt to bypass the fuse or fit one of the incorrect value.
6. MAINS INPUT
Your amp is provided with a detachable mains (power) lead, which is connected here. The specific mains input voltage rating that your amplifier has been built for is shown on the back panel. Before connecting for the first time, please ensure that your amplifier is compatible with your electricity supply. If you have any doubt, please get advice from a qualified technician. Your Marshall dealer will help you in this respect.
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