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10. Gain
The VBA400 is an all valve bass head and as such is ideally suited to creating thick musically overdriven tones or warm clean tones. If you require a clean bass sound turn this control up until your bass just starts to distort and then back it off slightly. If on the other hand you would like a distorted sound, simply turn up the Gain control until the required amount of distortion is achieved. Another tip, for those of you who have got active basses who want a distorted tone, is to try plugging your bass into the Passive Input. This will cause no harm and may provide the sound you are looking for.
may give you the sound that you are trying to capture.
If you are using a Tuner
13. Passive
This input is designed to take the signal from a passive bass. If your bass guitar is passive plug it in here. We recommend that you always use a high quality screened cable for this to help prevent noise, interference and unwanted feedback.
5. D.I. output
The VBA400 features a low impedance, balanced XLR D.I. Output for connection to professional recording or P.A. equipment.
See Item 15 on front panel for more details.
6. Impedance Selector
It is imperative that the output impedance selector on this amplifier matches the impedance of the speaker(s) that it is driving.
The VBA400 delivers 400 Watts R.M.S. into 2 or 4 Ohms. Both the VBC810 and VBC412 cabinets are 4 Ohm cabinets. Therefore if you
To ensure optimum cooling of the amplifier in all operating environments, the fan has two operating speeds, low and high. Low should be selected for normal operating situations. However, if this amplifier is going to be used in close proximity to other units generating appreciable amounts of heat, or if the ambient air temperature is high, the higher fan speed should be selected. The VBA400 features over temperature protection which will shut the unit down should internal temperatures become excessive, due for example to obstructed front or rear air vents. This protection is
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Tuner Mute
The VBA400 features a Tuner Mute facility. On the rear panel there is a tuner output, item 1, which allows you to keep a tuner connected permanently
11. LED
Indicates when the Tuner Mute facility is in use.
12. On/Off
Allows you to switch the Tuner Mute facility on and off.
Inputs
Though the Passive and Active inputs were designed around the signal from an active bass and a passive bass guitar respectively, you should experiment to see which input best suits your style. Don’t worry, connecting your bass to the wrong input will not harm your VBA400 but
14. Active
This input is designed to take the signal from an active bass. If your bass guitar is active plug it in here. Again we recommend that you always use a high quality screened cable to help prevent noise, interference and unwanted feedback.
15. D.I.
The VBA 400 features a D.I. Output, item 5 on the rear panel, designed for connection to professional recording or P.A. equipment.
By selecting ‘Pre’, the signal for the DI will be taken from a point in the signal path before the front panel controls and will only be affected by the Tuner Mute, Item 12. This means that you will have no other influence over your sound being sent to the external recording or P.A. equipment connected to the D.I. output socket. By selecting ‘Post’, the signal for the DI will be taken after the Gain and Equalisation controls (but before the master volume control), giving you tonal and level control over the signal being sent to the external equipment.
are using one cabinet ensure that the impedance selector is set to 4 Ohms, and if you are using 2 cabinets ensure that the impedance selector is set to 2 Ohms.
Failure to do this can result in serious damage to the amplifier.
7. & 8. Loudspeaker Outputs
For connection to VBC810 and or VBC412 cabinets. See above for impedance details.
Always use short, high quality, heavy duty speaker leads to connect this amplifier to the loudspeaker cabinets. Two speaker leads are supplied with the amplifier for this purpose. Do not use screened, guitar type, leads.
9. Fan Speed - Low & High
The VBA400 features 12 valves in total, 8 of which are power valves. Normal air convection would not be sufficient to keep such an amplifier cool, and the VBA400 therefore features a fan which sucks cool air through the front vent and pushes the resulting warm air out through the rear vent.
10. H.T. Fuse
Always ensure that the correct value fuse is fitted - see rear panel for details.
If this fuse fails repeatedly, you should refer the amplifier to a qualified Marshall service agent.
11. L.T. Fuse
Always ensure that the correct value fuse is fitted - see rear panel for details.
If this fuse fails repeatedly, you must refer the amplifier to a qualified Marshall service agent.
12. Mains Input
Connects the amplifier to the mains power supply.
The VBA400 is able to operate on 100, 115 or 230 Volts A.C.
ESPAÑOL DEUTSCH
VBA400
Rear
Panel
Features
(page
26)
Valve
Replacement
1. Tuner Output
The Tuner Output allows you to keep a tuner in- line at all times. See Tuner Mute in the Front panel Functions section for a full overview of this facility.
Effects Loop
The VBA400 features a series effects loop for optimum connection of external effects. As this is a series loop, all of the
2. Send
For connection to the input of an external effects processor.
3. Return
For connection to the output of an external effects processor.
4. D.I. Normal / Earth Lift
Linking one piece of earthed electrical equipment to another earthed piece of electrical equipment can result in an audible hum, due to the formation of an earth loop. In the past people would get round this problem by removing the earth of one of the appliances, which is of course extremely dangerous. The VBA400 features an Earth Lift which allows you to safely ‘lift’ the D.I. signal earth on the amp, should you be experiencing earth loop hum problems.
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The valves fitted at the Marshall factory have been extensively tested and selected to ensure close matching of electrical characteristics, which, in conjunction with the amplifier’s internal bias and balance controls (which are not user adjustable) should ensure long and reliable operating life.
As with any valve amplifier, the valves (particularly the output valves) do not have an infinite life and will require replacement at some point. The life expectancy of a set of valves depends on many factors including how frequently the amplifier is used, the quality of the valves fitted and proper use of the mains and standby switches when powering the amplifier up and down.
Signs that the valves are nearing the end of their useful operating life include loss of perceived output power, increase in valve microphony (detectable as a background ‘ringing’ type noise) and deterioration in tone. When the time comes to fit new valves it is strongly recommended that only Marshall replacement valves, tested to the same specification as the originals, be used, and that these are installed by an approved Marshall service agent who has access to the measuring equipment required to set the internal bias and balance controls to optimally suit the new valves being fitted.
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