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Powering an amp from a generator


alhbass
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Advice welcomed. Apologies if there are other threads that would answer my question, but I'm very short of time to get sorted, so I'm leaping right in to ask....

Just learned that an outdoor gig I have tomorrow afternoon has no provision for power. I've arranged in the last half hour to borrow a 3kva petrol generator, but the owner expressed doubts about whether it would be up to powering my rig. I'm not up with the electrickery, so don't really know myself. I would like to use my markbass LMK head, rated at 300w into a single 8ohm cab. It wouldn't be powering anything else. Can anyone enlighten me? Thanks in advance....

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My experience is that class D amplifiers have better filtering than old school amps, so you are less likely to get a whine from your bass.Wost case scenario, your bass will pick up generator brush noises and whine, most of which can be reduced by EQ settings, and by keeping one hand on your strings - at all times.

With regard to power ratings, my Ashdown 500 Watt amp takes 24 watts on standby, and about 35 watts when I play through it. This is a major advantage of class D amplifiers - my class AB amplifier has the same standby power, but takes about three times the power in use.

In general, a bass amplifier's average power (what the generator must deliver) is about an eighth of the peak power (which your amplifier is designed to deliver).

David

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Power wise it will be fine, Should run the whole band without traditional lighting. But have had issues with generator gigs, Frequency is an issue if not maintained, Should be 50Hz as the mains, but could be anywhere either side. Do you know any sparks to check if it is earthed properly, They are also usually center tapped to earth to give 55 volts to earth through the yellow sockets, but this also means the blue socket and or 13 A socket is also connected this way, It shouldn't affect it but confusing when testing it. Use an RCD socket outlet on your extension to be safe

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Class D heads tend not to have such stiff power supplies - no large reservoir caps - so are more susceptible to shutting down when the power supply sags. My PA sometimes doesn't like generated power. It will just cut out as the safety circuitry kicks in, but it's annoying.

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It's biker rally season at the moment so I'm on a generator every other week. I always use a surge protected power supply, no idea if it helps but it makes me feel better!

The only problem I've ever had with generator gigs have been where the supplied generator as been too small for the PA and so it's tripped it. Once, I think we got to 7 times in the first set before the sound man saw sense and turned the thing down and disconnected one of the sub stacks. Never hurt the amps on stage though, or the PA amps as far as I know, I think most modern amps have a whole heap of protection so if anything goes wrong with power they'll shut down immediately. Annoying but better than letting themselves get damaged.

I wonder if generator power might actually be an argument for those rack mounted power conditioners that don't really seem to do anything?

Edited by Jack
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You'll be fine. The supply frequency is effected by the engine speed. The engine will be so lightly loaded that the frequency should be rock steady. The same with the voltage, there shouldn't be voltage drops, again because the alternator is putting out a small fraction of its full power.

Frank.

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[quote name='deepbass5' timestamp='1498375458' post='3324094']... Use an RCD socket outlet on your extension to be safe
[/quote]

Sorry but I disagree with this - domestic 'plugtop' RCDs are intended to be used on electrical systems where there is a connection between the neutral conductor and earth at the distribution board.

On small generator powered system, if the generator is connected to the earth by a metal stake, and not electrically connected to the generator neutral, many RCDs of that type will not allow you to power up.

David

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