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Post subject: Using the Passport PD150Pro on 12V inverter
Posted: Thu May 19, 2011 10:54 am
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Hobbyist
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Fender used to come out with a DC-DC inverter for their Passport sound systems. This made it ideal to operate in a 12V application for sound reinforcement from a vehicle. These are no longer available. Have any people operated the PD150Pro from a inverter? We have tried to operate the PD150 using a 400W modified sine wave inverter, however it does not even power up the Fender amp. What are others doing? Suggestions?
Thanks


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Post subject: Re: Using the Passport PD150Pro on 12V inverter
Posted: Sun Jun 12, 2011 7:47 am
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Aspiring Musician
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You either need a true sine wave inverter, or a line conditioner to smooth out the stepped wave that comes out of a modified sine wave inverter. I'd recommend you go for the true sine wave inverter. They are less expensive than they used to be, and they are more efficient than a line conditioner.

The latter has a heavy overhead and will cost you a lot of amp hours in not much time.

Digital sound amplification doesn't tolerate stepped wave power sources.


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Post subject: Re: Using the Passport PD150Pro on 12V inverter
Posted: Sun Jun 12, 2011 8:57 am
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Aspiring Musician
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To be clearer here:

The original square wave inverters would basically deliver DC electricity at 110 volts positive, and then electronically switch to 110 volts negative, switching 120 times a second in order to create 60 cycle AC power. The square corners to the wave would create havoc with electronic devices because electricity doesn't really turn a corner like that. It has momentum. Instead of a real sharp corner, it forms a squiggle, which comes across as an infinitely high frequency harmonic.

Electronic stuff like sound amplification systems don't like infinitely high frequency harmonics. It makes them spill ones and zeroes all over the place. Very messy.

Modified sine wave inverters do the same thing, except they have more intermediate steps and they switch more rapidly. They go from off to 55 volts positive, to 110 volts positive, to 55 volts positive, to off, to 55 volts negative, to 110 volts negative, to 55 volts negative, to off, and they do all that switching 60 times a second. More devices tolerate this, but it still has square corners to the steps, and that still creates infinitely high frequency harmonics.

True sine wave inverters have line conditioners built in which are tuned to the inverter. The ones I understand have high mass 1:1 transformers built in which create a kind of electrical momentum that smoothes out the waves of a modified sine wave inverter creating actual sine waves with no steps. These transformers are among the most efficient "machines" created by humanity. They don't heat up a lot and they don't use a lot of power to do their work.

Oh, and most of these inverters have a low power mode that kicks in when they don't sense an electrical load. They basically shift the timing so that the "off" part of the wave gets a bigger slice of the time pie, and the powered part of the wave becomes a brief pulse used just to sense load. Inverters consume less power when they are off, and so, an inverter that normally consumes 10 to 50 watts overhead (mostly in the form of heat generated by the switching transistors) instead consumes two watts, or one watt or half a watt.

If anything starts trying to get power from the pulse, then the powered part of the wave fattens out and the inverter starts acting like a power station again.


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