Date: Tue, 17 Apr 2007 10:23:53 -0700
Reply-To: Robert Fisher <refisher@MCHSI.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Robert Fisher <refisher@MCHSI.COM>
Subject: Portable instument amplifiers in Vanagons was Re: Everybus photos
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While I'm as much a sucker for reinventing (or at least jerry-rigging) the
wheel as the next guy, they do make battery-powered combo amps just for this
purpose. Well maybe not specifically for playing out in a field at a VW
gathering, but you get my drift.
Cya,
Robert
----- Original Message -----
From: "Matt Roberds" <mattroberds@COX.NET>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Tuesday, April 17, 2007 4:49 AM
Subject: Re: Everybus photos
>> From: The Bus Depot <vanagon@BUSDEPOT.COM>
>> Date: Mon, 16 Apr 2007 23:04:12 -0400
>>
>> Electronic keyboards are no better, since these are usually acoustic
>> jams in the middle of a field with no electricity; wandering up with
>> a cheesy Yamaha plastic keyboard with 4 inch speakers and D batteries
>> just wouldn't cut it.
>
> Get a guitar amp with a good speaker but thrashed electronics, or an old
> stereo speaker. Also get a two-channel car stereo amp (50 to 100 watts
> or so) that has bridgeable outputs, and a couple of gel-cell batteries.
> Put the amp and the batteries in the bottom of the cabinet and wire it
> up. Also wire the batteries to a connector on the outside of the
> cabinet, so you can (Vanagon content) plug it into the van to recharge
> while you're driving home. If it's an old stereo speaker, mount a
> handle to the top so you can schlep it around. For a guitar amp or a
> speaker, you could even put some lawnmower wheels on it if you're feeling
> really lazy. :)
>
> Using the power of math, I will try to show that this isn't an insane
> idea. 50 W is 4.2 A at 12 V; the amplifier won't be 100% efficient but
> you could probably get 66%, making it draw about 6.3 A. The keyboard
> itself probably doesn't need much - maybe another 1 A @ 12 V, giving you
> a total draw of 7.3 A. A 12 V, 12 Ah (20h) gel-cell weighs about 8.8 lbs
> (4 kg) and could give you 7.3 A for an hour before being completely dead.
> This is an hour of tunes at 50 W continuous - in other words, turn the
> volume up all the way, tape down the lowest key on the keyboard, and walk
> off. At less than full volume, and with not playing speed metal on the
> piano, the average draw will probably be less, making the battery last
> longer.
>
> Matt Roberds
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