smalljoshua Posted April 8, 2017 Share Posted April 8, 2017 We've got an event coming up where we (for a few reasons) need to run two lots of 10x 100V line speakers tapped at 30w each so a 300W load at the amp. We're struggling to find a suitably sized 100V line amp that's not going to bankrupt a small country to purchase and still be good (ish) quality. Considering the load of 10 of these speakers in parallel would be around 33R and I'd need to drive approx 300W into this load. Could I not just use a suitably powered low impedance amp (such as a Lab FP6400 of which I have a number available) which can drive say 1300W into 8R. I'm a bit rusty here but I think it would work? Thanks, Josh Link to comment Share on other sites More sharing options...
boatman Posted April 8, 2017 Share Posted April 8, 2017 Power = Voltage squared divided by resistance. So 1300W into 8 ohms gives 102V which sounds about right. Try it and see what happens. Link to comment Share on other sites More sharing options...
Simon Lewis Posted April 8, 2017 Share Posted April 8, 2017 Josh,You've probably forgotten some old guy saying, "An amplifier that can deliver 1250 W/channel into 8ohms or 2500W/channel into 4ohms will generate 100 Volts across its output terminals and so can drive a 100 Volt line directly.Also, an amplifier rated at 2 x 625W into 8ohms or 2 x 1250W into 4ohms may be used in bridge mode to provide balanced drive to a 100Volt line system, provided the loudspeaker cable system is not connected to ground at any point". http://www.blue-room.org.uk/public/style_emoticons/default/rolleyes.gif Simon Link to comment Share on other sites More sharing options...
sunray Posted April 8, 2017 Share Posted April 8, 2017 Typical, I started writing a reply then got engrossed in a film before finishing and posting so Simon beat me to it.We've got an event coming up where we (for a few reasons) need to run two lots of 10x 100V line speakers tapped at 30w each so a 300W load at the amp. We're struggling to find a suitably sized 100V line amp that's not going to bankrupt a small country to purchase and still be good (ish) quality. Considering the load of 10 of these speakers in parallel would be around 33R and I'd need to drive approx 300W into this load. Could I not just use a suitably powered low impedance amp (such as a Lab FP6400 of which I have a number available) which can drive say 1300W into 8R. I'm a bit rusty here but I think it would work? Thanks, Josh 625W/16ohm, 1250W/8ohm or 2500W/4ohm all come out to 100V. I often do it on a 500W/8ohm amplifier for sports/fete hire type use (there's a 500WPC amp fitted in a booth trailer normally used for lowZ cabs), that runs speakers at 40% of their tap. Typically 200W worth of speakers comes out at 80W which covers a school sports field with loads to spare. We replaced about 100 lowZ speakers on a job which were wired in stupid unpredictable series parallel combinations and choc block junctions. We replaced them with 100V speakers tapped at 12W, pulling out all of the junctions and some 1000+M of surplus cable The on-site maintenance guy put loads of messages to his superiors saying the new system would not work on their existing 2.4KW/4ohm amplifier without a matching transformer and he would not be prepared to sign the acceptance paperwork. The final impedance was around 9ohms and worked perfectly well but they did get in another company for a second opinion before accepting it. Link to comment Share on other sites More sharing options...
smalljoshua Posted April 9, 2017 Author Share Posted April 9, 2017 Josh,You've probably forgotten some old guy saying, "An amplifier that can deliver 1250 W/channel into 8ohms or 2500W/channel into 4ohms will generate 100 Volts across its output terminals and so can drive a 100 Volt line directly.Also, an amplifier rated at 2 x 625W into 8ohms or 2 x 1250W into 4ohms may be used in bridge mode to provide balanced drive to a 100Volt line system, provided the loudspeaker cable system is not connected to ground at any point". http://www.blue-room.org.uk/public/style_emoticons/default/rolleyes.gif SimonI vaguely remembered that being said however wanted a sanity check! Thanks, Josh Link to comment Share on other sites More sharing options...
soundspider Posted April 10, 2017 Share Posted April 10, 2017 Or alternatively, if you're buying new? http://cpc.farnell.com/pulse/vs360/slave-amplifier-100v-360w/dp/DP33519 Link to comment Share on other sites More sharing options...
Stuart91 Posted April 11, 2017 Share Posted April 11, 2017 Or alternatively, if you're buying new? http://cpc.farnell.com/pulse/vs360/slave-amplifier-100v-360w/dp/DP33519 It's worth pointing out that these amps only have unbalanced inputs on phono connectors. Might be an impediment in certain situations. Link to comment Share on other sites More sharing options...
Chris Beesley Posted April 11, 2017 Share Posted April 11, 2017 Josh, would this be of any use? https://prolight.co.uk/product/sl-350-100v-350w-slave-amplifier Link to comment Share on other sites More sharing options...
smalljoshua Posted April 12, 2017 Author Share Posted April 12, 2017 Hi Chris, this would work but I'd need two of them which would be a good amount heavier than a single fp6400 @ 10kg. I must admit I missed that on your site though! Now if you've got 20 of your 50w music horns hidden in a corner I could buy that'd be great ;) Josh Link to comment Share on other sites More sharing options...
Original Beef Posted April 12, 2017 Share Posted April 12, 2017 Hi JoshMy listing on Ebay may be of some use to you www.ebay.co.uk/itm/292081935703?ssPageName=STRK:MESELX:IT&_trksid=p3984.m1555.l2649 Link to comment Share on other sites More sharing options...
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