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Time to step up!


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Hi All.


I have a 150w 8 Ohm Amplifier with an external 100v line step up audio transformer with 3 secondary taps of 100w/200w/300w. Now here is the problem. I have 2 taps to choose from of 100w or 200w. I have a load of 111.11 Ohms (90W) on the secondary side of the transformer. The problem is at 200w there is increased resistance of the transformer insertion and of course the amplifier only puts out 150w which is fine for the load but there will be less voltage and thus less current and risk overdriving the transistors in the amplifier to increase the overall output.


Option 2 is to use the 100w 100Ohm Transformer on the same load but there is increased voltage and current from the amplifier which will saturate the transformer at full power and risk damage to the amplifier.


Option 1 seems the best course of action and just generally accepting overall volume. IS THERE a CALCULATION in ohms law I can use. I cannot determine the amplifiers voltage or current output as it obviously changes by the millisecond! Would I need to take an reading worst case scenario perhaps.


Many Thanks,






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To be honest I'm a bit confused. I've always treated the taps on a 100V line transformer as 'volume' settings - and always simply added up the total number of tap levels and if these are less than amplifier output wattage capability, I've not worried at all.


So with a 100W amp, the old horns I had had 1,5 and 20W taps. If I had 10 speakers using their 5 watt tap, and a couple on 20W, then that's 90Ws so I was happy. It never occurred to me to try any maths - as all historic practice seems to simply add up the wattage taps.


Is there a need to measure impedances and do this kind of maths, when 100V systems are usually foolproof?

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