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Hercules  
#1 Posted : Tuesday, February 4, 2014 1:46:35 PM(UTC)
Hercules

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Location: Hong Kong

My Sympatico was powered with 400w transformer with 24V AC winding, one transformer per channel, each module mounted on Class A amplifier case for Pass DIY (each side with heatsink of 20"x6"x3" long fin), no problem with my KEF LS50, but my magnepan MMG( most magnepan will dropping the impedence dramatically around 2 ohm at low frequency) will clip at low frequency playback of drum, organ.etc. so I can't play It very loud. currently using single ended input, in- shorted to ground. 16AWG wire to speaker terminal.

The heat dissipation should be a problem as the clip will happen even just a bit warm, from the datasheet, I think the Spike protection been triggered due to over current issue.

Can I change any resistor value to push the limit higher before the spike protection cut in?
Russ White  
#2 Posted : Wednesday, February 5, 2014 4:27:07 AM(UTC)
Russ White

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Unfortunately probably not... The weakness of he LM4780 is its ability to push lots of current. Your speakers are a particularly tough load.

For this reason I am working on a version with more current capability.

Until then, I would suggest 4-8 ohm speakers.
Hercules  
#3 Posted : Wednesday, February 5, 2014 9:59:21 AM(UTC)
Hercules

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Joined: 4/16/2009(UTC)
Posts: 56
Location: Hong Kong

Thanks... Russ, so that's the limit for this combo.......feel so pity it can't play with the Magnepan.
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