5 channel transformer rating for LM4780/LM4781 - diyAudio
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Old 5th June 2007, 07:05 PM   #1
wjp007 is offline wjp007  United States
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Join Date: May 2007
Default 5 channel transformer rating for LM4780/LM4781

Noob here. Great forum. I need some advice on a budget 5 channel systems I'm designing for use with a PC. I'm planning on using a seperate powered subwoofer so I only need something for the other speakers. I'm looking at an LM4780 for the front and LM4781 for the rear. The speakers I'm planning to use are 4ohms and won't be asked to drive anything below 100Hz. I'm thinking of getting single transformer and run the LM4780 at +/- 18V unregulated and use some linear regs at +/- 12V for the Lm4781. Do you think this setup would work, and what rating transformer should I use (I'm thinking 160VA should be more than enough)?

Any advice would be greatly appreciated.

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Old 6th June 2007, 08:35 AM   #2
YFW is offline YFW  United States
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160VA could work but not work at the best condition.
Do you need full output of the 5 chanels?If yes,300VA is much better.
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Old 6th June 2007, 01:11 PM   #3
wjp007 is offline wjp007  United States
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Thanks for the note. I would think I do need the full output. I'll go with the higher rating.
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Old 6th June 2007, 05:28 PM   #4
AndrewT is offline AndrewT  Scotland
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Join Date: Jul 2004
Location: Scottish Borders
I need some advice
use stereo amplifiers.
one to the front pair, another to the rear pair, and a third to the centre channel and the sub. That allows long interconnects and much shorter speaker cables to at least some of the speakers.
regards Andrew T.
Sent from my desktop computer using a keyboard
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Old 7th June 2007, 02:52 AM   #5
YFW is offline YFW  United States
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The sound quality depends greatly on the power supply.
If you could feed good power supply to the amplifiers,you will get a very good sound.You will benefits more compared to hign end parts.

Of course,you should choose better transformers and capacitors.
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Old 10th June 2007, 12:12 PM   #6
Ponz is offline Ponz  United States
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the spec of transformer for 5 channel's +-18V unreg. and +-12V reg. voltage should be 14-0 5A x 2 and 12-0 1A x 2 or more power rating.

besides enough power of transformer, the filter capacitor needs
exceeds 2 x 10000uF, than get good sound quality.
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