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Old 27th October 2006, 01:29 AM   #1
ew is offline ew  United States
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Default How big of an amp can I make with this?

Greetings, I recently picked up a rather large transformer 30-0-30 670VA & am looking to make a ridiculously large chip amp. Any ideas?
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Old 27th October 2006, 09:21 PM   #2
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at 30-0-30 the supply voltage will be pretty high so you will probably need to run into 8 ohm loads unless you parallel some chips. If you went with straight LM3886 you should be able to get 6x60W into 8 ohms, give or take. So 360W of output power. If you wanted one large amp then you'd need to do 4xLM3886 bridge/parallel (BPA) or a 6 chip version, 3 in parallel on each side of the bridge. Just some ideas. Power output is a guesstimation.

-SL
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Old 28th October 2006, 08:48 AM   #3
AndrewT is offline AndrewT  Scotland
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Hi,
30-0-30Vac would be a good start for a 4ohm amplifier.

BUT

It would better suit a discrete design with that sort of voltage.

Parallel pairs or triplets of chipamps starts getting beyond the simple intention for using a chipamp.

working backwards from your transformer rating
670VA supports about 420W of output power.
This could be 210W+210W into 4ohm
but this needs 35-0-35Vac to get the necessary DCrail voltage.
or
140W+140W+140W into 4ohm. That is about perfect for 4ohm drivers and running on +-44Vdc
Ah! a three channel front of house amp for a 5.1 system.
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Old 28th October 2006, 10:13 PM   #4
ew is offline ew  United States
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the 140x3 sounds interesting & just oddball enough to get my attention. Would how many LM3886's per channel would such a beast require? thanks again!
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Old 29th October 2006, 07:06 AM   #5
AndrewT is offline AndrewT  Scotland
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Hi,
Quote:
Parallel pairs or triplets of chipamps starts getting beyond the simple intention for using a chipamp.
how many? a lot! an awful lot!!
and the voltage does not suit chipamps.
Have another read of the datasheet, particularly the
supply voltage vs load impedance
and dissipation/heatsink vs (load + voltage).
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Old 29th October 2006, 05:43 PM   #6
ew is offline ew  United States
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Could the high voltage be taken care of by using a regulated ps? Also, could I use something like Brian GT's LM3886 Stereo Kit x3, one for each channel to keep things simple? Thanks again.
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Old 29th October 2006, 06:17 PM   #7
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This is simple

http://www.diyaudio.com/forums/attac...amp=1114046322

http://www.diyaudio.com/forums/attac...amp=1114369981


This post will explain implementation

Lm3886 Bpa

Parallel as many as you like. I went up to four with good results.

You will have to find a really high current regulator. There are people on this site, who reported using +/-42 volts without problems
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