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Old 20th March 2009, 02:03 PM   #1
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Default Need a good amp for a pair of 4ohm, 40w nominal fullrange speakers

Hi,
I'm planning to make an amplifier for a pair of 4ohm, 40w nominal fullrange speakers (mostly for PC use).........
.......can anyone please suggest me a good one??
I don't want it to be to costly or a hard to find one (most importantly I'm a novice,so I don't want it to be a very complex one either)
PCB designs or images are very much welcome.
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Old 20th March 2009, 04:39 PM   #2
rajudp is offline rajudp  India
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use lm4766
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Old 20th March 2009, 04:50 PM   #3
AndrewT is offline AndrewT  Scotland
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or build a mono amplifier and when it is operating successfully add a second amplifier to the PSU.
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Old 28th March 2009, 10:23 AM   #4
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HI!
I'm Planning on a dual mono lm3886,
but available 18-0-18
transformer gives only 3A,
Should it do? i wd use it for 4ohm speakers,
how much power should i get?
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Old 28th March 2009, 10:33 AM   #5
AndrewT is offline AndrewT  Scotland
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your 18-0-18 3A transformer has a VA rating of 108.
This will work for power amps with a maximum total output of 54W to 108W.

You could run one channel from this transformer or you can choose to run two channels if you wish.

Calculate the smoothing cap voltage from the AC specification.
Use that DC voltage to read off the maximum output power declared in the chipamp datasheet.

Check the size of heatsink recommended in the datasheet. Double it for cooler operation.
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Old 28th March 2009, 01:04 PM   #6
star882 is offline star882  United States
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If you're using them with a PC, pure digital is the way to go. However, pretty much all the digital chipsets are SMD, which is not recommended for a beginner. (There might be kits with the SMD components already soldered onto the board, but I'm not aware of any.)
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Old 28th March 2009, 07:12 PM   #7
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Thank u very much AndrewT

I shall use one transformer each for the two separate channels
(afraid of burning out the transformer)

I see there are lots of pcb layouts for lm3886 in this forum, I don't know which one to choose. Can you link me to one that you prefer most (have to be simple though).

Please keep helping, thanks.
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Old 28th March 2009, 07:18 PM   #8
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Hey Star882,
thanks for your post.

I shall keep the digital ones for later projects......
( hope you'd help then )
..............still got many things to learn & concepts to clear
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Old 29th March 2009, 08:36 AM   #9
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Whats the basic difference between the non-inverting & inverting designs of lm3886??
which is better??
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Old 29th March 2009, 01:11 PM   #10
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Quote:
Originally posted by AndrewT
or build a mono amplifier and when it is operating successfully add a second amplifier to the PSU.
Won't this hum?
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