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Old 10th September 2013, 05:22 AM   #11
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The case arrived today!!

The power supply is connected to a switch on the back and a power plug. There is also an LM388K adjustable regulator connected to some resistors and one big capacitor. There are three LEDS wired into that mess.

Anyway back on to what to do next, ingenius that is cool but i think i will just get one channel working for now so i dont have to get another Toroid.

Yeah Jaycee it doesnt look like i will be able to build something very powerful but thats ok i guess. If i can get an amp going with what I have got curently I will be happy, if not its not the end of the world.

Thanks Ian! Hopefully I dont get electrocuted at any stage

So guys with what i have got can I get one LM3886 up and running? And what should i do with the regulator and capacitor?

Thanks everybody
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Old 10th September 2013, 08:34 AM   #12
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Also I measured the case and it measures 80mm deep so I can fit a new transformer if need be
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Old 10th September 2013, 09:44 AM   #13
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Quote:
Originally Posted by ingenieus View Post
The transformer will give you a DC output voltage of 21V. The LM3886 specifies a minimum of 20V, but this is not enough for a 100W amp. The good news is that you can bridge the LM3886 for more power. Here is the application note that explains how it is done:

http://www.ti.com/lit/an/snaa021b/snaa021b.pdf

Here is an example of such a project:

DIY BPA300 6x LM3886 300W audio Amplifier

It uses three LM3886 per board in parallel to increase the current capability. Two of these boards are then bridged. Doing this will probably exceed the 160VA that your transformer can deliver, but it goes to show that the LM3886 can be used in all sorts of ways.
the 20V minimum = +/-10V.
2*15V transformer will give you about +/-19-20V loaded.

Last edited by AudioSan; 10th September 2013 at 09:47 AM.
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Old 12th September 2013, 07:02 AM   #14
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So what is the best option for me?
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Old 12th September 2013, 02:42 PM   #15
jaycee is offline jaycee  United Kingdom
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Location: Norwich, UK
I wouldn't bother with bridging if this is your first amp. You will be surprised how loud 30-50W can go with good speakers. You need to have pretty inefficient speakers to justify 100W in a domestic listening environment.

Find a simple straightforward LM3886 kit (or make a PCB make 2 for stereo, and start there. If you find the 20-ish watts with a 2x15VAC transformer isnt enough, you can upgrade it to 2x18 or 2x25 later. Make sure you use 35V rated capacitors if you go up to 2x18VAC (will give +/-25VDC supplies), or 50V rated if you go up to 2x25VAC (will give +/-35VDC supplies)

You will still learn a lot, particularly about mechanical construction and power supply wiring.
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Old 12th September 2013, 03:31 PM   #16
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If i make one onto a PCB rather then buying pre soldered is it going to be far more expensive?

And can i go stereo? Wont i then be really, really short on power?
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Old 12th September 2013, 04:12 PM   #17
jaycee is offline jaycee  United Kingdom
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Quote:
Originally Posted by cjflis View Post
If i make one onto a PCB rather then buying pre soldered is it going to be far more expensive?

And can i go stereo? Wont i then be really, really short on power?
If anything it will be cheaper buying a bare PCB or even a self-assemble kit rather than a finished board.

160VA of transformer is plenty of power for a stereo pair - this is what most off-the-shelf integrated amps use anyway. Back it up with a decent amount of power supply capacitors (I used 2x4700uF per voltage rail) and it'll be just fine.
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Old 12th September 2013, 04:17 PM   #18
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chipamp.com have a kit with PSU Board and part. 2x LM3886 Board and parts for $70+ $18 shipping.
all you need then is conections, wires and nuts, bolts and speacers.
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Old 12th September 2013, 05:41 PM   #19
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OK thats good JayCee, i dont know about a full kit though audiosan.

This is what I am looking at:

LM3886 Power Amplifier PCB FOR DIY NEW | eBay

I cant see much cheaper then that. Are there different PCB layouts of the LM8336 or is it all uniform?
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Old 12th September 2013, 06:06 PM   #20
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there is a lot of layouts.
chipamp.com also have PCB kits. 1xPSU+2xchipamp PCB's for $18+$18shipping.
i doubt you can source the part yourself for $52inkl shipping.
so why not a kit? this is quality parts. not China mic mac
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