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Old 26th September 2013, 12:43 PM   #21
AndrewT is online now AndrewT  Scotland
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Using a 3886 reliably with a 28-0-28Vac transformer depends very much on the transformer specification and your mains voltage.

A 230:28-0-28 Vac 7% regulation transformer running on 243Vac will give a very different voltage from a 240:28-0-28Vac 4% regulation running on 228Vac !!!!!

You must know your transformer and you must know your variation in the mains supply voltage.
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Old 26th September 2013, 12:53 PM   #22
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5A output seems low. Is 2x5 ampere or 5A total.
38 volt is also at bit high. I don't think the amplifier will be happy if you have 4 ohm subwoofer.

read more here
http://chipamp.com/docs/lm3886-manual.pdf
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Old 26th September 2013, 12:55 PM   #23
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Quote:
Originally Posted by Kjeldsen View Post
5A output seems low. Is 2x5 ampere or 5A total.
38 volt is also at bit high. I don't think the amplifier will be happy if you have 4 ohm subwoofer.

read more here
http://chipamp.com/docs/lm3886-manual.pdf
Wait, wait, wait.... I think there is a confusion, let me clear a bit.

My sub amp kit is different : Wintek - 200W Mono (Toshiba 2SA1943 / 2SC5200)
The transformer is 28-0-28, 5A for this kit. Isn't that enough for this 200W kit which will drive my 4ohm sub driver?

I am using LM3886 only for my 5 main channels. where I am going to use 24-0-24, 5A

In total there are two different transformers and I am keeping both the application separate from each other. Sub amp and transformer will go into a separate cabinet and rest of the five LM3886 main channel kits will go into a separate cabinet with a separate transformer.

rakesh_sharma23 may through more light on the transformer choice part. I had a detailed talk over phone with him before deciding on transformers and he cleared lot of my other doubts also.

Last edited by Jack Sparrow; 26th September 2013 at 01:07 PM.
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Old 26th September 2013, 01:09 PM   #24
AndrewT is online now AndrewT  Scotland
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Jack,
that link showing 200W into 8r0 cannot be a reliable truth.

1943/5200 cannot give 200W into 8r0. They will blow up when you try to test that level of power output.
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Old 26th September 2013, 01:33 PM   #25
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5 channels LM3886 with only 5A. I haven't build gainclones, but to me it seems to be very little power. I know that for normal audio input 1/8 of power is fine, but if you really want's to crank up the volume with moderne heavily compressed music, I think it's not enough.
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Old 26th September 2013, 02:17 PM   #26
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Quote:
Originally Posted by AndrewT View Post
Jack,
that link showing 200W into 8r0 cannot be a reliable truth.

1943/5200 cannot give 200W into 8r0. They will blow up when you try to test that level of power output.
My sub driver is 160W, 4 ohm rated, and I will be using my setup at home, is my SUB AMP choice and transformer not right for my application?

Quote:
Originally Posted by Kjeldsen View Post
5 channels LM3886 with only 5A. I haven't build gainclones, but to me it seems to be very little power. I know that for normal audio input 1/8 of power is fine, but if you really want's to crank up the volume with moderne heavily compressed music, I think it's not enough.
What we calculated was some 50W for 4ohm speakers. And there will be a PSU also to regulate the power.
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Old 26th September 2013, 03:50 PM   #27
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Please have a look at the PSU for LM3886:

Red and blue wires are coming from 24V supplies and black is coming form 0.
35A bridge rectifier : green is from (-) and yellow is from (+)
10000uf, 63V : right side - yellow is connected at (+) and left side green is connected at (-). Black is connected at opposites.

20130926_211215.jpg

Is that correct?
will the wire from the blue 0.1uf, 100V will go into the amp board?
Where the black wire will go then?
Now can I connect all this to the transformer and power it on?

Last edited by Jack Sparrow; 26th September 2013 at 03:57 PM.
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Old 27th September 2013, 04:06 AM   #28
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NO NO.. Do it like this.. and use 18GWS wire for power supply. these wire can't handle more than 1 amp of current.

0.1 uf caps should be parallel to 10000uf caps..

PLEASE.....PLEASE Sir, read all basics about power supply and electronics ones more... try to understand why each components is used and more...
If you continue like this than you will end up with a disaster.
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Last edited by rakesh_sharma23; 27th September 2013 at 04:14 AM.
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Old 27th September 2013, 04:58 AM   #29
Mihkus is online now Mihkus  Estonia
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Ive once killed a petty expensive class D amplifie boad...
Got "nice" readings fom the powe supply but you know what...

My cente taps was wired like... I had 48 volts on both sides but 0 between both 48s
What i mean... You transfome has 4 output wires, get multimeter...
Measure resistance to find 2 of the coils, mark the wires...
Now plug the transformer in without nothing on the outputs...
Now connect one of the 24V outputs to the other 24V ouput...
Now measure voltage between both 24V outputs that are alone
You should get eading of 48V or something very close.
If you dont, switch one of the 24V outputs and measure again until you get measurements between both 24-0 as 24V and 48 between both 24V outs.
If you have done that... Go and find serious wires... 1,5mm2 would be good...
Solder one to 0 of the transformer and 2 to the outputs.
Like green 24, 0 black 0 , green 24
The green ones go to your bridge rectifier and 0 remains open till you connect the capacitors.
Now you have connected and soldered everything together. Soldering is one hell of a drug
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Old 27th September 2013, 10:01 AM   #30
AndrewT is online now AndrewT  Scotland
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Post27.
The black wires form a three way PSU Zero Volts.
The picture looks correct electrically.
There are 3 output wires: +ve -ve and Zero Volts.

BUT !!!!!!
your picture shows ENORMOUS radiating LOOPs, that will emit interference and will affect all low level receiver circuits inside the chassis.

You MUST make all the LOOPs small. Very SMALL.

Look at the three wires from transformer to rectifier. Two connect directly to the rectifier AC1 and AC2. The 3rd is the centre tap. This centre tap wire must be twisted with AC1 and AC2 to form a triplet. Leave the centre tap long. Solder AC1 and AC2 to rectifier. Solder +ve and solder -ve to the rectifier. Now using that long centre tap and + & -, form a new triplet. Run this new triplet to the capacitors. Solder + to cap, solder - to cap. solder a wire across the caps zero volts. Solder the 3rd wire of the triplet to that zero volts wire.
Now solder + & - and zero volts to the caps. Form yet another twisted power triplet. Run this triplet to the amplifier.
All the twisted triplets ensure the minimisation of the LOOP areas.
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