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Old 2nd April 2011, 08:25 PM   #1
bs1777 is offline bs1777  Canada
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Default Building an amp

Hi. i am building an amp and i need some help. This is what i have so far.

Amplifier board

L12-2 Power Amplifier 2-CH Assembled boards + heatsinks on eBay.ca (item 110596887783 end time 08-Apr-11 12:05:43 EDT)

PreAmp

http://cgi.ebay.com/Audio-Pre-amplif...#ht_3830wt_833

-Thats all i have. I need help or recommendations on a case, and i way to power the amp. And possibly a way to wire it all and hook it all up.

-Thanks
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Old 3rd April 2011, 04:11 PM   #2
Minion is offline Minion  Canada
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Seems like you are asking a lot ..... only you would know how to wire it up , I"m sure the instructions came with the kit which should show how to wire it up .......

As for a case there are places that sell cases like "Par Metal" .....

Par-Metal

I generally either make a case out of wood and use a metal paceplate (from a metal supply house or steel/sheet metal shop ) or I salvage a case from an old amp and re-use it ......

To power the Power amp you are going to need a Power transformer that is 35v-0v-35v AC and 500vA and a Power supply board (rectifier and large caps) and for the preamp you need a Transformer that puts out 6v-0v-6v AC , the Preamp has it"s own rectifier and caps ......

Generally the case and Power supply is going to cost you more than the amps and preamp boards , a lot more .....

Good luck ......
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Old 3rd April 2011, 05:27 PM   #3
bs1777 is offline bs1777  Canada
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Ok. thanks for the feed back, but one question. Why a 35v-0v-35v AC transformer? The amp wants 50 volts. And for the power supply, could you recommend anything?

-Thanks
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Old 3rd April 2011, 06:10 PM   #4
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When you rectify the output from the transformer your effective voltage is the output of the transformer multiplied by 1.414 (square root of two). You can read up about why this happens here:

Rectifier - Wikipedia, the free encyclopedia

I am sure there is also some good info in the power supply section in this forum.

You can easily create your own power supply, have a look at the 4xPA150 Amp thread and you can see one I knocked together with a couple of bridge rectifiers, some caps and a couple of resistors.
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Old 3rd April 2011, 06:51 PM   #5
Minion is offline Minion  Canada
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Like Ian said , The AC voltage gets multiplied by 1.4 when rectified to DC , And because each channel of the amp is 125w or 250w total you need about double that amount of power in the power transformer as most amps of this type are at best 50% effecient .....

You can make a DC PSU board quite easilly , just a 20a bridge rectifier , and say 4 10,000uF 63v capacitors and that is about it ...... might cost $20 max , The power transformer on the other hand is going to run you upwards of $50 -$100 , for this reason I usually try to salvage transformers from dead amps ......


Cheers
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Old 3rd April 2011, 08:16 PM   #6
bs1777 is offline bs1777  Canada
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Quote:
And because each channel of the amp is 125w or 250w total you need about double that amount of power in the power transformer as most amps of this type are at best 50% efficient
Im a little confused on what your mean. Could i not just run the wires from the transformer to the PSU then double the wires on the PSU output to have one going to each amp?

-Thanks
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Old 3rd April 2011, 08:25 PM   #7
Minion is offline Minion  Canada
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What I"m saying is that you need a 500va Transformer (which will put out close to 500w) because the amp will dissapate half the power in heat .... so even though the amp only puts out 250w you will need a 500w transformer ......

Cheers
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Old 3rd April 2011, 11:21 PM   #8
bs1777 is offline bs1777  Canada
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So my two amps put out 120 watts RMS each. Does that mean ill need a 240 watt transformer for each amp, so in total ill need a 480 watt transformer. Is that right?

-Thanks
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Old 3rd April 2011, 11:43 PM   #9
Minion is offline Minion  Canada
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Yes , accept the don"t sell transformers in watts generally , they go by a vA rating so 500vA or larger will do ......
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Old 3rd April 2011, 11:49 PM   #10
bs1777 is offline bs1777  Canada
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Ok. Thanks. and i think i found a perfect one. In case you want to see it...

Avel Y236803 500VA 35V+35V Toroidal Transformer
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