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JozzaG 3rd February 2010 11:12 PM

LM1876 power amplifier
im new to this amp building thing and im having difficulty.
ive bought a few parts and im just having difficulty with the power supply, ive got a 240V 50Hz input to 24V AC max 3A output transformer, however it has only 2 leads and is not centre tapped like i orignally planned or was told. its model is the M2158L transformer and i was looking for some help on how to wire it up and use it in my amplifier.

i have also got a bridge rectifier and most necessary parts for the power supply im just stumped by the transformer as i got my power supply drawings from another persons original schematics

Iain McNeill 3rd February 2010 11:55 PM

Sorry, but you got the wrong transformer. This one right?
Altronics - Your One Stop Audio Visual & Electronics Supplier

I think you'll have to chalk this one up to education. Try searching for a 24+24 output. Remember that AC voltages rating is multiplied by 1.414 when you rectify for a 24V winding will produce about 34VDC.

Running the amp single ended with a big cap on the output isn't worth the hassle neither is trying to create a phantom center tap.

The only thing I can think of is to wire it up so that the transformer drives the +ve supply on one half cycle and the -ve supply on the other half cycle. Tie one wire to the center tap and then a single diode from the other wire one to each cap. Half wave rectifier. It'll have a lot of ripple.

JozzaG 4th February 2010 01:45 AM

Would it be simplier to just scrap the transformer i have an buy a new 18-0-18 toroidal transformer.
Altronics - Your One Stop Audio Visual & Electronics Supplier
my only difficulty then is wiring it because of the very minimal datasheet info on toroidal transformers.

what other uses would the M2158L transformer have i.e other electronics that would use this particular transformer

AndrewT 4th February 2010 01:23 PM

buy the correct transformer for this project. 18+18Vac ~4Aac will be about right for one or two channels into 8ohms.

Put the single secondary into stock for a future project, maybe a headphone amp or an active pre-amp.

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