24-0-24-5 transformer for LM3875

[danielnaveen]

Hi,
I have a transformer with 24 - 0 - 24 - 5 volt secondaries which came of a DPA amplifier. Can i mask the 5 volt out and use it to power a LM3875 based amp?

Thank You

 

[AndrewT]

Hi,
yes, you can insulate the the 5V tapping and just ignore it.

Is the 5V tapping connected to the others or a separate winding?

Are the 24V tappings connected together or separate windings?

If they are connected you have a centre tapped secondary and must use a single rectifier to generate your +-V for the chipamp.
This is different from many of the chipamp PSU schematics, but all of them can be made to work with a centre tapped transformer.

 

[danielnaveen]

Thank you for the reply,
The taps are connected together so i guess i'll have to use a single rectifier, will a 6amp rectifier to enough to power the amp and will a GBU802 rectifier work with a 50Hz AC power supply?

Daniel

 

[AndrewT]

Hi,
the current rating of the rectifier is closely bound to the value of the smoothing capacitance after it.
If you go for typical 4.7mF to 10mF then 6A seems about right.
You may even get away with 1n5402 diodes which have a 3A rating.

If you were to go with +-20mF then 12A to 25A would probably be more suitable.

 

[Leolabs]

How many VA of your transformer???

 

[danielnaveen]

its 200VA

 

[Leolabs]

Wow.Plenty power for the LM3875.But the voltage is a bit high for it to drive a 4 ohms load.

 

[danielnaveen]

Wow.Plenty power for the LM3875.But the voltage is a bit high for it to drive a 4 ohms load.

I know but it should be alright with my modified PSB alpha's