Reducing AC voltage safely

[Meerkat 70]

Does anyone have a simple method to reduce 25 volts AC to 12 volts AC.. I have a small speaker protection board that needs AC not DC/ I want to tap into the existing transformer secondary that is putting out 25-0-25 volts. I do have a small transformer that I can use but the chassis space will not let me use it.

Any help is appreciated, The circuit needs very little current to operate so I do not believe the existing mains transformer would be taxed as it puts out about 3-4 amps full ooad Thanks Wayne

 

[nigelwright7557]

Use two back to back zener diodes in series.
12 volt zeners should work ok.

 

[Meerkat 70]

Thanks Nigel How big do they need to be. will a 1 watt work.. Do they have to be in each line or across the ac line Thanks

 

[nigelwright7557]

Thanks Nigel How big do they need to be. will a 1 watt work.. Do they have to be in each line or across the ac line Thanks

How much current will they be passing ?
A 5 watt 12v zener can pass up to about 400mA.
A 1.3 watt 12v zener can pass up to about 100mA.

They have to be in line.

 

[Sorento]

in one line, not across;
however if your 25-0-25 powers the amp and anything of the protection circuit connects to the amp as well, unexpected things may happen - protection may not work correctly or become damaged or ... depends on particular circuit;
also 12v ac will no longer be sinusoidal.

 

[Meerkat 70]

Thanks Payloadde, given the problems that could occur, I am going to reorient the Toroid that I am using to allow enough room for the small 12 volt 1.2 amp transformer that will power the protection circuit. This will also give me room for the pc board as well. Thanks for the tips everyone. I did post pictures of my amp under Dynaco 120, I changed the power supply from the one pictured to a pc board with 20,000 mfd on each channel. Cheers