Transformer question

[ambulancevoice]

i plan to build a ruby amp, with a 10 inch speaker and transformer that has 240V to 12v and 9v, on the transformer there are three lugs on the secondary connection, one is marked 12v the other 9v, and the other says 0V (which i know is ground), the primary connection has 200m fly leads

my quesitions
i wanted be able to switch from 9V to 12v, is this possible with the 12v/9v seperate lugs? (out of my own initiative, i think it would be possible) and would i have to use a ON(9V) - OFF - ON(12V) (which can act as a power on off switch) or just On(9V) - ON(12V)?

[ambulancevoice]

http://www.jaycar.com.au/productView.asp?ID=MM2014&CATID=19&keywords=&SPECIAL=&form=CAT&ProdCodeOnly=&Keyword1=&Keyword2=&pageNumber=&priceMin=&priceMax=&SUBCATID=411

there is the transformer

[brett]

Hi
9 V AC and 12 V AC are very different to the DC that you'll want to connect to the 386 in the Ruby.
Given the low currents involved, you could use just the 12V AC tap, a rectifier diode (1N4001/4/7) and a smoothing cap (e.g. 1000uF 25V) to get about 15V DC.
Then, feed the 15V to two regulators - a 7812 for 12 V and a 7809 for 9 V.  A SPDT switch can be used to choose between 9 and 12 V as you've indicated above.
Apologies if you already knew all this.

[petemoore]

  http://geofex.com/Article_Folders/Power-supplies/powersup.htm
  Just so you aren't searching everywhere else for hours and hours..like I was two days ago, 'for effects' is what threw me off of the very applicable content in that folder, coz I'm buildin' an 'amp'.

[jmusser]

I see someone else is an Escher fan. I have his "Rind" tattooed on my left arm. Of course that's not DIY related, but I saw your "hand drawing hand" picture.

[ambulancevoice]

damn, sounds like two much work for me
eh, @#$% the transformer
ill just use a dc jack and a power adaptor with switchable voltage

[sfx1999]

That transformer is overkill.