Looking to build a power supply

[MmmPedals]

I have a few hundred thousand 9v PS laying around and they all make my pedal go HMMMMMMMM.
So I would like to make myself a PS for my pedal board to power them quietly. I like the look of this http://tonepad.com/getFile.asp?id=111
I would wire it up so i could plug any PS into it (i guess like its meant to be) BUT...
I have 9v PS. can this be used or adapted to be used with a 9v?

[.Mike]

The LM-317 has a dropout voltage around 2 volts, so you won't get 9v out if you put 9v in-- you'll get closer to 7v max.

I don't know if it's a good idea or not, but depending on how much current you draw, and how much current your adapter can provide, you might be able to use a 9v adapter. I have a few 9v adapters that are rated at 1 amp at 9 volts. Unloaded, they put out more like 18 or 19 volts. The more current you pull, the closer the output voltage of the adapter gets to 9v. So, my thinking is that if you have a 9 volt 1 amp adapter that puts out 18 volts, and you only pull a small fraction of the available current-- 150 mA, for example-- maybe the adapter's voltage would remain high enough to cover the dropout of the regulator.

Do you have any 12v adapters...? 

Mike

[Taylor]

That circuit is made to accept the 120 volts AC coming out of your wall (or a different, higher voltage if you live outside the US). You don't plug a 9v PS into it.

If you want to stop hum, you may just need to add better power supply filtering or possibly a regulator.

[.Mike]

Darn... didn't look at it close enough...  

It looks like it actually takes a 12V AC adapter. It's listed right there in the parts list. Go figure.

[Taylor]

It's a 12v transformer, not adapter, no?

[.Mike]

Yup, but no place to mount it on the board, so something like this would provide the 12v AC that it needs.

Of course, you could mount a transformer inside the enclosure.

Sorry for the confusion.

Mike

[linny1982]

hi all. i've been looking at making a ps for a while and was wondering if this trasformer http://www.jaycar.com.au/productView.asp?ID=MM2013&keywords=mm%2D2013&form=KEYWORD is suitable for the tonepad project. i found one of these in my parts box (can't remember why i got it). would you just hook up the two outside wires and leave the 0v disconected? 

[Fender3D]

hi all. i've been looking at making a ps for a while and was wondering if this trasformer http://www.jaycar.com.au/productView.asp?ID=MM2013&keywords=mm%2D2013&form=KEYWORD is suitable for the tonepad project. i found one of these in my parts box (can't remember why i got it). would you just hook up the two outside wires and leave the 0v disconected?  

If you connect the 2 outside wires you'll supply 24Vac that, with the tonepad's full wave rectifying will provide ~ 33.6Vcc at the input tip of 317
Not a real problem though, since 317 allow for a max 40V input to output differential voltage, but you'll have to mess with the adj. resistors in order to provide your 9Vcc.

EDIT:
sorry I just realized it's 6,3+6,3Vac 

[linny1982]

thanks.

[Tubebass]

My son gave me a 9 volt 1 amp wall wart that is screwed together. It puts out about 13v unloaded. I just took it apart and added a 7809 regulator. It will deliver around 200 ma at 9v, enough to power lots of pedals. Works great.

[petemoore]

  Most of the 9v dapters with modest load are measuring well above 9v.
 12v or more is common.
 ''Under load'' being the operative deal, too low and the regulator quits [needs two volts over it's output].
 Feeding the regulator a voltage about what it needs is nice...too low and it doesn't work, too high [large voltage drop across the regulator] and heat dissipation becomes more of an issue.
 If you've wired one you can wire 100, they're not too expensive, if it seems they'll get hot [increase heatsink] or otherwise have undervoltage shutoff [start with a higher ma. or otherwise loadbearing voltage source..different adapter] or distribute the load over a greater number of independant regulators.  

[MmmPedals]

  Most of the 9v dapters with modest load are measuring well above 9v.
  12v or more is common.

So i took out my dmm and measured my adapters and what do you know. 12-14 volts.

[geertjacobs]

It looks like it actually takes a 12V AC adapter. It's listed right there in the parts list. Go figure.

If a rectifier and regulator circuit can take 12VAC, it can also take 12VDC. (*)
The rectfier is just not very useful useful with the 12VDC input, although it is a guarantee that you will never have polarity problems on the input.
Which is a nice side-effect IMO :-)

I built this power supply and use a 15VDC unregulated (puts out up to 18V without load) wallwart to feed it.
So as long as you heat sink the LM317, this can really be quite a universal and very clean power supply.

(*) edit: maybe 12V DC is right on the edge here: 12VDC minus two diode voltage drops, might just not be enough for the LM317 to supply 9V under full load. See datasheet.
But the DC input prinicple works fine and polarity free for my 15VDC wart.