Idea I need help with

[ambulancevoice]

hello 

i really wish to use a power transformer for my ruby build
cause i need my adaptor for my pedals
what i was thinking of doing, was using a IEC male socket going to a 30v ct transformer with the contacts on the secondary connection being "15v - 0v - 15v" fly leads which will go to this (with one 15v going to the positive, the other 15v going to the negative, and the zero to a seperate ground) http://www.thesquarewaveparade.com/images/ac-to-dc-bipolar.gif after the 12 v positive to a 100k lin "feed/starve" pot then to a power switch then to the rubys power connection

what else would i need to add/do?
and what are the basic IEC connections? im guessing (pin 1 left voltage - pin 2 middle ground - pin 3 right voltage)?

[Seljer]

err, I don't think the LM386 can take that much
the datasheet lists 12V max (a bit more depending on what version of the chip you have), and I think running it off +-15V would basically mean running it off 30V?

[ambulancevoice]

read it again
and click on the picture

[gez]

Simon is right, with your 'starve pot' set to 0 resistance you're feeding the amp from a 24V supply, which exceeds the max ratings for this device...unless you only intend to use the +12V, in which case why the split supply? 

Even if you needed split supply, you've only half-wave rectified the AC going to the regulators, in which case you could have done this with nothing more than a 15V secondary.

[gez]

Everything you need to know for basic PS design:

http://www.amazon.com/Power-Supply-Projects-BP-Penfold/dp/0900162961

Cheap too!

[ambulancevoice]

listen!!!! stop assuming that im giving an ic that can only handle 12 volts 24!! stop assuming that i dont know shit about the lm386!
im not feeding it 24v!!!
im giving a maxium of 12v +, with the starve pot giving the possibility of going down to 9 and 6 volts
im using the 30v transformer (which has connections for 15v - 0v - and another 15v) to the AC TO DC BIPOLAR 12v supply (im only using the + side, and im omitting the 12v - side, cause i dont need it) and then to the power supply
maybe you should accually READ what i wrote

[ambulancevoice]

the other fifteen volt secondary will go to ground because i only need one
this is pretty much the only way i can do this
i can find any 12v transformers here, and if could, it would be on the net
and im not buying something off the net because im not to keen on it yet

[gez]

listen!!!! stop assuming that im giving an ic that can only handle 12 volts 24!! stop assuming that i dont know shit about the lm386!
im not feeding it 24v!!!
im giving a maxium of 12v +, with the starve pot giving the possibility of going down to 9 and 6 volts
im using the 30v transformer (which has connections for 15v - 0v - and another 15v) to the AC TO DC BIPOLAR 12v supply (im only using the + side, and im omitting the 12v - side, cause i dont need it) and then to the power supply
maybe you should accually READ what i wrote

We can only go by what you wrote in your first post.  It would have been useful had you given the above info in the first place: if you don't give enough detail - your post may have been clear to you, but it wasn't to me - don't expect us to understand what you're trying to do...

[spudulike]

You might have problems with a "starve" pot - the 386 amps can still pull a fair bit of current at high volumes.
Why not use an LM317 to vary the feed voltage ?

[R.G.]

Alex, they're trying to help.

What you have said - which is all we have to go on - shows that you don't have a solid understanding of power supplies. We can't know exactly how much.

The AC-to-DC bipolar is a poor choice of power supply for you. It solves a different problem than you are trying to solve. You want +12V. You are using a 15-0-15 transformer, throwing away half of it (actually, shorting out half if "the other 15V secondary will go to ground"), then putting half the power transformer into a circuit which takes one AC signal and half-wave rectifies it into two DC power supplies, then throwing away half of that to get regulated 12V.

That transformer you have can be set up with two diodes to make full wave rectified DC and run into one regulator, no funny connections and no tossing out 3/4 of the available power to get ripple-y DC.

The IEC connector is a poor choice for a connector, not because it won't work, but because one day someone will forget or never have known that it's a transformer voltage outlet and plug an AC power cable into it. There will be smoke and flames that day. You are setting a trap for yourself if you ever use an AC power line connector for anything other than AC power line.

For the power supply, you need to ground the "0" which is the center tap of the 30V transformer, then take one diode in series with each 15V lead, tied to the diode anode (arrow). The two cathodes (banded/bar end) are tied together and then to a filter cap between the cathodes and the centertap/ground. From there, you can use a single 12V regulator to supply your regulated 12V. It makes much more sense to vary the voltage in a LM317 style regulator than putting in a "starve pot" unless you know exactly what a starve pot does.

[ambulancevoice]

You might have problems with a "starve" pot - the 386 amps can still pull a fair bit of current at high volumes.
Why not use an LM317 to vary the feed voltage ?

how would i do this? i look up at data sheet later

[ambulancevoice]

i was thinking of using the power supply from the Joe D guitar amp (25 watt) but addapting it with some sort of reasonable transformer
the only transformer i can find is 12.6 volt

[ambulancevoice]

i found a 9v - 24v 60VA 5A multi-tapped transformer
its primary connection are 200mm fly leads
its secondary is terminals marked "12v - 9v - 0v"
here is what it would look like on a schematic

http://www.jaycar.com.au/productView.asp?ID=MM2014&CATID=&keywords=9v+%2D+24v&SPECIAL=&form=KEYWORD&ProdCodeOnly=&Keyword1=&Keyword2=&pageNumber=&priceMin=&priceMax=&SUBCATID=

[ambulancevoice]

http://www.generalguitargadgets.com/pdf/ggg_reg_power_supply.pdf
or this