possible mods (aka questions!) for AMZ DC Power Supply

[therealfindo]

I'm thinking about building a power supply box - but not a mains voltage one (e.g. Spyder) because I don't want to die. Basically. I'm looking at this AMZ schematic http://www.muzique.com/power.htm which is powered by an 18v dc wall wart.. but I don't need the 18v out and I don't need the tip+ out either. What I do need is at least one output which is minimum 300ma, because that's what my delay draws (I currently have a harley benton powerplant jr but the delay doesn't like being a part of that relationship).

here's the schematic:



So, am I right to think that I can ignore ic5 and the 17.3v output on the bottom? Can I just repeat IC1-4 a few more times, e.g. 8 outputs?
If I use a wall wart like this one http://schneidermusik.de/shop1/product_info.php/products_id/159312/ref/2/language/de?gclid=CLDM78-0jroCFU5f3god7VEAng which is 2000ma, is it possible to make one or two of the outputs 500ma each, or with that amount of current available, doesn't it matter?
(also, anyone know what those cap values should be?)

Thoughts?

Thanks!

[PRR]

You just need the 9V for one or a few pedals, all the same polarity?

They have other power supplies:

http://schneidermusik.de/shop1/index.php/cPath/87_105_1000265/search_in_categories/1?osCsid=250cubijp6krqlr3gfmfgioea1

A couple of "RockPower NT 10 Power Supply, Euro 230V - 12V DC/1000 mA" may do you, and a lot cheaper.

"RockPower NT 50 EU Power Supply "Combo Pack All 5" 230V Euro - Netzteil 9V DC/1300 mA" has multiple outputs. And I would suspect it has decent filtering.

A well-known pedal supply is the 1 Spot, which ought to be available in your market.

[therealfindo]

I'm already running a powerplant Jr which has 5 outs - and already I'm doubling up on some of those outs, and in addition I've got one of Thomann's single adapters for the delay. That set-up is fine, and I could easily just stick a second powerplant jr under the board, but where would the fun in that be? I want to build something that will do what I need

[duck_arse]

you can, yes. the 78xx in the "T" package will supply 1 Amp before they shut themselves down. the 78Lxx is only 300mA I think, but you can check specsheets for that. the pedal you attach will decide how much current it wants, the regulator doesn't care, to a point.

C6/7 can be anything between 100uF and 2200uf or more. what you have on hand, with higher values providing more smoothing. C8 would probably be 100nF ceramic or monolitihic, to clean-up high freq hash. C1-4, you should check the specs, they might be as low as 10uF or 100nF. you might also search for protecting regulators with "backwash" diodes.

you can chuck IC7 if you don't need the -9V as well.

[therealfindo]

you can, yes. the 78xx in the "T" package will supply 1 Amp before they shut themselves down. the 78Lxx is only 300mA I think, but you can check specsheets for that. the pedal you attach will decide how much current it wants, the regulator doesn't care, to a point.
C6/7 can be anything between 100uF and 2200uf or more. what you have on hand, with higher values providing more smoothing. C8 would probably be 100nF ceramic or monolitihic, to clean-up high freq hash.

Thanks! really helpful.

C1-4, you should check the specs, they might be as low as 10uF or 100nF. you might also search for protecting regulators with "backwash" diodes.

Check which specs? the voltage regulator? I found this onehttp://www.banzaimusic.com/7809.html but can see any specs.. perhaps the better question (for learning!) is: how would I figure out the value?

[Buzz]

Google 7809 datasheet.

alldatasheets site comes up pretty quick...

http://www.alldatasheet.com/datasheet-pdf/pdf/33410/UTC/LM7809.html

You'll see a box that says download, next to that is a blue clickable LM7809. Click that, goes here:

http://pdf1.alldatasheet.com/datasheet-pdf/view/33410/UTC/LM7809.html

( edit: this link won't work from here, the site will only allow access from it's own link, the blue clickable LM7809 on the first link )

Now you should see a scrollable pdf file at the bottom of the page. You can right click on it and "save as" if you want to keep it for future reference.

Different datasheet sites work in different ways, but that kind of pdf file is the kind you're looking for.

The trick is using the term datasheet in your search.

Have a read through, see if you can find the info you need. It's there.

[therealfindo]

Have a read through, see if you can find the info you need. It's there.

Cheers - this is good... I appreciate learning in the process!

So.. at the end of the datasheet is the application diagram - that's what I'm after, right? input cap 0,33uf and output cap 0,1uf - and they correspond to C8 and C1-4 on the AMZ schematic?

[Buzz]

I'm not sure what information you are after.

I've recently built a very similar unit. I'm currently looking for the layout file, will post when found.

[Buzz]

[therealfindo]

I'm not sure what information you are after.

the cap values for the schematic I posted...

[Buzz]

Sorry, yes, those are the correct values.

BTW well done finding it on the data sheet. It's like cracking a code with those things.

[therealfindo]

Sorry, yes, those are the correct values.

BTW well done finding it on the data sheet. It's like cracking a code with those things.

Thanks.

btw - what is the circuit you posted? What is SAG?

[Buzz]

Oh, and as per the original question, just run more output plugs in series of off IC1.

They'll all get ~9v and just suck whatever milliamps they need.

One 7809 will pump out 1.5 amps, depending whats behind it. Let's call it 1000ma to be safe.

that's plenty of pedals.

The circuit I posted was my solution to almost the same problem as yours.

I wanted a power box to supply a number of pedals. I had plenty of wall warts hanging around for free, and wondered how I could put them to use. The 9v ones were usually 12 -15 volts and badly regulated so I came up with this design ( eventually, lol. )

The LM78xx regulators can handle 5 - 18v ( page two, datasheet )

But becuase we want 9v out ( LM7809 ) we're going to have to put at least 12v in. So this power supply box can take any wall wart putting out 12 - 18v.

The sag is a voltage divider.... it has a separate output and the pot allows you to give less voltage to a pedal, starve them for power. Can have some very interesting effects on pedals.

[Buzz]

If you want separate ( isolated ) outputs, you would have to have multiple lm7809s.

I don't know the max you can run off of an 18v supply.

I would consider one 7809 one for all the things that play together well and just run a daisy chain from it.

Then add another/more 7809/s for your troublesome pedal/s.

Every regulator you put in there will suck up some power and create some heat so I think the less the better.

[therealfindo]

Oh, and as per the original question, just run more output plugs in series of off IC1.

They'll all get ~9v and just suck whatever milliamps they need.

But they wouldn't be isolated in that instance, and would be akin to daisy-chaining a single 9v adapter, right? If I give each output its own IC, they'd be isolated, right?
I just drew up a draft schematic with 9 x 78L09 outputs, which are 100ma each, which is plenty for most pedals, and then use the 7809 (which allows) 1500ma as an output for the delay. so with a 1500ma plug driving it, that would be 9 x 100ma outputs and 1 x 600ma.. I just want to be sure that there is at least one output which I know will power the delay.

One 7809 will pump out 1.5 amps, depending whats behind it. Let's call it 1000ma to be safe.

I could go with 12v 1500ma or 18v 2000ma plugs - the latter being double the price..

[therealfindo]

Are you going to need the voltage inverter?

All my pedals are the normal tip-negative, so I can't see a need for it at this stage.. is that what you mean?

[therealfindo]

another question - the diode and fuse... how do I figure out what values / parts they should be?

[therealfindo]

I could go with 12v 1500ma or 18v 2000ma plugs - the latter being double the price..

ah.. crud... just realised the 12v & 18v adapters are center + I can get a 9v 1300ma center-negative.. but a 9v running into this circuit is not going to be the best idea, I imagine.
I suppose I could just wire the input dc jack backwards... right?

[Buzz]

Are you going to need the voltage inverter?

All my pedals are the normal tip-negative, so I can't see a need for it at this stage.. is that what you mean?

OK... tip negative or tip positive is just a way of wiring the plugs and sockets.

Most effects you will come into contact with are negative ground. They are run by +9v.  You just have to make sure your plugs are all wired the right way ( tip negative ) and you are good to go.

A voltage inverter is a different thing. Some pedals ( mainly old fuzz type pedals ) are positive ground. In this case, they are run by -9v.

It's just a thing about how old transistors were made to work. It's a huge subject and worth looking into... some searches on this site will lead you into many years of reading. And yes... it's a mindfrack.

[Buzz]

ah.. crud... just realised the 12v & 18v adapters are center + I can get a 9v 1300ma center-negative.. but a 9v running into this circuit is not going to be the best idea, I imagine.
I suppose I could just wire the input dc jack backwards... right?

Absolutely. just remember you did it before using another wallwart. mark the outside of the box with the polarity.