Pedalboard Power Supply

[Zsarko]

I needed a little bit more grit for slide playing so I got a Fulltone GT-500. I really like the combo boost/od. I read somewhere that if you run it on 18VDC it sounds really good. It says right on it 9-18 volts. So I went to my job and grabbed an old laptop PS that puts out 18 VDC at 2.23 amps. I also have a Memory Toy delay and a Morley ABY switch.

The GT-500 uses 500ma at the most and the delay uses about 200ma. The ABY switch just powers a couple of LED's so it's draw is negligible. So I have plenty of amps to run both pedals just not the right voltage.

Is there a way to take another line off the 18V and turn it into 9V so I don't have to use two different supplies.

Mike

[ampgeek]

Hey Mike,
Take a look at the "Project File" pdf here:

http://www.generalguitargadgets.com/index.php?option=com_content&task=view&id=135&Itemid=26

It includes a schematic that shows where to insert a voltage regulator (9V in your case) that ought to set you up in great shape.  Just tap into the 18VDC supply line and....away you go!  You will need to double check the current capacity of your selected regulator to make sure that it will adequately supply the delay pedal demand.

I have built a  handful of power supply boxes (4 to 16 isolated outputs) with varying voltages (9, 12 and 18 VDC) based on this circuit.  I use sockets for the regulator so I can swap them in and out quickly and easily.  This makes for a VERY flexible power supply.  This is a great circuit.  Nice and clean!!

Good luck,
Dave O.

ooops...just realized that my builds were based on this project:

http://www.generalguitargadgets.com/index.php?option=com_content&task=view&id=23&Itemid=26

Same concept as above but uses a different regulator.  Again, double check the regulator current capacity against the demand.

[Zsarko]

Thanks, I'll check it out.

Mike

[sluckey]

You could get by with just a 7809 and a cap. (May not even need the cap if your pedal has input filters. It probably does.)

Here's a supply I built to run my board. I know it will power at least 10 Boss pedals. You could run your 18v supply directly to the LM123K input. I used a LM123K only because that's what I had on hand.

[Zsarko]

That looks easy enough. Thanks.

I was thinking about this at work the other day and wouldn't a couple of resistors do what I need? I mean the PS I have is already regulated so couldn't I just solder a 1 ohm resistor to the - wire, a 1 ohm resistor on the + wire, then solder the other two ends of the resistors together and take my 9V from there?

I really hate when I almost understand something

Mike

[sluckey]

The idea of using a voltage divider is sound, but your 1Ω example would draw 9 amps from the PS. If you want simple, it ain't any simpler or cheaper than a 7809. One component, but it will need a heatsink. Cost maybe a dollar.

There are several ways to drop 18V to 9V and still deliver sufficient current for your additional pedal. Your voltage divider (but use higher resistance and high wattage resistors, or use a resistor and 9V 5W zener. The 7809 VR chip is as cheap and sturdy and simple as it gets though. There's one probably hanging on a dusty pegboard wall in a RadioShack near you. And if you ever need to add another pedal the circuit is already done.

[Zsarko]

I see. I guess I'm off to the Rat Shack.

How hard do you think this would be to design?
http://guitars.musiciansfriend.com/product/Fryette-Valvulator-I-V1-Line-Driver-Buffer-and-Power-Supply?sku=582549

Mike

[G._Hoffman]

If you want the ultimate in DIY pedal power supplies, go to Geofex, and look at the Spyder.  Weber has a great transformer available for that type of isolated power supply.  You could even tie two of the transformer's secondaries together and get your 18V power supply.

If you just want to drop what you have down to 9V, then use a 7809 - though the Rat Shack near me only had a variable regulator when I last checked (I needed a 3.3V regulator for my tap tempo tremolo pedal).  You can certainly make the variable regulator do what you want, though.  I would make sure to put a cap both before and after the regulator though, if I were you.  They may not be required, but they are a good idea.

The one problem with your plan is that it may (and in some situations, it WILL) cause ground loops.  When and if that is an issue for you, that's when you will wish you had an isolated PS, like the Spyder or one of the commercially available versions (I have the Voodoo Labs Pedal Power 2+, which I highly recommend!)


Gabriel

[Zsarko]

Okay so I finally got down to the nearest rat shack and there was no 7089. But I did pick up a LM317T. I think it's pretty much the same thing. I got this circuit off the data sheet and made a couple of substitutions for what I have on hand and what they have and came up with this:

The diodes are probably overkill but I want to protect my $3.00 investment.  

The VR dissipates a little under 2 watts. Should I heat sink it? I was hopping to keep the whole thing enclosed in a little box.

Mike

I just realized that the box i bought comes with a metal lid or a plastic one so I guess I'll stick it to that.

[Jennings]

Hmmm...I like that Spyder idea.  Quite tempted to try building one, as I was about to post a thread about hum-free supplies (after battling with hum for some time now) but then got reading this one.  However, as I'm in the UK it's sometimes more costly to get hold of the bits by the time I've added shipping and taxes.

So, before I devote the money and the hard to find time (not least as I'm devoid of all electronics theory, albeit pretty handy with a soldering iron and a layout diagram!)...what commercially available options are there for powering between 8 to 12 9v pedals, hum-free (well, at least no hum from the power block!)?  I don't need any alternative voltages at the present, but I do need 8 - 12 9V.  What are the best options there?

[G._Hoffman]

Hmmm...I like that Spyder idea.  Quite tempted to try building one, as I was about to post a thread about hum-free supplies (after battling with hum for some time now) but then got reading this one.  However, as I'm in the UK it's sometimes more costly to get hold of the bits by the time I've added shipping and taxes.

So, before I devote the money and the hard to find time (not least as I'm devoid of all electronics theory, albeit pretty handy with a soldering iron and a layout diagram!)...what commercially available options are there for powering between 8 to 12 9v pedals, hum-free (well, at least no hum from the power block!)?  I don't need any alternative voltages at the present, but I do need 8 - 12 9V.  What are the best options there?

The Voodoo Labs Pedal Power 2 Plus has 8 9VDC outputs, which are transformer isolated and individually regulated.  6 of the outputs can support 100mA, and 2 can support 200mA for use with power hungry digital effects (like my Boss DD-20).  It does not have any AC outputs, unfortunately, so you could not use it with, say, a Digitech Whammy, and their are some pedals out there which will draw more than 200mA DC.  Check with your pedals manufacturer, though most comercial pedals will give their current draw right by the power jack.  The PP2 has and advantage over the Spyder, by the way, in that it's transformer is a torroidal transformer, so it puts out less EMI.  But, its pretty expensive too. 

There are a couple of clones on the market, so do your research, but what you need to look for in the specs is transformer isolated and regulated.  I've got a PP2, and I'm quite happy with it.  I wish I could get one of those toroidal transformers, though, so I could make my own.  I find myself in need of a second one, and I'm poor.

You can usually run two pedals off of one of the PP2 outputs.  You may need to do some experimenting to figure out which pedals can be daisy chained without causing ground loops.


Gabriel

[Jennings]

Thanks for the replies...I've currently got a Voodoo Labs PP2 on order, so we'll see what that turns out like for me.  I might look to building something larger and more flexible in my own time then.  Just out of interest, have people tried the T-Rex Fuel Tank range?!  Any good?