My store bought Effects power supply has been annoying me lately, it's buzzing both from the box and in the guitar signal,it's bad tempered and cuts out and generally just puking up it's entrails, I've been fixing it over and over for years and I finally thought "bugger it I will make a new one" so I did.
It is a very simple build however it is not one to be taken lightly as it involves the mains so you need to take all due care and attention.
Use a metal enclosure and Earth the Chassis, this both adds safety and cuts any stray noise.
Make sure you use a fuse - in my case I used a connector that had a fuse compartment built into it
You will notice that I used a uncommon type of regulator, you can of course substitute this with a LM7809 Regulator, they are pin compatible though I suggest you try and find the ones noted on the stripboard layout.
Be Careful
Hey I'm interested in building my own power supply for my pedals, I was thinking about noise though and would the design be improved by using a toroidal transformer or is that what the ferrite beads are for?
ReplyDeleteCheers, Danny
I built this specifically for the problem I had with noise. a screened transformer is much better that a toroidal one
ReplyDeleteferrite beads also help.
then you just need to make sure it's in a metal box, you earth it and your transformer is very tightly screwed to the box and by screened I mean one that looks like this - http://sphotos-d.ak.fbcdn.net/hphotos-ak-snc6/704074_10152322988050195_883245267_o.jpg
or at the very least has copper strapping around the transformer bobbins
mine is noise free
Thanks man Im gonna put one of these together and get rid of all these daisy chains
ReplyDeleteIf I wanted more than 4 outs, would I replicate the structure of Out 2 or Out 3? Also, would changing the number of outputs change which power transformer I would need or other component values like C17?
ReplyDeleteThanks!
technically as long as you use a good heatsink and a transformer hefty enough in the current department you can connect four outputs to each regulator with no trouble. C17 is overkill as it is so you don't need to change it.
ReplyDeletenormal commercial PSUs will just have the one regulator.
but if are absolutely headstrong on having separate regulators for each pedal then yes, just replicate the structure of out 4
So you saying that it is possible to connect up to four leads (to female 2.1mm DC) to each "Out" path on the board (for example, A26)?
DeleteIs there an advantage to using more/separate regulators over less?
Where did you find your screened transformer? I cannot seem to find a transformer that is screened and also puts out enough mA...
Also, where does the heatsink come into play in the wiring/layout diagram? Is it just what the transformer is attached to?
Thank you very much for your help.
you use heatsinks on the regulators.
Deletethe only advantage to using more regulators is you're less likely to get noise when using high gain pedals.
I found my screened transformer inside an old subwoofer
however another option is to use an old 22 volt 1.8amp "wallwart" or something like this http://www.maplin.co.uk/ac-ac-fixed-voltage-high-current-power-supplies-240 (L55BR)
then you don't have to deal with the mains stuff
Ok, so does the mA matter as much on the transformer as V and VA? If not, is there a way to estimate how much mA I should have on hand for the number of outputs?
DeleteCheers
it's all directly related - to work out the current (mA) you divide VA by V for example 6VA / 30V = 0.2
Deleteor in other words 200mA
pedals take anywhere between 10mA to 100mA (maybe more if they are DSP type pedals) so when I work that kind of thing out I make sure each output can supply 100mA
1 Amp is 1000mA
That makes a lot of sense. So in your case, the transformer could hypothetically power 16 outputs at the same time (assuming 100mA draw and no wiggle room), right?
ReplyDeleteSo then do input/output values matter (within reason) as long as the input is above 9V and the output is at least 100mA? (if hooking up to a single pedal, wall wart-style)
Sorry, my math was dumb. I meant hypothetically 17 simultaneous outputs with 70mA left over...
Deletethe regulators need a few volts over the regulated output voltage to work (which is why I used a 13.5v transformer) and can handle upto 35 volts though they get hotter.
ReplyDeletethe regulators only allow 1 Amp to be drawn from them so you could only power 10 100mA pedals from a single output. and you would need a good heat sink.
Sorry, I meant if I have 17 output channels, each with their own regulator.
ReplyDeleteSo (because I am over in North America) would this product work? I am not sure what the CT means though... (120V primary, 12.6V secondary, 3.0A)
http://www.radioshack.com/product/index.jsp?productId=2102702&filterName=Type&filterValue=Transformers
yeah that should be fine.
DeleteCT means "center tap"
on the secondary side (low voltage bit) there will be 3 wires - 2 the same colour and one black or something.
just tape off the CT wire with some heatshring or something (the black or whatever colour it is)and ignore it.
the two wires of the same colour go to the "AC in" on the board
Thank you very much!
DeleteI think there is a discrepancy between R1 & R2 between the first/second diagram and the third.
ReplyDeleteAlso, if I only had 10K 1W resistors would it be alright to go down to 10k or up to 20k for (the first or second diagram's) R2?
Thanks
the third diagram is just for people who wanted to do their own layouts so I didn't bother to change the component numbers around.
Deleteboth are non critical parts so you can use anywhere between 470R and 1K for the LED and yes you can use a 10K 1 watt resistor. that resistor is there to bleed the energy out of the capacitor once you disconnect the power so you don't electrocute yourself.