DC Power Supply Recommendations for Eurorack Synth and Guitar Effects Pedal Prototyping

Thread Starter

Dolmetscher007

Joined Mar 21, 2019
34
I have to tell you guys... for those of you who have been designing and building devices for years, as a totally n00b'ster, it is very hard to tell where to begin. I have a ton of ambition, a ton of time, but very little money, and very little experience. My end goal is to create a sort of "Eurorack" style modular guitar effects unit. For those who are not familiar with the term "Eurorack," it simply refers to a standard group of dimensions for rack-mounted electronic audio device enclosures. In the 1970-80's when electronic synthesizers were really ramping up, rather than build one massive "synthesizer," people would build much smaller "modules" that only did one or two things. For example... If you have an oscillator tone generator, you can build a tiny passive RC high-pass filter, attach it to the back of a "Eurorack" faceplate, and you could sell it to anyone who had a "Eurorack" and wanted a high pass filter, and all parties could be sure that it would fit. The user would have to use patch cables to patch the output of the oscillator into the high pass filter etc.

Guitar effects pedals are essentially the same idea. You buy 2, 3, 4, maybe 24 of these little boxes and use really short patch cables to connect them all in a specific order that you design to accomplish your audio goals. The problem there, however, is that there has never been an iron clad standard for much of anything. The Eurorack standard not only standardized the physical size of the panels, but also the +12V_0V_-12V power supply that all modules use. Guitar effects pedals, for the most part run on 9V, and most of them can either use a 9V battery or a 9V power supply. But you can tell by all the different tips of the power supplies that the various guitar pedals run on, there is a cottage industry built up around adaptors and weird power supply daisy chains.

I have bought a nice breadboard and a couple of distortion pedal kits, that I would like to build this weekend or the next, but I do not have a benchtop power supply. I know that I could just buy a 9V battery for the time being and get started, but 9V batteries are so expensive, I don't want to drop $10 on 4 stupid batteries when I know that I will want to buy a $65 benchtop power supply soon. The terms are killing me though...Variable, LInear, Switching, Reverse Polarity, Selectable, Digital, Regulated, Adjustable... I'm not asking for anyone to dedicate an afternoon to teaching me about Benchtop power supplies. But given all that I've explained in this thread... can anyone point me in the right direction towards a benchtop power supply that I can use to breadboard 9V, +12V, -12V audio applications like guitar effects pedals and analog synthesizers. And when I said that I don't have a lot of money, I am not so broke that I can't spend some good money on something that is high quality. I just hate wasting money on 9V batteries that I'll never use in 2 months.
 

mvas

Joined Jun 19, 2017
538
How many amps do you need at each voltage
amps @ +12 volts = ?
amps @ +9 volts = ?
amps @ -12 volts = ?

A "Bench" power supply might be expensive
Fixed Voltage power supplies will be less expensive

Some ideas ...
Meanwell multiple output Switching Power Supply ( add external +9 Regulator IC )
https://www.ebay.com/itm/RQ-65B-Mea...:y70AAOSwRKtcbcVX:sc:USPSPriority!43962!US!-1

Modify this for ( +12V, +9V & -12V ) DIY Linear P/S ...
https://www.instructables.com/id/Build-A-Power-Supply-For-Your-Guitar-Pedals/

Prebuilt ...
https://www.ebay.com/itm/Donner-Gui...290650?hash=item51d91396da:g:KGUAAOSwjeJalPm1
-12 volts appears to be less common
 

Thread Starter

Dolmetscher007

Joined Mar 21, 2019
34
This is excellent mvas!!! I should have thought to go check out Instructables.

I have a question about Transformers. In the parts list and schematic of the power supply project you suggested, it says to get an 18V transformer. The schematic calls for a 120V AC primary winding / 18V AC @ 300mA secondary winding. I know what all of that means, but when I go to Digi-key's website and type in 18V transformer, there is an overwhelming amount of options that I do not fully understand. I know that it is not a "wall adapter." So I went to "Power transformer" and started applying filters to the results. 120 V AC primary... etc. But it does not look like they even sell anything with an 18V secondary winding. So, I cannot tell if I am just looking in the wrong place, if DigiKey doesn't sell things like this, or what is wrong. I triest Isolation Transformers, Step Down, Pulse Transformers... I still cannot find an 120V in, 18V out transformer. Am I missing something really obvious?
 
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