Bipolar Power Supply

-minus- · Joined: Oct 26, 2008 Posts: 787 Audio files: 13

Hi,

This is probably in the wrong section on E-M... but I need to start thinking about powering future builds. I have only built one thing which requires a bipolar power supply: a TR-808 kick drum module and have gotten around this issue in a fashion with two 9V batteries. I wouldn't want to have to resort to this for an entire modular though!

What I would love to know is how do others power their machines? I don't mind buying some kind of off the shelf device which you just link up to all your modules and simply plug it in. I'm not too concerned about actually building something from scratch to do this, though I guess I could if I had to.

In regard to the 808 kick module... it was suggested I try one of these:

http://au.mouser.com/Search/ProductDetail.aspx?qs=8YYpzd7qSxKByFByuBGUcA==

I have yet to do this. Going down this path would eliminate the two batteries, but it would get pricey if I needed one for every module!

I have looked at the MFOS bipolar supply board of Ray's. Is this a sensible solution for me? The further I progress with this hobby, the more I am confronted with this bipolar dilemma. I am clearly not going to go far without sorting out this foundation first. If anyone has any sugestions as to what I should be looking at, I would much appreciate it! No rush on this.... it is something to address next year. I still have plenty of other projects to complete.

I have a basic understanding of bipolar power in terms of +/-/GROUND, and the options regarding +/-15V, 12V, 9V etc. Some links from someone would be great though. Something along the lines of "BUY THIS:" followed by a link to a website! Laughing

Thanks!

PS: I'm sure this has been discussed on countless other threads elsewhere on E-M, I just can't dig them up! Embarassed

the architech · Joined: Oct 29, 2010 Posts: 55 Location: Philadelphia

weird, I just came on here to ask this exact same question Laughing

darkomen · Joined: Jun 21, 2010 Posts: 40 Location: USA

I was faced with the same situation a few months back. I ended up building the MFOS wall wart power supply. Didn't take too long to build, and it produces a pretty clean bipolar supply. I used http://www.mouser.com/ProductDetail/Triad-Magnetics/WAU12-1000/?qs=ZNtr8jqNHF5DHcgbMbmRPA%3d%3d power supply from mouser, just in case you wanted to go with this solution and need a cheap 12vac wall adapter.

RF · Posted: Tue Nov 30, 2010 6:57 am Post subject:

Buy This.

http://www.groveaudio.com/onlinestore/power_supplies.aspx

(I have two of them - they are linear supplies - just add line voltage and get +15 and -15 out.)

"INTRONMODPS
Modular +15V, -15V Power Supply
This epoxy cast analog power supply will supply up to 200 mA from both +15V and -15V outputs. Input is 115 VAC 60Hz. The supply is 1 1/8 x 2 1/4 x 3 1/2 inches. EACH $10.50"

Or if you want ample room to expand and power an entire modular synth...

Buy This
http://cgi.ebay.com/POWER-ONE-HCC15-3-A-POWER-SUPPLY-/330481535498?pt=LH_DefaultDomain_0&hash=item4cf23c0a0a

I have several of these in my modular - Rock solid - nearly bomb proof.
If you are patient you can likely find them for half that price....

The MFOS supply is a good option if you want to build. I have used that circuit often for smaller projects.

Good luck
bruce

the architech · Joined: Oct 29, 2010 Posts: 55 Location: Philadelphia

how many units can that power? I was looking through Jameco's catalogue at something like this
http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_323300_-1
But I can't really tell how many units one of these will power, and I'm not sure how many Watts or Amps I need in my power supply. And when you guys build large modular synths, do you typically wire everything to one internal power supply running to the wall?

I started the MFOS Power Supply, but while going through his instructions I became more afraid of all of his warnings. Is it really that dangerous? How could I test it before posibly lighting it on fire?

inlifeindeath · Joined: Apr 02, 2010 Posts: 316 Location: Albuquerque, NM

the MFOS power supply is an excellent choice. it's easy to etch your own board, with only one topside connection. Low count and easy to find parts, and very adaptable to your needs (9,12,15v).

RF · Posted: Tue Nov 30, 2010 9:57 am Post subject:

That Jameco supply you pointed at (the Mean Well) is a switching supply. You will hear many people tell you that's not a good choice for synths....
I kind of think they have gotten better over the years and most people might not have any real issues using them for synths... but I use linear supplies myself.

The Soundlab "Ultimate" and the "Expander" each draw from 90 to 100 ma. Single modules run from 20-30 ma each - maybe up to 50. (I'm just saying those module numbers based on a few I remember off the top of my head - so there are, I am sure, some modules that run way more... some less.

For my modular, I run 20 to 24 individual modules off a single Power one supply. My cabs are two rows of 12 spaces each. 2 of my cabs have a 1.5 amp Power One's (if I recall correctly) and two of them use 3 amp Power One's like the ones I linked to on e-bay. FWIW - I run +12 and -12 volts on my modular.

That "Wall Wart" supply is about the safest power supply you will be able to build. Using a Wall Wart offers a great margin for error. Smile

It seems like everyone who talks about building your own supply gets all "Mr. Safety says..." Sometimes its a bit over the top, but seems like everyone has the disclaimer "IT CAN KILL YOU!!!. Rolling Eyes

Be aware and think...You'll be fine. If you've build anything electronic before - it's simple stuff.

Good luck!

bruce

the architech · Joined: Oct 29, 2010 Posts: 55 Location: Philadelphia

what's the difference between switching and linear?

thanks for the help! perhaps an admin could sticky some of these beginner questions so they won't get asked repeatedly? I imagine we're not the first.

RF · Posted: Tue Nov 30, 2010 1:50 pm Post subject:

A switching supply rectifies the AC, then transistors turn completely on and off very quickly to create a lower voltage output - like turning a light switch on and off very quickly so the average voltage out of the switch and to the bulb is less than if you left the switch on all the time.
The switch mode supply measures the output and adjusts the length of time the switch is ON or OFF to regulate the voltage. The frequency of the switching is very fast - 50 thousand cycles per second up to perhaps a million per second.
The switch mode supply is more efficient - but much more complex to build. Switching transients from a switch mode supply have been said to cause interference to other equipment - either that it's powering, or can sometimes even send noise to other devices on the same line voltage circuit.

A linear supply uses a large transformer to lower the AC line voltage to a more manageable level. It's then rectified to DC, and regulated by linear transistors, and filtered. Very simple circuitry to build - but more of a brute force method that dissipates excess voltage as heat.
The linear supply uses a much heavier (and more expensive) transformer. The linear supply runs hotter, but voltages used throughout the circuitry are lower voltage with the exception of the primary of the power transformer.

bruce

-minus- · Joined: Oct 26, 2008 Posts: 787 Audio files: 13

Ah, I was thinking or hoping you might see this Bruce. Been meaning to PM you!

Anyway, I think that these won't be of much use to me as in Australia we run on a different mains AC voltage to the US. I've just got home and need to look at this more closely.... There is always the MFOS one which I could manage. All I'd need is to track down the AC wall wart...

RF · Posted: Thu Dec 02, 2010 5:26 am Post subject:

Hi minus -
Although I've not had reason to do so...
The data sheet for the Power One supplies list input voltage as 'jumper selectable' from 100 to 240 VAC. Does that fit your requirements?

Really - If you want something for more than a supply to experiment with or use in small projects, it's the way to go.

bruce

-minus- · Joined: Oct 26, 2008 Posts: 787 Audio files: 13

Ok so the Power One supply is the way to go...Thanks Bruce!

-minus- · Joined: Oct 26, 2008 Posts: 787 Audio files: 13

Just thought I'd update this. I actually ended up buying a kit from Jaycar for around $14 for the bipolar supply board, and an AC adapter/wall wart for $25. It was SO simple to build! And now I have BIPOLAR POWER! I'd suggest to anyone coming up with this problem of +/GROUND/- issues to perhaps just do what I did. Admittedly it won't power a HUGE modular, but it will certainly run a few modules from it at once. This was such a headache for me and in the end it needn't have been. It has really opened up my options now! I can look at schematics and not limit myself and get scared off from power requirements! Laughing