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 Forum index » DIY Hardware and Software » MusicFromOuterSpace.com designs by Ray Wilson
Power source question
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chuck



Joined: Apr 26, 2005
Posts: 58
Location: cincinnati, oh

PostPosted: Fri Apr 16, 2010 8:32 am    Post subject: Power source question Reply with quote  Mark this post and the followings unread

I'm just now getting into the DIY build and I am enjoying it. I want to build a modular synth for my 7th grade electronic music class. For reasons of class use and ease of instruction, I want to put each module in its own enclosure. This leads to a power source problem.

I need to have a +/- 12VDC power for most of the units I'll be building, but I don't want to have to pay for a separate power board for each box.

Here's the question: Can I build one unit with a power source in it and send the power out via several XLR panel mounted jacks? This way I could power whatever modules I had out for the students by connecting the modules to the PSU with standard XLR mic cables. I know I'll have to keep track of the amperage, but I can always have a couple independent PSU's.

Does this seem like a do-able system?

thanks,
chuck

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kkissinger
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PostPosted: Fri Apr 16, 2010 9:01 am    Post subject: Re: Power source question Reply with quote  Mark this post and the followings unread

chuck wrote:
I need to have a +/- 12VDC power for most of the units I'll be building, but I don't want to have to pay for a separate power board for each box.

Here's the question: Can I build one unit with a power source in it and send the power out via several XLR panel mounted jacks?

Does this seem like a do-able system?

thanks,
chuck


edit: sorry thought you said TRS plugs...

You could probably use XLRs and be ok -- phantom power is more voltage than +/- 12v.

However, seems kind of expensive by the time you purchase all the hardware.

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chuck



Joined: Apr 26, 2005
Posts: 58
Location: cincinnati, oh

PostPosted: Fri Apr 16, 2010 9:42 am    Post subject: Reply with quote  Mark this post and the followings unread

I hadn't considered TRS plugs cause of the short that would occur as the plug was put it (I suppose one could connect before power-up).

I wouldn't be using fantom power, just the XLR as a three wire connector. I just seemed like an easy connection. Any microphone cable would work then with the +, - and ground.

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kkissinger
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PostPosted: Sat Apr 17, 2010 8:44 am    Post subject: Reply with quote  Mark this post and the followings unread

chuck wrote:
I hadn't considered TRS plugs cause of the short that would occur as the plug was put it (I suppose one could connect before power-up).

I wouldn't be using fantom power, just the XLR as a three wire connector. I just seemed like an easy connection. Any microphone cable would work then with the +, - and ground.


Right, what I meant was that XLRs handle phantom power without any problem so they should be able to handle 12 volts, which is considerably less.

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chuck



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PostPosted: Sun Apr 18, 2010 5:54 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thanks.

Now, if my power source is +/- 12VDC and I power a unit that only requires +12VDC is that a problem?

What if I power with the -12VDC rail, will the unit still work in the same manner?

Thanks for your time.

chuck

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kkissinger
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PostPosted: Sun Apr 18, 2010 8:15 pm    Post subject: Reply with quote  Mark this post and the followings unread

chuck wrote:
Thanks.

Now, if my power source is +/- 12VDC and I power a unit that only requires +12VDC is that a problem?

What if I power with the -12VDC rail, will the unit still work in the same manner?

Thanks for your time.

chuck


Excellent questions.

To answer your first question, if the circuit only requires +12 VDC then you may power it from the positive side -- you wouldn't have to connect the negative side to your circuit.

However, there is a caveat. Some circuits implement a bipolar power supply with a voltage divider -- that is a circuit may tap a simple voltage divider at 0, +6, and +12. If this is the case, then you would be advised to do away with the divider and run from your positive, ground, and negative rails making needed adjustments for voltage.

As far as running off the negative rail -- there could be a few ramifications -- namely that you would be using the
-12v buss as your ground point and your system ground as your positive source. I believe that you would want zero potential between any ground points on your synthesizer -- at least I certainly would. In other words, if your module is DESIGNED to run on the negative side then it will likely be ok. However, if if designed to run off the positive side then to move it arbitrarily to the negative side will likely cause problems when you try to connect your module to other modules on your system. Bear in mind that any parts on your circuit that are referenced to ground (i.e., op amps, etc) will not be referencing the same ground as any input signal to the module. This issue could get very thorny.

Having said this, I have never tried to do this -- however I would approach this issue with caution if I approached it at all. Wink


edit: spelling errors

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Last edited by kkissinger on Mon Apr 19, 2010 6:16 am; edited 3 times in total
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chuck



Joined: Apr 26, 2005
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Location: cincinnati, oh

PostPosted: Mon Apr 19, 2010 3:38 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks for your comments. That helps a lot.
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