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Mull3t 24th May 2012 05:44 AM

Need some advice where to install LED, also power socket advice.
I'm going to be building "The Wire" and I'm trying to come up with a way to integrate an LED. I'm going to use this 15V power supply that I don't think comes with an LED.

PS-12 Bipolar Low-Voltage PS

So I'm thinking that the LED would have to fall somewhere between this supply and the amp. How would I wire it in? To make my calculation for my LED resistor I'm assuming my source voltage would be the +15V from the supply. The LED I want to use has a forward voltage of 2V and a forward current of 10mA, so I'd need a 1.5k ohm 1/2W resistor to do the trick. Are my assumptions correct?

Also, I want to try and put this in the smallest case possible. Would this work for my power connector?

6160.0012 Schurter Power Entry Modules

I'd like to avoid using the standard IEC socket, but if this socket doesn't work then what part is the smallest and works best?


1SaGing5 24th May 2012 06:01 AM

that connector should probably work, no reason why it shouldn't, but theres a risk of the connector being easily disconnected though

-cheers :D

sofaspud 24th May 2012 06:08 AM

That power connector will not work. It is a 2-pin connector, and you need a 3-pin connector (+15/Gnd/-15).
A mini-DIN may be your best bet for a small power connector that's readily available and reasonably priced.
I would connect the LED across +15 and -15. That would be with a 2800-ohm (1%) or 2700-ohm (5%) resistor. 1/2W power rating.

benb 24th May 2012 06:32 AM

I think with reference to the larger "IEC socket" the OP wants to use the connector for line power which then goes to a small power transformer to power the regulator board. I certainly would argue against using the standard IEC power input connector for anything but line voltage power input.

Is this thing going in a metal chassis? A metal chassis is good for audio shielding, but as I recall, any metal box that has 120VAC or 240VAC coming into it has to have the chassis tied to the ground of the power cable as a safety measure, so that an internal fault doesn't put line voltage on the chassis where someone could touch it.

Mull3t, maybe you could clear up what exactly is going in the case. This power supply board certainly, but also the power transformer that feeds it? "The Wire" also? What material will the case be made of?

Mull3t 24th May 2012 06:39 AM

Ok, so it looks like the best option is an IEC socket. Something like this...

161-R30148-E Kobiconn Power Entry Modules

The mini-DIN looks interesting but would require more jiggering to get it to work. Where as with the IEC socket all I'd need is a power cable. Is there a better option as far as IEC C-14 sockets go?

As far as the LED goes... I'm still confused on wiring. My weird logic says you'd need two wires coming out of +15V and two coming out of -15V. One set goes to the LED and the other goes to the amp board. The resistor is on the +15V wire.


Mull3t 24th May 2012 06:45 AM

Here's a clarification of what is going on with this amp.

"The Wire" starts out with a 15-0-15 transformer that goes into a bipolar 15V supply that goes into the amplifier board.

I would think that line voltage is going into the transformer so then the IEC socket is probably needed. I have to have the ground pin tied to the case, right? I plan on using the smallest case possible. I haven't figured out what yet and figured I'd do that once the amp is built and working then I could figure out my casing. I know it will be metal at least. Maybe something from Hammond or Box Enclosures.

sofaspud 24th May 2012 07:12 AM

I misunderstood. You're looking for an AC input connector. The power entry module in post #1 will work, then. It is a good safety measure to connect the metal case to protective earth, but it's not absolutely necessary unless you plan to ship your Wire off for UL approval. Some here may jump up and down over that statement, but that's the truth of the matter. Just be sure an internal fault doesn't put line voltage on the case (which isn't terribly difficult). If you doubt your abilities in the slightest, by all means use a grounded 3-wire cord.
You need 3 wires from the bipolar supply to the amp. I explained the LED hookup.

boywonder 24th May 2012 03:04 PM

If it were me I'd use a 3 conductor grounded cord and a std IEC power entry. The "shaver" type power entry module shown in post #1 is for products that are double insulated, which your home brew stuff will not be. If you are trying to save space skip the power entry module and use a strain relief to connect the power cord to your chassis.

Mull3t 26th May 2012 04:27 AM


Originally Posted by sofaspud (
I would connect the LED across +15 and -15. That would be with a 2800-ohm (1%) or 2700-ohm (5%) resistor. 1/2W power rating.

This is where I'm going to show my newbishness. Can you further elaborate on connecting the LED "across" +15 and -15. My guess is that I could connect my + wire and - wire from my power supply and connect that to the ampflier board. Then on the underside of the power supply board where my + point is and - point is wire in my LED there.

Mull3t 26th May 2012 04:29 AM

I'm going to stick with the standard IEC socket. Any recommendations for a smaller one. No fuse needed.

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