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3-pin power connector choice for 0V/ +15V/ -15V?
3-pin power connector choice for 0V/ +15V/ -15V?
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Old 14th February 2019, 10:22 PM   #11
Gnobuddy is offline Gnobuddy  Canada
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Quote:
Originally Posted by Tubelab_com View Post
Another option for low powered stuff is to just use a single positive 15 volt supply and place a inverting converter inside the box.
That was one of the options I had been thinking about. Then, quite recently I found this at Digikey: https://www.digikey.com/product-deta...6-5-ND/7807874

How can you beat that? Small, cheap, light, super simple. Only five pins to deal with, two wired to AC mains, and the other three spit out regulated +/- 15V DC at up to 340 mA, for under $12 USD. Amazing!

So the plan is to build one of those into a box, with a little extra RC filtering, and then use it to power multiple op-amp based guitar projects, in the same way I use a single 9V power supply to run several of my store-bought guitar pedals.

It would have been nice if the guitar FX pedal industry had switched to +/- 15V DC power by now. The old 9V DC standard is really not quite enough voltage, as witnessed by several "boutique" pedals that have internal charge-pump circuitry to raise that to 18 volts.

Better to go all the way to 30 volts, and then you finally have a little headroom when building a circuit that is not supposed to clip. Like the speaker / cab emulation filter that's been on my mind lately.


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Old 14th February 2019, 10:29 PM   #12
Gnobuddy is offline Gnobuddy  Canada
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Quote:
Originally Posted by scottjoplin View Post
I've used aviation connectors for low voltage supplies
Thanks for the suggestion. These? CPC from Aircraft Spruce Canada


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Old 14th February 2019, 10:39 PM   #13
Gnobuddy is offline Gnobuddy  Canada
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Originally Posted by leadbelly View Post
3 pin barrel connectors like on laptops are fine, but I would source from ebay, which you say you are unwilling to do.
Thanks for the suggestion!

Yeah, I don't use Ebay much...I bought some stuff from Ebay in the past, and found I hated the whole process of making a bid, waiting for days, and invariably getting outbid by someone who got auction fever and was willing to pay twice what the item was actually worth.

I once saw someone pay three times the brand-new purchase price to an Ebay seller for a set of quite ordinary Dodge automotive floor-mats. The same mats could be bought right at your local Dodge dealerships parts department.

After that I would only buy something if there was a "buy it now" price that was reasonable. That only happened once for every ten or so things I was interested in. So I just stopped using Ebay altogether. It's too frustrating.


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Old 14th February 2019, 10:42 PM   #14
scottjoplin is offline scottjoplin  Wales
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No, these aviation plugs | eBay

I've used both 16mm and 12mm. They are like the plugs on CB radio mics
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Old 15th February 2019, 01:54 AM   #15
thoglette is offline thoglette  Australia
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Originally Posted by Tubelab_com View Post
.... I have wrapped its cord with bright red and yellow tape, but it would be really easy to do something STUPID with this setup. I think that Samson made a poor choice here.
Yup. That's the trouble with reusing any "standard" connector that doesn't already have +/-15V DC. Especially there's no current limiting

The answer I usually end up with is either D-sub; "Molex" (automotive e.g. 172767-0014) or MIL-C (surplus or COTS equivalent) depending on the environment. All a bit more bulky than you'd like

But I'd suggest half an hour with the Mouser or RS Components online catalogue will likely toss up a range of options....
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Old 15th February 2019, 03:15 AM   #16
dotneck335 is offline dotneck335  United States
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Originally Posted by Gnobuddy View Post
..... I found this at Digikey: RAC10-15DK/277 Recom Power | Power Supplies - Board Mount | DigiKeyHow can you beat that? Small, cheap, light, super simple. Only five pins to deal with, two wired to AC mains, and the other three spit out regulated +/- 15V DC at up to 340 mA, for under $12 USD. Amazing!-Gnobuddy
It would be very interesting to see how much noise that little module kicks out----both emanated and riding on the output rails. If you try it, let us know!
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Old 15th February 2019, 04:17 AM   #17
Gnobuddy is offline Gnobuddy  Canada
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Originally Posted by thoglette View Post
But I'd suggest half an hour with the Mouser or RS Components online catalogue will likely toss up a range of options....
I did that before I started the thread. I wouldn't be taking up your time on this thread if I had found a good answer myself.

RS is not a good choice in my corner of the world, but Digikey and Mouser are, so that's where I looked.

The only good options I found were mentioned in post #1, with links.

I like the first of those ( https://www.digikey.com/products/en?...1838839-1&v=17 ), and it looks very much like exactly what I need. But $14 (Canadian) per connector is too much for the budget. Heck, that's more than the cost of the entire die-cast aluminium box that will house these projects.


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Old 15th February 2019, 05:08 AM   #18
oohms is offline oohms  Australia
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Another vote for aviation plugs.. that way you won't mix them up with other gear
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Old 15th February 2019, 05:09 AM   #19
Gnobuddy is offline Gnobuddy  Canada
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Originally Posted by dotneck335 View Post
It would be very interesting to see how much noise that little module kicks out----both emanated and riding on the output rails.
Digikey is good about providing links to product datasheets. I've attached the relevant page. Typical ripple is 60 mV, and max ripple is 1% of the DC voltage, which is 150 mV in this case.

The datasheet ripple is probably at the maximum current draw of 340 mA, and is likely ten times lower at the currents I will be using (a few mA per op-amp.)

However, being at 100 kHz, it is pretty easy to filter out ripple on the rails. A 10-ohm series resistor and a 10 uF ceramic cap should provide a ripple attenuation of 60 times at 100 kHz, taking that nominal 60 mV ripple down to 1 mV (and maybe 0.1 mV at 34 mA current draw instead of 340 mA.)

Either of those ripple numbers is excellent, probably better than I could extract from a DIY traditional 60 Hz power supply and analog voltage regulator.

One reason I want to put the power supply in an separate housing at the end of some sort of power cord is to reduce any radiated noise.

Here are the 10 uF ceramic caps I mentioned: https://www.digikey.com/product-deta...3-3-ND/5866225
Quote:
Originally Posted by dotneck335 View Post
If you try it, let us know!
Will do!


-Gnobuddy
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File Type: png RAC10-K_277_B.png (157.3 KB, 44 views)
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Old 15th February 2019, 05:30 AM   #20
JMFahey is online now JMFahey  Argentina
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Ive been thinking a lot about that, and for the same reason.

Anything using rings , no matter how many, plus tip, is doomed, and for good reason.

Earliest power supplies in the 60s (then called "battery eliminators") used standard 1/8" miniplugs, think transistor radios and early tape recorders, and early effects pedals too, the BIG problem being, as you mentioned, dead shorting when plugging in-out.

Somewhat acceptable with early high DCR transformers and tiny filter caps, but as soon as supply is 1A capable, is regulated and has a large capacitor, it turns into an arc welder ... literally.

Hollow plugs were the "solution" but still for single ended supplies.

Any power connector needs parallel pins so they never ever short, period.

Yes, XLR and DIN have been used, but either its not their job or are too large/heavy/expensive.

On the other side chosen connector should be available everywhere and inexpensive, yet capable of carrying at least 1A per pin.

Im becoming very fond of .156" connectors: they meet all above needs, surpass current specs, are keyed so as to prevent wrong insertion, are already usable as cable connectors, we only need a suitable chassis/pedal wall connector and agree on pinout.
Did I say cheap and plentiful?

We need to agree agree on "flat" 3 pin connectors or some more compact "square" 4 pin ones:

something suitable from this family:
Click the image to open in full size.

these are the square ones:
Click the image to open in full size.
not exactly the .156" 4 pin 2 row connector, but to give an idea of shape.

A 4th pin is not needed but since a square connector will have one anyway , it can be an asset, maybe carry an optional "other voltage", signal something, extra clean ground, LED power, 5V supply, whatever.

Again: since they are designed for "straight to PCB" duty nobody (I know of) has (yet) designed a chassis mountable connector ... altghough strictly speaking most modern pedal power connectors are not chassis mounted either, they are straight mounted to the PCB and (hopefully) they face a proper sized casing hole, so ... we might not be that far away from our goal, most important problem to solve would be agreeing on pinout and layout to allow standardization.

And even if nobody manufactures a "plug type" plastic housing for the floating cable connector,simple heatshrink wrapping is acceptably strong.

Again, just "thinking aloud".
Attached Images
File Type: jpeg 4 pin square.jpeg (14.9 KB, 41 views)
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Last edited by JMFahey; 15th February 2019 at 05:36 AM.
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