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Building an Audio Circuit...
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subego
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Dec 28, 2011, 12:29 PM
 
A really simple circuit. Like, three resistors.

Normally, I'd take my time and do it right, refresh my skills at soldering, build offsets in the project box, etc., but I'm in a bit of a hurry.

My plan is to wire it on some perfboard. Twist the leads, see if it works, and if it does, cram the project box full of non-conductive epoxy.

The key here is it needs to be bulletproof. It's going to be used in the field, and I can't have it die from a bad joint or a poorly engineered strain relief.

Is there anything I'm missing here? Is this a bad idea?

In my favor, it's for digital audio, so the signal doesn't need to be audiophile clean, I just need the bits to get through.
     
subego  (op)
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Dec 28, 2011, 12:56 PM
 
Writing it out makes me realize I can probably lose the perfboard.
     
Waragainstsleep
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Dec 28, 2011, 01:11 PM
 
Soldering has to be better than just twisting the wires together.
I have plenty of more important things to do, if only I could bring myself to do them....
     
BLAZE_MkIV
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Dec 28, 2011, 02:22 PM
 
They make conductive glue too. I doubt it's a really good conductor though.
     
subego  (op)
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Dec 28, 2011, 02:54 PM
 
Originally Posted by Waragainstsleep View Post
Soldering has to be better than just twisting the wires together.
It's not just twisting them, it's twisting them and then packing it with epoxy.

The only way I can see solder being better is were I to need to desolder it. The only reason I can think of for that would be replacing a blown resistor, which A, won't happen, and B, I can just rebuild the whole thing anyway.
     
Waragainstsleep
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Dec 28, 2011, 03:42 PM
 
Originally Posted by subego View Post
It's not just twisting them, it's twisting them and then packing it with epoxy.

The only way I can see solder being better is were I to need to desolder it. The only reason I can think of for that would be replacing a blown resistor, which A, won't happen, and B, I can just rebuild the whole thing anyway.
If you want bullet proof, I'd twist and solder.
I have plenty of more important things to do, if only I could bring myself to do them....
     
subego  (op)
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Dec 28, 2011, 03:47 PM
 
Fair enough, but is there some mechanism by which you can imagine them untwisting themselves once buried in epoxy?
     
BLAZE_MkIV
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Dec 28, 2011, 03:49 PM
 
Wirenuts.
     
turtle777
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Dec 28, 2011, 08:31 PM
 
Originally Posted by Waragainstsleep View Post
If you want bullet proof, I'd twist and solder.
FTW.

-t
     
ghporter
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Dec 28, 2011, 09:42 PM
 
Twisted wire is nowhere near as good a connection electrically as a soldered connection. Twist away THEN solder - it shouldn't take much - and you'll have a truly bulletproof connection.

Glenn -----OTR/L, MOT, Tx
     
subego  (op)
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Dec 28, 2011, 11:07 PM
 
Okay, okay. Jeez.





Thanks all!
     
reader50
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Dec 28, 2011, 11:50 PM
 
How literal are you about the 'bulletproof' part? Soldering is good of course, but perhaps we should be talking about the project box more. Soldered wire in an ordinary plastic box will do exactly squat to stop a .22, much less a .306. A double layer of lucite with kevlar in between would be a better bet.
     
subego  (op)
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Dec 29, 2011, 01:14 AM
 
Well, I have three project boxes. One is made of straw, one is made of sticks, one is made of magnesium.
     
ghporter
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Dec 29, 2011, 07:40 AM
 
You need titanium to stop serious rounds. Best if you make it by molecular deposition, since you can make the box around your circuit that way. Of course you'll never be able to change out any of the components with this method, but it's still going to laugh off high powered rifle bullets.

Glenn -----OTR/L, MOT, Tx
     
BLAZE_MkIV
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Dec 29, 2011, 08:17 AM
 
All the guys I know swear by sodium. It the next big thing in armor plating.
     
chabig
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Dec 29, 2011, 02:22 PM
 
Encase it in reactive armor. And for what it's worth, I think twisting the leads will work fine provided you get a good length of contact.
     
Waragainstsleep
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Dec 29, 2011, 03:13 PM
 
Originally Posted by BLAZE_MkIV View Post
All the guys I know swear by sodium. It the next big thing in armor plating.
You're kidding right?
I have plenty of more important things to do, if only I could bring myself to do them....
     
BLAZE_MkIV
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Dec 29, 2011, 03:43 PM
 
My DM had a great trap back in the day, it was a priceless marble statue of a goddess, in a cave, behind a waterfall.
     
subego  (op)
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Dec 29, 2011, 03:55 PM
 
Didn't James Bond have a sodium watch acting as a concealable explosive?

Or was that The Man From U.N.C.L.E.?
     
subego  (op)
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Dec 29, 2011, 03:59 PM
 
There was a gal at the local hot dog shack that would always ask "sodium on your fries?"

One time I answered "sure, but put some chlorine in there too, I don't want my taters to explode."

She looked at me like I had just killed her dog.
     
turtle777
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Dec 29, 2011, 04:27 PM
 
Originally Posted by subego View Post
She looked at me like I had just killed her dog.
Wait, now I'm confused. I thought SHE was servings the dogs.



-t
     
subego  (op)
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Dec 29, 2011, 04:42 PM
 
Let's all pretend I'm posting the Korean twentysomething dog barbecue pic.
     
hyteckit
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Dec 29, 2011, 10:00 PM
 
Breadboard, twist wires, and wire cap. Done.
Bush Tax Cuts == Job Killer
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2.21 million jobs were LOST after 2 years of Bush Tax Cuts.
     
subego  (op)
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Jan 4, 2012, 03:30 AM
 
Only time will tell it this was a bad idea, but I went with wire nuts.
     
ghporter
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Jan 4, 2012, 07:50 AM
 
Wire nuts is better than just twisting the wires together. If you make another one, solder it and see if you find a difference in function or longevity.

Glenn -----OTR/L, MOT, Tx
     
turtle777
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Jan 4, 2012, 12:36 PM
 
Logically, I can't see how wire nuts could be possibly any better than twisting & soldering for low voltage / power applications.

I never thought of wire nuts as a professional tool. They seem to be a US centric thing, I have never seen them in Europe.
In German speaking coutnries, they use this:

http://de.wikipedia.org/wiki/L%C3%BCsterklemme

-t
     
subego  (op)
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Jan 4, 2012, 05:00 PM
 
Originally Posted by ghporter View Post
Wire nuts is better than just twisting the wires together. If you make another one, solder it and see if you find a difference in function or longevity.
Exactly my plan.

I'm not 100% comfortable with this build. The leads from the resistors are hair thin, and I'm worried twisting on the nut where the three resistors met stressed the leads to near their breaking point.
     
olePigeon
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Jan 4, 2012, 05:18 PM
 
Originally Posted by subego View Post
Well, I have three project boxes. One is made of straw, one is made of sticks, one is made of magnesium.
Are you expecting a wolf?
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Spheric Harlot
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Jan 4, 2012, 05:18 PM
 
Originally Posted by subego View Post
Only time will tell it this was a bad idea, but I went with wire nuts.
I had to look up wire nuts.

Oh boy, you'd get laughed out of a job over here for using those. I got laughed at for using a "Lüsterklemme" (what turtle linked to above) for an audio connection (on solder-covered wire ends), which actually works quite well.
     
olePigeon
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Jan 4, 2012, 05:18 PM
 
Wire nuts still confound me. Wires go in, become twisty. Can't explain that.
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Spheric Harlot
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Jan 4, 2012, 05:20 PM
 
Originally Posted by turtle777 View Post
Logically, I can't see how wire nuts could be possibly any better than twisting & soldering for low voltage / power applications.

I never thought of wire nuts as a professional tool.
     
BLAZE_MkIV
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Jan 4, 2012, 05:32 PM
 
The trick is on the non-crap ones there's a spiral of wire inside which grabs and increases your contact area. The other big reason is re-work but that's not important in this case.
     
subego  (op)
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Jan 4, 2012, 05:39 PM
 
Originally Posted by Spheric Harlot View Post
I had to look up wire nuts.

Oh boy, you'd get laughed out of a job over here for using those. I got laughed at for using a "Lüsterklemme" (what turtle linked to above) for an audio connection (on solder-covered wire ends), which actually works quite well.
You'd have to know I'd used them:

     
subego  (op)
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Jan 4, 2012, 05:43 PM
 
Originally Posted by turtle777 View Post
Logically, I can't see how wire nuts could be possibly any better than twisting & soldering for low voltage / power applications.
Rusty soldering skills.
     
turtle777
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Jan 4, 2012, 05:53 PM
 
Originally Posted by subego View Post
I'm not 100% comfortable with this build. The leads from the resistors are hair thin, and I'm worried twisting on the nut where the three resistors met stressed the leads to near their breaking point.
Rightly so. Wire nuts are NOT meant for low voltage electronic applications.
Their use is in high voltage / hihg power wiring (like 110V in a home.)

-t
     
turtle777
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Jan 4, 2012, 05:56 PM
 
Originally Posted by Spheric Harlot View Post
Oh boy, you'd get laughed out of a job over here for using those. I got laughed at for using a "Lüsterklemme" (what turtle linked to above) for an audio connection (on solder-covered wire ends), which actually works quite well.
In the same way, Lüsterklemmen are not meant to be used for low voltage electronic application (such as audio). Soldering is.

And yes, Lüsterklemmen can work well in establishing a reliable electronic connection (better than wire nuts), as long as shielding is not a concern.

-t
     
turtle777
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Jan 4, 2012, 05:59 PM
 
Alright, let's ask teh intarwebs:

To Solder or not to solder:

-t
     
subego  (op)
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Jan 4, 2012, 06:00 PM
 
Originally Posted by turtle777 View Post
Rightly so. Wire nuts are NOT meant for low voltage electronic applications.
Their use is in high voltage / hihg power wiring (like 110V in a home.)

-t
Meh.

They make them way smaller than you could ever use for AC.
     
turtle777
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Jan 4, 2012, 06:06 PM
 
Originally Posted by subego View Post
They make them way smaller than you could ever use for AC.
That doesn't make it right and a good tool/connection.

After reading this, I conclude that the appropriate alternative to soldering is crimping:

solder vs wire nuts - DIYMA.com - Scientific Car Audio - Truth in Sound Quality

The issues with wire nuts are manifold. Oxidation and vibration are some of the ones you might encounter in your application.

-t
     
subego  (op)
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Jan 4, 2012, 06:07 PM
 
Originally Posted by turtle777 View Post
Alright, let's ask teh intarwebs:

To Solder or not to solder:

-t
I'm not arguing solder would be worse, however this article makes the exact points which led me to using the wire nuts.

1) They're fine if you have the space and don't expect a lot of vibration.
2) They act as insulators.
3) They act as a strain relief.
     
subego  (op)
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Jan 4, 2012, 06:09 PM
 
Originally Posted by turtle777 View Post
That doesn't make it right and a good tool/connection.

After reading this, I conclude that the appropriate alternative to soldering is crimping:

solder vs wire nuts - DIYMA.com - Scientific Car Audio - Truth in Sound Quality

The issues with wire nuts are manifold. Oxidation and vibration are some of the ones you might encounter in your application.

-t
As I said, I wouldn't mind rebuilding it "properly" with solder.

As I also said, this is for digital audio. The quality of the connection is irrelevant as long as the bits get through.
     
turtle777
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Jan 4, 2012, 06:13 PM
 
Every bit has its limits. A poor connection (high resistance) might kill the bit.

-t
     
subego  (op)
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Jan 4, 2012, 06:21 PM
 
Originally Posted by turtle777 View Post
Every bit has its limits. A poor connection (high resistance) might kill the bit.

-t
Hence my desire to rebuild it.
     
Spheric Harlot
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Jan 4, 2012, 06:29 PM
 
Originally Posted by subego View Post
As I also said, this is for digital audio. The quality of the connection is irrelevant as long as the bits get through.
On the contrary.

Bad connections can at worst introduce either drop-outs/errors, but invariably cause jitter.

If this is within a circuit that stays digital (i.e. leads to a digital interface that will then re-clock the signal anyway), then jitter is irrelevant.

If the circuit carries a digital audio signal that is used to clock a DAC, then bad connections will result in audible degradation due to reflections within the cable leading to clock jitter (especially if the leads themselves are too short).
     
subego  (op)
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Jan 4, 2012, 06:29 PM
 
I also wouldn't mind using resistors rated for more that a 1/4 watt too, just so the leads aren't so wimpy.
     
subego  (op)
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Jan 4, 2012, 06:31 PM
 
Originally Posted by Spheric Harlot View Post
On the contrary.

Bad connections can at worst introduce either drop-outs/errors, but invariably cause jitter.

If this is within a circuit that stays digital (i.e. leads to a digital interface that will then re-clock the signal anyway), then jitter is irrelevant.

If the circuit carries a digital audio signal that is used to clock a DAC, then bad connections will result in audible degradation due to reflections within the cable leading to clock jitter (especially if the leads themselves are too short).
Digital to digital. My mixer is AES out and my recorder is S/PDIF in. This drops the voltage from 3.3v to 1v.
     
ghporter
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Jan 5, 2012, 07:53 AM
 
Wire nuts hold wires together, in contact, quite well, But the only contact between those wires is where they touch each other and the metal liner of the wire nut. Solder, on the other hand, provides a much larger contact surface encompassing the entire surface of both connected wires. Further, a soldered connection can be smaller and less bulky. And soldering forms a chemical bond between the solder and the included wires, making the connection both more efficient and more physically secure.

Wire nuts are for power connections, and they work great for those, where they're appropriate. For a signal connection, a better choice is always solder. With a caveat: if your soldering ethic is "the bigger the blob, the better the job," go with wire nuts-at least those won't fail the way a bad solder joint will. Of course since it really is quicker, simpler and easier to make a good solder joint than a horrible one, I have to wonder why so many bad joints get made in the first place.

And I'll echo Spheric's statement on digital connections. A bad connection may "let the bits get through," but it will also let other stuff get through. Further, with a digital circuit, excessively long leads are a problem because they can pick up stray signals. Digital circuits work best with minimal lead length outside what is necessary for the circuit. The higher the bit rate, the more important minimizing extraneous lead length is.

Glenn -----OTR/L, MOT, Tx
     
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Jan 5, 2012, 09:22 AM
 
:guffaw:

In the time it's taken to argue about how crap wire nuts are I could have soldered half a loom.
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Doofy
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Jan 5, 2012, 09:28 AM
 
Originally Posted by subego View Post
Digital to digital. My mixer is AES out and my recorder is S/PDIF in. This drops the voltage from 3.3v to 1v.
Don't forget the silicon to rewrite all the control words.
Been inclined to wander... off the beaten track.
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Spheric Harlot
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Jan 5, 2012, 10:24 AM
 
Originally Posted by ghporter View Post
And I'll echo Spheric's statement on digital connections. A bad connection may "let the bits get through," but it will also let other stuff get through. Further, with a digital circuit, excessively long leads are a problem because they can pick up stray signals. Digital circuits work best with minimal lead length outside what is necessary for the circuit. The higher the bit rate, the more important minimizing extraneous lead length is.
If you're going to use cables with plugs, anything shorter than about one meter will introduce extraneous jitter.

Not important if the signal is going to be re-clocked on the receiving end, anyway, but if you're going to a signal-clocked DAC, audible deterioration.
     
 
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