# What is this strange adapter?



## calkew5 (Jan 12, 2010)

The question is simple.

I am a lighting designer at a small professional theatre that has survived long enough to accumulate decades of random stuff.

The other day, I found a strange little sort of adapter. It's a female edison plug connected to a 1/4" TRS jack by about four feet of 18 gauge copper wire, a red strand and a black strand.

What is this for? Any thoughts?


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## jfleenor (Jan 12, 2010)

I know this response is of no real use, but:

Perhaps it's meant to create a heat/fire source, for the purpose of burning down important stage props and curtains, or shorting out audio boards? 

I wouldn't trust it...

Janell


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## Van (Jan 12, 2010)

What ever it was originally it needs to be garbage now.


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## epimetheus (Jan 12, 2010)

I would guess some poor mis-guided soul decided it would be convenient to create an adapter to allow a common extension cord to be used as a speaker cable. The disastrous adapter you now question is the result.

Cut it up into many small pieces immediately.


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## seanandkate (Jan 12, 2010)

calkew5 said:


> What is this for? Any thoughts?



Um . . . the remnants of a contract hit?


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## Footer (Jan 12, 2010)

Its an extension cord adapter. I have seen them before. I have also seen a house that used to have all twistlock lighting move over to stagepin only to have the sound dept. take ALL of the old twistlock connectors and started putting them into speakers....


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## calkew5 (Jan 12, 2010)

I suspected the device in question might not have...traditional applications. Out of curiosity, can you actually transmit sound over extension cord?


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## Footer (Jan 12, 2010)

calkew5 said:


> I suspected the device in question might not have...traditional applications. Out of curiosity, can you actually transmit sound over extension cord?



Yup. Its copper.


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## MNicolai (Jan 12, 2010)

calkew5 said:


> I suspected the device in question might not have...traditional applications. Out of curiosity, can you actually transmit sound over extension cord?



Can you? Yes. Sound is transmitted as electricity.

The most serious issue is that all it takes is for one cable to be unplugged that connects to some equipment and someone who thinks they're being helpful then plugs that extension cable in, now someone's electrocuted, a speaker is blown up, or an entire audio system is destroyed.

The reason people like to do this is because extension cords are everywhere. It's very easy to get a hold of more if you run out, and in this case if you don't need as many power cords for a gig, then you have extra speaker cables. That is, until your sound system _literally explodes like a hand grenade_ at which point you'll really wish you had just bought the right cables the first time.


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## SHARYNF (Jan 12, 2010)

Back in the Day as the saying goes, there were not a lot of options for connecting speakers to panels and amplifyers. on the Speaker side you have Standard 1/4 jacks and on the amp side typically binding posts. Speakons were not even Designed at that time, and so a lot of setups used a lot of weird and potentially dangerous setups. Twist locks were used a lot, and on the amp side of things I am guessing someone decided to use edison males for the AMP outlet. Sounds Insane today, BUT in those days a lot of crazy things were done. So I am betting someone had an amp rack where the Binding posts were connected to a set of edison females, and then standard extension cords to 1/4 inch jacks were used to connect to speakers. 

we Laugh today, but a lot of really unsafe things were done in those days, Just look at the whole ground issue with Tube Guitar Amps... Lethal current could easily flow from the Amp to the performer/mic/stand when the Guitarist touched both the guitar and the amp at the same time

It was quite common during sound check to very carefully check to see if you the guitarist got a shock when touching the mic stand, if so, then you switched the ground switch.

Old Amps

http://www.fender.com/community/forums/viewtopic.php?p=263798&sid=8f7d634099480210b807a32e2287eb00

Sharyn


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## derekleffew (Jan 12, 2010)

MNicolai said:


> ...The problem is that extension cords are not shielded like speaker cables are. This makes for a lot of extra noise in the signal. ...


Um, Mike, no.


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## epimetheus (Jan 12, 2010)

derekleffew said:


> Um, Mike, no.



My thoughts exactly...


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## Chris15 (Jan 12, 2010)

Yes you can be shocked by a speaker line. Consider that say a lab Gruppen FP14000 has a peak output voltage of 195V. And a peak output current of 83A. More than enough to kill you.

Extension cord makes great speaker cable, when and only when its plugs are replaced with something appropriate, say Speakon.

As to the original adapter, at least it wasn't a male mains connector (you'll find that half soon no doubt)


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## MNicolai (Jan 12, 2010)

Post cleaned up.

Please, do tell me why I'm wrong. I've asked electronics teachers before and haven't ever been given reason to think getting shocked by touching a 1/4" TS connector is possible, or at least likely. (I'm not being cynical, I actually do want to know the physics and logic behind it.)


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## fx120 (Jan 12, 2010)

SHARYNF said:


> Back in the Day as the saying goes, there were not a lot of options for connecting speakers to panels and amplifyers. on the Speaker side you have Standard 1/4 jacks and on the amp side typically binding posts. Speakons were not even Designed at that time, and so a lot of setups used a lot of weird and potentially dangerous setups. Twist locks were used a lot, and on the amp side of things I am guessing someone decided to use edison electric outlets for the AMP outlet. Sounds Insane today, BUT in those days a lot of crazy things were done. So I am betting someone had an amp rack where the Binding posts were connected to a panel of edison outlets, and then standard extention cords to 1/4 inch jacks were used to connect to speakers.
> 
> we Laugh today, but a lot of really unsafe things were done in those days, Just look at the whole ground issue with Tube Guitar Amps... Lethal current could easily flow from the Amp to the performer/mic/stand when the Guitarist touched both the guitar and the amp at the same time
> 
> ...



At my shop, we still have 4x Renkus-Heinz SR-1's, 12x SR-2's, and 12x LR-2's which all came from the factory with male L14-20 twist locks on the back for input.

It was actually quite the ingenious solution for high current multi-conductor speaker cables back in the days before the NL4 Speakon connector. All of our cable was shared with our split phase 20A A/C distribution system, and all of the the cable is 10AWG so it was great for driving those heavy subs and high power bi-amped top boxes. Of course all of the amplifier cube racks built for the system had L14-20 outputs.

To my knowledge at no point did the power and speaker lines get crossed on any of our events. 

Somewhere buried deep upstairs in our shop we have parts of our old Perkins system, which used actual Cannon-branded 3-pin XLR's for the speaker level inputs, although I believe only the subs are still intact. Nothing like driving a pair of 18" subs off of a single 14 AWG XLR cable...


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## Chris15 (Jan 12, 2010)

MNicolai said:


> Post cleaned up.
> 
> Please, do tell me why I'm wrong. I've asked electronics teachers before and haven't ever been given reason to think getting shocked by touching a 1/4" TS connector is possible, or at least likely. (I'm not being cynical, I actually do want to know the physics and logic behind it.)



Honestly the likely reason is your teachers don't know what they are talking about in this instance.

Consider say a "1000w" amp driving say a 4 ohm load. Say you have 400w RMS being drawn. By Ohms law, you have 40V and 10A (both RMS). Change this to an 8 ohm load and the voltage goes up to 57 volts. Make it 800w and 8 ohms and you get 80 volts.

Derivation: P=v^2/R so V=SQRT(P*R).

Making sense?


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## Les (Jan 12, 2010)

MNicolai said:


> Post cleaned up.
> 
> Please, do tell me why I'm wrong. I've asked electronics teachers before and haven't ever been given reason to think getting shocked by touching a 1/4" TS connector is possible, or at least likely. (I'm not being cynical, I actually do want to know the physics and logic behind it.)



Heck, I was shocked by a 50w home theater speaker. It wasn't major, but it was there!


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## MNicolai (Jan 12, 2010)

I'll admit that it's stupid, that I, the electrical engineering student, would let myths of my early theatre days get the better of me and electricity is still electricity, be it for a power cord or an audio signal. It's probably never been an issue (at least for me and the people I regularly work with) been because the likelihood of messing around with the TS connectors while pumping a loud signal into the speakers is rather low.

Still, getting shocked being possible, how did 1/4" TS connectors ever make it to market for amplified signals? Especially given how most of them even have metal jackets to them. (to which now that I think back, I do remember a couple occasions getting shocked by these connectors)


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## Anonymous067 (Jan 12, 2010)

Chris15 said:


> As to the original adapter, at least it wasn't a male mains connector (you'll find that half soon no doubt)



Funny how that works usually...


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## gafftapegreenia (Jan 12, 2010)

The 1/4" TS connector is very, very old. It's original application was in telephone board switch panels. 

Much like the Edison screw base socket, which is clearly a shock-hazard, its just something that has been "grandfathered" in even if it has inherent hazards.


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## fx120 (Jan 12, 2010)

MNicolai said:


> I'll admit that it's stupid, that I, the electrical engineering student, would let myths of my early theatre days get the better of me and electricity is still electricity, be it for a power cord or an audio signal. It's probably never been an issue (at least for me and the people I regularly work with) been because the likelihood of messing around with the TS connectors while pumping a loud signal into the speakers is rather low.
> 
> Still, getting shocked being possible, how did 1/4" TS connectors ever make it to market for amplified signals? Especially given how most of them even have metal jackets to them. (to which now that I think back, I do remember a couple occasions getting shocked by these connectors)



Back before the days of the NL4, there weren't a whole lot of other options.

Some of the larger shell Cannon connectors were around in both three and four position, but the cost was high and they were physically large and clunky connectors. XLR's were used as I described in my previous post but were probably dropped in favor of the 1/4" TS to avoid confusion with mic level connections also coming off the stage. 

You've also got to keep in mind that in the early days amplifiers were at a practical limit of 60W, voltages were lower and cable gauges were smaller. 1/4" connectors were a convenient and available connector that was fairly inexpensive. 

So it became standard, and has just stuck around as power has increased and loads have gotten more demanding.


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## rwhealey (Jan 12, 2010)

I had the pleasure of using god-awful two prong Hubbel mini-twistlocks as speaker connectors where I worked last. They would never quite work right and were completely incompatible with everybody else's equipment.

I ripped them out and replaced everything with Speakons.

Really, I think the devil made that connector just to torture sound techs...


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## MNicolai (Jan 12, 2010)

Alright, devil's advocate. I'm in a bind and really need a speaker cable but I've run out of them and all of audio shops are closed. I have these old extension cords laying around with the connectors crapping out and some spare 1/4" TS connectors floating around. Is there any reason not to just slice the ends off and solder 1/4" TS connectors?


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## fx120 (Jan 12, 2010)

MNicolai said:


> Alright, devil's advocate. I these old extension cords laying around with the connectors crapping out. Is there any reason not to just slice the ends off and solder on NL4's, bananas, or 1/4" connectors?



Most of our 12 and 14 AWG NL4 speaker cable is just 4 conductor 300V SJEOOW Seoprene of the kind you'd normally use for A/C mains.

Of course all of our AC mains cable is 600V SOOW or SEOOW.


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## derekleffew (Jan 12, 2010)

fx120 said:


> Back before the days of the NL4, there weren't a whole lot of other options.
> 
> Some of the larger shell Cannon connectors were around in both three and four position, but the cost was high and they were physically large and clunky connectors. ...


Before Speakon, most professional shops used P4, P6, or P8 connectors, and some still do.



RapcoHorizon | Cables>Speaker>Multi Channel


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## fx120 (Jan 12, 2010)

derekleffew said:


> Before Speakon, most professional shops used P4, P6, or P8 connectors, and some still do.
> 
> 
> RapcoHorizon | Cables>Speaker>Multi Channel



Oh, believe me I know. I've got a stack of 4 conductor cable sitting upstairs.

If my memory serves me they were known as the P-series back in the day, and started out as a 3 position connector suitable for use with microphones. I haven't seen them on any gear dating back past the early-80s however, but I have seen Altec horns from 1968 with 1/4" connectors on them.


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## zuixro (Jan 12, 2010)

One of my friends thought he found an Edison to BNC adapter. It turned out to be something else later though.


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## epimetheus (Jan 12, 2010)

Texas A&M, College Station uses 4-pin XLR for all their speaker runs. Some of the bigger boxes (subs, larger mids & tops) have speakon, but 90% is 4-pin XLR, or at least it was when I attended several years ago.


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## Footer (Jan 13, 2010)

MNicolai said:


> Still, getting shocked being possible, how did 1/4" TS connectors ever make it to market for amplified signals?



You have to remember, this was the same time this thing was being dragged around the country... 



I did not matter if it was the best connector for the job. They had a ton of them laying around because every guitar and amp had that connector. 1/4" is a horrible connector to use for an amplified signal, hence the reason everyone has been trying to replace it with better solutions.


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## SHARYNF (Jan 13, 2010)

A lot of us back in the late 60's-70's wound up using two prong twist locks. The xlr'sat that time called Cannon connectors (after ITT cannon) would not accommodate the awg wire for a speaker. Amps were more than 60 watts, most folks were using Crown DC300's and a few of us Phase Linear 700s so the power level was reasonable. 1/4 were just too unreliable in the pro world (remember if you had a failure you had to climb up that "wall of sound" 

Sharyn


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## rwhealey (Jan 13, 2010)

MNicolai said:


> Alright, devil's advocate. I'm in a bind and really need a speaker cable but I've run out of them and all of audio shops are closed. I have these old extension cords laying around with the connectors crapping out and some spare 1/4" TS connectors floating around. Is there any reason not to just slice the ends off and solder 1/4" TS connectors?



This is fine as long as you but 1/4" on both ends. Better if you have Speakons sitting around. You're wasting one conductor, but if you need it now, you need it now.

Just NEVER make an adapter that could connect a speaker cable to AC mains.


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## FMEng (Jan 17, 2010)

Audio guru Rick Chinn has some great pictures of AC plug to audio adapters on his Uneeda Audio website. He has a lot of great stuff there. It's worth spending some time reading.

PZM Modification kit, Phantom Powering, Attenuator Pads, All Things Audio


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## jared555 (Jan 21, 2010)

Chris15 said:


> Honestly the likely reason is your teachers don't know what they are talking about in this instance.
> 
> Consider say a "1000w" amp driving say a 4 ohm load. Say you have 400w RMS being drawn. By Ohms law, you have 40V and 10A (both RMS). Change this to an 8 ohm load and the voltage goes up to 57 volts. Make it 800w and 8 ohms and you get 80 volts.
> 
> ...



If you have a 400w at 8 ohm amp does it put out 400w or 200w at 16 ohms (is there a point where the output stabilizes?)

Human skin typically has a resistance of 1,000 to 100,000 ohms. I think 1,000 is wet and 100,000 is dry although it may be lower for wet. So unless you have broken/burnt skin or are sticking the plug in your mouth I would think the resistance would be high enough to limit shock potential.

Not that I am saying that there isn't a slight chance of it happening (I wondered this myself at one point) but I have a feeling you are a lot more likely being shocked by a faulty ground connection.


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## fx120 (Jan 21, 2010)

This will probably freak some people out:







Yes, they came from the factory with a L14-20 twist lock on the back, and no they're not powered.


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## avkid (Jan 21, 2010)

That was fairly common up until Speakon connectors became common.


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## Chris15 (Jan 22, 2010)

jared555 said:


> If you have a 400w at 8 ohm amp does it put out 400w or 200w at 16 ohms (is there a point where the output stabilizes?)



Neither. It's not a simple relationship. The source impedance is the main factor, but just assume it's not linear. Take for instance a lab.gruppen FP14000. At 2 ohms it's rated to 7000W/ch, at 4R, 4400W, 8R, 2350W, 16R, 1200W.


jared555 said:


> Human skin typically has a resistance of 1,000 to 100,000 ohms. I think 1,000 is wet and 100,000 is dry although it may be lower for wet. So unless you have broken/burnt skin or are sticking the plug in your mouth I would think the resistance would be high enough to limit shock potential.
> 
> Not that I am saying that there isn't a slight chance of it happening (I wondered this myself at one point) but I have a feeling you are a lot more likely being shocked by a faulty ground connection.



You start to feel a tingle with about 1mA of current. If you've got wet skin, this is going to occur at a mere 1V. At 10-20 mA, you experience muscular contraction and can't let go. 10V at worst, 100V at best, normal being somewhere in between. With AC, a current of 60mA can cause ventricular fibrillation. With wet skin, ie. 1k ohm resistance, 60V can cause this...

So yes, it's very much possible...


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## jared555 (Jan 24, 2010)

Chris15 said:


> Neither. It's not a simple relationship. The source impedance is the main factor, but just assume it's not linear. Take for instance a lab.gruppen FP14000. At 2 ohms it's rated to 7000W/ch, at 4R, 4400W, 8R, 2350W, 16R, 1200W.
> 
> 
> 
> ...



I was basing it off of a linear relationship, so yes I definitely think it is possible (I did before but after doing some calculations thought I must have been wrong about it being possible)


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## dafunkmonster (Jan 25, 2010)

It only takes 100mA to kill you. Once your skin burns through, your body has an internal resistance of roughly 500ohms. Muscle paralysis happens at 20mA, breathing stops at about 50-75mA. 

Now, 100mA through your hand (thumb to pinky) probably won't kill you. It will hurt like a b***h and result in injury, but it probably won't kill you. However, 100mA through your heart will kill you...or your brain...or anything else vital. 

Problem with electricity is...you can't control where the current flows, nor can you predict it. 

Also, lethality partially depends on frequency. AC is dangerous, because it induces muscle contractions and sweating, and 60Hz is in the most dangerous range. As little as 25V @ 60Hz can kill you. However, people have survived 40,000V at a million Hertz. 

Bottom line is...don't lick cable ends. 

And always do green first.


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