Single wire Digital Audio transmission

[P~0]

Hi Folks,

I am checking out this forum for some time now and it I think it is very inspiring to see what is happening here.
As being a sound engineer I have some basic knowledge about electricity and magnetism, and always had an interrest in harmonics and the interaction between sounds.
I've built some tube amps (KT88 PP UL) and speaker systems which perform way beyond todays standards regarding giving a true sense of "reality"

I am not really into the "free energie" thing, I think there is none, but I do think there is a "different" energie that we have not tapped in to, or we have been tapping into without fully understanding it.
I think it is all consiousness related but that would be a different story for now.

Reading along here I see some interesting experiments regarding coils, which led me to the following question.

Would it be possible to set up a single wire digital audio transmission using two coils and one "ground wire" ?
Without using any active amplification circuits ? Some impedance matching should be done I guess.
To take the digital output @ 88.2 KHz from a BNC 75Ohm output, connect it to a coil which is tuned to 88.2 KHz (or a harmonic vallue) send it across the room for aprox. 7 meters to a matching coil connected to a DA converter ?
Having a single wire as a "ground" connection between the two coils.

Could this experiment be done or am I overlooking some stuff, my gut feeling says it might just work when done right, but I am no expert on that.

Would it be wise to tune the coils @ 88200 Hz ?

This is the experiment that came to my mind reading about coils and resonance, I live in a city appartment having no garden, so I am convicted to small indoors experiments I guess.

The small Tesla coil I built some time ago really performed well having it out on the roof terras under a clear starry night, I did for only one second so, the whole thing lit up in a purple aura and sparks were everywhere while the spark gap made a loud hissing noise.
Now it just makes sparks, I think it got dammaged somehow, but I was really surprised to witness that comming from a small two AA battery powered coil.

This "accident" got me really interrested in this stuff.

I have noticed some very smart people here, my question for now is, would it be worth it to experiment with this digital transfer setup, or am i totaly being silly ?

Yes I know, Tesla would probably just hook up a 75 Ohm terminated cable to get this signal across the room, he was a smart guy

[dR-Green]

Hi there.

Would it be possible to set up a single wire digital audio transmission using two coils and one "ground wire" ?

I see no reason why not. But not with spark gaps.

Without using any active amplification circuits ? Some impedance matching should be done I guess.

No, the speaker will need enough power to drive it...

To take the digital output @ 88.2 KHz from a BNC 75Ohm output, connect it to a coil which is tuned to 88.2 KHz (or a harmonic vallue) send it across the room for aprox. 7 meters to a matching coil connected to a DA converter ?
Having a single wire as a "ground" connection between the two coils.

Could this experiment be done or am I overlooking some stuff, my gut feeling says it might just work when done right, but I am no expert on that.

Would it be wise to tune the coils @ 88200 Hz ?

That would work in theory I think, but in my opinion it's not very practical to use the digital signal itself as the carrier because a coil that's resonant at that frequency would need a lot of wire. In my opinion it would be better to drive a coil with a modulated carrier like regular radio, but with the digital signal. I don't know how your audio equipment might like this at the receiving end though. It would probably be a good idea if you started with analogue, then you can use normal AM and come up with appropriate changes. With an RF amplifier at the transmitting end the power will be supplied to the speaker at the receiver like a crystal radio so you won't need remote amplification.

If you devise a circuit that can do the job with hi-fi quality let me know

Tesla Wireless Transmission Of Signal And Power Through Bucket - YouTube

TMT With New Circuit Prototype Test Run-03 - YouTube

[P~0]

Hi Dr Green, thanks for your reply.

Regarding the amplification I was refering to any addition of external amplification between the soundcart's digital output and the transmitting coil, and between te receiving coil and the receiving DA converter.

From some simple calculations I did using some of Eric's formulas I also come to the conclusion that a resonant coil @88200 Hz would not be very praktical.
Size is roughly come up with is;

LS 54421 cm
WS 861.67 cm
HS 170.068 cm

And then I'll need two, this will not fit in my studio.

Maybe a coil is not the way to go, maybe some clever constructed waveguide might perform the trick better when having them in a straight line on opposing walls ? The coaxcable which now is connecting the units can also be seen as a waveguide (the frequency of 88.@KHz might be to low to really have it working as a waveguide)

Modulating the digital signal would work for sure, but that would require extra circuits with powersupplies and for me personally that would take the fun out of this experiment.

I came up on this idea clicking on a link that linked to a company that sells pancake coils with 3.5mm jack adapter, stating "you can hook ik up to your mp3 player" .... yes, and then what ?

Then I ascend to the astral plane and listen to my music from there ?

I guess I will try the following experiment, I'll make two equal pancake style coils, I hook one up to the output of my studio wordclock ( wich just sends out a 88.2KHZ squarewave) and have one coil connected to the digital input of my DAC just to see if I can get the "signal present" LED lighting up.

If so, music is the next step.

Building the crystal radio as suggested by the smart people here to get an understanding of what is actually going on and then scaling it up step by step was already on my to do list.
I'll have to do some more research first before I'll take that project up.

This digital audio transfer idea just got in the way of that, my personal interrest is in the realm of audio reproduction and the transfer of information.
I take part in a research group doing practical experiments regarding the way we perceive reproduced audio maybe I will elaborate more on that in the future, I'll have to ask first if it is ok to publish the results and theory the group have come up with so far.



Disclaimer: Please forgive my spelling as English is not my native language.

[P~0]

project Update 1

Project Update 1

I've been reading a lot on the forum lately, and all the math and formulas started to dazzle me, my brain works on a different opperating system I guess... so I just decided to stick to my first idea setting up a wireless signal transmission for low voltage signals and take it from there to see if there are any interesting audio qualities to obtain with this.

I'll just follow my gut feeling and I'll be happy to take advise from more experienced members.

I could not wait to get my hands on something so I started to look around for any materials with potention to make a coil of... Easy find;



What you see is a bamboo sandwich plate with some wooden wireguides on it, the secundairy is a 0.6mm goldplated copperwire, 20 turns, the outside ground termination is soldered to the black socket.

The primary coil is a copper strip 0.04mm 72 cm 27 mm, two turns, isolated by a 2mm cork layer, the ouside has a cottonwrap on it, the inside left bare copper.

The secundary coil is mechanicaly 'tuned' like I tune my guitar, I put tension on it from the outside increasing towards the inside hitting the wires with a little wooden stick in the proces of tightening. Beewax is applied afterwards on the holes the wires run trough using a hot air gun.

The cotton strip is soaked in linseed oil aswel as the inside of the coil to prevent from oxidation.

The red sockets are soldered to the primary coil for input.



I also find this wooden rings and sticks in a local hardwarestore, thought it was a cheap and fast way to make a frame for the extra coil, though I have some doubts about its dimensions (too small) but it wil probably be used is my first test run.

I will be making a copy of the bamboocoilthing somewhere this week.

Should I mirror the windings on that ?

[dR-Green]

I could not wait to get my hands on something so I started to look around for any materials with potention to make a coil of... Easy find;

Not bad at all!

Should I mirror the windings on that ?

Yes.

Regarding the amplification I was refering to any addition of external amplification between the soundcart's digital output and the transmitting coil, and between te receiving coil and the receiving DA converter.

I guess I will try the following experiment, I'll make two equal pancake style coils, I hook one up to the output of my studio wordclock ( wich just sends out a 88.2KHZ squarewave) and have one coil connected to the digital input of my DAC just to see if I can get the "signal present" LED lighting up.

I see. Well I wouldn't connect my sound card sync output to what's basically a direct short that's for sure. I don't know what circuitry is at the output but I doubt it will like it. I would recommend putting something in between so the more expensive equipment is isolated. Other than that, I don't think it will work with a small coil because the driving frequency is too low. The best option as far as I see is to make a modulator and use the sync signal for the modulation. Then you should easily get the "signal present" indicator through one wire, with minimal risk of damaging anything, and you won't need an amplifier at the receiver. Assuming the worldclock isn't two way communication??

Size is roughly come up with is;

LS 54421 cm
WS 861.67 cm
HS 170.068 cm

And then I'll need two, this will not fit in my studio.

It would be a nice studio if it did!

Modulating the digital signal would work for sure, but that would require extra circuits with powersupplies and for me personally that would take the fun out of this experiment.

Depends how you look at it, the advantage is that then you'll have a lot more versatility/flexibility for testing other ideas. And if you already know it will work...

Disclaimer: Please forgive my spelling as English is not my native language.

Never mind that

[P~0]

My plan of driving the coil has changed in the meantime of building.

I will be building a small DC pulse signal generator and a friend of mine will lend me a scope, I,ll have the coils out on my roofterras connect both coils to ground using a Y lead fead one with the pulse generator and have the scope on the other one.
And I guess I will need a small cap on both primary coils, someone already offered me some variable caps from old radio's.

It gets even better, I'v come across this guy who told me he once put a whole lot of copper in his backyard configured as a starground system, it is still there.

So I will now focus on building a mirrored replica and a signal generator, realising I will need a broadband sweepable DC pulse device and a broadband scope to find the 'sweetspot' resonance frequency on these coils.

My initial plan of using the wordclock was because the unit has isolated outputs that don't mind shorting, I don't know how tht will affect it's performance it likes to see a 75 Ohm termination.

And I will keep it away from any precious gear, my first little coil driven by a boosted electric flysquatter circuit and a magnetic sparkgap was able to trigger the fire alarm in the buiding (hitting some sweetspot I guess) and killing my wireless mouse, it also drained (ionized) batteries whil still sealed in their package...

And yes it does the neon bulb thing

This triggered my interrest in the "real deal"

[P~0]

Today I got my DC pulse generator up & running it puts out max 12 Volts, starts at +/- 100 Hz and disappears from the screen of my multimeter @ 50 KHz, so I dont know its limit yet.
There is a 15 Volts lightbulb connected in series with the output so it ligts up when the output is shorted by the coil.

There is a 0.7 Volts output for reading its output frequency.

The box it is in was a left over never finnished project and turned out to be perfect for this.

I am stil waiting for the wire to come in for my second coil and extra coils.