Dragon's Den - Analogue Optical Guitar Cable

[spectoremg]

[quote name='ikay' timestamp='1470155602' post='3103682']
I just emailed David Holmes with a link to this discussion and suggested he join Basschat and explain a bit. So he may be along in a bit
[/quote]I'll be interested to read what he has to say having seen mostly negative but knowledgeable comments about his product.
You get lots of people in the Den who seem to have done absolutely no market research beforehand and are frankly total dreamers. If Mr Holmes seriously thinks that compared to high quality cables or affordable wireless technology the market needs his product then I think he is indeed a dreamer.

[Guest bassman7755]

[quote name='4stringslow' timestamp='1470133775' post='3103430']
Nope - changing the carrier frequency would be FM.
[/quote]

I didn't say change I said modulate (by amplitude implicitly).

[quote]
It's quite simple really. The light is the carrier - it must be, it's the only thing to travel along the cable. The brightness (amplitude) of the light is varied (modulated) according to the varying voltage from the pickup. That's AM, by definition.
[/quote]

I disagree, yes light has a frequency but thats an irrelevant innate property of the transmission mechanism and there is no overt combination/splitting of a signal ergo the claim that its not AM is fair and reasonable IMO.

[TimR]

[quote name='bassman7755' timestamp='1470166270' post='3103822']


I didn't say change I said modulate (by amplitude implicitly).



I disagree, yes light has a frequency but thats an irrelevant innate property of the transmission mechanism and there is no overt combination/splitting of a signal ergo the claim that its not AM is fair and reasonable IMO.
[/quote]

In this case light is acting as a wave, not particles.

You are modulating the intensity or volume or amplitude of the light. The light is fixed frequency. AM.

You are not altering the frequency of the light or digitally pulsing it. So it is not FM or PWM.

[3below]

[quote name='bassman7755' timestamp='1470166270' post='3103822']
.... I disagree, yes light has a frequency but thats an irrelevant innate property of the transmission mechanism and there is no overt combination/splitting of a signal ergo the claim that its not AM is fair and reasonable IMO.
[/quote]

If there is no overt combination of the signal, how is the guitar signal amplitude (electrical) being converted to light intensity (amplitude)? As I see it, light is propagating (travelling) along the optical fibre. It is carrying the information (amplitude of guitar signal) through the intensity (amplitude). This is simply amplitude modulation by any other name. We can of course look at the patent disclosures and establish the circuits used, they may be novel and a 'new' form of non-modulated signal transmission has been developed. If this is the case they will have 'big players' in the communications technology sphere chasing them. Guitar cables will be small beer.

[luckydog]

[quote name='4stringslow' timestamp='1470143139' post='3103547']
Yes, I've often wondered why XLR connectors have not been more popular for guitar leads. [/quote]I think it's because, from the early days, amp inputs were single ended. As we know 99.9% of the time this is fine......

LD

[4stringslow]

[quote name='bassman7755' timestamp='1470166270' post='3103822']
I disagree, yes light has a frequency but thats an irrelevant innate property of the transmission mechanism and there is no overt combination/splitting of a signal ergo the claim that its not AM is fair and reasonable IMO.
[/quote]

I agree that the frequency of the light is irrelevant (any frequency, or colour, of light could be used) but there is most definitely a combination of the signal and the light, because how else could the signal from the pickup be conveyed along a piece of plastic or glass?

Look at it another way; the pickup electrical signal cannot be directly conveyed along an optical fibre because it's an insulator. The only way to transmit the signal is to somehow combine it with the light. In this case, by AM.

[stingrayPete1977]

Are plastic cables good for metal?

And can sound traveling by light work with heavy music?

[EBS_freak]

I think what you are asking is...

Does it djent?

[lojo]

Is the short cable from my bass to my wireless transmitter suggested to be upgraded to optical cable (not that I would) or is it just for long stage leads ?

[AttitudeCastle]

[quote name='4stringslow' timestamp='1470046596' post='3102840']
Agreed. The voodoo is probably the biggest issue

Edit: as for the tone issues (ie frequency response), this chap is not at all convinced:
[media]http://youtu.be/YljQyirf1RM[/media]
[/quote]

David jumped into the comments of that video too.

Not too impressed by his response; however it's human nature to be protective over one's product design, and I agree YouTube clips are far from the [i]best [/i]way to compare sounds, the chap should test them before making a judgement, though no explanation, or constructive conversation was had...

[Note: When I open one link to this video the comments chain where Mr Holmes has posted is there, and in another they are not, despite being the same URL? Maybe just a weird thing on my end]

[quote name='gelfin' timestamp='1470082144' post='3103201']
They also had a go at kickstarter.

[url="https://www.kickstarter.com/projects/1536327222/lightleadtm-world-1st-analogue-optical-audio-cable"]https://www.kickstar...cal-audio-cable[/url]
[/quote]

I'm only vaguely keeping up with the physics of the product (in theory, anyway as things have been explained here) and once more BassChat wonderfully surprises me with all of your knowledge!

In the Kickstarter video, the explanation of change in sound from the normal copper cable (no indication of price point, but the DI test they do has a regular/high end/light lead comparison) and the Light lead, now from the explanation I believe I'm right in say it's then no different to a buffer (a people have pointed out already).

So unless I'm missing something, I don't really see the point, but I'd love to actually try one, and A/B vs a buffered set up.

In the Pro tools expert interview they talk about a band having radio interference from a long cable, again pardon my possible ignorance, but would that possible be a shielding issue of the cable used, as they also said the guitarist switched cables, and went on his way.

And I would also agree with as has been said on this thread, that for many they use wireless, especially for bigger venues, though that is no different to anyone trying to sell long cables regardless.
Would be curious as to battery life, and prices of the bundle, and of the cable (in the "Snake oil" video comments section David states £25 for the cable part) and the ends.

Don't really have an opinion either way, beyond the science behind it seems very interesting, and it seem like a cool product, that as of yet I can't quite understand what it may be needed for! Hopefully David drops in here, and can give us a full explanation of the Light Lead!

[fretmeister]

[quote name='DorsetBlue' timestamp='1470132041' post='3103411']
They normally do a "catch up" programme at the end of each series.
[/quote]

A mate of mine used to work on the show.

Less than half of the deals offered actually happen. Lots fail in due diligence, sometimes the "offer" is actually given as a straight loan, sometimes the applicant doesn't take it as the publicity from the show is enough to get them what they want without giving up equity.


Oh - and the cable needs TWO batteries. 1 at each end.

It's a solution looking for a problem.

They were on the fretboard forum (the biggest UK guitar forum) in 2014 trying to flog them and there wasn't a single forumite who wanted one. Not even the Russ Andrews power cable buying audiotards.

[EliasMooseblaster]

[quote name='4stringslow' timestamp='1470143139' post='3103547']
Yes, I've often wondered why XLR connectors have not been more popular for guitar leads. A balanced connection would have many noise/interference advantages and the possibility of phantom powering could eliminate the need for batteries in active guitars.

[/quote]

Didn't some of the very early Alembic basses come with a second cable input than ran power up to the onboard preamp from a transformer on the floor? Combining phantom power into the signal cable seems like a good idea (as long as you're not trying to go wireless!)

[TimR]

[quote name='4stringslow' timestamp='1470188074' post='3103976']


I agree that the frequency of the light is irrelevant (any frequency, or colour, of light could be used) but there is most definitely a combination of the signal and the light, because how else could the signal from the pickup be conveyed along a piece of plastic or glass?

Look at it another way; the pickup electrical signal cannot be directly conveyed along an optical fibre because it's an insulator. The only way to transmit the signal is to somehow combine it with the light. In this case, by AM.
[/quote]

It's exactly the same as a radio wave. Just, in this case the frequency of the electromagnetic carrier wave (light) is so high that you can see it.

You're still generating a carrier wave, it's just that you're generating light instead of an invisible radio wave.

.

Edited August 3, 2016 by TimR

[4stringslow]

Precisely.

[tauzero]

[quote name='dannybuoy' timestamp='1470003052' post='3102669']
I don't think LEDs/LDRs would be able to respond quick enough to deal with signals in the 20kHz range?
[/quote]

I don't know what's actually used as the transmitting and receiving devices as I haven't looked into it, but as broadband uses fibre, something must be able to modulate light at frequencies well above 20kHz, and something else must be able to respond to that modulation.

I think it does count as AM, incidentally - the carrier goes on at one end and is removed at the other end, otherwise light would come out of the speaker. But it's not something I'd generally think of in terms of AM. It differs from radio AM in that with radio AM, you rectify the signal to chop off the bottom half of it, but with a light modulation system, the polarity of the light wave at any given point is irrelevant, all that matters is its intensity. I think people who understand AM will know what I'm going on about, and it'll be as clear as so much mud to everyone else.

[4stringslow]

[quote name='AttitudeCastle' timestamp='1470217225' post='3104109']
Not too impressed by his response; however it's human nature to be protective over one's product design, and I agree YouTube clips are far from the [i]best [/i]way to compare sounds, the chap should test them before making a judgement, though no explanation, or constructive conversation was had...
[/quote]

Very fair point. I found it difficult to hear any difference
in that YouTube clip, but that was probably because of the PC speakers I was listening through.


[quote name='AttitudeCastle' timestamp='1470217225' post='3104109']
In the Kickstarter video, the explanation of change in sound from the normal copper cable (no indication of price point, but the DI test they do has a regular/high end/light lead comparison) and the Light lead, now from the explanation I believe I'm right in say it's then no different to a buffer (a people have pointed out already).
[/quote]

Yes, it's not really a fair comparison.

What would be interesting is blind testing with a long cable, a Light Lead and a wireless link and all with an active and passive guitar.


[quote name='AttitudeCastle' timestamp='1470217225' post='3104109']
Don't really have an opinion either way, beyond the science behind it seems very interesting, and it seem like a cool product, that as of yet I can't quite understand what it may be needed for! Hopefully David drops in here, and can give us a full explanation of the Light Lead!
[/quote]

My thoughts as well. There's no doubt it works but after that all the other claims seem somewhat subjective and possibly a bit over-hyped, though that's not an entirely unknown phenomenon with new products.

Edited August 3, 2016 by 4stringslow

[12stringbassist]

I think the dragons would mainly have been interested in what else the technology could be applied to.

[TimR]

[quote name='12stringbassist' timestamp='1470226236' post='3104228']
I think the dragons would mainly have been interested in what else the technology could be applied to.
[/quote]

Definitely.

Although I'm sure the BT engineers would have looked at both analog and digital data transmission when working on fibre optics.

They're pretty clever guys.

[4stringslow]

[quote name='12stringbassist' timestamp='1470226236' post='3104228']
I think the dragons would mainly have been interested in what else the technology could be applied to.
[/quote]

They might have been at the time, but a couple of hours of due diligence would reveal that this technology has been around for so long that AM was left behind decades ago, for pretty much all the same reasons that AM radio transmissions are rarely used these days.

I'd be very interested to know what exactly their patent actually covers, because I can't believe it can be for the basic technology.

[4stringslow]

[quote name='tauzero' timestamp='1470222232' post='3104168']
I don't know what's actually used as the transmitting and receiving devices as I haven't looked into it, but as broadband uses fibre, something must be able to modulate light at frequencies well above 20kHz, and something else must be able to respond to that modulation.
[/quote]

There are plenty of semiconductor devices that provide these functions. You can buy them online, eg
http://uk.rs-online.com/web/c/displays-optoelectronics/fibre-optic-components/fibre-optic-transmitters/

I'm not suggesting that any of those devices are suitable for this specific application as I've not checked the data sheets, but it gives an idea about how mainstream these sorts of components actually are, and have been for decades.

20kHz modulation is really very, very low frequency stuff in the grand scheme of things. Could probably switch a simple LED at that frequency and recover the signal with a photo diode. Of course, you'd need to get the light down an optical fibre, which is where the packaging of those Tx devices I've linked to come in, but you get the idea.

As TimR pointed out, BT (among many others) have been researching and developing optoelectronics for decades and run optical networks that operate at many GHz. The Light Lead technology really isn't the issue here and is nothing new - it's the application.

[tauzero]

[quote name='4stringslow' timestamp='1470235023' post='3104365']
There are plenty of semiconductor devices that provide these functions. You can buy them online, eg
[url="http://uk.rs-online.com/web/c/displays-optoelectronics/fibre-optic-components/fibre-optic-transmitters/"]http://uk.rs-online....c-transmitters/[/url]

I'm not suggesting that any of those devices are suitable for this specific application as I've not checked the data sheets, but it gives an idea about how mainstream these sorts of components actually are, and have been for decades.
[/quote]

They're digital rather than analogue - it would require either transmitting and receiving devices having very linear responses, or for them to at least match, or some form of compensating circuitry at one or both ends to cope with the non-linearity. Come to think of it, I've got some laser diodes and photodiodes, maybe I could do some experimenting.

[TimR]

The ear is pretty forgiving when it comes to audio. The light doesn't have to be that good. Once the decoded signal hits the capacitors it's all smoothed out anyway.

[Dad3353]

The early Morley pedals used modulated light (operated by foot pedal...) for volume, 'wah' and 'fuzz' control. There have been several tremolos using this principle in amps, too. The only real difference here is the use of a plastic 'light pipe' as a support; light-controlled sound and sound-controlled light are not new at all.

Edited August 3, 2016 by Dad3353

[BigRedX]

Plenty of light controlled opto-compresssors too.

[JoeEvans]

On a parallel note, it can be instructive to temporarily replace your expensive speaker leads with bog standard mains cable. Sounds just the same to me and many others.