stingrayPete1977 Posted August 1, 2016 Share Posted August 1, 2016 But it is "my sound" Quote Link to comment Share on other sites More sharing options...
4stringslow Posted August 1, 2016 Share Posted August 1, 2016 (edited) [quote name='gapiro' timestamp='1470066128' post='3103020'] Just because they are using the brightness (ie amplitude) to control the signal - doesn't make it AM. AM uses the input to control the output level of a carrier wave - Ie as per the bottom one here They are saying they can just use the modulating signal as the signal transmitted. [/quote] I don't understand your point. The modulating signal is the electrical output of the guitar, which cannot be directly sent down an optical fibre. You have a light source and an electrical audio signal. How are you going to use that light source to carry the information in the electrical audio system? The easiest method is to convert the signal voltage into light intensity. No signal voltage = no light, peak signal voltage = peak light brightness . . . and all signal voltages in between. The receiver just does the opposite thing to convert light intensity into voltage and voila, there's the audio signal back again. But it is very definitely amplitude modulation. There are other techniques that don't require ADCs and DACs but they require switching the light source on/off and so could be regarded as a 'digital' transmission system (e.g. Pulse FM or PFM - check it out in wikipedia). Given that they clearly state its a purely analogue system then I'm betting they use AM. Edited August 1, 2016 by 4stringslow Quote Link to comment Share on other sites More sharing options...
4stringslow Posted August 1, 2016 Share Posted August 1, 2016 [quote name='gapiro' timestamp='1470066429' post='3103022'] I'd be interested to know how tight you can have the cable in terms of bends. I would have thought the (presumably glass) optic carrier would be susceptible to breaking at a kink/bend in the cable? [/quote] Good question. In the YouTube interview I mentioned above, the designer said they used plastic cable. This makes perfect sense because the cable lengths are so short that multi-mode issues are pretty much irrelevant and plastic cables are relatively thick (large c/s area) which means it's very easy to launch light into the fiber at the Tx end and receive it at the Rx end. The 'proper' high speed glass optical fibres used in datacomms are really small (to eliminate multi-path distortion - hence 'single mode' as opposed to 'multi-mode') and consequently it's a precision job to correctly terminate them, which means higher cost. The other big advantage of plastic optical fibre is that it's very robust and highly resistant to bending and stretching, so I don't think that looping such a cable through a guitar strap would be a problem. Quote Link to comment Share on other sites More sharing options...
gelfin Posted August 1, 2016 Share Posted August 1, 2016 They also had a go at kickstarter. https://www.kickstarter.com/projects/1536327222/lightleadtm-world-1st-analogue-optical-audio-cable Quote Link to comment Share on other sites More sharing options...
luckydog Posted August 1, 2016 Share Posted August 1, 2016 Foolish me, but what is wrong with my trusty old cable ? Luddite yoda is......... ! LD Quote Link to comment Share on other sites More sharing options...
3below Posted August 1, 2016 Share Posted August 1, 2016 I am with 4stringslow on the AM modulation, not that being a Physicist has any bearing on this. Being an older git, luckydog makes the connection, what is wrong with my old cable. Yes, if I gigged rather more I would probably go wireless , then again virgin unicorns have been seen in this part of Mid Wales, so who knows. I do know I will not be forking out for the Analogue Optical Guitar Cable. Quote Link to comment Share on other sites More sharing options...
Guest bassman7755 Posted August 2, 2016 Share Posted August 2, 2016 (edited) [quote name='4stringslow' timestamp='1470010588' post='3102696'] Edit: here's an interview with the two behind Iconic Sound and if you listen carefully to the designer of the system it is stated that the system is purely analogue and works on the principle of 'light brightness' - I.e. AM. [media]http://youtu.be/cQWsECxpBDM[/media] [/quote] If the amplitude of the light is solely controlled by the source signal than that is not AM since AM is where a carrier frequency is modulated by the source signal and then the carrier is filtered out by the receiver. Yes you could consider consider the frequency of the light itself as the carrier but then air molecules are also in a constant state of vibration at room tempurature in the absence of any sound so taking that absolutely literal approach you could also argue that all acoustic sound transmission is AM. For me the acid test would be - If there is no light transmitted at a zero signal level then that would not qualify as AM. Does seem like a a bit of a pointless technology for a guitar lead though, you'd surely be better off in every respect using a wireless system. I guess it could be useful in studios though if you need a high number of signals transmitted without noise. Edited August 2, 2016 by bassman7755 Quote Link to comment Share on other sites More sharing options...
TimR Posted August 2, 2016 Share Posted August 2, 2016 (edited) If you modulate the frequency then it is Frequenxy modulation. Sound doesn't have a carrier wave. It is a wave of its own (compression wave) and doesn't require any encoding, decoding. You could argue the encoding is done by speakers and the decoding is done by the ears but there are no electro mechanical waves involved at any point. Here, it's AM, it's just that you're using light wave frequency THF instead of radio wave frequency or VHF/UHF. https://en.m.wikipedia.org/wiki/Electromagnetic_spectrum Edited August 2, 2016 by TimR Quote Link to comment Share on other sites More sharing options...
ikay Posted August 2, 2016 Share Posted August 2, 2016 I emailed them re battery life and got this reply: [i]The battery life is around 18hrs of continuous play.[/i] [i]The low battery indicator will give you a 2hr of battery life warning.[/i] [i]The signal will not degrade as the battery life dies.[/i] [i]Yes the unit will switch off once battery is flat.[/i] [i]We are also working on a LightLead that doesn’t use batteries.[/i] Wonder how the battery-less version works? Quote Link to comment Share on other sites More sharing options...
BigRedX Posted August 2, 2016 Share Posted August 2, 2016 [quote name='ikay' timestamp='1470126747' post='3103346'] Wonder how the battery-less version works? [/quote] In theory with an appropriately sensitive light source it could be possible to drive it directly from the voltage generated by the pickups. I would imagine that there would still be a power source needed at the receiving end to amplify these signals but that could be provided by a mains PSU. Quote Link to comment Share on other sites More sharing options...
DorsetBlue Posted August 2, 2016 Share Posted August 2, 2016 [quote name='PaulWarning' timestamp='1470050635' post='3102866'] yes I suspect a lot of these 'offers' don't come to fruition, there does seem a lack of 'what happened next' programmes [/quote] They normally do a "catch up" programme at the end of each series. Quote Link to comment Share on other sites More sharing options...
4stringslow Posted August 2, 2016 Share Posted August 2, 2016 In theory perhaps but I'm not aware of any device that could convert the tiny amount of power from a passive pickup into a suitable light source. Another approach might be to use a composite copper/fibre cable and supply power from the Rx end, but really, what's the point? Quote Link to comment Share on other sites More sharing options...
4stringslow Posted August 2, 2016 Share Posted August 2, 2016 [quote name='bassman7755' timestamp='1470115749' post='3103298'] If the amplitude of the light is solely controlled by the source signal than that is not AM since AM is where a carrier frequency is modulated by the source signal and then the carrier is filtered out by the receiver. Yes you could consider consider the frequency of the light itself as the carrier but then air molecules are also in a constant state of vibration at room tempurature in the absence of any sound so taking that absolutely literal approach you could also argue that all acoustic sound transmission is AM. For me the acid test would be - If there is no light transmitted at a zero signal level then that would not qualify as AM. [/quote] Nope - changing the carrier frequency would be FM. 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. The level of light transmitted at a zero signal level is irrelevant and depends on the bias applied to the Tx device. The important thing is the variation in brightness, which conveys the information, not the actual brightness. Any applied bias at the TX is simply removed at the Rx end. Quote Link to comment Share on other sites More sharing options...
PaulWarning Posted August 2, 2016 Share Posted August 2, 2016 [quote name='DorsetBlue' timestamp='1470132041' post='3103411'] They normally do a "catch up" programme at the end of each series. [/quote]yes, but it's very selective Quote Link to comment Share on other sites More sharing options...
stingrayPete1977 Posted August 2, 2016 Share Posted August 2, 2016 They invest in crap then when someone brings a product I'm ready to buy right now they laugh them out of the room, how these people make millions I'll never know! Quote Link to comment Share on other sites More sharing options...
stingrayPete1977 Posted August 2, 2016 Share Posted August 2, 2016 They should do a flop show, remember the band they took on? ! Quote Link to comment Share on other sites More sharing options...
EBS_freak Posted August 2, 2016 Share Posted August 2, 2016 (edited) Re : battery-less version Phantom power for Xlr leads I guess - but doesn't that go against the whole idea of getting rid of copper cable? Edited August 2, 2016 by EBS_freak Quote Link to comment Share on other sites More sharing options...
4stringslow Posted August 2, 2016 Share Posted August 2, 2016 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. Such connections are well proven for microphones and would undoubtedly be just as effective for guitars. It would also mean a more universal 'signal cable' for all band equipment and eliminate the possibility (or near certainly in my band) of someone using a guitar jack lead as a speaker cable! Perhaps we just like to make things difficult for us all? Quote Link to comment Share on other sites More sharing options...
zero9 Posted August 2, 2016 Share Posted August 2, 2016 I'd love to combine this with a Lightwave Systems pickup for total optical overload Will it make my playing lightning fast I wonder? Quote Link to comment Share on other sites More sharing options...
EBS_freak Posted August 2, 2016 Share Posted August 2, 2016 [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] You can get phantom power on a standard stereo Jack to jack. Quote Link to comment Share on other sites More sharing options...
4stringslow Posted August 2, 2016 Share Posted August 2, 2016 Yes, I suppose you could. The important thing is to have three conductors. I'd say an XLR is a generally better connector than a jack, but it's a fair point. Are such connections widely used though? Quote Link to comment Share on other sites More sharing options...
TimR Posted August 2, 2016 Share Posted August 2, 2016 You don't need a balanced line for a guitar. The longest run is going to be 5m max. Balanced lines are for long runs. That's why you use DI boxes. Short run to amp, then DI for long run out to mixer. The optical cable could replace the XLR at that point, other than that it's just unnessecary. You don't even need an optical cable. Quote Link to comment Share on other sites More sharing options...
stingrayPete1977 Posted August 2, 2016 Share Posted August 2, 2016 I wonder if the inventors have seen this thread? Maybe they could explain it better. Quote Link to comment Share on other sites More sharing options...
ikay Posted August 2, 2016 Share Posted August 2, 2016 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 Link to comment Share on other sites More sharing options...
4stringslow Posted August 2, 2016 Share Posted August 2, 2016 [quote name='TimR' timestamp='1470151164' post='3103633'] You don't need a balanced line for a guitar. The longest run is going to be 5m max. [/quote] Agreed, not entirely necessary, though even a high impedance 5m unbalanced cable is susceptible to noise interference and the longer the cable the higher the risk. It would do no harm to standardise on balanced cables. Not all mic leads are particularly long (eg PA amp on stage with the band) but they are mostly balanced XLRs these days so why not guitars? Quote Link to comment Share on other sites More sharing options...
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