[sdiy] Patchable polyphonic synth with FM or AM transmission idea

Joel B onephatcat at earthlink.net
Sat Dec 29 02:16:33 CET 2018

Not sure why you couldn’t send analog signals via fiber - probably use the wave angle to multiplex over the same cable just like networking signals do, and convert the amplitude or frequency back to an electrical signal.


Sent from my iPhone 

> On Dec 28, 2018, at 4:46 PM, Ben Lincoln <blincoln at eventualdecline.com> wrote:
> Your original post included a suggestion of using fiber-optic connections, which - unless I'm greatly mistaken - inherently means converting between analogue and digital at every patch point.
> I think you're getting the sort of responses you're getting because your overall goal is unclear. I.e. trying to somehow multiplex a bunch of analogue signals onto a single pair of wires is going to result in poor audio quality. If you're OK with reducing the quality, why aren't you OK with using digital connections, or doing the whole thing in software? If you're not OK with reducing the quality _and_ want to stay entirely analogue, you're basically stuck with two wires per signal. If you're just curious from a theoretical perspective of what's physically possible, why are you pricing out parts? Etc.
> Someone else mentioned the "XY problem", and I tend to agree. You're asking for help with a very specific part of an overall approach that doesn't seem to be practical, so people are trying to guide you toward an overall approach that makes more sense based on what you've described so far.
> Maybe it would make more sense, and maybe you'd get answers you were happier with, if you explicitly stated what you were hoping to end up with. A working analogue modular polysynth that you built yourself? A design to have someone else build? A theoretical design that you want to patent and hope to license? Etc. 
>> On 28 December 2018 14:17:59 GMT-08:00, cheater00 cheater00 <cheater00 at gmail.com> wrote:
>> cat5 cables are pretty terrible for repatching, as are the jacks.
>> In case someone wants to mention some other more or less obscure type
>> of cable, PLEASE DON'T, I really considered them all.
>> Can we please have the thread return to the original question, which is below:
>> How to use multiple FM transmitter ICs to succesfully transmit
>> multiple FM stations over a single copper cable? What are suitable ICs
>> to use? Is there an inexpensive IC that will transmit multiple bands
>> at once?
>> Can we please NOT talk about whether this is feasible, provide good
>> results, or be cheap. Can we please not talk about crossbar ICs,
>> digital transmission, or multi-conductor cables. If you want, you can
>> start your own thread, thanks. We've had those exact conversations on
>> this mailing list a dozen times over the last 20 years at least,
>> please look in the archives. There's absolutely nothing new to be said
>> here.
>>> On Fri, Dec 28, 2018 at 7:48 AM john slee <indigoid at oldcorollas.org> wrote:
>>> >
>>>  Yup, done plenty of that. I'm not sure it's a good example to look at because datacentre cabling isn't designed with frequent repatching in mind. I've worked in places that had "patch once then throw it in the trash" policies for Cat5e/etc cables — you don't have to waste many hours on troubleshooting problems that turn out to be caused by damaged cables before it's cheaper to operate that way. Wasteful, perhaps, but typical Cat5/etc cables, regardless of how much you pay for them, aren't really that resilient. Not good for modular patching.
>>>  John
>>>>  On Fri, 28 Dec 2018 at 17:16, Joel B <onephatcat at earthlink.net> wrote:
>>>>  Weeeell... tangles happen if you allow them to - have you ever wired up an office building and server room with Ethernet? Lots and lots of cables in a very tiny area. Typically 32 cables per 1 rack unit high device...
>>>>  I’m not aware of a smaller form factor cable with equal or higher wire count, but perhaps one exists.
>>>>  Joel
>>>>  Sent from my iPhone
>>>>  On Dec 27, 2018, at 8:43 PM, john slee <indigoid at oldcorollas.org> wrote:
>>>>  In a large-format system, perhaps. Large tangles of Cat5 patch leads can be pretty inflexible and annoying to manage
>>>>  To the OP, I would ask: have you tried building something like what you want with pre-existing hardware or, possibly, with virtual hardware? eg. in Max? It would be unfortunate to go through all that analog hardware engineering pain (and it does sound like pain!) only to find that any or all of the below are true:
>>>>  - the result is musically uninteresting
>>>>  - you rarely or never go beyond patches that are essentially a fixed-architecture polysynth
>>>>  - the user interface required to manage it all is horrible
>>>>  It's a very hazy memory now but didn't Creamware/Sonic Core's DSP modular have polyphonic capability?
>>>>  John
>>>>>  On Fri, 28 Dec 2018 at 15:18, Joel B <onephatcat at earthlink.net> wrote:
>>>>>  Cat5 cable might be a nice small footprint way to send multiple signals from module to module with easy connect/disconnect-ability. 8 wires per cable, nice little phone-jack...
>>>>>  Joel
>>>>>  Sent from my iPhone
>>>>>>  On Dec 27, 2018, at 5:55 AM, Roman Sowa <modular at go2.pl> wrote:
>>>>>>  Frequency domain multiplexing was used long time ago in telephony.
>>>>>>  How nice and easy solution this was can be simply put in two questions:
>>>>>>  - why nobody remembers that?
>>>>>>  - why it was abandonned so quickly?
>>>>>>  I mean you have ready to use multichannel digital standards and multichannel ADc and DACs, why bother using an ancient idea that was so troublesome to manage that even 0.3-3.4kHz bandwith audio was a challenge.
>>>>>>  And if you want full analog, I'd go with multipin connectors, there are lots to choose from. OK expensive patch cable then, but still a tiny fraction of the price of any 16-voice module.
>>>>>>  Polysynths are hardwired for a reason.
>>>>>>  Roman
>>>>>>  W dniu 2018-12-25 o 20:49, cheater00 cheater00 pisze:
>>>>>>> Hi everyone,
>>>>>>> I was thinking again about how you could do a modular polysynth well,
>>>>>>> and it occurred to me that you might be able to use frequency domain
>>>>>>> multiplexing (FDM) to put several signals over a single conductor
>>>>>>> pair. A quick search found the Si4710 which is a bit pricey at ~$12 on
>>>>>>> digikey but it's a tiny 3x3mm QFN device that performs complete FM
>>>>>>> transmission. In a 16 voice system, at about 5 output functions per
>>>>>>> module, and 12 modules, you can easily use up ~1000 of those, which
>>>>>>> drops the price to $4. I was wondering what everyone thinks about this
>>>>>>> sort of scheme.
>>>>>>> Given that metal patch cables could function as antennas and cause
>>>>>>> both cross talk and external signal pick up, one could also use
>>>>>>> multimode glass fiber and transmit signals this way. The question is,
>>>>>>> does anyone know whether support electronics could be found that are
>>>>>>> integrated enough (small in footprint) and inexpensive? The idea would
>>>>>>> be to build an electronics module that takes 16 analog audio channels
>>>>>>> and outputs a signal that can be then converted to glass media
>>>>>>> signalling.
>>>>>>> Merry Christmas everyone!
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>>>>>>> Synth-diy at synth-diy.org
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