[sdiy] Digital modular backplane - update

Mon Mar 31 20:25:58 CEST 2014

Hi Roman,

Haha, well... actually.... I have done a Brain-to-MIDI interface. I hooked up a Brain-Computer Interface system to my Clavia Nord Modular G2, and to a Yamaha DiskKlavier. In both cases it was triggering patterns in Ableton Live. It did work well in the lab, but control signal quality was a problem outside the lab (more electrical interference, more distraction of the person controlling it, etc). So while the interfacing is totally possible, the quality of the control signal that comes from the Brain-Computer Interface is the problem. It would be a mean pseudo-random noise source though :). If you like, I could make a Eurorack module that interfaces a DIY EEG electrode to a modular synth.

Best,

Rutger

On 31 mrt 2014, at 11:16, Roman Sowa wrote:

> hi, and welcome!
> 
> I'm wondering why you didn't mention anything about "Brain Controlled MIDI", which seems obvious project for you. I bet you have working prototype hidden somewhere in a drawer... Please show us!
> I'd be surely interested in that. But sorry, don't expect a job position from me, can't afford an emplloee at Dutch level of sallary yet ;)
> 
> Roman
> 
> W dniu 2014-03-30 20:06, Rutger Vlek pisze:
>> Hi Damian,
>> 
>> Thanks for collecting and sending all the info! Looks great. I am a
>> list member for quite some time already, but have become more
>> "active" in the last months. Here's a brief introduction for anyone
>> interested:
>> 
>> My name is Rutger, 31 y/o, living in Nijmegen (Netherlands). Have
>> been playing keys for various (prog) rock bands and doing synth DIY
>> since age of 21. Have a masters degree in artificial intelligence and
>> just finished a PhD in Brain-Computer Interfacing (with EEG). Looking
>> for job opportunities to move away from academia. I love science, but
>> I hate present academic climate (pressure, ego's, competition, etc).
>> Thinking about starting a small company to share some of my recent
>> DIY efforts with a wider audience. Have recently been working on
>> prototyping a new idea for a discrete OTA and obtained pretty good
>> results! Also very much interested in the "bigger picture" of synths
>> and other new instruments, large innovations, a new standard to
>> replace MIDI, digital modulars, etc :).
>> 
>> Best,
>> 
>> Rutger
>> 
>> ps. And did already mention that I'm looking for job opportunities in
>> synth design (sorry, shameless pluggin' going on here).
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> On 30 mrt 2014, at 15:27, cheater00 . wrote:
>> 
>>> Hi John and Rutger, thanks for your emails. First of all, welcome
>>> to the list - I have not spoken with you before, and I guess this
>>> is one of the first posts for each of you.
>>> 
>>> I am guessing you don't recollect, or haven't been involved with,
>>> the original conversation from November 2013. I have had to ask
>>> Paul for permission, but I have now forwarded the whole original
>>> thread to the list. The thread is not all in the synth-diy archive,
>>> which is troubling.
>>> 
>>> 
>>> On Thu, Mar 20, 2014 at 4:00 AM, john slee
>>> <indigoid at oldcorollas.org> wrote:
>>>> Hi,
>>>> 
>>>> On 17 March 2014 22:24, cheater00 . <cheater00 at gmail.com> wrote:
>>>>> Some time ago we have spoken about what it would take to make
>>>>> a digital backplane for a modular synth.
>>>> 
>>>> What problem is this attempting to solve? Being able to save
>>>> signal routing and control state in a patch would be nice, I
>>>> suppose, but
>>>> 
>>>> - physical settings != patch settings => replace controls with
>>>> "soft equivalents" => encoders/momentaries => current state no
>>>> longer obvious => more indicator lights etc => may require more
>>>> front panel real estate than "real" controls => more $$$
>>>> 
>>>> What other benefits of going all modern do you see?
>>>> 
>>>> John
>>> 
>>> The basic idea (which you will find more details on in the
>>> original thread I have just forwarded) is that you use analog
>>> modules. Those modules are connected via digital patch cables. Much
>>> like Rutger suggests below...
>>> 
>>> 
>>> On Sat, Mar 22, 2014 at 12:05 PM, Rutger Vlek
>>> <rutgervlek at gmail.com> wrote:
>>>> I've been thinking about the concept of digital modulars too, but
>>>> I think that until digital technology advances much further
>>>> (lower latency, higher sampling rate, more CPU power, high bus
>>>> speeds) the key differences between analog and digital domains
>>>> will limit the usefulness of a 'digital modular' approach. Some
>>>> things sound better, and are more cost effective, in the analog
>>>> domain: such as oscillators and filters with lots of character, a
>>>> little bit of drifting, etc. And some things sound better, or are
>>>> more cost effective in digital: noise properties, patch storage,
>>>> complex connections that would otherwise require lots of messy
>>>> cables.
>>> 
>>> 
>>> ...the idea is to take the best of analog, and the best of
>>> digital. Analog is obviously better at generating and processing
>>> sound. Digital is better at moving it around, meaning recording and
>>> playback. Michael Jackson's album Thriller was multitracked in
>>> digital.
>>> 
>>> My latest update, which I again include below (as it's been 10
>>> days and many readers have likely deleted the original post), talks
>>> about a possibility of realizing a modular bus for hauling a lot of
>>> audio around in digital with as little latency as possible. Ideally
>>> the latency should be as much as it takes to digitize a single bit
>>> of signal, send that single bit, and then reproduce it with a DAC.
>>> This should make even feedback topologies useful.
>>> 
>>> Naturally, for situations where feedback isn't good in digital,
>>> front-panel patch points should still be available.
>>> 
>>> Cheers, Damian
>>> 
>>> On Mon, Mar 17, 2014 at 12:24 PM, cheater00 . <cheater00 at gmail.com>
>>> wrote:
>>>> Hi guys, Some time ago we have spoken about what it would take to
>>>> make a digital backplane for a modular synth. One of the issues
>>>> was that most common digital interconnects will introduce large
>>>> delays in transporting the audio which are not acceptable in
>>>> modular synthesis. A requirement was mentioned of ideally having
>>>> the delay as low as the transmission time of 1 bit. This has to
>>>> take into account the situation that an ADC or DAC will operate
>>>> at low clock speeds, while the backplane would operate at very
>>>> high clock rates, in order to accomodate many ADC-DAC links in
>>>> the switched, TDM fabric.
>>>> 
>>>> I have come across the idea of using a SerDes:
>>>> 
>>>> http://en.wikipedia.org/wiki/SerDes
>>>> 
>>>> They are basically shift registers with additional ISO OSI Layer
>>>> 1 processing. in specific, it seems a popular type uses 8b/10b
>>>> encoding which limits the RFI impact, and makes the layout much
>>>> easier as the lower bandwidth limit of the physical links goes
>>>> further up, while the upper bandwidth limit doesn't move.
>>>> 
>>>> In addition this device family addresses the issue of having
>>>> slow links on fast backplanes:
>>>> 
>>>> "Bit interleaved SerDes multiplexes several slower serial data
>>>> streams into faster serial streams, and the receiver
>>>> demultiplexes the faster bit streams back to slower streams."
>>>> 
>>>> It seems in this case there is no bunching or buffering so the
>>>> latency can be kept to a minimum.
>>>> 
>>>> Silicon for SerDes applications exists and is popularly used in
>>>> loads of consumer technologies:
>>>> 
>>>> "Among the areas in which 8b/10b encoding finds application are
>>>> the following:
>>>> 
>>>> PCI Express at speeds below 8.0 GT/s IEEE 1394b Serial ATA SAS
>>>> Fibre Channel SSA Gigabit Ethernet (except for the twisted pair
>>>> based 1000Base-T) InfiniBand XAUI Serial RapidIO DVB Asynchronous
>>>> Serial Interface (ASI) DisplayPort Main Link DVI and HDMI Video
>>>> Island (transition-minimized differential signaling)
>>>> HyperTransport Common Public Radio Interface (CPRI) OBSAI RP3
>>>> interface USB 3.0 CoaXPress MIPI M-PHY[6] ServerNet (From
>>>> ServerNet2 onward)"
>>>> 
>>>> It might be possible to find switched fabric chips that can route
>>>> the links on an X/Y grid for best bandwidth utilization, and
>>>> which can do so without buffering. At least that is what I would
>>>> expect of what Infiniband, Gb Ethernet, and Fibre Channel are
>>>> doing.
>>>> 
>>>> Cheers, D.
>> 
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