## Analog2CV

Scope and XITE Development

Original topic on PlanetZ: https://forums.scopeusers.com/viewtopic.php?t=28690

#### Analog2CV

Posted: Sat Jan 16, 2010 10:43 am
by Neutron
Capacitor and I are working on sending control voltages to hardware synths through normal AC coupled converters such as the A16.
What happens is a scope device is sending a constant waveform similar to a (very primitive) TV signal, when a certain negative value is reached then a trigger pulse sets off timers for 4 sample and hold chips.
the scope device is modulating those parts of the wave with your control signals.
sample and hold chips chips will measure the voltage of the wave at teh appropriate time.
It is looking quite good so far if it all works out i believe it will be able to respond in 1.5 mS to changes (with 689 HZ carrier wave) which is fast enough for all but the snappiest of envelopes. (scope envelopes default to 3mS, but can go as low as 1 on some devices)
Unfortunately I have no CV analog gear any more since i sold the revolution, but i have ordered 10 SEM2044 Chips and i am going to build a filterbank to test it with.
The reason I have provisionally picked that frequency is that it gives 64 samples per wave at 44.1k sampling rate, which should hopefully be enough to get a decent flat part of the waveform to measure.
The hardware consists of an arduino microcontroller board and a few other chips, and possibly an LCD to give feedback of what it is recieving.
I think scope uses a korg like V/HZ rather than volts per octave. hopefully that can be converted in scope with the help of some math genius
Here is the trigger outputs being tested at 1 khz. very stable.

  scope_ardiono_sm.jpg (160.54 KiB) Viewed 3759 times

Capacitor is doing 8 steps per cycle but i think we can at least use the same scope device to control it.
If it works out, and there is interest (maybe a VST as well?) There are a few options for releasing it. seeedstudio has something called "fusion kit" where you can set up everything through them, or it could just be a bill of parts with the arduino code, with or without custom circuit board.
I do not expect to make any money except recoup the cost of any custom circuit boards i have made.

#### Re: Analog2CV

Posted: Sat Jan 16, 2010 1:38 pm
by HUROLURA
Nice project Neutron.
Just imagine merging scope modular with a true anlog modular synth !!!
It was already possible for audio signals but not that easy for control signal (except for MIDI control but then you need a MIDI to multiple CV interface).
Add up a MIDIBOX.org midi controller and you will have something which can be really customized.
All the best success wishes to your project ...
CheerZ

#### Re: Analog2CV

Posted: Sat Jan 16, 2010 2:07 pm
by Neutron
Thank you!. I am thinking of making a single filter board with the SSM2044 and using it as part of a scope device everything would be controlled on the scope interface as usual but with a real classic analog filter IC as used in the PPG wave and various classic korgs.
i have built the 4x sample and hold board today and tested it.
sorry for crappy cel phone pic, battery was flat in the camera!

  s_h_board.jpg (53.22 KiB) Viewed 3722 times

and started on the scope device. the little scope comes in very handy!
basically what i need to make is a 6 way rotor.

  dsonano.jpg (93.2 KiB) Viewed 3722 times

#### Re: Analog2CV

Posted: Sat Jan 16, 2010 6:56 pm
by dawman
This is the only weak link in Digital synthesis IMHO.
Analog synthesis' weak link is routing and lack of Digitally modified Oscillators.
This new merger should be called Borg synthesis....
This is awesome Neutron.
Now developers and SDK guys can get really sick.
I already have imagined a 1U Analog Filter rack w/ dual filters. Parallel and serial.
A +24db LP 6 pole, and +24 BP for Oberheim & CS80 tones.
Can you imagine the new CZ Resonator 1/2 & 3 Oscillators and this.........??
SaWheeeeeeeettt..

#### Re: Analog2CV

Posted: Sat Jan 16, 2010 8:02 pm
by Neutron
Yeah i am looking forward to building some SSM2044 filters to try this with. a stupid youtube video with not very good sound, but it showed me that was exactly the filter sound i have been trying to get scope to do but never could. http://www.youtube.com/watch?v=FjKCUPv4gXI he is just changing the filter manually, imagine it being modulated
I bought 10 of them already but i may buy 50 or 100 more of them
Device 1
scope mono synth device with audio and control output to A2CV and back in. all presets will work like in scope the Filter freq and Q (and maybe a bit of modulateable analog distortion) will be controlled from scope devices internal LFOs and Envelopes just like a scope filter. the filter could be in a small black box you just plug in to the ad/da converter. it would have an A2CV(without display) built in and so would the scope synth.
Device 2
8x SEM2044 arranged so each one can be high or low pass 24 db oct or any pair can be a bandpass/bandstop/48db oct. eat your heart out spectralis filterbank!
I have made another blog about my other projects (starting with this) besides the physical guitar synth,
it is at http://neutron-synth.blogspot.com so i wont keep spamming this thread with pictures showing how proud of my progress but nobody else could probably give a toss about

#### Re: Analog2CV

Posted: Sun Jan 17, 2010 3:38 am
by dawman
You beeter hook me up Brosky.
I am stashing away the cash as we speak.
SEM FIlters have that seriously deep resonance and the levels stay the same throughtout the range when the resonance is added.
I wanted to do this 2 years ago and had the MOTM guy design the Modular. But since it was polyphonic the rack was around 9 large. I decided the Solaris and XITE-1 would be a wiser choice.
So just having filters and CV should do the trick then 'eh?

#### Re: Analog2CV

Posted: Sun Jan 17, 2010 3:38 pm
by capacitor
It looks like it'll fly
Good to know about the 2044's resonance characteristics.

#### Re: Analog2CV

Posted: Wed Jan 20, 2010 5:48 am
by HUROLURA
I was more or less thinking about a remote controller combining MIDI + something like your Analog2CV principle to achieve control over the Scope Modular from a hardware solution like this one :
http://mungo.com.au/zero.html
Using MIDI through + a MIDIBOX or Arduino based plate and then managing CV-like control by using audio signal ...
My first idea was a Hardware MRC but this already possible for a set of module thanks to the BCM ...
The difficult thing is more about patching cable but I guess a Luna 2496 I/O or even an A16 (ultra) could provide such patching capabilities with some smoothing and electronics.
The over difficulty is to remote control patch cabling from something else than a mouse which I do not figure out how to handle. I would love being hable to identfy modular module I/O and remote connect them from a hardware device ...
Actually the ASB are just the right user interface for their Scope counterpart (BCR-2000 is nice but ASB is just so simple...).
The modular is much more flexible though (especially with the new Mod IV modules). Now I miss a smart hardware user interface for it !!!
CheerZ

#### Re: Analog2CV

Posted: Wed Jan 20, 2010 8:09 pm
by Shroomz~>
Very cool stuff...

#### Re: Analog2CV

Posted: Sat Jan 23, 2010 12:44 pm
by HUROLURA
Just noticed this one:
http://www.tiptopaudio.com/zdsp.php?goto=features
Imagine you can achieve something like this powered by Scope technology...
- One providing a collection of OSC from the scope available type (MultiOsc, Vectron Type, Waldorf Type, CZ type, FM type, Morphing type...) providing modulation inputs for both frequency and waveshape
- One providing a collection of Filter including the MINIMAX, PRO12, PRO-ONE, PRODYSSEY type beside the classic 12/24 dB R or V types, the UKnow Filter provinding the main parameters
They could use just one of the Xite-1 DSP (the target would be a monophonic signal with stereo path) with a slightly different front panel.
Actually a kind of multipurpose mini-ASB dedicated to specific task to be integrated in analog modular. And you could even imagine an autonomous version in the same spirit as the Doepfer Dark Energy (a mini-modular ASB, simple but flexible) extending the good idea of the Prodyssey ASB with its filter select...
... excuse-me, I was just dreaming once again ...