The dsp micro modular

Technology Synth-DIY
#1

I’m developing a VA synth that is patched like a Nord modular but with hardware cables like a real modular.

I had the discussion in another thread of doing a virtual synth with hardware patch cables.
The cables are just like a keyscanner matrix that the MCU reads and figures out where to route digital signals.
Anything can modulate anything as it is virtual patching.

I then also got the question about what to do if someone plugs external signals into the 3.5mm jacks on the synth with the intension of controlling something?

I solved it in a nasty and clever way.
The scanner routing uses the ring or ground of the cable as the patch matrix signal and the tip is unconnected.

That way nothing happens if some external voltage is applied to one of the 3.5mm jacks and no MCU fried.

#2

That type of patching is not novel: see http://mungo.com.au/zeroPatch.html

I suppose your MCU won’t be fried until someone plugs an unbalanced stereo line out jack into one of your input and turns the volume right up.

#3

And the price for the Mungo State Zero is also not novel, $12000, ouch!
A patch scanner fronting a VA synth should not cost that much.

I don’t understand your comment about an unbalanced stereo line out jack?

#4

> A patch scanner fronting a VA synth should not cost that much.

It’s certainly not VA in the traditional sense of the term. Everything is done with FPGAs (I think every submodule runs its own FPGA) and the code is running at sample rates in the MHz range to do everything without aliasing issues (and without the limitations of band-limited approximations). Audio-rate modulations are possible and sound “analog” - not like washes of aliasing.

For a one-off, it’s fairly priced. Taking taxes into account, it’s only 2 months of the salary of a seasoned electrical engineer…

#5

> I don’t understand your comment about an unbalanced stereo line out jack?

If someone plugs by accident a stereo jack, then the “sleeves” of the jack connectors on your patch matrix will receive a signal. Potentially below the -0.5V threshold below which your MCU pins get fried.

External clamping diodes such as BAT54S would be a nice addition.

#6

Sorry, the diodes where there in the original discussion for MCU input clamping.
But they will short whatever external signal you plug in.

#7

@janost this is intriguing. What’s the interface for this DSP monster? Do you envisage patches wing programmed using a computer-based editor, or a large builtin screen and multi-function encoders and buttons? Or a touchscreen, perhaps?

a|x

#8

@janost hmm… just reread your original post. I must say, I’m a bit confused as to how this will work. If you’re using external patching, but allowing a patch to contain different modules of your choosing (like a Nord Modular), how do you get around the fact that there will be a limited number of actual hardware sockets available, and how are these going to be sensibly mapped to patch-points on the selected modules?

I can see how this approach could work really nicely with a fixed architecture synth. In this case, you could have a physical socket for each virtual patch-point, a bit like the old Korg MS-20 emulation software and controller.

a|x

#9

It works like a Nord modular but yes, the number of modules are fixed and limited.
So is any modular rack, you have a fixed number of modules.

Inputs can be wire-ored by paralleled input sockets or through-parallel plugs.
You can also have parallel socket patch bays on the panel.

It will be sample accurate patching so you can for example feed back an oscillator to itself.
or have audiorate modulation of all modules.

#10

I sent my synth to a professional demo maker to get something rolling.

To Firechild

I saw he had some MI modules as well?

#11

> I saw he had some MI modules as well?

Cool! Do you have a link for the video? I’ve never seen it…

#12

Can’t seem to find it now but it was there yesterday when I went through his videos?
Check his channel. It should be there.

#13

I have found out that the postal services within the EU really suck, big time.
All strange looking envelopes or packages get stuck in customs for a week.

I can understand if it’s Russia or the US but not within the EU.

If this continues I stop using any kind of postal service and only use DHL and UPS.

And the customers will have to pay for that.

#14

I spent yesterday evening replicating the Juno DCO on an Arduino.
Not as dsp but as the real thing like it’s built on the original.

Shit, that thing sounds good.

#15

I didn’t implement the charging of the integrator cap through a dac yet.
The level is reasonably stable up to about 2.5KHz charging from the 5v line.

But adding a dac for the cap charge would make it the same level, 20-4000Hz.

#16

Say hi to the Jupiter-X synthesizer :slight_smile:

#17

Would really like to listen to this thing. Any demos?

#18

Sorry, I wont do that mistake again.
So I’m sending away all my synths for demos.

There isn’t any demo yet.

It’s really a hardware copy of the Juno oscillator and my dsp filter.

#19

And I used the Arduino for the DCO and the ARM for the filter.

So end of platform wars?

#20

The hardware osc is a copy of the Roland Juno’s
And the frontpanel is Roland inspired so I hope not to wake any lions.

Walking on the boarder.