Friday, September 25, 2009

Another Euro rack Synth Tech module "Z-plane morphing"

In a departure from the usual proceedings at Synthesis Technology, there's another module in development that will be released in Euro rack first.
Paul tells us that this is basically to generate additional cashflow, in order to develop the more advanced versions in MOTM format, which have a longer R&D period. Getting the Euro and other formats on the market creates a bit of a buffer, and budget to retool some of the classic MOTM modules in the future too (some of them going to SMT in in time where possible).
Back to the E-350..

Here is strictly a *TEST* showing the E350's Z-Plane morphing function using control voltages. In this test, there are 3 banks of waves (NOT, repeat...NOT what will ship, these are place holders) that are morphed from one to the other using the front panel pot (so, a linear sweep).

Each bank is 64 waveforms. Right now, the interpolation has 64 "in-between' waveforms (it's like a cross-fade between adjacent wavetables). So, you are hearing 64 x 64 = 4096 *distinct* waveforms in the sweep.

The very end of the demo shows the aliasing noise for frequencies over ~3KHZ that occur. As you can hear, lower frequencies are extremely "smooth" and alias-free. The aliasing is due to the 256 byte samples (longer samples would alias at highter audio frequencies).


Sequence of audio is:

* starts out at min frequency, bank 3 minimum wave
* frequency increases somewhat
* upward sweep through all waves in bank 3
* increase frequency some more
* downward sweep through all waves in bank 3
* switch to bank 2
* upward sweep through all waves in bank 2
* switch to bank 1
* downward sweep through all waves in bank 1, ending up at pure saw
* sweep saw down to min
* sweep saw up to max - notice the aliases at top end

There are some fairly harsh waves in this set - some with nasty glitches in them. Not my fault!
We will contiue to work on the DSP code to make it sound as best we can. Also, the MP3 compression muddies up the sounds a bit.


About the future MOTM version, and how it differs from the E-350, Paul writes:
"There will be a 5U version but it will have more wavetables, better interpolation and cost more. No timetable for that, probably Q1 2010.
The rate at which the morph CV inputs (yes, there are different sorts of morph inputs) can be modulated will probably be fairly "low", say 400-600Hz. The 'Pitch' CV input can be modulated much higher, say 5KHz. There is a tradeoff between the update rate and the "smoothness" of the morphing. I am intentionally going for the cleanest, smoothest morphing possible within the constraints of the HW. Which in the E350, is really the SW. The MOTM version will have a large FPGA which is like a math co-processor in that the interpolations can all be done in real-time hardware.

Also, I am trying to keep the price of the module as low as I can (if one can associate me with the term 'low price'), which will be < $400 retail.

The wavetables cannot the field upgraded like a MiniWave. The wavetable data is part of the actual DSP code. Maybe I can make E351/352 versions with different sorts of wavetables. Again, we are spending *much* time and effort hand-tweaking every single data point in every table, so that you will not be able to tell this is a wavetable VCO at all. There are plenty of "glitchy" wavetable options available. This is sort of.....different."



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