[sdiy] Wondering about function generators for envelopes

[Metrophage]

--- Grant Richter <grichter at asapnet.net> wrote:

> We already did that.
> 
> It's called a Blacet Mini-Wave, a very practical arbitrary function  
> generator. Which very many people already own.

I would love a Mini-Wave, but my strategy was to sink all of my money
into parts (almost all of which can be used for various circuits), and
not buy any pre-built modules, or even kits. Who knows, maybe I'll get
a "real job" some day but I have no income for the forseeable future. I
am too intense and honest so nobody around here ever wants to hire me
to do anything, it's surreal. No cash = no MW. But I am *very* slowly
working on some wavetable experiments here. 

Also, I don't consider an EPROM/DAC device to be a real function
generator. Like comparing a sampler to a synth, you can pre-compute a
function and store the results easily. Why not do it in real-time,
without the stepping? I know that there are various ways to make
multi-stage envelopes, but I am wondering about use of function
generators specifically. The functions can be done with a CPU; but with
scanning the controls, crunching the numbers, and sending out to DACs -
I'd guess that hi-speed analog would be faster, and obviously without
stepping. Mind though that I am no where near the circuit-design wiz
that you are, Grant!
 
> Take your "vanilla" (preferably linear) ADSR and process it through  
> the Mini-Wave on the 0 to 10 volt range.
> 
> This converts each envelope segment into a 256 step sequence of  
> voltages with adjustable "playback" time for each segment. An  
> adjustable slew limiter after the Mini-Wave allows you to convert  
> multi-segment sequences in multiple "sub" envelope sequences and will
> remove any 8 bit "zipper" stepping.
> 
> The "Socket Rocket" PROM contains a large range of variants of  
> exponential and anti-exponential (logarithmic) envelope curves. These
> are the m to a power banks.
> 
> To get fancy, use the gate voltage to change Bank or Wave between ADS
> and R sections. For really fancy, bring out the attack latch bit from
> the ADSR and sum with the gate signal to change segments between A to
> DS to R. Or route one to external Bank input and one to external Wave
> input.
> 
> There are a number of Banks which contain multiple events (4089 pulse
> bank for example and Morse code bank). These pulses when processed  
> with the following slew rate limiter produce multiple "sub" envelopes
> from one A and/or D and/or R section. This sounds like strummed  
> envelopes (ala Subotnick).
> 
> For echo effects, multiply (with DC coupled VCA) the original ADSR  
> envelope with the processed/slewed envelope to get echo release type 
> envelopes (DA-Da-da-da).
> 
> Modular synthesizers are VERY versatile and creative new applications
> for existing modules can save money and time.

True, but since my modular is only beginning to come together, there
isn't much that exists here for me now. I have some nice EFM RADSR
boards, and versions of TomGs 3046 ADSR. NIce stuff, and as I was
saying, much more musical than my drum synths and the MG-1. But since I
have a blank slate of parts and perf here, I need to plan for my synths
future. I already spent the money, and I have the time. I don't doubt
that ADSRs and wavetables are versatile, I'm just trying to figure out
what I want to do. And wondering if there was an avenue of analog synth
design which has been little explored.

Interesting thoughts though!

CJ

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