[sdiy] Wondering about function generators for envelopes

[Grant Richter]

I did not mean to suggest that the method is either the only way, or  
the best way.

It is A method to produce a complex envelope function.

If you think about it, and ADSR is rectangular functions being  
integrated by a capacitor into a continuous function.

The DAC produces rectangular functions which are integrated by the  
slew limiter capacitor into a continuous function.

The DAC can just produce more variation in the rectangular functions,  
which will produce more wiggles and curves at the capacitor output.

If you come up with a different approach, would love to see it.

The difference is
On Jul 8, 2005, at 2:37 PM, Metrophage wrote:

> --- 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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