[sdiy] Voltage controlled FPGA based synth?

[Scott Gravenhorst]

"Anthony Rolando" <goldenechos at hotmail.com> wrote:
>If you read the fine print the designer states that the VCA is actually 
>analog... so that is "correct terminology there.
>
>Besides, VCO reads easier and sounds better then FPGACO. That is a good 
>enough reason to call it so imo.
>
>TR

For me, it depends on how the FPGA is used.  In my FPGA synth, the embedded MIDI
controller transports digital data to the synth internals which is all digital, hence the
oscillators are called NCO (numerically...) along with NCF and NCA.

Tough call when the FPGA is used as a digital engine between an ADC and DAC, since one
would supply analog voltages for control, it could be "V" controlled, though internally
quantized.  Internally to the FPGA, however, any oscillator would have to be digitally or
numerically controlled.  So the term used would appear to depend on one's perspective.

>
>>From: Tom Wiltshire <tom at electricdruid.net>
>>To: karl dalen <dalenkarl at yahoo.se>
>>CC: synth-diy at dropmix.xs4all.nl
>>Subject: Re: [sdiy] Voltage controlled FPGA based synth?
>>Date: Fri, 13 Jul 2007 11:48:19 +0100
>>
>>
>>On 12 Jul 2007, at 22:55, karl dalen wrote:
>>
>>>But why name things Voltage Controlled, (e.g VCA) when its FPGA
>>>generated?!
>>
>>What do other people think about this? If a circuit is controlled  from a 
>>voltage that then goes to an AD convertor, is it a voltage- controlled 
>>circuit? Obviously it's a digital circuit, not an analogue  one, but is it 
>>a voltage-controlled digital circuit? Perhaps the AD  isn't really a part 
>>of the circuit and that what controls the circuit  is the digital output 
>>from the A/D? What about if the A/D is on the  same chip?!
>>
>>Or is this just a question of terminology?
>>
>>Personally, if you can grab a LFO from somewhere and feed the output  of 
>>that to it to make something happen, I'd call it a voltage- controlled 
>>circuit. It might be digital inside, but it's still  voltage-controlled.
>>
>>
>>
>>
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-- ScottG

-------------------------------------------------------------

-- Scott Gravenhorst
-- GateMan I - Xilinx Spartan-3E Based MIDI Synthesizer
-- FatMan: home1.gte.net/res0658s/fatman/
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-- When the going gets tough, the tough use the command line.