[sdiy] 1v /oct with ADC question

[Mike Boracci]

Vinicius,
Thanks. I'm not using the adc for anything other than addressing. The binary is almost irrelevant except that i need at least 61 steps to be generated by the voltage that will be present from one side of the pot to the other. ⁣

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On 4:15PM, Nov 30, 2016, at 4:15PM, Vinicius Brazil <brazil.v at gmail.com> wrote:
>Hi Mike,
>
>At 1volt / oct the step of each note is 1/12 = 0.08333volts.
>
>However, in order for the ADC deviation not to be perceived as
>detuning,
>this deviation has to be less than 1%.
>
>(1/2) / 100 = 0.0008333volts
>
>5 Volts / 0.000833 Volts = 6000 steps, so you need a 13-bit converter.
>
>12 bits is already satisfactory.
>
>regards,
>Vinicius Brazil
>
>On Wed, Nov 30, 2016 at 6:41 PM, Gordonjcp <gordonjcp at gjcp.net> wrote:
>
>> On Wed, Nov 30, 2016 at 02:10:30PM -0500, Mike HEQX wrote:
>> > Hi folks,
>> >
>> >  I want to use an ADC to create discreet note values so I am
>looking
>> > at an 8bit ADC.
>> >
>> > I only need 6 bits to get to 64 values. ( I really only need 61 of
>> > those values to make 5 octaves plus 1 )
>> >
>> > I want to scale the voltage across my pot so that I get 1v / oct
>> > output for cv usage at full scale, and I also need to produce 61
>> > discreet values from the adc at the same full scale. So it looks
>> > like I have to do something mathematical, but I know not what do
>do.
>>
>> You need to run your 6-bit DAC off 5.333V because that way you will
>> automatically get 1V/octave.
>>
>> 5.333V / 64 = 0.08333V/semitone
>> 0.08333 * 12 = 1V/octave
>>
>> Build it just like in the DAC section of the TB303.
>>
>> --
>> Gordonjcp MM0YEQ
>>
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>
>
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