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elektroda.net NewsGroups Forum Index - Electronics - **Equation for LFO rate on Moog analogue synth**

Guest

Mon Jun 30, 2014 4:52 am

I have a Moog Voyager synth and it has an LFO with a rate setting. It is some sort of exponential scaling. On the front panel it goes from 0.2 to 50Hz, with 3Hz in the middle. These three values correspond with with the A to D values 0, 254 and 131 respectively on the LCD display. I was wondering if there is a likely equation that describes the circuit so I can approximate the rate (Hz) for each digital setting. I tried to fit an exponential curve and a quadratic curve to the values but neither worked out. Any ideas? In the meantime I may try a cubic spline.

Guest

Mon Jun 30, 2014 7:30 am

On Sun, 29 Jun 2014, danwgrace_at_gmail.com wrote:

I have a Moog Voyager synth and it has an LFO with a rate setting. It

is some sort of exponential scaling. On the front panel it goes from

0.2 to 50Hz, with 3Hz in the middle. These three values correspond with

with the A to D values 0, 254 and 131 respectively on the LCD display.

I was wondering if there is a likely equation that describes the circuit

so I can approximate the rate (Hz) for each digital setting. I tried to

fit an exponential curve and a quadratic curve to the values but neither

worked out. Any ideas? In the meantime I may try a cubic spline.

is some sort of exponential scaling. On the front panel it goes from

0.2 to 50Hz, with 3Hz in the middle. These three values correspond with

with the A to D values 0, 254 and 131 respectively on the LCD display.

I was wondering if there is a likely equation that describes the circuit

so I can approximate the rate (Hz) for each digital setting. I tried to

fit an exponential curve and a quadratic curve to the values but neither

worked out. Any ideas? In the meantime I may try a cubic spline.

Well, three points determine a quadratic so there isn't enough for a

cubic. The quadratic would be

..00142x^2-.16464x+.2

but

..2*16 = 3.2 ~=3

3*16=48 ~=50

so something like

..2*256^(x/256) =.2*2^(x/32)is suggested

for this

0->.2

131->3,414

254->49.03

and

127->3.13

maybe the 256s should be 255s or something but I'll bet

it's exponential and the marks are approximate. can you measue the LFO?

--record it AM modulating and look at the distance between peaks.

Ron

elektroda.net NewsGroups Forum Index - Electronics - **Equation for LFO rate on Moog analogue synth**