RE for analysing (CV) LFO Rate?

This forum is for discussing Rack Extensions. Devs are all welcome to show off their goods.
Post Reply
User avatar
dioxide
Posts: 1780
Joined: 15 Jul 2015

23 Apr 2017

Is there a tool that allows you to find the rate of a CV LFO in Hz? Or perhaps this could be done by converting it to audio first?

Does anyone have any tips or ideas? Thanks!

User avatar
ljekio
Posts: 962
Joined: 21 Jan 2015

23 Apr 2017

you can only create cv-note-to-freq calc by the chronologist's RE.

User avatar
dioxide
Posts: 1780
Joined: 15 Jul 2015

23 Apr 2017

ljekio wrote:you can only create cv-note-to-freq calc by the chronologist's RE.
Which device does this?

User avatar
ljekio
Posts: 962
Joined: 21 Jan 2015

24 Apr 2017

dioxide wrote:
ljekio wrote:you can only create cv-note-to-freq calc by the chronologist's RE.
Which device does this?
CMD: Equation and Constant.
Formula:
Freq = 13.75 * 2 ^ (( P - 9 ) / 12)
Where P is pitch in semitones.

User avatar
Loque
Moderator
Posts: 11170
Joined: 28 Dec 2015

24 Apr 2017

dioxide wrote:
ljekio wrote:you can only create cv-note-to-freq calc by the chronologist's RE.
Which device does this?
CVA-7 does this or just connect a CV to a Combinator note input.
Reason12, Win10

User avatar
ljekio
Posts: 962
Joined: 21 Jan 2015

24 Apr 2017

Loque wrote:
dioxide wrote:
ljekio wrote:you can only create cv-note-to-freq calc by the chronologist's RE.
Which device does this?
CVA-7 does this or just connect a CV to a Combinator note input.
Note, but not Frequency.

My calculator here:
CV Note to Frequency Calc (ljekio).zip
(2.53 KiB) Downloaded 56 times

User avatar
ljekio
Posts: 962
Joined: 21 Jan 2015

24 Apr 2017

Clarification: the calculator will not be able to convert a live input of CV, only the parameter CV-Pitch that you set in the device.
Frequency analyzer of the live LFO signal is impossible, IMHO

User avatar
dioxide
Posts: 1780
Joined: 15 Jul 2015

24 Apr 2017

ljekio wrote:you can only create cv-note-to-freq calc by the chronologist's RE.
Ah sorry I think I misunderstood. I need to feed a CV LFO into a device, either as CV or converted audio, and find out its frequency in Hz.

User avatar
ljekio
Posts: 962
Joined: 21 Jan 2015

24 Apr 2017

If this is real, then the output data will be very coarse. And then if the LFO is simple, not combined.
You can convert CV to audio and open saved audiofile into some editor like Sound Forge for precision frequency analyse.
Last edited by ljekio on 24 Apr 2017, edited 1 time in total.

User avatar
dioxide
Posts: 1780
Joined: 15 Jul 2015

24 Apr 2017

ljekio wrote:If this is real, then the output data will be very coarse. And then if the LFO is simple, not combined.
It will be a Sine wave.

User avatar
ljekio
Posts: 962
Joined: 21 Jan 2015

24 Apr 2017

dioxide wrote:
ljekio wrote:If this is real, then the output data will be very coarse. And then if the LFO is simple, not combined.
It will be a Sine wave.
But audio analyzers usually show signals from 20Hz or higher.
How catch low freq?

User avatar
dioxide
Posts: 1780
Joined: 15 Jul 2015

24 Apr 2017

ljekio wrote:
dioxide wrote:
ljekio wrote:If this is real, then the output data will be very coarse. And then if the LFO is simple, not combined.
It will be a Sine wave.
But audio analyzers usually show signals from 20Hz or higher.
How catch low freq?
That's exactly what I thought. It's a difficult one.

User avatar
eusti
Moderator
Posts: 2793
Joined: 15 Jan 2015

24 Apr 2017

Couldn't you just speed it up somehow by a known amount, then measure it and divide the result for a correct measurement???

D.

User avatar
dioxide
Posts: 1780
Joined: 15 Jul 2015

24 Apr 2017

Perhaps, although the value might not be linear.

User avatar
PSoames
Posts: 278
Joined: 15 Jan 2015
Location: Somerset, UK

25 Apr 2017

dioxide wrote:Is there a tool that allows you to find the rate of a CV LFO in Hz? Or perhaps this could be done by converting it to audio first?

Does anyone have any tips or ideas? Thanks!
If I've got this right no RE required, but you do need to record the LFO's curve into the sequencer and use the position marker to note the time position of a completed period, dividing the number of cycles by the time position of last cycle.

To explain further;
  • Load an instance of Thor and reset the device.
  • Hook up your LFO cv output into the Thor's CV1 input.
  • In Thor's modulation matrix select; Source: CV1. Level: 100. Dest: Audio 1. Level: 100.
  • Click Rec Source in Thor's Mixer Channel
  • Load an Audio Channel and choose Input Source for Thor 1 Left
  • Reset song to time position 0 and hit record. The LFO wave form should now be drawn in the Audio Channel's track.
  • Hit stop and move position marker to the point where a full period or cycle has been achieved.
  • Divide 1 by the time position and you have the frequency.
  • To make it easier to identify where one cycle has been achieved, trim the start of the clip to coincide with the first trough on the wave form. The next trough will be first period.
  • Doing the same over more cycles may increase accuracy, but don't forget to change the dividend to suit. In other words if you record the time position over ten cycles your calculation will be 10/time position.
As I say, I think this works. It has in my limited trials.

:geek: :idea: :ugeek:

User avatar
dioxide
Posts: 1780
Joined: 15 Jul 2015

25 Apr 2017

PSoames wrote:
dioxide wrote:Is there a tool that allows you to find the rate of a CV LFO in Hz? Or perhaps this could be done by converting it to audio first?

Does anyone have any tips or ideas? Thanks!
If I've got this right no RE required, but you do need to record the LFO's curve into the sequencer and use the position marker to note the time position of a completed period, dividing the number of cycles by the time position of last cycle.

To explain further;
  • Load an instance of Thor and reset the device.
  • Hook up your LFO cv output into the Thor's CV1 input.
  • In Thor's modulation matrix select; Source: CV1. Level: 100. Dest: Audio 1. Level: 100.
  • Click Rec Source in Thor's Mixer Channel
  • Load an Audio Channel and choose Input Source for Thor 1 Left
  • Reset song to time position 0 and hit record. The LFO wave form should now be drawn in the Audio Channel's track.
  • Hit stop and move position marker to the point where a full period or cycle has been achieved.
  • Divide 1 by the time position and you have the frequency.
  • To make it easier to identify where one cycle has been achieved, trim the start of the clip to coincide with the first trough on the wave form. The next trough will be first period.
  • Doing the same over more cycles may increase accuracy, but don't forget to change the dividend to suit. In other words if you record the time position over ten cycles your calculation will be 10/time position.
As I say, I think this works. It has in my limited trials.

:geek: :idea: :ugeek:

Thanks, that is a good solution!

Post Reply
  • Information
  • Who is online

    Users browsing this forum: RhysHuntley89 and 20 guests