LFO Sync problems

[Thalassa]

I know....I've posted this message yesterday in "LFO problems" , but I think that is better to start a new topic


Hello , I just finish to built the LFO version 2. Everything works fine after calibration Smile but I have a problem with the sync input.

When I connect gate / trigger signal to de sync input I get a pulse that instead a cycle restart. The length of the pulse is dppendent of the flo frequency.

I've made a few tests before post this, I've changed the BS170 for a BC547 , I've changed the BS170 for another BS170.

I've changed the C6 capacitor for new one.

All of this tries didn't solve the problem.

I've attached a picture with the output of the lfo where you can see the pulse when the sync signal is received.

Also I've attached an audio file where the LFO is modulating the filter frequency , and as you can see the (not normal ) pulse length changes when LFO frequency changes.

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lfo_sync_834.mp3
Description:
Filesize:	1.18 MB
Duration:	0:39
Viewed:	1762 Time(s)
▶ Play   ⇩ Download

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lfo_sync.jpg
Description:
Filesize:	125.6 KB
Viewed:	14623 Time(s)

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[yusynth]

Hi Thalassa

I will check this, I think two things can be done, first reduce the value of C6 to 1n, then change the value of R39 (may be just bypass it !).

[Thalassa]

Hello Yves, I've done what you said, I've changed C6 for 1,2 n ceramic capacitor ( I don't have here 1n capacitor and this one was the most similar one ) and bypassed R39 and the problem still there

[quattroman]

This problem can be solved by changing and adding few things

You need to recalibrate waveshapes and bias.

I hope this helps!

[yusynth]

Thanks for the mod I will integrate it in the PCB design.

[quattroman]

You welcome!

Is spend 2 nights to resolving this - now the core is ~1v to 10v and resets perfect at 0v than starting imediately!

Btw. 120pF and 4.7nF supress triangle/sine glitch (mine is unvisible and unaudiable).

[Calkce]

Hi, i just finished LFO v2, everything is working great! Very happy, except i have the exact same sync issue. Have you find a way to fix it ?