Caesar Chorus High pitch Noise problem!

[d.d.sound]

Hi! I'm new to this forum! I have a problem with the Caesar Chorus I built. When I turn up the Lag potentiometer, a high pitched noise appears. Synchronized with the Rate pot.
What could be the problem? Can someone help me? I used the "mn" integrated instead of the Cool Audio "v". I don't know if this could affect it. Thanks in advance!
D.

 

[Cybercow]

If the MN3207s are indeed genuine, there should be no issue. CoolAudio's V3207 is supposed to a clone of the original MN3207. So it may depend on from where the MN3207s were sourced.

 

[Cybercow]

Does tweaking the trimpot change the high pitched noise?