Well I built a MS20 style LPF, but I have some problems with it 
When I set the cutoff pot up to the maximum frequency setting, the filter stops and there are no sound and no LEDs anymore. I don’t know if it’s because of the input signal (±12V) or the components value (Schmitzbits)
So if anyone of you know what I’m talking about well I’d like to have your explanation 
I will send a video to show the Problem!
The TL07x can lock up if the signal gets too close to the negative rail. There are some earlier threads about it, including suggestions for different input resistors. Using a different opamp is also an option.
I’ll look up for that! Thank you ^^
Well I will try to replace the 10k input res with a 100k
For me it only happened with a square signal (stronger than the others), I added an attenuator pot on the Input of all my MS20, which allows to fix this problem, and also with the other signals to lower the entry to have more resonance 
This post links to an article that explains when and why this happens:
Yeah! Exactly the same thing happens to me: square wave the worse, sawtooth it’s medium and triangle it’s okay
possibly need to add a resistor to that pot to extend the full cutoff cycle and should stop that , hopefully So 100k pot and 10k then from the last pin on pot extend that to resistor …
Maybe Try a different Tl072 op amp and see if the results change and tweak the values of the resistors. It is called Opamp Destructive latch up some op-amps are more prone to it then others. Could also try a NE5532 they are better at handling this problem and is featured in kassutronics KS-20 Filter for this reason.
As mentioned earlier in the thread, this is phase reversal, it’s inherent to the TL07x series (and similar opamps) when you go outside the input range, and it’s (luckily) not really destructive.
Thanks for that write up on that other post. That explains a why my Tl072s started to act weird when I would try and set my CV Joystick controller beyond -8V Range.
Hello!
I think I also have the same problem. With a square wave, the filter is killed about halfway the cutoff level.
I’m not entirely sure what would be the best solution.
Should I swap the 10k input resistor to 100k?
Or should I add a 10k to one of the pins of the cutoff pot? Which one?
Thanks for the information on phase reversal, I was not aware of this!
some explainations here
Thanks Dud! Yeah, this makes sense. I would not like to use a built-in attenuator (mainly because I’ve already drilled the panels and I’m stubborn), but a simple attenuator module is something I’m missing and would be extremely useful - so this might be a solution.
I finally got to building an attenuator. Solves the cutoff problem as stated, thanks a lot!