Problems with the stripboard Lp vcf layout

I also just built this same filter and have the same low volume issue. It’s significantly lower…

I haven’t tried using it passively yet, but were you able to figure out your low volume issue?

Mmm… Having some troubles. But will check everything over once more… Didn’t see anyone having the same issue as me.

It will just stop working when opening op the frequency control… I’ll have to reconnect the power, to make it work again. (also the frequency pot, doesn’t cutoff like my ms20 does. It’s not really responsive… )

Sometimes it self-oscillates and you can’t get it back to normal. (which I assume is normal?)

Maybe I just need to attenuate the input? We’ll see…

Odds are you’re overloading the TL07x opamps (they don’t like it when the input goes too low), and need to attenuate. Lots of references to that in this thread:

Consensus seems to be that changing the input resistors to around 20k is about right for most users (the performance filter’s 100k is too high, the stripboard layout’s 10k is too low).


Thanks for the reply… Mostly fixed. (it doesn’t shut down when swiping the cut off and resonance.)

The power connection was acting a bit weird. I have to put it in halfway. If I fully connect, it doesn’t always turn on… Seems like an easy fix. Even if it’s just making a new cable…

So it’s working now. Although the resonance doesn’t do a whole lot. It makes a change somewhere around 3/4 of the way… But otherwise, not noticeable. I remember seeing someone else having a problem with range… So I’ll read all the threads again…

Thanks again for the reply. It’s amazing how active you are. Greatly appreciated. Sometimes you can’t see the forest for the trees, so thanks for heading me in the right direction.


omg. I have just been in breadboard hell for the last week trying to figure out why this filter hates me…and it was the input resistor. Granted I made a myriad of other errors but this, this was my last hurdle. Resonance isn’t a screamy as I’d like, but I can live with that for now. Thanks @fredrik mvp all the way.


I also have 2 pieces, the first one is simply built with components as I bought them. With the second, I wanted to make everything a little “better” and measured every component separately so that everything was exactly. The first screeches wonderfully, the second hardly at all … strangely strangely strangely strange
:). So you are not alone :slight_smile:


Someone speak about fake chip in an other thread or maybe a bad chip, have you try another LM13700/TL074 ?


I noticed quite some difference with different led colors! Red has more resonance than yellow/orange had…


There is an interesting thread going on the SDIY mailing list all about input impedance and noise. Much of it is over my n00b brains but I figure if I keep reading it will make sense years from now…


Thanks for this. I hadn’t really investigated that list, but now I find it’s full of expert knowledge. Some of the content is mundane but there’s a very high proportion of gems.


Dear Kosmofriends,
My Ms20 filter on breadboard works beautifully. Stripboard, not so much.
It only makes a high pitches oscillation when the resonance pot is turned to it’s extreme ends.

Perhaps someone can spot my errors.

A few caveats

  • Yellow Square on the upper right. My stripboard is short so I moved them over a few row to the left
  • Purple square this is .5u cap on the output.
  • I ran out of 10k own resistors so I used 12k, how much does that matter for the voltage dividers?

Also any suggestions on a more elegant way of dealing with power headers are welcome.


  • david



I was wondering what this cap add was, is not in schematic.

also it is difficult to see well with the photo but it looks like in the red circle the resistors all seem the same color (10k / 220R), not an error value?

you use 12K instead 10K for all the 10K in the schem ?

a resistor is missing, is not in you photo, but perhaps you put the 10K on the input jack socket ?

maybe another pic of the back can help us

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I could be wrong, but my understand is that resistor values +/- 20% doesn’t really matter too much, except in filters, where the math makes it important. If you don’t have the desired values, can you make them by adding other values in series?

Are your chips real? Sometimes chips from AliExpress are fake and act weirdly.


I imagine a trimmer pot is a good choice for situations where a resistor value is likely to be critical. They’re widely available and inexpensive.


Just confirmed. These are 220R and 12k [in place of 10k]

Yes, just verified. I used 12k where it called for 10k

I have a 100k pot replacing that resistor value.

Here is the solder side:



I’ve got a few 20k trimmers I can use. For this layout I went with a pot on the panel, not shown in the image above - replacing the the 10k resistor in the design.

I was thinking this - re: if I get close enough I’ll be good.
My chips should be legit - I got them from Tayda.
I have an order arriving soon with 10k resistors but I couldnt wait…

If you have any 68k resistors you can put one in parallel with each 12k to make a 10.2k.


nice. I’ll try that.
So the thought is the 10k/220r voltage divider is critical ratio, right?

Actually 56k gets you closer, 9.88k.

I have no idea if any of the 10k resistors are critical. In fact my guess is that’s not your (main) problem. Still, if no better ideas come along, it’d be something to try.

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