Bullsh** lm13700?

Been trying to build the ms20 clone. I’m using Juanito Moore’s version of the rene schmitz circuit. I got this circuit to work for about five mins. Every lm13700 I put in gets nothing. I’m done tearing down and rebuilding this simple circuit. I’ve done 3 different times. Is there a chance I just got the worst rip off lms? I am ready to give up on this badass filter I should easily be able to build…should I order more lm13700 and from where?


Not cheap, but more reliable sources than many eBay and AliExpress vendors.


I’m so impatient I already ordered 9 nationalsemiconductor brand from jameco… I remember reading somewhere it was a good source…

Yeah the first round I ordered was from Amazon and they were bridgold. For just a bit more and shipping jameco only cost me double what Amazon charged. I’m in the States. National semiconductor is what jameco carries…

Looks like taydaelec carries the nationsemiconductor brand so we’ll see what happens. I know my opamps are good. I’ve built three fully resonant filters with the same opamps. I just really want the ms20. The cv control is not the same with the led/ldr elec tape vactrols, you know? It’s really annoying me that I can’t get the ms20 working.

They’ll be new old stock, National Semiconductor was bought up by Texas Instruments 12 years ago. But they should work. Assuming they’re not counterfeits, that is — and Jameco is not immune to counterfeits.

The ones I have are marked NS (with less dodgy looking markings than the linked one, they’re probably real), bought from Tayda, and they work.

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Ive been checking out the posts in the forum for this topic. I’ve seen the pics you’ve posted and I’m going to compare the chips from jameco. I will definitely try tayda if the jameco are crap. I can verify that I have been using the same counterfeit nation semis as per the pics in the thread you posted on. Thanks again. It’s super frustrating. I really like this filter setup. I’m not gonna give up so soon!

Before writing off the ICs you have and buying new ones with no guarantee that they will work in your circuit I would like to make a suggestion. In the datasheet of the LM13700 you can find some simple example circuits like a VCO. To test your ICs you could build one of these on a bread board. All that is required are some resistors and a few bits of wire and a power supply. If you do not have an oscilloscope you can connect the VCO to an amplifier to check whether it is working. Of course you can also try one of the other circuits.


I’ve already ordered more chips. I’m impatient like that.:rofl: Also, I have seen a few posts with pictures of the same chip I’ve been using suggesting that it is bogus. However, I will take your suggestion. No reason I can’t throw together a simpler circuit while I’m waiting for the next batch to arrive. :100:

Hi @Dogstar13, I found this article helpful when I was building a VCA:

And if it might help, this is my VCA with schematics.

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I like that ota book. I actually have it already just haven’t sat down for a real look at it. Thanks for the schematic, too. Id rather build a circuit one of you have already verified than most others. It seems you wouldn’t go through the trouble of sending me your own schematic if it didn’t work you know what I mean? I do have a question Id like to put out there, however? What do you think of the as3320? I plan to build the 3360 VCA eventually. I have already built the 3340 vco. I just want to learn how to make these things with their raw components as well. Not just plug in a specialized VCF or vco chip every time. I would however be open to any suggestions for a good 3320 build because I will probably end up buying the chip eventually…

The data sheets for both the AS and CEM chips are pretty good and have examples. If you look at the service manuals from some of the old synths, you will see that several of them used the chips with just slight variations of the data sheet examples.

The manuals for the Erica diy edu series is also really good, tells you why things are used and have you breadboard stuff to try it out.

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There’s also this:

I used the AS3320 for a pole mixing filter based on an Electric Druid design:

Electric Druid pole mixing filter

(Schematics and PCBs available)

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I like the Erica edu stuff! I just watched Moritz Kleins analog kick video and I didn’t realize they have downloads for the edu series manuals. I’ve got to check more of those out. I got the kick manual for sure! Do they have a 3320 filter module?

Yeah I found the elec druid article I really like the schematics!

I tried the simple single amp vco from ray marstons ota article. It made noise but it was more like a high pitch feedback.

The lm13700 I got from Jameco seem to be legit. I got the circuit (juanito Moore’s version of Rene Schmitts circuit) to work with the first one out of the box. :metal::fire: The resonance is nuts. I need to get some better opamps too probably, I admit…anyway it works.