Everyone is observing Chinese New Year! 
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Thanks! With this info in mind, I will hold my order, so that I can add the upcoming synth voice. No rush, I appreciate all the work you put into this!
finally managed to finish this thing, but I obviously fucked up. as soon as I plug in the power R4 starts to burn up, actually smoking and âwhistlingâ
I checked the value and it is correct.
Any idea what I might have done wrong?
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Yes of course you are right Rich, canât get around doing due diligence. Was hoping someone would say, âOh R4, it has to be thisâŠâ But thatâs not how it works, I know that.
Thanks for sharing that video, hadnât seen it yet
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R4 is just one of the 10Ω resistors used as a fuse, it burns up if the module is drawing too much current, usually because there is a short somewhere or the power supply voltages are reversed or an IC is in backwards or something like that. There are lots of possible causes.
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Well thatâs embarrassing, I had one diode AND one elco the wrong way roundâŠ
It works now, no magic smoke and seems to be actually filtering.
Although it does kind look like the low pass seems to be self oscillation more than filtering, if that makes sense? Anyway, its past my bed time and I will have to test it out some more later.
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My 4.7k pot knob isnt filtering the sound as it should, it is instead cutting from one distinct sound to another when it is turned half way?
sounds like a sorry case of the hooby goobyâs
twisting knob and change suggests ther voltage control circuit works
something around the lm13700 isnt doing its job. check all soldering. especially the capacitors around that chip. i think some should be going to the ground plane. wiggle them and look closely as the solder joints, make sure none wiggle in their holes from the back, make sure all solder is doing its solder job as molten glue. good luck!
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Success! Managed to rectify my funky filter and it started functioning correctly for a time!
Now however it appears to have created its own voltage that it filters when the cut off is too high. Very strange
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The BOM calls for 2x 1N4004 diodes. Does this 1113 filter module really require such heavy diodes? Wouldnât 1N4148 diodes be sufficient?
(I do not have 1N4004 diodes laying around, but more than enough 1N4148 diodes⊠:-D)
These diodes appear to be power reversal protection. Theyâre not shown in Schmitzâs schematic, but if theyâre 1N4004 then Iâd guess they go from the power rails to ground. If you connect power backwards theyâll short the PSU output â which is less likely to cause damage than reversed power.
You definitely donât want 1N4148 signal diodes, this is a job for rectifiers like 1N4004.
On the other hand, if you make sure your power isnât reversed, you could just leave them out. Order a couple and solder them in later, because you will reverse power at some point in your life.
(Conceivably they could be in series on the power rail, blocking current but not shorting the PSU if power is reversed, but that approach usually uses Schottky diodes for a smaller voltage drop. In that case leaving them out would prevent anything from working, theyâd have to be replaced with jumpers. Or 10Ω resistors or fuses or ferrites.)
Thanks Richard!
Looking in my parts boxes, I found a strip of 1N4002 diodes, that seem to be interchangeable for the 1N4004 diodes in this case. The only difference seems to be that 1N4004 is rated for max 400V, and 1N4002 is for max 100V. Or am I overlooking some important difference?
Nope, any 1N400x is fine.
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I finished building the 1113 Filter this evening, and everything seems to work straight away!
And OMG, it sound awesome!!!
I had the PCB set laying around for almost two years, and kept thinking: a 20cm wide module with limited options takes up too much space. But now that I finally built it, I can say I have been so wrong, it is totally worth the 20cm in my case. Thank you, Sam!
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Im having issues with the cutoff dial on my filter, it appears to only be active at around the halfway mark and then then goes quiet once you go any further, whereas I guess it should operate across the entire potentiometer?
Iâm hoping someone can give me some guidance. I built the 1113 and managed to fry the 10r resistor on the positive rail when I powered it up. Iâve used my multimeter to verify that I have no shorts between ground and the rails, and the ICs have continuity on the correct rails. Iâve looked over the traces and donât see any obvious issues. Iâm still a noob at this so I imagine there is actually some obvious issue. My other modules work fine with the power supply Iâm using, but when I connected this module I seemed to lose power on the +12 rail and other modules didnât power on. I just got the white smoke from that 10r resistor and everything worked normally again once I disconnected the 1113. I replaced that fried resistor and reflowed some joints, but then fried the resistor a second time. The other odd thing is that I have a little USB to 12v power supply that I use to first test my modules before putting them in my case, and that one did not cause the resistor to pop, but the filter still didnât work. The mixer section worked and I got amplification on the output, but the lowpass filter did nothing and the high pass filter just cut all sound completely. Any help on steps I should take to troubleshoot would be greatly appreciated!
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Are you sure diode D13 is orientated correctly? In the picture on LMNCâs projects website, it is shown the other way around.
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Thatâs it! Thank you! I knew it would be something pretty obvious.
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Yay, I also now acquired and built one! It works, however I still need to tweak the resonance way down, at some point it is just pure distortion. I needed to drill some holes and cut the PCB a little to fit in my case. (I use Adam Hall 6161 rails to screw in the modules) I replaced the cutted traces with wires (seen in the last picture) Also, I used JST PH 2mm connectors instead of the Molex ones.
