That’s very good work! You’ll enjoy this filter.
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Have any of you tried building the ARP2600 filter using my stripboardlayout? If so, and you were successful could you comment below the article on my website. This is the best sounding filter I ever build but I haven’t heard of anyone else building it and succeeding. Now it can’t be that difficult and the layout is a-okay, I used it myself.
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Here’s my MS20 Bergman style. Seems to be working well. One question. Should the sound completely be gone at zero on the cutoff? That was the case with the 3-4 other MS20 filters i’ve build, but not this one. Maybe I botched something. Also…LED color. Does it make a difference in the resonance? I’m using UV. I find it a bit wild. I see you used yellow, and the original schematic uses green.
Demo
!
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Good knobs…
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Hold my beer…
Really, though, I’m about to go camping in the wilderness for a few days, but I’m putting this on my list!
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I just need a chip and some matched transistors and I’ll be doing that one too. I’ve also done his Digisound 80.6 Filter I like it a lot. Nearly finished the Yusynth Sync Lfo as well. Trying to get my oscilloscope to work. No luck. 
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not big enough.
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Awesome!! I look forward to seeing the result 
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Wauwww you’ve been busy!
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Looks great! I’m curious to how it sounds. Should be the same as mine of course
Those big knobs look ancient. Got them from some jurassic piece of equipment?
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A friend of mine ordered a box of em from China one time for amp building. Strangely, they arrived pre-worn. He gave me a bunch. I love them.
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I like it. Sounds good. I find it a bit wild compared to my others, but i’m wondering if that has to do with my res pot being linear? Also, led color? Does it make a difference? And last, does yours completely cut audio when cutoff is at zero?
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Yes it completely cuts the audio at zero. That’s normal.
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Yeah, thought so. Mine doesn’t. I have 4 others i’ve built and they all do. So something is up with it. Would it be a pot grounding issue? 
The LEDs are in the resonance feedback loop, and clamps the feedback signal. The lower the LED’s forward voltage, the earlier it kicks in. In general, the shorter the wavelength, the higher the forward voltage, so Sam’s red ones clip a bit earlier than the Schmitz’ version, and your UV ones much later (especially if it’s an actual UV LED, and not just a very violet one 
).
the original schematic uses green
The original original, the one in Korg’s MS-20 (which is pretty much the LM13700 datasheet lowpass/highpass design plus resonance) uses three diodes. Schmitz replaces that with “a green LED” without specifying which kind of green LED it is (newer ones tend to have a higher forward voltage, but if the idea is emulating three diodes I’m pretty sure he meant the old ones, which aren’t very common these days). Everyone else uses their favourite color, and tweaks the resonance knob after taste to compensate.
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Gotcha! So they don’t make a difference on how much resonance, but more about when it kicks in while shifting the pot?
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I always use yellow LEDs in my Korg filters. They have a forward drop of 1,8V which is exactly the voltage drop that three diodes in series would produce.
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Yeah, the feedback loop looks like this:
so when the voltage is too low for the diodes to turn on, this acts like a 1+10k/1.8k = 6.6× amplifier, but as the diodes turn on it turns into a 1× voltage buffer. The transition is somewhat soft, due to the diode curve’s “knee” shape:
(curve from a random datasheet for a red LED with a typical forward voltage of 1.85 V)
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