DIY Moog Ladder Filter Help?

[xombiexplox]

Hello everybody!

After a little over an hour of searching through these forums, I haven't gotten a hit that's relevant to what my situation is. I am wanting to take a schematic for Moog's ladder filter and build it myself to add to a little Arduino-based setup I'm trying to build.

I'm pretty sure this is a little out of my abilities to pull off easily, but I'm going to give it a shot! I'm only doing this to learn more about electronics, Moogs and reading schematics in general. I understand that this isn't an 'Engineering 101' forum, but since it is a Moog schematic I believe it is still considered a General Topic

I found the following schematics, and they are completely different. I would like to have the Minimoog's filter, but it looks extremely complicated!

http://www.fantasyjackpalance.com/fjp/s ... -schem.gif

I have a very infantile understanding of schematics and schematic symbols (read: almost none), so I found the following schematic that looks a bit simpler:

http://dropmix.xs4all.nl/rick/Emusic/Mo ... ematic.gif

But I still don't understand why some portions aren't connected to each other? I'm not asking anyone to do the hard work for me, I am completely willing to dedicate time and effort into understanding the "big picture" here, I am just diving into the deep end and I need help finding the kiddy pool first! Is this too hefty of a task to try as a beginner? I'm sorry to ask such a HUGE question to everyone, but I want to eventually be able to build my own synth and I want to start with this. I have a Safari Books Online account so I'm checking out a bunch of beginner electrical engineering books, I just have to actually pick ONE and push through it.


tl;dr I want to build a Moog filter, preferably the Minimoog's, by myself. I have no previous experience building things like this, but I do have the required tools! (I bought a bunch yesterday, hee hee) Where can I find the relevant information to help me build this as soon as mentally possible? What books/websites would you recommend?

THANK YOU THANK YOU THANK YOU THANK YOU

[EMwhite]

I posted the text below to another forum that was looking for some basics pertaining to control voltage and an understanding of electronics. The books ahve loads of examples from simple to ...umm less simple. I strongly urge you to get your hands on this kit. If not, study the pdfs (books) you'll be able to learn most of what you need to know from them.

I think I saw you write something about moving overseas? Not sure from where to where but if you are in America now, the Radioshack stuff is pretty easy to get (mail order that is).

I wanted to build the Oberheim mini-sequencer but the schematic was an absolutely mess (very complicated). I've done circuit board repair for solid state pinball machines and have actually had some pretty good experiences. Take your time and maybe ask a relative to buy you a gift certificate at Mouser.com or Digikey. Interested to hear about your progress.

Final comment for now... I like your "gear list" : )

-- -- --

Not sure if you are in the U.S. or not, but RadioShack (yes, they still do something good) have a few electronic experiment style kits that come with some of the boy genius Forrest Mims materials.

The "Electronics Learning Lab" is great: http://www.radioshack.com/product/index ... absetBasic

Has an onboard meter, potentiometers (attenuators), comes with all sorts of ICs, caps, you name it. Seriously, the basic experiments and some detailed experiments; The breadboard is small but with the add of a decade IC you can surely build up a rudimentary analog sequencer... What could be better than that !!

See the table of contents of this book: http://www.radioshack.com/graphics/uc/r ... _PM_EN.pdf and page 26 which shows how to strap the meter to measure voltage accurately up to 9 Volts (very handy). There are also experiments and ICs to build basic VCOs.

The first 23 pages or so, after introduction get your feet wet with some basic experiments meant to draw you in without boring with theory and technical detail. Pg 24 begins a good lesson on current; voltage; amperage, etc.

Pg. 8 begins with some basics on components and the schematic representation of said components. There are also some simple examples and very importantly, the basics on how to use a breadboard. It will be in your best interest to pick up a decent breadboard (another good use of this kit) with some standard voltages, or just buy a board and pickup a power supply on eBay. DO NOT run out and buy a high end synth.com power supply if you are just getting started; best to get something used that has the typical +15/-15 and also 5V.

Even if you don't buy the kit or any kit, you can get your hands on about $10 worth of components from Mouser.com, Digikey.com or MAYBE even your local RadioShack and build up a few of the voltage related experiments. But I would recommend buying this exact kit from their web site and spending a few hours a week plowing through it. You can read all of the make mags etc. (they are an incredible resource) but this represents the fundamental basis of everything all of our modular gear depends on right up through the microcontrollers that many now depend on to drive switch sensing and voltage generation in the most sophisticated modules that are out there.

Here is the 2nd book (also posted on RadioShack's web site):
http://www.radioshack.com/graphics/uc/r ... _PM_EN.pdf

[xombiexplox]

I posted the text below to another forum that was looking for some basics pertaining to control voltage and an understanding of electronics. The books ahve loads of examples from simple to ...umm less simple. I strongly urge you to get your hands on this kit. If not, study the pdfs (books) you'll be able to learn most of what you need to know from them.

I think I saw you write something about moving overseas? Not sure from where to where but if you are in America now, the Radioshack stuff is pretty easy to get (mail order that is).

I wanted to build the Oberheim mini-sequencer but the schematic was an absolutely mess (very complicated). I've done circuit board repair for solid state pinball machines and have actually had some pretty good experiences. Take your time and maybe ask a relative to buy you a gift certificate at Mouser.com or Digikey. Interested to hear about your progress.

Thanks for the awesome response! A few months ago I was seriously considering getting that exact same kit, but I ended up getting a "Getting Started with Arduino" kit which comes with a handful of components, a book, wires, and an Arduino Uno. I bought a soldering iron, a ton of extra components and switches, and a little soldering station with little arms and a magnifying glass :3

While I don't feel like I will get to the point of understanding why pieces are placed where they are and how to calculate their outputs, I do want to at least be able to read a schematic for a Moog filter and build it by purchasing whatever it says they use for it. But judging from your response, I probably will have to understand the underlying logic of electronics before I should tackle something like copying a schematic? In my Arduino book, there's almost nothing about reading schematics, and I'm not sure how to get more experience with reading them if every one of them is so different!

So I guess my only real question to your answer is: will reading these Forrest Mims books give me a good understanding of schematics? I want to build first, and understand later. Whether or not this is a bad move education-wise is up for discussion
:3

Final comment for now... I like your "gear list" : )

Why thank you! :3

[EMwhite]

... and by the way, the circled #'s in the first schematic go 'elsewhere', ie. connect to a point on a different schematic that is not shown here; in some cases it's simple (ie. an audio input jack in which case the other lead is tied to ground).

Speaking of ground, the first schematic has them properly represented as a series of horizontal lines starting wide, then less so and centered, and so on, ultimately it looks like a downward arrow. You'll see dozens of them.

The 2nd for some reason just shows a single horizontal line. If you knew this already, apologies!

[xombiexplox]

The first 23 pages or so, after introduction get your feet wet with some basic experiments meant to draw you in without boring with theory and technical detail. Pg 24 begins a good lesson on current; voltage; amperage, etc.

Pg. 8 begins with some basics on components and the schematic representation of said components. There are also some simple examples and very importantly, the basics on how to use a breadboard. It will be in your best interest to pick up a decent breadboard (another good use of this kit) with some standard voltages, or just buy a board and pickup a power supply on eBay. DO NOT run out and buy a high end synth.com power supply if you are just getting started; best to get something used that has the typical +15/-15 and also 5V.

Whooops, I guess I somehow missed these paragraphs! I guess this will be next on my "to buy" list.

So would trying to build a Moog filter at my skill level be too difficult? I am ready to start now, I just don't know what I"m doing, hahahaha.

[EMwhite]

Hmmm... that ground symbol didn't render so well now did it.

But to answer your question, YES, the book will help you, and a breadboard is WAAAAAYYYY better than trying to solder straight away and you have zero risk of frying components.

Have a look at the pages I reference above (you likely have already) and you'll see what I mean (hopefully). And btw: the 1st of the two schematics looks correct. You'll realize the diff once you compare the BOM (bill of materials aka parts list) with what is on the schematic and then see that everything is represented.

One thing that you will notice is that the nature of schematics is that grounds are 'left' all over the place and if you look on boards, you'll see this clearly. FWIW, don't bother trying to take apart a modern Fooger or a LP because the surface mount board components which are tiny and a board which is several layers thick (thin) will make your head spin.

But with a minimal parts investment of like $25 you can get something working. Keep your Arduino on the side for now. It's awesome but the basic basics are more rewarding (but possibly not immediately as satisfying) if that makes any sense?

[EMwhite]

(Should you?) Yes do it. I haven't, just too busy with other things, but should. I'd love to hear that it works out for you.

Let me give you a few hints/help re: schematic. Feel free to keep typing to this thread or just hit me with PM if you have any specific questions.

Components are numbered arbitrarily, meaning r1, r3, r18 are just resistors which pertain to the parts list below. And commonly you'll see "r" for resistors "c"apacitor "d"iode "p"otentiometer and sometimes there is notations such as on P7 they are calling for a 50K (value) logarithmic (not exponentially scaled); that just means that the pot is more linear than growing in value exponentially.

The "q"s are transistors and "a" are op-amps, (buffers, etc) typically housed within integrated circuits. You can look these up in Mouser or just search for PDFs on google. The instructions and sheet that accompanies the chip will indicate that pins 1,2,3 pertain to the first circuit and 4,5,6 to the second (hypothetical example).

If you are not fussy about packaging, you can build up an arsenal of synth makings in Altoids tins, etc. (I'm sure you know this already from your Arduino research). There are TONS of DIY sites with synth schematics and kits, etc. Check out Bride Chamber (http://www.bridechamber.com/Home.html) and also, you should join MuffWiggler.com for their DIY forum.

Done typing for tonight! Enjoy.

[xombiexplox]

Hmmm... that ground symbol didn't render so well now did it.

But to answer your question, YES, the book will help you, and a breadboard is WAAAAAYYYY better than trying to solder straight away and you have zero risk of frying components.

Have a look at the pages I reference above (you likely have already) and you'll see what I mean (hopefully). And btw: the 1st of the two schematics looks correct. You'll realize the diff once you compare the BOM (bill of materials aka parts list) with what is on the schematic and then see that everything is represented.

One thing that you will notice is that the nature of schematics is that grounds are 'left' all over the place and if you look on boards, you'll see this clearly. FWIW, don't bother trying to take apart a modern Fooger or a LP because the surface mount board components which are tiny and a board which is several layers thick (thin) will make your head spin.

But with a minimal parts investment of like $25 you can get something working. Keep your Arduino on the side for now. It's awesome but the basic basics are more rewarding (but possibly not immediately as satisfying) if that makes any sense?

It definitely makes sense! I completely understand the benefits of starting with this kit you mention, but I really like diving into things a little out of my ability! So thanks to you I am going to cover the basics, but at the same time go over schematics for basic low-pass filters!! Bwahahahhaa! Win-win, I say! When I get frustrated trying to understand the low-pass filter schematic little Timmy drew during recess, I will build a light switch to make me feel accomplished, hahahahaha.

Thanks so much for your help!! I wish there were 'Moog Karma' on here (like reddit) hahhaa.

[muksys]

Have you considered purchasing pre-printed pcb's? Like what you can get at MFOS or mutable instruments. There are a ton more out there, but these two I have personal experience with and both are top notch. I especially like the mutable stuff. The filters sound great and they would pair up with an arduino board pretty well.

[xombiexplox]

Have you considered purchasing pre-printed pcb's? Like what you can get at MFOS or mutable instruments. There are a ton more out there, but these two I have personal experience with and both are top notch. I especially like the mutable stuff. The filters sound great and they would pair up with an arduino board pretty well.

I've seen those before! Those mutable ones! Gah, they're so awesome. I would seriously LOVE to have one of those Shruthi-1's in my arsenal. I see in your avatar you must know first-hand how sexy they are! (sidenote: would you happen to have any songs posted online showing that little thing off? haha) But for this, I want the learning experience and satisfaction of knowing that I put my own filter together and actually use it in music that I make.

To be clear, I'm in the middle of modifying some old school 1989 DMG-01 Gameboys to be able to play music, and I want to add an analog low-pass filter to them that I built myself! I'm also using my Arduino to make a MIDI interface for it that's already pretty popular, it's called "Arduinoboy" and it's so coool!!! While I know it seems weird to have an awesome filter on an 8-bit synth, it's a weird things that I want to do!
:3

[Voltor07]

And here I am using my Little Phatty for Game Boy sounds. Seriously though, I can totally see why you'd want a Moog filter on an 8-bit synth. There are a few synth designs I have seen using Atari, Commodore 64, and Nintendo chips. Some of these designs feature custom filters, and they sound nothing like the machine the chips came from.

[xombiexplox]

And here I am using my Little Phatty for Game Boy sounds. Seriously though, I can totally see why you'd want a Moog filter on an 8-bit synth. There are a few synth designs I have seen using Atari, Commodore 64, and Nintendo chips. Some of these designs feature custom filters, and they sound nothing like the machine the chips came from.

Hahahah I haven't even tried to get 8-bit sounds from my Moogs! Idk why I haven't tried yet, I guess because I have no clue where to start! Hahahaha.

And I'm real excited about it, I've spent all night looking through old Moog schematics and reading up on how the 'eff to read them!!

[Voltor07]

To get an 8-bit sound, start with the CALIBRATION preset. Add Osc. 2, preferably a square or pulse wave. You'll want a triangle or saw wave for Osc. 1, depending on the voice you are trying to get, as not all 8-bit sound chips used one or the other. The Gameboy used a saw wave. You'll want a fast attack setting on the volume env. and the DSR set to taste. Same with the filter env. You might want to use the KB amt knob on the filter, and add a hint of resonance, have the cutoff light at 3 o'clock or so, and use a bit of overload. That should get you started.

[xombiexplox]

To get an 8-bit sound, start with the CALIBRATION preset. Add Osc. 2, preferably a square or pulse wave. You'll want a triangle or saw wave for Osc. 1, depending on the voice you are trying to get, as not all 8-bit sound chips used one or the other. The Gameboy used a saw wave. You'll want a fast attack setting on the volume env. and the DSR set to taste. Same with the filter env. You might want to use the KB amt knob on the filter, and add a hint of resonance, have the cutoff light at 9 o'clock or so, and use a bit of overload. That should get you started.

Thank you!!! :3 Hahaha this is gonna be AWESOME! I'm checking this out ASAP!!

So after a few hours of deliberation, I have figured out step one of my filter building process:

Separate the filter from the rest of the Minimoog in the schematic!

I am sure I'll figure it out soon, I just don't know whether or not I need the "adder" Bob put in his original patent, nor do I know what exactly goes into the Input or Output Buffers!

SCIENCE!!!!!
:3

[Voltor07]

I goofed. You want cutoff at 3, not 9. Sorry bout that.