White Noise Sample-and-Hold My Beer: Part I

Dedication: This post is dedicated to the memory of Ray Wilson, author and DIY Synth genius who passed away 10 years ago on July 21st, 2016.

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TLDR; i started this post midway through a surprisingly challenging project that caused a dark night of the soul. It worked out okay. Still, the flow/tone may reflect this.

Summer is great. It’s a time to relax, drink beers, take stock, start projects, finish projects, be happy, return to teaching in the Fall a new and better person. Right? RIGHT??

Not really. Summer is a time of drudgery, errands, endless minor home improvements and garden/weed management, pickups and drop-offs for camps, and on and on. There’s usually a project somewhere in there that gets lost in the shuffle, but nothing that really amounts to much.

This Summer is different, however. I was playing with my Field Kit (and FX) because it’s just a fun thing to do, and I noted (as I always do) that a low frequency noise circuit would be really great to have on it. As it is, you can get a squarangle, but it’s periodic even if it is neither a square nor a triangle. So I thought to myself, how hard can a low frequency ramp noise circuit be?

Turns out it’s … complicated. In this, part I of a two-part post, I’ll detail the cosmological pain points of basically any electronics-from-scratch project as well as some pain points in my personal process. In part II, I’ll detail the actual circuit and how I am using it.

Hardware is hard! (Software is … soft?)

TLDR; i need to organize my components and clean my working space. Then, I need to buy 10 more multimeters.

I don’t care what this guy says, hardware is hard and anyone who says it ain’t is lying or has a lot more patience and interest (and smarts?) than you I do.

There are so many variables to making a circuit work it’s hard to list them all.

1. power source (does it work? right voltage? dual rail or single supply? variable? BATTERIES??)
2. are you soldering right away? guaranteed failure. go directly to jail.
3. prototyping? do your cables work? banana clips? those resistors you got outside the engineering department when they restocked – do those work? how about your capacitors? how about the protoboards you got for $3 from Amazon, are those good?
4. Is it humid?
5. How long are your connections?

The above are questions for when your circuit is possibly correct. When your circuit doesn’t work (wired incorrectly, wrong component values, etc), which it likely will not for a while, you have an endless and seemingly impossible string of variables that might be the problem and have to be eliminated. Personally, I have never found a bad resistor in my bins, but I have had bad caps here and there and, more rarely but more annoyingly, bad proto cables and banana clips. Also, if it’s soldered it’s a risk. That includes banana clips, potentiometers (pots), some cables, probes, etc. Pots, unless heat wrapped, are pretty easy to eyeball. Clips and probes not so much.¹

Keep your multimeter handy in continuity mode to check your soldered stuff and your cables. Have another permanently set to whatever DC voltage you are looking for. Have another ready on capacitor checking mode. I’m serious, just surround yourself with multimeters. At this stage, it’s too much bother cranking the selector around, you just need more multimeters. (Okay, maybe this is a bit unhinged.)

The above assumes you actually have everything you I need for your my project, which you I don’t.

Remember when you could just drive to Radio Shack and have the parts you need in an hour? Holy Mackerel do I miss those days. The decline of modern society began in earnest with the closing of local electronics parts stores. You cannot convince me otherwise.

Now, we log on to Digikey, well, Mouser, because we can never figure out our Digikey login, and order the parts we need and spend $9 in shipping (double the price of the parts) to get them in a week. But okay, I’m in a hurry, $14 shipping (three-times the cost of the parts) for 2 business days. It’s Friday. I’ll get them Wednesday. F#*$!²

Anyway – if you have a good project outline or a comprehensive parts bin, you either have or can get all the parts you think you need for a project. But your collection is only as good as your circuit diagram/BOM. If the circuit is off, you’ll need different parts. I have trouble even finding my stuff because I haven’t done a good enough job of labeling and tracking my parts. That changed with this project. I now have an *electronic_components.md* list of all my ICs, transistors, diodes, etc, so I can easily search to know if I have a part or an equivalent. This will save hours of pulling out, rummaging through, and frustratedly returning bins to my electronics cabinets.

It also assumes you know how your oscilloscope works. You don’t.

Maybe it’s me. Maybe it’s the RIGOL DCblahblahblahnumbers. I find working with this scope absolutely infuriating. The results are neither intuitive nor easy to obtain. The auto feature kinda works, but I’ve found the live-updating of this scope to be very poor. Half the time I have to disconnect or even power off then back on to get an accurate reading. Maybe it’s hosed. Maybe the probes are bad… I guess I’ll just troubleshoot my scope for another 8 hours… cause yeah, that’s what I want to be doing right now…

Get Your Bench in Order!

Why? How?

Ultimately, this all points to a couple of questions: 1) why we do what we do and 2) how we learn to do it. The why part should be easy, especially given how hard electronics is. The learning part is really interesting to me and, again, is complicated. I’ll start there and then move to why below.

Learning Electronics (for sick Synths)

I imagine most beginners today wanting to learn electronics first try to use LLMs because that’s where all the kids start. Next, they probably go to YouTube for videos/tutorials. Social media is probably third (Hey guys, how can I get …. to work?? PLEASE HELP) followed by a distant fourth which would be original research using textbooks or niche websites/electronic resources.

Web searches and circuits found online are DOOMED.

Search is dead. Search is absolutely, positively, and permanently cooked. What’s left is the detritus floating on the moat. Unless search leads you someplace awesome like MFOS (hint: it won’t.) you are doomed. Just forget it.

AI still sucks with circuits. It’s okay with parts ID and specs (mostly).

As a parts reference I have found Claude to be pretty good, though I have sometimes had to double-check a datasheet. I’ve also had some luck with OPAMP component relationships, transistor/resistor values, etc.

Where AI really fails is anything experiential or perceptual. It’s also not great gleaning context. An example – ask for a component outline for low frequency ramp noise and, like me, you will get components (and a circuit description) for low-pass filtered white noise. These are not the same. Follow-up pointing that out and you will be led down the garden path to a dark forest. Do not go in. Do not follow the confidently wrong but encouraging text prompt.

Tutorials are largely still great.

Tutorials rule because, like a workshop, they are designed to accomplish a specific goal in a limited amount of time and have been worked-out to ensure that’s the case. No one makes a tutorial on how to do X without actually figuring X out, especially on video. The same is not true for LLMs. They constantly outline and/or describe entire complex circuits with absolutely no clue of what is actually required to make it all work (when it probably shouldn’t in the first place.)

I should probably assemble a list of my favorite YouTube electronics folks. Maybe someday…

The Right Book for You & Me

Standards

Another thing that makes the right book or tutorial work is that they provide a context that creates a standard for everything within. Even if it’s not Standard (capital S), it’s standard in that context. More widely, electronics (everything really) has a problem with standards.

Part of the problem of aging, beyond having your hair fall out of your head and come back out your ears, is the problem of standard parts, conventions, and building on a past that was not standardized or was only *specified* within a domain. Often, places where you think there would be standards, there isn’t or it’s changed. For a long time, and to this day, a lot of electronics research is incredibly specific to one domain. But components and applications span domains making standards a problem.

Electronic sound synthesis, for example, relies on parts used across domains, but implements them specifically for control and production of synthesized sound (or signal filtering/processing). If you don’t find *the right circuit* outlining how to accomplish x with your component in the sound/instrument domain, you will have trouble. In other words, the data sheet will probably not save you.

The reader will encounter many circuits in the wild that, while they should and could still work, do not because the parts are not made anymore or they use outdated conventions like ±18V which you do not have on your bench and certainly anyone you would share your circuit with will not have either.

The Voltage Dilemma

TLDR; Now I understand why 500 Series/Eurorack (and standards in general) is the literal best thing in the world

One of the many things that Eurorack and 500 series solve is standardized interface with a standardized voltage range. When you design for one of these form factors you do so knowing that your circuit must operate within a known set of parameters, also knowing that your circuit will interoperate with all of the other components in the rack without problem. This is a miracle.³

Anyway – the circuit (i know I haven’t really talked about it… I’ll get into that in Part II) I’m working on requires ±18V or at least ±12V. I don’t have it, so I’m going to split my +12V via a virtual ground @ ~6V and just work with a smaller range.⁴

This New Part is 35 Years Old

Many circuits that, admittedly still work, come to us from the before times: when Radio Shacks were open, Mimms was still writing books, and cell phones hadn’t ruined an entire family of precocious hominids. (My childhood friend Jim Manly’s dad had a cell phone — a CAR PHONE — in his Volvo wagon in the 1980s. To 10 y/o me he was the literal coolest and probably richest dude in town. He could just call anyone he wanted at any time IN HIS CAR! Wow!..)

If there’s no broad industry use for component x, it’s going to be retired. Sometimes it will be replaced. Sometimes parts that should be updated/replaced aren’t, so you are stuck with parts designed in the 1980s for an application different from yours. This means that part isn’t just going to slide into your circuit design. Now what?

Well, some theory is inevitably required. You *can* make due and work with voltage differences, dividers, VREFs, etc. Sometimes this will work, sometimes it won’t. It’s … complicated. Sometimes you will have to scrap a planned project and go back to the drawing board (or text book or PeerTube…)

Standards: This White Noise Isn’t White Enough

Sometimes, the circuit was never going to work as described. I don’t care what John Q Randomblog says about his “white noise” Zener Diode circuit, it ain’t white noise. Do a bunch of research into white noise circuits (god help me) and you will find a lot of lazy “simple white noise” examples that, at best, approximate white noise. I mean, it’s noise, it’s just more an annoying mosquito-like noise than broad-spectrum noise. So you move on. You try another. It also sucks. Try again. Or… remember that bin of modules you made from Wilson’s synth book?? Yes, you left them all boarded-up and, yes, there’s a white noise module sitting there! Thank you past me!

All In Service of Art

I’ll jump off the electronics rant train here because, well, I’m not sure where it’s going. You/I can get better at this. We can plan, organize, and strategize better. That’s the takeaway. Hell, we could, if we wanted, start from theory and build our knowledge from the ground up. But that’s not the point… unless it is. But it’s not my point.

After years of dedicating myself to deeply understanding things (programming, electronics, etc) I’ve come back to the importance of “why” I’m doing it in the first place. For a long time that was interest in the subject itself and a commitment to understanding deeply. These days, what’s most important to me is making stuff. That’s *my* point. Making noise, making art, making… anything. The circuit is a means to an end. You/I have to maximize our strategy as best as possible to that end. That will likely require time up front, but in the end, it should *save* time, not suck it away. Don’t be distracted.

Next Time…

I never set out to make the worlds best S&H circuit and I didn’t. I don’t care if it’s half jank, I just want to be able to plug something into my FX CV input that provides LF noise. Maybe noise I can speed up or slow down, add or remove portamento from.

In Part II, I will detail that circuit (which, yes, works… mostly) and talk specifically about my process of discovery, but with focus on the sound, the noise, the point of it all. Mash the subscribe button to get an email when that post goes out.

Thanks for reading!

— Footnotes —

1. Why not just check them and have known-good parts *before your start*? Because, magically, parts that worked when they went *in* the bin do *not* work when they come out. Just another joy of working with hardware. It’s like the tide, you can’t explain it. /s ↩︎
2. I don’t know what’s wrong with me, but my brain shuts down when I search these electronics sites. There are a billion parts they all have the same description (ish) but there are minuscule non-obvious differences that mean you better get it right or it won’t work. The only thing I fear more than ordering components is a colonoscopy. This is not an exaggeration. ↩︎
3. Forget for now that you still cannot connect these two “standards” together because, obviously, they are different… standards… ↩︎
4. My +12V DC power supply (with four channels, max 6 amps/4) has been good, but in the end I think I need an upgrade. ↩︎