INA217 Mic Pre for Guitar Pedals

I’ve been seeing a bunch of threads on the Unofficial DIYStompboxes Facebook group about plugging microphones into guitar pedals. This is a road I’ve explored for years now, and I’ve decided to whip together a simple project. Note: this layout assumes you’ll be using a dynamic microphone so a phantom power supply section is not included. If you add a phantom power supply that is always on, flip the polarity of the input capacitors. If you add a phantom power supply that will be switched on/off you’ll need to use bipolar capacitors with a proper voltage rating (might be a tight squeeze on the board). This isn’t a perfect solution, but it is quiet and uses very few parts. Feel free to make as many boards as you want, sell them, start a new audio electronics empire, but if you make money using these files please consider kicking some back my way.

 

Gerber Files

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Electro-Etch Part 1: Electronics

I hate using nasty chemicals at home. Hate it. If you work with them long enough you will damage yourself and/or your property at some point. I went 15 years using FeCl at home without any issues until one day I happened to spill a liter of it all over my work bench. That bench was covered in metal shavings created by the nearby drill press. It was an absolute nightmare that took about 4 hours to clean up, and I still get panicky when I think about it.
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A Very DIY Screen Print

cow

Here is another tutorial I dug up that was created by my wife at least 14 years ago back when we were still dating. She is an avid DIY’er with a reputation of being a crafty hacker type…with yarn and fabric instead of a keyboard and software. Before things like pre-sensitized screens were a thing it was pretty complicated to try making your own screens at home. My wife came up with this solution in the PDF linked below. At the time, this tutorial blew up on craft message boards, and over the years I’ve seen a few variations of this method. I haven’t tried it on electronics enclosures because it’s hard to use this method with that amount of detail, but some of you might be more brave than me.

DIY Screen Making Tutorial PDF

Here are some Amazon links to items listed in the tutorial.

 

Home PCB Etching

41wmUdb+zPL._SY445_So this tutorial is a blast from the past that I found on an old hard drive. I wrote this back in the early 2000’s when there weren’t a whole lot of resources on the internet with regard to etching boards. This method is now pretty widely used throughout the DIY community so there isn’t really anything new here. It’s pretty rough, and there are much better tutorials out there, but I figured I’ll post it anyway just in case anyone needs a laugh at my pitiful tutorial making skills of 12+ years ago. I’ve also compiled a list of links to items needed for this process available on Amazon.

DIYPCB

I’m sure there are laminators on the market that cost less, but I have the Apache AL-13P that was recommended on the Pulsar website, and the unit linked above seems to be a copy of the AL-13P. The mods required for the laminator are here. The Apache AL-13P is a solid unit that performs miles above what the GBC laminator in the tutorial could do.

 

Bazz Fuss

bazz3The Bazz Fuss is easily one of the top five of my favorite fuzz circuits. It’s super simple to build, costs next to nothing, and it sounds incredible. The low parts count and straightforward layout makes this a great first build. I’ve probably done at least 50 different board layouts of this circuit using parts packages ranging from 0402 SMD chips to huge “Orange Drop” caps. The boards have varied from the size of a postage stamp to the size of a credit card. I decided to spend this afternoon putting together a really straightforward single sided layout that is friendly to the home etch process.

BazzFussTopPCB Layout

B.O.M.

R1 – 1M
R2 – 10k
C1, C2 – 100nf
Q1 – MSPA13 (experiment with other NPN BJTs)
GAIN – 100kA

555 Timer Continuity Probe

555PCBTop

Thanks to the folks over at 555 Timer Circuits I threw together a quick PCB layout for their continuity tester. Yes, most multimeters contain a continuity buzzer, but this is going to be part of a prototyping fixture that is currently in the planning phase. The idea is that I’ll have a breadboard, power supply, signal generator, headphone amplifier, and this continuity tester in one unit.

PCB Layout

Home Etch Friendly PDF

B.O.M.

R1 – 10k
R2 – 33k
R3 – 1k
R4 – 39R
C1, C2 – 10nf
Q1 – 2N3904 (any general purpose NPN)
Q2 – 2N3906 (any general purpose PNP)
U1 – 555 Timer

Hammond (4site) 1590B center punching jig

Printing out drilling templates on paper, aligning them, and taping them down to center punch the hole placement kinda sucks. I’ve been working on a 3D printed jig that goes over the enclosure and self centers securely. This is a modified version of the paper template made by General Guitar Gadgets. You can then center punch these areas of your choosing:

  • 3×3 grid for potentiometers
  • Stompswitch
  • 3 LED placement options
  • 1/4 jack on both sides
  • DC jack option on both sides

This item is available on Thingiverse for those of you with access to a 3D printer.

Dremel Idea Builder

FullSizeRender-2

Warning: Wall of text ahead!

I got obsessed with 3D printing, at least the idea of 3D printing, about a year ago after building and running a couple of Shapeoko 2 CNCs. Where a CNC is subtracting material to create an object, a 3D printer is doing the exact opposite, but using similar hardware (obviously). Stepper motors, pulleys, acme lead screws, etc make up both machines, but with a slightly different learning curve for each.

I started following /r/3Dprinting on Reddit, and read about all of the pitfalls and triumphs that go along with this hobby. There is a lot of tweaking and experimenting that requires patience and time. I have very little of both. I bit the bullet a couple of weeks ago by purchasing a Printrbot Metal Simple. The whole experience was a train wreck, and I’ll save the gory details, but the short story is that the machine wasn’t what I was looking for. It works great for a lot of folks, but I’m not one of them. Back to Amazon it went.

I hemmed and hawed about what machine to get. I don’t get lots of time to dedicate to my hobbies so I wanted something that as close to plug ‘n’ play as possible. I had some criteria in my head:

  • Easy to setup and use
  • Responsive USA based tech support (I’m not a racist xenophobe, but instead want to be able to get someone on the phone at a decent hour when shit hits the fan)
  • Quality prints
  • Repeatability with minimal fuss

After a ton of reading, I came across only a few reviews for the Dremel Idea Builder from seasoned 3D printer users. The ones that I did come across dubbed the printer as “a stripped down Flashforge Dreamer”, “too basic”, and “expensive for what you get”. However, within those reviews a few things stood out. “I was printing within minutes”, “I have over 200 hours on this machine with minimal failures”, and “I contacted tech support and got help immediately!” were common amongst the reviews I was finding. I’m willing to pay a premium for a “basic stripped down” product if it means I can setup and print my parts without farting around.

I received the Dremel Idea Builder yesterday, unboxed it, and powered it on. I attempted to load the filament, but half of the screen would go blank and the machine would restart. WTF!?!? I went on the Dremel website and was chatting with a helpful tech support person in less than a minute. They suggested that the TF card (not the SD card) had come loose in shipping and e-mailed me the instructions to fix it. That included removing the bottom panel of the machine and plugging in the loose micro SD card. About five minutes later the unit was working, and the filament was loaded. Add on to that a few minutes to level the bed and apply bed tape. Grand total it took about 30 minutes from delivery to being able to start my first print. After printing a child’s dice as my first print I confirmed the machine was dialed in. Next was a coffee bag pouring clip (pictured below). I spent the rest of my evening printing random objects with the goal of learning the quirks of the machine (if any). Here is what I’ve come up with:

  • Clean the bed with rubbing alcohol before printing
  • Print something small before printing something large. That way heat transfers to the bed minimizing warping on larger prints. A hair dryer could do the same thing.
  • Don’t fill the bed with stuff to print. This filament oozes from the nozzle a little more than I’d like and will leave strings of filament on your parts as it cruises the bed printing in different sections.
  • When the nozzle is coming up to temperature pull the string of oozing filament off of the nozzle right before the machine starts running the build. That way you won’t have a string off cool filament on the bed to possibly impede your first layer.

About 24 hours in to owning this machine I’ll say that it is worth every penny of the $999. I still have lots of experimenting to do, but as of now I’m getting usable prints with almost zero messing around. I don’t want to jinx myself, but I haven’t had a failed print yet. While I wish the proprietary software allowed just a bit more tweaking than the “advanced” setting provides…so far I don’t feel like it’s hurting the quality of my prints.