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Cheap, Easy Wall-Mounted Monitors

May 27th, 2017

For my home recording rig, I use a 7×3′ desk (made out of an old door) to hold my audio interface and any instruments or effects I’m using - keyboards, pedals, mics, preamps, etc. I don’t like that real estate to be cluttered up with stuff that could live somewhere else. The computer, the speakers, lighting and monitors should ideally be sitting somewhere other than the desk.

At my last place, I solved the problem by attaching picture hanger D-rings to the backs of my monitors and hanging them from drywall screws. That meant having a big ugly piece of wood spanning at least two studs, and lots of room for error when it came to making things level and straight.

So here’s my new method. It cost about $10, looks a lot nicer and is a lot easier to get things hung straight.

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It’s all based on this stuff I found at Menard’s. It’s a rail used for hanging garage shelving. It’s steel and it already has holes every 8″ which should line up with the studs in most walls. I bought one 7′ piece for hanging on the wall and a smaller 40″ piece to cut up and attach to the monitors.

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To cut the stuff, I used a jigsaw with a fine-tooth metal cutting blade.

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I also used a drill press and a step bit to drill the holes for the bolts that go into the back of the monitors.

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An orbital sander with a 60 or 80 grit disk is handy for removing the burrs so the screws fit tighter.

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I cut the smaller rail into 8″ chunks, and drilled two holes 10cm apart, which will line up with the mounting holes on the backs of my monitors.

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To hang the long rail — a drill, a level, some long drywall screws and some washers.

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I used three screws, figuring the material is strong enough. The idea behind using such a long piece is that I can slide the monitors anywhere along the rail. The center screw is going into a known stud. The other two I didn’t check because it’s a plaster and lath wall and the wood lath should hold it well enough. Going into drywall you may either want to be sure there’s a stud or use some heavy-duty anchors.

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Detail of the wall rail. The brackets on the monitors are the same material but upside down. You can see how they will interlock that way.

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The back of the monitor without the bracket. I’m using just the top two holes.

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Back of monitor with bracket installed.

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Detail of the bracket. The top of the bracket will click into the bottom of the rail.

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The monitors installed.

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And here’s everything hooked up and powered on. Now, if I want to set up synths or mics on my big table and need to move the monitors down, I can. I can also make pegboard panels that hang the same way to store cables and stuff. And no more wasting space on the table with monitor stands.


INA217 Microphone Preamp

July 17th, 2016

This project incorporated a lot of firsts: my first working circuit powered by mains electricity, my first preamp and the first time I actually took some design initiative — I designed the (very simple) power supply and incorporated a clip detector into the circuit.  I opted for a “wall wart” input to supply phantom power for a couple reasons.  First, it kept the power supply design simple.  Second, it allowed me to eventually use the same supply to get power to multiple preamps, so long as I add the same input jack to all of them.

The preamp design is straight off the INA217 op amp’s datasheet.  The clipping indicator design was sourced from the Elliot Sound Products website. I source a lot of my parts from ebay, looking for multiples of the same item so I’m always building an inventory for future projects.  As a result, I have no idea how much the total supply cost is.  The expensive parts were the transformer ($24) and the case ($12).

Some other design considerations were to use a 1/4″ TRS jack instead of the standard XLR connector.  They’re cheaper, and I was intending from the get-go to incorporate the preamp into a patchbay setup.  Using a TRS connector doesn’t change its ability to take a balanced line.  What it does do, however, is allow the careless user to damage a mic by using a TS cable with phantom power.  For the single-engineer home studio this isn’t a problem.  It actually gives me a really good excuse to keep my roommate from using my gear.

The op amp’s datasheet does not specify a design for balanced output, and while that may be a minus on a commercial unit, it’s of little consequence to me since the pre will always be in my control rack with about a 3 foot cable run to the audio interface.

I opted for stripboard construction over more compact methods because I just wanted a working, reliable preamp.  For me, that requires plenty of soldering room.  I actually like the industrial look and size of it.  Perfboard irks me to no end and at the time I hadn’t yet worked up to etching.

For the phantom power supply, I found a 48v 375mA wall wart on ebay and rehoused it with a standard output power jack in the front and a standard mains IEC connector in the back.  To get the power to the pre, you can use a run-of-the-mill pedal daisy-chain cable.  With microphones typically consuming 10mA of power tops, there’s plenty of capacity in this supply.

Circuit design sources:

Schematic:

Stripboard Layout:

The schematic for project 146 specified a pot between pins 2 and 5 of the TL072, and in the notes, it is recommended that the pot be replaced with a 10k resistor for fixed-gain applications so I ended up going for the 10k resistor.

I had a hard time finding the right pot, but in the end — contrary to what’s recorded in the schematic — I went with a 2.5k reverse-log taper.

Build Photos:

Designing the circuit board.


Building the circuit board.


Putting the box together.


Rehousing the phantom power adapter.


Label of the phantom power adapter specs copied from the original housing.


The transformer.


Power supply detail.


Installed circuit detail.


Power section all put together.


Open box with front panel.


Open box with rear panel.


Top View

Finished Preamp:


Front panel: Pilot light, +48v input, phantom power switch, phantom power indicator, clip indicator, gain pot.


Rear panel: Input (TRS), Output (TS), power on/off switch, mains power jack.


Hooked up and powered on.


In the rack.

This pre definitely holds its own alongside the stock preamps in my interface, which was exactly what I wanted: simply more channels of clean gain. Considering the ART TubeMP retails at about $50, this maybe wasn’t the cheapest option. On the other hand, the DIY build is more elegant, not to mention repairable — should something go wrong.


Between the Walls and the Sea

July 28th, 2013

cassette layout

There’s actually news on the solo project front. My next record is complete. I have preliminary masters for it and I’ll be releasing it on cassette and MP3 in the fall. No physical CDs to start out, but I’m offering the MP3s on my Bandcamp page on a pay-what-you-want basis.

Between 1997 and 2009, I released at least one recording every year. There’s been nothing since then. I wrote a bunch of new songs in 2009 and then tabled them. In late 2011 I started recording some of them. I’ve been working on those tracks slowly since then, and recorded a few new songs along with them. That means I’ve been working on this release for four years. I think it shows. Every step was a very deliberate process, and I’ve gotten to know the tracks very well. This is a very different record from Open or Exits — I’ve gotten pretty enthusiastic about analog synth sounds and keyboards in general, so this record is way less guitar-dominated. There’s also a shit-ton of reverb and drum machine. Warning: the rest of this paragraph is geek-talk. I recorded it all in my room using Cubase LE (which I’m done with — I recently switched to Reaper,) an Alesis SR-18 drum machine, an M-Audio midi controller and a handful of free VST synth plugins. Guitar and vocals were mic’d but everything else was done in the box. A big part of the sound is a result of using the same very wet reverb settings on the vocals and the software synths in addition to a lot of spacey delay guitar. To master for the cassette, I ran everything through a PSP Vintage Warmer plugin and a very conservative limiter. For the MP3s I might add a multiband compressor and a little more limiting to get louder tracks if they don’t sound hot enough. They might be good enough already, I’m not sure.

Maybe this goes against what you’re “supposed” to do, but this record is mixed for headphone listening. I’ve been trying to get it to sound OK in a room with speakers, but when it comes down to me having to choose where it sounds great, I chose headphones. In other words, I’m not sacrificing the headphone sound as much as I’ve done before trying to cater to different listening environments. I’m not that great of an engineer anyways and I think I’m talking about pretty subtle differences, so maybe it’s not worth mentioning. I tried to make the kind of record that I would want to listen to privately, from beginning to end, either in a dark room or going out for a walk.

The in-progress tracks are all currently up on Soundcloud, where I’ve been posting them as they come into being. I won’t be putting the finished tracks up on there. Instead, they’ll go right up on Bandcamp as soon as I finish the “hot” masters (for digital distribution) and the cassette will probably be released at a record-release show.

My last record, Open, is currently available on Bandcamp — also pay-what-you-want. You can download it for free or throw some cash at me to help get the cassette produced. Here’s the link again to go get it:

geraldprokop.bandcamp.com/album/open

Here’s the final track listing for the record:
Between the Walls and the Sea
Side One

  1. On a Road
  2. Dwell
  3. Groundless/Flightless
  4. Background
  5. Tornado

Side Two

  1. Cellar Door
  2. Follow Apart
  3. Can of Worms
  4. Let Go

DIY Education – Second Year Capstone

July 21st, 2013

Two years ago I posted on here a declaration of self-education and a strategy to get me started with an autodidactic education program. The strategy didn’t last long, but I’ve been experimenting with different things to accomplish my goals. It took on a life of its own. Then, this spring, a lot of plans hit their climax all at once. I finished my Minnesota Master Naturalist class, got on payment plans to pay off back rent and a debt to the IRS, and I officially started my residential-contracting-via-utility-bicycle business. My brain was, at this point, crammed with unsorted information and experiences. I figured the next step in my personal education should be a sort of capstone project – to unpack and synthesize everything I’ve encountered in the spirit of this project since beginning it. That includes, but is not limited to:

  • Volunteer seed collection and native plant identification
  • Taking a MetroBlooms Raingarden workshop
  • Minnesota Master Naturalist training
  • Taking part in Occupy MN
  • YouTube videos or free online documentaries with Timothy Morton, Slavoy Zizek, Alice Roberts, etc.
  • Filling notebooks with half-baked essays on anthropology and human history
  • Visiting state parks by bicycle
  • Hiking
  • Conversations with naturalists, park rangers, landscape architects and environmental science students
  • Reading (but not always finishing) Small is Beautiful, The Ecology of Commerce, The Expanding Circle, Collapse, Sex at Dawn, Thoughts Without a Thinker, A Primer in Environmental Literacy and the Ecology of Freedom

My second year capstone is a two part writing project.

Part one is a sort of self-assessment where I attempt to unpack the last two years and pick out some key ideas and synthesize multiple lines of thought. This is for myself — as writing practice and as a way of taking stock. I’m going to use it sort of as a cheat sheet for the last two years, or as an external hard drive for my brain.

The second part is a paper putting Timothy Morton’s concept of “The Ecological Thought” into context in terms of ecological stewardship and political economy. I want to focus on some of the conceptual traps we fall into when we consider the intersection between human societies and the natural world, and how the Mortonian “Ecological Thought” turns those traps into new questions. The goal is twofold: to complete a finished philosophical essay and to combine my three focus areas of philosophical anthropology, landscape ecology and nonfiction writing in such a way that all three things feed off of each other.

This essay will be posted here when I’m done, maybe as a new version of my zine, “It’s a good day to face the hard things.” I’m exited to write it, but I first need to read Morton’s book entitled The Ecological Thought, and possibly also Ecology Without Nature. I’m familiar with his thinking through a series of videos and podcasts I’ve taken in. That kind of learning is adequate for forming thoughts and getting a sense of his ideas, but in order to write, I need to read the book.

As soon as this capstone is complete, I will return to the self-assessment and figure out what to do next.


A cheap solution for a shitty couch

August 16th, 2011

When I moved into my friend’s house in April there were three couches, a console TV and a dining room table in my new room. I decided to keep one of the couches in there, and we moved the rest of that stuff downstairs.

My initial plan was just to sleep on the couch, but the springs were removed and replaced with a couple of motors from a massage chair to make the couch vibrate, as well as to scare any squirrels living in the roof or wake up anyone who may be sleeping anywhere in the house. When you sat down, you just sunk into the back of it, almost as if you were a quarter about to get lost in the cushions. So I built a loft bed with a foam mattress to sleep on. I’ll publish the design some day.

As I was reading and sinking into the cushions and getting irritated, I looked up at the slatted support structure I used for my bed, and I got an idea. I went into the basement where I knew there were some scrap 1×3 furring strips and I experimented with fitting them on top of the couch frame.

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After sticking some temporary supports under a few cushions and feeling it out for about a week or so, I eyeballed what seemed to be a good placement interval for the 28″ slats.

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To make it secure, I ran two 5′ 4″ furring strips underneath the slats and used 1 1/4″ gold screws. The corners each got two screws diagonal from one another to keep the boards at right angles.

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It’s a much more stable couch now. It feels a lot firmer obviously, but it’s comfortable. And the supports slide out all in one piece with a little work. Still a junky looking couch, but who am I trying to impress?

I could’ve gone to a thrift store and bought a different couch with everything in tact. The estimated cost would be at least $40, plus the hassle of borrowing a truck and moving it, plus the hassle of throwing away the old one. (Also, I designed my bed so that the couch fits perfectly underneath it, with a long shelf running along the back.  I’d be losing design points.)

I also could’ve tried to figure out how to respring it. Uh-uh, no way.

Instead, I spent about $8 to rig up wooden supports — $4 on wood and $4 on screws. Nothing was wasted. When I get a spring mattress someday, I’m going to cut up the one I’m using now and use the foam to re-stuff the couch cushions.


Frying Pan Ashtray

May 12th, 2011

What do you do when your new roommates are using an old frying pan as an ashtray on the porch?

You reclaim the Ikea Bargain Bin speaker stand you dumped there a long time ago, and make a standing ashtray out of it.

Frying Pan
Figure 1. A dirty old frying pan from some long-gone renter’s trash.

nuts and bolts
Figure 2.  Three holes, three nuts, three bolts.

Finished
Figure 3.  Instant class, i.e. “no more having to crouch down to extinguish your smoking materials.”

Oh yeah, and after you’re done, you spend more time blogging about the project than you spent working on it (but at least you didn’t spend more time doing either than you spent thinking about it.)

The end.


Electronics Projects

June 8th, 2009

Digitizing vinyl and mixing my next album has inspired me to build the CMoy headphone amplifier.  I’ve been taking regular walks to the bar with a set of headphones and a cheap MP3 player loaded with in-progress mixes.  Since these are unmastered tracks, and thus uncompressed audio signals, the little USB-charged MP3 player doesn’t have the juice to bring the tracks up to normal listening level.  The more complex the track, the greater the build-up of transient peaks and the quieter the mix.  Vinyl tracks are also uncompressed, which means there’s more difference between the loud parts and the quiet parts.  The CMoy amp adds an extra 18v of power, which means I can plug in the MP3 player and leave it at its default volume, using the amp to drive the headphones.

CMoy Headphone Amp
I’m almost done.  The tutorial I was using suggested a dual pot with a built-in power switch, which I had to order separately from the other parts.  This particular pot works so that when you turn the volume all the way down, the power clicks off.  It’s a wise feature considering that you can seriously damage your hearing with this amp.  This way, it’s always turned all the way down when you power it up.  I tested it out before I housed it (in the standard Altoids tin) and it got pretty loud with one 9v battery.

I took another look at the looper project I’ve had put off to the side for about a year:  three toy sound samplers with pitch shifting that you can hack into and add to a simple mixer circuit to create a lo-fi, multi-channel looping effect.  I drew up a wiring diagram, planning on using a chunk of steel stud to house it:
bent looper

I still have the power supply, mixer and one channel hooked up to a breadboard. Last I checked, it worked, and I haven’t touched it since:
Toy guts on a breadboard

Three Channel Live Looper
I decided instead on an enclosure from an old whatever-the-hell-it-was from ax-man.  You can buy old machines for $5-$10, take the guts out and use the case for new stuff, which is cool because electronics enclosures are really expensive.  The drawback is that it’s harder to get a space efficient design since the housing was meant for something else, but I’m starting to realize that I like things to be life size, sturdy and clunky with plenty of soldering room.  The last looper circuit I built, I think I fried the chips because everything was crammed too tight on the board and I couldn’t troubleshoot it.

All the knobs are where the pots will go.  The nuts represent toggle switches, the plastic grommets (LED holders) represent LEDs, the washers represent momentary switches, and the pots represent foot-switches.


My Cheap Rackmounting Idea

April 25th, 2008

One of the most expensive parts of any project is the case, often the most expensive. I read somewhere about using metal studs to make enclosures for pedals, and that got me thinking. I went and got some supplies today and threw this together. Its a new housing for my headphone splitter (which will eventually house other things too since there’s plenty of room.)

Cheap Rackmount
I bought a blank rackspace panel from Guitar Center for $6.49. They’re meant to just cover up empty spaces in your rack, but that’s kind of silly. I got some machine screws and nuts, and drilled the two holes in the panel, and two holes in a 17″ section of aluminum stud and bolted them together. Studs are a couple bucks per 8′ section, so this is totally the cheap way to go for simple projects.
Cheap Rackmount
Then I drilled more holes to mount the jacks and the switch. This got frustrating with my cordless drill because those panels are 1/8″ steel. I need a drill press. I also should have drilled all the holes and then bolted the panel to the stud, because a bunch of burr got caught in the middle.
Cheap Rackmount
I drilled a little too high for the input jack. I had to snip a little piece so the jack wouldn’t short out. The whole enclosure acts as ground for the circuit.
Cheap Rackmount
Installed. Nice blank mystery box. Obviously this only works for projects that don’t take up much space, and that aren’t heavy, but “real” rackmount enclosures start around $60 last I checked.