Learning C (again)

August 9th, 2015

A Post! How weird is that? I can’t believe it’s been over 3 years since my last post. Actually, I can; I’ve completely neglected this site save for installing the security updates from WordPress. I’ve occasionally (yearly, when the Domain registration comes due) thought about ditching this site altogether, but so far haven’t gone to that extreme.

But today I got a chuckle, and had to post it (to the zero people who actually read this). I’m learning the C programming language (again; I did have some knowledge of it in college, but that was over a decade ago). Ultimately my goal is to code 8051 Microcontrollers, but until I get to the point of controlling hardware with code, I’m working though the Absolute Beginner’s Guide to C (3rd Edition), and am all the way up to Chapter 8 (of 32), which discusses user inputs using the scanf( ) function. Intentionally trying to break the code, I came up with:

Screenshot 2015-08-09 17.34.05

Pretty good, if you ask me!

Group Buys are Lots of Work

June 26th, 2012

I’ve been a little quiet around here because I really wanted to get started with the MSA. However, there were 3 ways to do it… either bite the bullet and have a set of panels built for myself; put out a plea to the Yahoo group asking for any spares laying around; or, organize a Group Buy to bring down the cost of each PCB.

Guess what I chose… Instead of trying to do anything easy, I have to make it complicated. I kicked off a group buy (you can see the results in the Yahoo group), and while I was really hoping for at least 10 participants, wound up with 70 participants, all over the world (Europe, Australia and the US were the big ones, but also Canada, Brazil, South Africa and India!). To say the least, I now know how to ship things internationally.

But because it was so much work, I want to show off my handiwork. First, opening the box of the bulk PCB order (which was 75 PCB’s for each of the MSA and Accessory designs).

That’s my cat, helping. She loves boxes, and couldn’t wait until I was finished to start gnawing on it.

The pile of PCB’s is almost 6″ high (each board is 0.063″, to give a sense of scale)

The next two pictures are of a Front/Back shot of both PCB’s; first the MSA PCB itself, then the Accessory board.



And the final shot; everything ready for shipping (boxes are destined for Europe and Australia, packages on the boxes are the other international shipments, and the pile on the left are for destinations within the U.S).


Phew. It was a lot of work. Fun to be sure, but not fun enough to ever do it again (okay, maybe some day, but not soon).

Modular Spectrum Analyzer

April 15th, 2012

Now that the speaker project is done, it’s time to get going on the next project, this one with a whole lot more soldering! Warm up those irons!

Actually, not quite yet. This next project is going to be a doozy. Remember the Tek 475 Oscilloscope repair? Oscilloscopes display signals in a format called time-domain, which essentially means that on a ‘scope display, the vertical axis shows amplitude, and the horizontal shows time. This way, you can measure the peak-to-peak distance between waves, and determine frequency (and a whole lot of other cool things).

Spectrum Analyzers display signals in a format called frequency-domain. The vertical axis still shows amplitude, but instead of showing nifty waves like you’d see in a 70’s Sci-Fi movie, it shows frequency. That way, instead of having to try and count, calculate, and guess as to what frequencies may exist in a signal (because signals rarely have just one frequency, which if it did would be called a perfect sine wave).

Anyway, back to the project. Scotty Sprowls is a genius. He invented a Modular Spectrum Analyzer, that uses a computer as the control interface, and competes in function and accuracy with the really $$,$$$ units.

Where cost is greatly reduced, build, test, modify, tinker, play, curse, tweak, swear, break, repair, etc, time is greatly increased. But that’s okay, because most of the fun of a project isn’t the finished product anyway, it’s the process! I estimate getting to a functional unit will take the better part of a year, and getting it calibrated, boxed up and in a place where it’s really usable may be another year.

It’s been interesting participating in the Yahoo! SpecrumAnalyzer group, where the MSA builders get together and share stories and offer solutions to questions. If you’re considering building an MSA, I strongly suggest you join the Y! Group, and lurk for a few months first, to see if it’s really something you want to take on. I’m kinda apprehensive about embarking on such a big project, but I really think it’ll be fun overall. There is lots of support available, and the guys on the Y! group are very helpful.

I’m sure I’ll be doing some other smaller projects throughout, but this will be the big one.

L-C-R Speaker Build

April 1st, 2012

L-C-R stands for Left, Center, and Right. Those are the front 3 speakers in my 5.1 surround sound system. Until now, I’ve been using some gigantic speakers that didn’t sound very good anyway. The LCR speakers are also Paul’s design, using the same drivers as the Overnight Sensations (using for Surrounds), called the Overnight Sensation MTM (MTM is Mid-Tweeter-Mid). One of the reasons I decided to go with the Overnight Sensation set is because Paul had designed them in such a way that they’re great for a surround sound system.

On to the build!

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Surround Speaker Build

March 31st, 2012

So it’s been a very, very long time since my last Speaker build update. That doesn’t mean I haven’t actually been working on it. On the contrary, I actually finished the Surround speakers in August, and being the height of Summer, wasn’t really thinking about sitting in front of my computer…

So here now is the Surround Speaker Build!

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On Changing my Home Phone Service

September 21st, 2011

I’ve never had a traditional home phone. For several years I used a cell phone as my sole contact with the outside world. This was very handy when I moved, as all I had to do was pick up my cell phone off the counter, put it in my pocket, drive to my new house, pull the phone out and put it on the new counter, and I had a phone. Same number and everything.

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Subwoofer Completion

July 31st, 2011

When we left off, the subwoofer enclosure had been glued. All the structure is now finished, and the box is very strong. The final seams are caulked. However, it’s fairly ugly at this point; the corners are all sharp, and the seams rugged.

Up now is beautifying the box!

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Subwoofer Construction – The Mechanics

July 16th, 2011

Mechanics in this sense of the physical structure of the enclosure… I won’t go into the operation of a Subwoofer, as a decent overview can be found here (Wikipedia).

Without a properly designed and built enclosure, even a phenomenal speaker can sound cheap. I don’t pretend to know much about enclosure design and construction; in fact, below is essentially my second enclosure design ever. The rest of the speakers (to come) are others designs, of whom I will give proper credit in due time. Read on to learn with me (and see lots of pictures).

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Introducing the Subwoofer

July 7th, 2011

In my younger years, I had a 1973 Chevy Impala with a very large audio system. It consisted of a Rockford Fosgate amplifier, dumping power into a pair of 15″ Pioneer subwoofers in sealed boxes. It was loud. Like able-to-hear-me-coming-3-blocks-away-loud.


Was in this:

A few weeks ago, I picked up a switching power supply capable of outputting 13.8V (the standard car voltage, commonly called “12V”), at 25 Amps (350W total power). It’s the MeanWell S-350 (pdf), and works great! I got it off eBay, from user modders_cn. I got it with the express purpose of powering a car amplifier. The only problem is that one channel of the R-F amp, along with one of the subs, blew up (it was loaned out to a friend…). So I’ve had one speaker, and a broken amp laying around for several years. I tried getting the amp working again, and while the main problem is a set of blown MOSFET transistors in the final amplifier stage, there are some other oddities that indicate a more sinister issue.

Instead of continuing with that project (that will be for another time), I picked up an MB Quart FX60.2 from Sonic Electronix (funny name, great company!). Everything is hooked up as you can see in the picture below.

It sounds terrific! The FX60.2 is driving the sub in bridged mode, which provides 240Wrms. While the speaker is rated to 200Wrms, the additional 40W doesn’t concern me; it’ll run most of the time at a fraction of that. The Power Supply is capable of providing 350W, so there’s plenty of overhead for inefficiencies in the amp. You may notice in the pictures a few screw holes in the mounting board. I had orignally used a third amp, which I was given by a co-worker, but while it looked spotless on the inside, has issues of its own (yet another project!).

The subwoofer itself is still mounted in the enclosure that was in the Impala (though only one, as opposed to the picture at the top). It’s coming out of there, and a custom box will be built to house it; the topic of another post.

My Eyes & Ears Hurt!

July 6th, 2011

My current movie-watching experience has something left to be desired. Actually, most things are left to be desired. The video source I’m currently using is a home-built projector, a project I did several years ago, and have been using successfully since then, but the picture has some vignetting, and focus across the screen isn’t consistent. It’s based off the old LumenLab (link opens deep in the website; the site focus has shifted to CNC mills) designs, and is due for an upgrade (and subsequently future posts). My light box leaks, and the general build-quality isn’t up to par (which is why I’m not providing a picture).

Beyond video is the problem of audio. I have a Pioneer VSX-815 receiver which has been working wonderfully, and does a very decent job of pseudo-surround sound, given a stereo input, it’ll nicely break the various frequency ranges in a respectable way to sound surround. The problem is the speakers; I got a set of 8 (L and R front, Center, L and R surround, L and R rear surround, and subwoofer), for a whopping total of $80 off Craigslist. They are big (VERY big), but the sound is still pretty weak, especially at the low end; the subwoofer has a built-in amp pushing 30 whole Watts. Taken with the 100W per channel capable Receiver, and there’s just nothing there.

There are all sorts of things wrong with that paragraph… 8 speakers at $10 each (and really worth only about that), 30W subwoofer, and a 7.1 channel setup being run by a freakin’ stereo input!

The next few posts will outline my plans and improvements to the Audio/Video position. Yes, it is summer, which is why I’m doing it now… lots of cutting, drilling, and painting are in my future. However, first comes the subwoofer, then the long process of building new speakers. I’ll leave some suspense, but it should be grand.