So recently a friend at work (the esteemed DJ Hedflux) had a problem with his speakers – he has a pair of powered speakers, and he outputs sound down a normal stereo cable into the speakers. Being a professional DJ, nothing in his system is particually cheap (he’s not spending £100 on cables, but he’s not buying £1.50 speaker modules from the market) so we can quickly rule out shoddy work and bad connections inside of the devices.

Anyways, he worked out that it was a combination of his computer and his touch lamp causing it – doing things on his computer that required lots of processing, and having the dimmer lamp “dimmed” caused the noise to appear and dissapear.

This is very common, and also, very easy to fix.

How to fix:

The solution is very simple, and very cheap. You’ll need a ferrite ring, which you wind the audio cable in just a couple of times, like in the above picture.

Maplins sell these for a couple of pounds, usually find them in the Radio section:

http://www.maplin.co.uk/Module.aspx?ModuleNo=29788

Image stolen from http://www.gbrcaa.org/ntoa/Filters,%20Chokes%20and%20OIs.htm on which site you can also find more information about other kinds of chokes.

The science:

In Hedflux’s case, its possible that his computer internals arn’t all grounded to the case correctly, or the case to the power supply, so its generating more electrical noise then ideal. The dimmer lamp however is a common source of Electromagnetic Interferance (EMI).

Because he’s using a set of powered speakers, the loudspeaker cable is acting as an antenna, and the amplification circuit is having a side effect of acting as a little radio, which is picking up the EMI from the computer and the lamp, and turning it into the annoying hissing noise.

The ferrite bands that he added to the audio cable basically change the frequencies of that cable, effectivly filtering the annoying frequencies out.

Why don’t these cables come with the bands installed? Well, the point is that it dosn’t STOP the frequencies, it shifts the resonance frequency of the cable. The cable and speakers will still produce noise if the EMI comes in on a different frequency, so it was just bad luck that the EMI in his room was the same frequency as the cable / speaker setup.

So I’ve started on a tinymush server, and its quite interesting scripting objects together, so here is my first object (which is actually version two of it) because the first version was a little cumbersome. Please note this is ready for copy and pasting into the mush (I’ve escaped the ; with backslashes)

It has two commands “write on board x” and “erase board” which reset an attribute &text. I suspect I should change the pose lines to emit lines. But apart from that, I think its pretty cool.

Ok, so theres this massive need I’ve found for good distributed bug tracking which is actually platform independent. And this brings me around to my gripe of the week. Platform Independence.

Firstly, I classify myself as an indie developer - that means that I use open source and free software tools in my tool chains, and I use developer / free to use sdk’s to develop applications.

So I’m not able to afford any of the larger programs and tools which are used - things like the Visual Studio or the Team system. Things like Bug Management and Tracking, things like support and ticketing. To some extent things like release managment.

And why would I want to? There are plenty of open source, free, and community based tools out there which do of these things. The problem is however is that they often don’t work across all platforms. They often have requirements or don’t “fit together properly”.

Last night I found a quote by Doug Vargas (I dont know who the guys is or I would have linked to it):

“It’s easy to cry ‘bug’ when the truth is that you’ve got a complex system and sometimes it takes a while to get all the components to co-exist peacefully”

So with this in mind, this is where things begin to get a bit more tricky. The first problem is that I don’t work on one project - I don’t have a single project which is “my baby” I dont have a single passion in life which takes my complete and utter concentration, instead I have a few - simple single use tools which I reuse in other projects. I have a collection of libraries and tasks and I treat each one as a new project and I keep them seperate.

So when it comes to using some of these tools - they are really only for one project. For instance, trac - awesome huh? But I dont want to have to configure one for every application that I write. And this is where some of the harder hitting application come in, but there really isn’t much for the small indie people.

Then we find that half these tools only work in linux. Or windows. Or they work in Cygwin and they require some bizaare libraries. Its very easy to write a tool which does what *you* want and then not worry about everyone else - in fact this is probably the only way that the tool gets written.

So I’m starting work on a platform-independant distributed bug tracking app (this is because I want to track bugs inside of the projects) and I’ve decided to write it in C# which means it will be dependant upon Mono or .Net being installed on the target platform.

I’ve worked out that I need a scriptable level inbetween my application and the SCM - because I want to make it independant of the SCM I am at the moment tying it into Git, however I can see how I need to make it indepenant by having a script wrapper around the SCM (which might be Git or might be SVN or something like that) which would provide the answers to a collection of questions that I want to put to it.

Its getting things to coexist peacfully which I think is the big Programming problem.

I’m having a real problem understanding the idea of an SDK. The entire concept is becoming more and more spleurgh (if you don’t mind my making up words). The concept makes sense when tit ties in with a particular IDE. And here’s the problem - why should anything tie into an IDE? The advantage of using something like Ant is that it allows you to build both inside an IDE and outside.

I built a “build bot” a while ago which took its own parameters and called csc.exe from the command line to help do building - because my knowledge was small, it seems that I had missed the point of msbuild. This takes the same project files that Visual Studio produces to do the same builds.

The only problem I have now is that I don’t know if there is a mono alternative to msbuild. If there is, that would be awesome, becuase I can define the build just as I would a java ant build, and know that it would work no matter what kind of system you where going to build for.

So is a SDK actually more then libraries? When it comes to mobile development, they seem to be libraries, maybe some tools which integrate into a particular IDE (for example Eclipse) and maybe also an emulator or test tools of some kind. Perhaps also, with an SDK is just a marketing thing - that you expect with an SDK a higher level of support. 

Why am I writing this? Well, I’m currently struggling with the Windows SDK for .Net 3.5 - I’m having massive problems with it and its compatibility with the Visual Studio C# Express. It would be nicer if instead of complex SDK installers (and from my experience, it is the installer which is the problem) they had Library versions or just “unzippable” folders to get the tools out. 

Anyways. Windows SDK and Visual Studio do not like to be installed in that order - Visual Studio first, THEN the Windows SDK (or at least, if you’re using Express editions because you’re an indie development like me)

Uhh.. ok. The biggest problem I have with EAGLE Cad (and I only have the freeware version here - my job lets me use design tools at work, but most of the stuff I talk about on here is actually for home, and I’m trying to finally get some of it online as part of my “open source” roots.) is…

the lack of parts. Too often I come across a custom part that I want to incorperate in my circuit. When I draw my circuits by hand, thats not a problem, but to get these things online, I need to digitise them, and scan’s of my lab book just really arn’t suitable.

This time, I found the need for a particular Triode - the 6S7L - now, before people start asking me questions about Triodes and Valves in general, I don’t know, this is the first time I’ve ever used them and I’m getting quite excited over the prospect. But, Eagle Cad just dosn’t contain the parts for some of these devices, so more and more I’ve been building my own versions.

Because EagleCad is designed to go from a schematic straight to a board layout, I’ve found that I’ve been using the schematics as close as possible, but I really have been just throwing pins at the package file, meaning that if anyone where to convert my schamtics to boards then they will certainly a) be wrong and b) could be quite ammusing.

Anyways, this:

is the current working diagram. Yes I stole it. The book in question actually, “22 Radio and Receiver Projects for the Evil Genius” was a Christmas present, and I’m getting quite annoyed with the number of typing mistakes I’m finding in it. I wouldn’t say its the best book - you have to be a genius (or be good at pretending to be one) to understand some of the bits in it, but forging onwards … high voltage valve radio soon.