Over at his site Krzysztof Marcinek has a simple little project that should be of interest to anyone who is thinking about amplifier construction.   He has built an elegant and useful little tool.

A passive load is pretty much just a pair of resistors that emulate the impedance of a set of speakers.  They give you the benefit of being able to test an amplifier without fear of destroying or damaging your precious speakers. 

Because these passive loads are designed to take amplifier output sized voltages and current, the resistors have to be pretty hardy to avoid burning up.  Personally I use resistors with large aluminium clad resistors to load test my projects. 

My analogue scope is able to withstand large voltages, but Krzysztof is using a computer soundcard to conduct measurements.  In his design he includes a low voltage output by using a stereo variable resistor to divide the voltage from his test amplifier. 

What’s very impressive is the construction that Krzysztof has applied to what is for most a common tool. (my passive load is simply a CPU heat-sink with the resistors tie wrapped to it!).  Check out his site for more information…

DIY, audio, electronics...

  Over at IEEE spectrum Brian Santo has an article about the silicon that has a massive impact on the electronics world.  Its an interesting article that I am afraid makes me feel old.  Born in the 70’s, I am very much a child of the digital generation. 

It’s fair to say that the innovation that I have experienced in my relatively short life has been dramatic.  I can think back to a time before push button telephones, answer-machines, mobile phones, portable music players, the boombox, streamed audio, internet access and a whole host of other “Tomorrows World never warned us about that” inventions

On the Audio front, Brian identifies several IC’s as being important:

• Fairchild Semiconductor μA741 Op-Amp (1968)
• Micronas Semiconductor MAS3507 MP3 Decoder (1997)
• Tripath Technology TA2020 Audio Amplifier (1998)

I think that the list has a major omission.  Whilst an MP3 decoder makes it into the 25, I think a more key invention is the Digital to analogue converter.  MP3 is one thing, but would we have ever got to this point in the history of digital media without the humble CD.  Should a Wolfson, AKM or Philips Dac chip not be in this list?

I think if we were to compile an audio only list I can think of a few more classic Microchips that would would be vying for space in the top 25.  Which would you put in there?

IEEE Spectrum: 25 Microchips That Shook the World

Brian over at Chipamp.com left this message on his site,

“ I have put up a new special, 20% off all kits. I will keep this special up until the end of the month.”

Chip amps are fairly simple circuits and can be made without a PCB with little to no experience of electronics building, however some prefer to stick to a kit for their first build.  Advantages are that you get to hear a tried and tested design.  This can serve as a benchmark for your next project

If you are thinking about dabbling in creating your own Gainclone type amplifier, a kit certainly makes things a little easier.

Brian has kits based on the lm3886 and lm1875 amplifier chips made by the daddy of integrated amplifier chips, National Semiconductor.  Now all you need is a good power transformer and a couple of reduced price kits….

DIY Chip Amplifier Kits, PCB's, Components and Information.

Gainphile is working very hard just now, It does not seem that long since I blogged about his Open baffle floor standing speakers and here we are again looking at beautiful set of Bookshelves.

For the uninitiated, open baffle loudspeakers offer a different way of reproducing sound and they have some very dedicated fans amongst home builders.  Instead of using a box to help in the reproduction of the music with all the design problems that creates, Flat boards are used as baffles. 

This of course has its own design issues, the speaker cones are no longer damped by the air pressure in an enclosure and drivers have to be chosen that are suited to this use.  Gainphile chose Seas L21RNXP & Tang Band W3-1346s for this set of speakers. 

His blog details his listening impressions.. 

Gainphile: S11 OB - Bookshelf open baffle with Seas 8" and Tangband Full-range

I am ashamed to admit it, but I have a DAC project that fell by the wayside a few months ago.  It is the γ1 miniature DAC.  I got so far with the build but hit an unknown problem with the usb receiver section.  I must get back to it when I get my new DSO Nano Oscilloscope and try and sort out the problem. 

Just to add to my shame AMB Laboratories has added a new kit to their repertoire, The γ2 Compact High Performance DAC.  Well to call it new is not exactly right, it is actually an expansion of the γ1 design.  So there is another good reason why I need to debug my stalled project. 

So what does it do?

If you have ever tried to design your own PCBs using a Computer Aided Design package, it is a good bet to say you tried out Eagle.  Ok there are other packages around (In fact Eagle is not my favourite), but Eagle as always been popular with hobbyists due to its freeware version and good quality feature set.  

Well today Premier Farnell, Electronics Components Supply Giant (Owner of Newark) announced that it has bought Cadsoft, developers of Eagle in a multi-million pound acquisition.  

In a press statement Farnell said:

"We are excited by the opportunity this acquisition affords us to attract new design engineering customers as we offer them access to industry leading software and our outstanding range of products and support. The EAGLE software will enable us to facilitate design exchange between engineers through element14, our design community, which when combined with our leading edge transactional websites
offers customers a complete online solution to their purchasing and design needs".

I am sure that there will be many hobbyists that will be watching closely to see what Farnell is going to do with the hobbyists favourite CAD software.  Hopefully this investment will see Eagle continue to thrive and continue to offer free-ware versions.  It would be very nice if they can add a quick purchase option to a completed design. 

On the other hand, there are other packages out there, I personally prefer Diptrace, again available in freeware.  I find it an easier package. 

Premier Farnell - Press Releases

On one of my regular late night forages I came across this project via Hackaday.  It’s builder Niclas has used an existing design to create a headphone amplifier based on the EL84 tube.  Finding casework for projects can be expensive.  To top it all, most cases around this size are either pretty ugly or fairly generic in design.  Personally my preference is to the aluminium Hammond enclosures.  For instance I used two in my DDDAC1543 build.

Niclas instead went for a PC power supply, now how many of them are discarded every year, I just threw out several on a recent cupboard clearout.  I also use one as a test power supply, the internals replaced with a toroid and a rectifier circuit.  He prettied it up with a wooden fascia and has something passable and unique at the same time design wise. 

Surprisingly Niclas opted to contain the valves within the case, most builders prefer to show off their glassware. 

You can see more pictures on his blog…

My Crazy Technology: Röhrenverstärker