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Pimp my board contest

Posted 19th March 2012 at 09:51 PM by rjm (RJM Audio Blog)

I just remembered I hadn't announced it here on the blog. Time to change that.

I'm holding a little contest, to encourage people to get into circuit board design, and to showcase the talent on tap here at diyaudio.

The idea is pretty simple. I hand out a circuit schematic, you design a circuit board based on the schematic. It's all done in Eagle CAD software, which is free to download and available on Mac/Windows/Linux platforms.

The circuit is a headphone amplifier of my design, and fairly simple. It's easy enough to come up with a workable layout, the trick is to come up with a really good one, that is small, convenient, clear, logical, good looking and that follows sound electrical design practice.

Winner will get a pair of boards, complete with all components, built by me. Runners up get sent pairs of the winning board design.

Deadline is the end of the month, so get on it!

All the info is here....
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Old

drawing the line

Posted 17th March 2012 at 11:04 PM by cberger

Finally!
After a century ride in January (
http://www.shadowtour.com/Century_Rides/Stagecoach.htm
)
A trip to Finland in February for training
And numerous other distractions...
I've finally drawn the first lines for my speaker panels. Once it stops raining I can start cutting...!
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ARM's cutest baby now has an even less hungry sister

Posted 16th March 2012 at 02:45 AM by abraxalito

Cortex-M0+ Processor - ARM

Just 11uW/MHz at 90nm so under 1mA current draw when running at 100MHz Freescale says they'll be first to show working silicon but I bet NXP will end up shipping the real volumes.
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Rating: 4 votes, 5.00 average.

Advices for the new SIMetrix/SIMPLIX Intro users.

Posted 4th March 2012 at 05:37 AM by Alain Poitras (The SIMetrix/SIMPLIS Intro Spice Simulator)
Updated 16th March 2012 at 02:36 AM by Alain Poitras

Introduction

I am a steady user of the SIMetrix/SIMPLIS Intro Spice simulator and many peoples ask me how to use it. Because the same questions come back all the times and the answers often need to be quite elaborate and are time consuming, I decided to open a new Blog for this subject.

Since I am a member of this forum, I noticed there was thousands of threads and they often get loss very far from the first page after few days, where almost nobody can see them.

This is not the case with the blogs because there is not many yet on this site, also, it is possible to edit a blog anytime and not a post in a thread after 30 minutes ... This make corrections easy and I am not perfect, I often make some little or big mistakes.

I will not accept other members comments until the blog is almost terminated. Anybody having a request or a comment for me about this blog can send me private message, I will be glad to answer it and update my blog if...
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Old

The end of Moore's law

Posted 26th February 2012 at 04:28 AM by abraxalito

Of late I've been enjoying snacking on this book EDAgraffiti which is a romp through various aspects of the economics of semiconductors. Recommended for those who are interested not just in the technical side of the digital revolution but also the commercial perspective too.

One comment from the book jumped out at me, which was a prediction made by Clayton Christensen a few years ago about the end of Moore's Law. He's reported as saying the following at an engineering conference organised by Cadence. Moore's Law will come to an end when the semiconductor industry tries to deliver more capability than the mainstream requires at a price which is higher than the mainstream wants to pay. 450mm wafer processing technology and EUV lithography pretty much do seem to fit the bill here.

This article on The Inquirer is saying pretty much the same thing - gaming and video transcoding have kept the push for faster PCs alive but even in those applications demand is now...
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Old

B-boards line/headphone buffer stage up and running!

Posted 25th February 2012 at 11:43 PM by rjm (RJM Audio Blog)
Updated 1st March 2012 at 01:29 PM by rjm

The B-board line buffer is back from the fab and running on the bench.

Cute little board. Diamond buffer with BD-135/136 transistors and a built in Z-reg. Designed to buffer the output of op amp circuits to help drive cables and otherwise isolate the op amp feedback loop from the big bad outside world. It can also be used as a unity gain preamplifier, or, with by changing a couple of resistors and adding small heatsinks, to drive headphones.

Development thread here.

UPDATE: Also finished a second set of boards, configured as a headphone driver (5x bias current, heatsinks).
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Old

Which college degree is best in audio systems?

Posted 25th February 2012 at 09:59 AM by renzuken101

I'm confuse what to take up in college, I'm really interested in audio systems what college degree should i take?
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Old

First Watt F5 Amp finished

Posted 19th February 2012 at 11:42 AM by dvb projekt
Updated 16th May 2016 at 01:58 AM by dvb projekt (Hifi-Tuning Supreme 3 fuse photo added)

My F5 is ready to burn in



Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.


The postman delivered today the last small part for perfection...

Click the image to open in full size.

The Hifi-Tuning Supreme 3 fuse


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Old

Voltage regulators and ... something almost as good?

Posted 17th February 2012 at 09:55 PM by rjm (RJM Audio Blog)
Updated 6th March 2012 at 04:21 PM by rjm

A real, honest-to-goodness voltage regulator has three parts: a fixed voltage reference, an error amplifier, and a pass element.

Most people only put eyeballs on the final, all-wrapped-up-in-a-tidy-IC-package version, typified by the LM7812, or with a couple of extra gain-set resistors, the LM317. These chips have a working bandwidth about about 2 kHz, as they are designed to 1) reduce 120 Hz ripple and 2) be rock stable no matter what abuse they are subjected to. As a result at audio frequencies and above they are pretty much noise generators...

Knowing this, many people have set out to build better regulators for audio work.

The most obvious route is to build a high performance LM7812 from discrete components. (Most excellent review here.) AD797 for the error amplifier, high stability, low noise voltage reference, etc. The trick though, is stability. The LM7812 is low bandwidth not because it's too cheap to manage anything better, but because...
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Old

The Not Passive Pre

Posted 16th February 2012 at 06:31 AM by hbc

Had this running for a few weeks now, and the sound coming from the Sonys altogether better, now just a bit bass heavy rather than treble shy. The speakers are mounted right next to the ceiling in the room corners, so not really a surprise.

I have simulated the crossover and equalisation circuit of the preamp section, and realised that I can add a variable resistor to adjust the amount of bass boost the circuit gives, not a horrible mod, just one pot, and a new cap, just need some time to do it.


The not passive pre has no muting circuit in at present, so power sequencing is required. I intend to make it direct coupled at the output. To do this I am planing to do a micro controller servo loop. When I made the Class A digital amplifier, mentioned earlier I used an opamp servo, and I can state that this circuit does definitely have an effect on the sound.


In the interests of minimalism the Not Passive Pre II is already being...
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