Intel's just held their 2011 investor conference. I'm not an Intel investor but after that performance if I were, I'd have sold out by now.

Welcome to the wonderful world of ARM guys!

If you want to get down and dirty, here are a couple of articles to get you started. Be sure to check out the comments!

Updated: Intel rewrites Atom road map

AnandTech - Intel?s 2011 Investor Meeting - Intel?s Architecture Group: 14nm Airmont Atom In 2014

If you'd like an illustration remarkably parallel to Intel's style of groupthink, go here:

Wake-up call | World news | The Guardian

Where is all this going I hear you ask? What's his point? Well to tell the truth I don't hear anyone asking this - the comments sections are remarkably empty save for jkeny egging me on

So here's my point, and its a single word: convergence. Convergence is coming to digital architectures - indeed its already here, just the majority of people have yet to notice.

The diverse marketplace for embedded processors is rather similar to the market for home computers in the early to mid-1980s. It was hard to make the choice - Acorn, Sinclair, Apple, Commodore, Atari, Amstrad, Dragon? Then convergence arrived in the shape of the IBM PC and those brands (with the exception of Apple) were relegated to the history books.

It took quite a while after the 1983 arrival of the PC for this to occur. I had an Acorn Atom which I built from a kit in the long summer vacation after I graduated, and I didn't make the jump into PC-land until the early 1990s. It wasn't...

Apart from an architecture which is attractive to program in, I also have several other demands on the checklist for the digital toys I'm going to pin my colours to. Ease of entry into the game and low cost development tools are a must.

Arduino is a phenomenon I did a little research into. Its become jolly popular over the past six years or so since its inception and I wanted to understand some of the reasons for its acceptance. One of the reasons has to be its open source nature. Another is the well written materials to get you going - they've put quite a lot of thought into the practical issues, even inventing their own vocabulary for elements in the process - 'sketches' springs to mind. If there's a weakness in what they're doing its this - its tied to Atmel as they're the vendors of the chips used. There are no second sources of the parts to my knowledge. This vendor-specific approach doesn't sit at all well with the open-source side - Atmel's architecture is unique...

When I began writing real-time code for the 68k, the price of entry into the development game was rather high. My first project was a tachometer processor which my boss was applying on a patent for: US patent 4924420. In order to develop this we purchased a hardware emulator which became my pride and joy - it cost a sum equivalent to around two months of my salary at that time. This was a considerably more expensive solution than the other commonly used development technique in those days - EPROM emulators - it did though provide a much faster development path by virtue of providing a window into the interior of the CPU as well as a history in its trace buffer of everything it had done. During the course of this and subsequent projects which also used the 68k (later we added a 68020 too) I became a confirmed devotee of the architecture. One of my nicknames in the company was 'the cycle stealer' - if someone had some 68k code that wasn't running fast enough, I'd find some way to get it...

My first brush with a micro as programmer was as a schoolboy - my maths teacher had a National Semiconductor SC/MP board with LEDs and toggle switches. It could be programmed in binary. I was hooked.

About a year later Science of Cambridge came out with adverts for their Mk14, using the same SC/MP. This though had a real hex keyboard and calculator style 8 digit 7 segment display. I ordered one almost immediately I saw the ad. Trouble is, it seemed to take an age to come. Someone joked that Clive Sinclair's approach was to gather up the cheques and when he'd got a few thousand pay someone to do the design! I dialled SoC's number so many times chasing my order that its still engrained in my memory over 30 years later: 0223 311488.

When I got to uni, it was clear my room-mate was in a league above me - he'd designed a system with a Z80. That was a real man's processor, compared to my little boy SC/MP. I felt a tad threatened by his prowess. Science of Cambridge...

The 1.8mm iron wire arrived and it did indeed have a 1.2mm internal diameter which is perfect for winding small chokes. I built a second box with steel chokes in but the third box I tried with the iron wire coils. Having insulated wire means the coils are smaller and I was able to fit the second tier filter into the same box.

I wound a couple of NiZn toroids with iron wire, but not as common mode chokes. When I did the sums I found that for the currents I'm running at (under 3A total draw) the toroidal core isn't close to saturation. Hence I decided on separate inductors to gain some differential mode filtering on top of the common mode.

The next stage of development has been trying to wind multilayer iron wire air-cored chokes. For this I've had trouble finding formers which allow more than 4 layers. The reason for wanting more layers is - this makes the chokes much more lossy. Proximity effect helps concentrate the higher frequency currents only in areas...

OK, slight change of plan. Due to a ****-up on the ordering front with the iron wire, I ended up with some wire which is a bit too thin (0.5mm inner diameter) as they specified the outer diameter on the ordering page, rather than the conductor diameter. On reflection of course, that makes perfect sense since this isn't wire for electrical purposes at all, what use is the 'conductor' diameter? Wire with an external diameter of 1.8mm's on its way, which I hope will have ~1.2mm diameter conductor.

So, in the meantime I've been experimenting with wire I have been able to get hold of, which is shiny steel. It turns out that only 30 paces from my home is a hardware store which sells it - so I've tried winding chokes with it, just to see what happens. I've also acquired an LCR meter to see what kinds of values I'm getting at different measuring frequencies.

The first pair of chokes I wound with some really thick stuff - 2.8mm. Having aimed for 20 turns...

I've been actively researching via Google on this project since the last posting and found out a few interesting things which I'll share here.

Firstly I checked out piano wire as the material for making the L1 & L2 input side chokes in my original schematic. I couldn't find any consistent figure for what the permeability of piano wire is - it seems steel comes in so many variants that its hard to tell. So I continued to look for alternative materials which have reasonably high permeability. Remember, its the high permeability which gives rise to skinny skin depths and hence higher losses as the frequency climbs. Normally this is really undesirable, but for our purposes its exactly what we're looking for.

Other elements which have high permeability include nickel, cobalt and iron. Nickel wire is available, but its expensive and not widely sourced. Cobalt is even more expensive with even fewer sources. Iron is the cheapest option and it turns out that iron...

Since Ostripper asked about mains filtration on the RF & Audio thread, here are some notes and ideas. I haven't built any of this yet - if you decide to, I'll be interested in any results - photos and listening reports. Be careful with this stuff, its at mains potential.

Pre-built mains filters are of some use in audio, but they're not really optimised for high-end sound. For audio source components, the draw is normally under 100W and so the current (assuming here 230V supply) is under half an amp. Few if any off the shelf mains filters are designed for such low currents.

Second, the commercial filters assume that we wish to stop conducted interference getting out as much as prevent muck getting in. The internal noise would normally only come from the rectifiers in a linear power supply (SMPSUs are a totally different matter). Once we've snubbed them (you have done that already right, or are using soft-recovery or schottky diodes?), with a linear...

Before describing the changes brought about by the mods I've described, here's a summary of what they've been:

• Crossover tweaked to flatten the lower end bass hump and knit the handover to the tweeter more tightly
  
• Power amp sensitivity reduced to allow the volume control operate closer to maximum with my Asus soundcard or a standard CD player output.
  
• Rectifier snubbers and additional filtering to the regulators fitted to reduce RF ingress on the power supplies.
  
• Power amp supply decoupling improved at both LF and HF.
  
• Signal grounds are now separate from power grounds and a star point established on the amp PCB. A ground loop between the two PCBs has been eliminated. The input signal ground is no longer connected to the tone control PCB ground - instead given its own dedicated wire to the star. Decoupling to ground on the tone control PCB has been removed.

Listening impressions

OK, so on to the part that you've been...