My brother was complaining about his vocals not coming through clearly in his (rather modest / amateur) band. It turned out that he was trying to use some old hifi speakers we had as kids!!!

I had a bunch of Beyma 12G125 bass drivers and some P.Audio PA-D26 compression drivers, so offered to throw some proper speakers together for him.

There were a couple of illustrations of design principles in here that are worth reiterating:
- The horn driver has a massive (and by this I mean both acoustically and electrically) resonant peakj just below 2KHz.

To use this driver and avoid horrible the resultant upper midrange peak, it is essental to put a trap on the tweeter to flatten out the impedance.

this at least gives the crossover a hope of working...

- The horn driver still has a big fat peak at 2KHz.

- The horn was CD - and needed compensation to bring the top end up to "flat".
...

The topic of JFET and MOSFET matching comes up often in the forums, so I thought I'd show you the jigs I use.

First up, is my trusty old JFET IDSS matcher.



There's a 9V battery inside, and the meter probes are conneted across a 10 Ohm resistor which is connected to the JFET drain. I included a polarity switch for convenience when testing P channel parts.

It's pretty easy to connect the microclips, count to five, and take a reading.



And here's what I use for the big stuff. This is my MOSFET Vgs matcher.



First, I install a sample part and let it warm up for about an hour. There's a thermistor hot-glued to the heat sink,...

Haven't had a chance to update last two months.. the a10 preamp was completed with a little help from my dad and is now integral part of my setup. I even put my Linn magik up for sale.. it's that good.

Last month I started to gather the parts for the objective2 headphone amp. I got about 50-100 units worth of PCB and parts. I will start to package them as kits and sell some assembled. It will be my first try at selling here.

Last two weeks I finish building and rebuilding my Ck2iii headphone amp. The initial build was with an outboard power supply and headphone amp. The cost was running a little high since I build it using momentary switch, etc..

Then I rebuild it two days back into a single enclosure with a switch at the IEC instead. Cut cost down a lot since I no longer have to deal with umbilical cord, etc

-joe

Re-purposed my HiVi M6A into these ZX Spectrums designed by Paul Carmody. They're a groovy little speaker with this crossover and the B&G Neo3 PDR which I am absolutely in love with now.

I hate facebook but I'm willing to give Google+ a go. Now they have "product" pages as well as "people" pages, I have made a little port to RJM Audio.

RJM Audio Google+ page

http://garysmitheda.com/paper/ARM-Techon-note.pdf

Its a single page review of ARM Techcon. At the end I think he means 'PC design' not 'PCB design' as he's written.

He says:

If Intel doesn’t do something soon this might not be much of a war.

He knows some guys at Intel read his analysis so I think he's sugaring the pill. Intel is rather like the hare in the old fable of the tortoise and the hare. The hare woke up and tried to catch up with the tortoise but it was too late. That's exactly where Intel is right now - they've become awake to the issue but they've missed the boat.

http://www.diyaudio.com/forums/wild-...eld-coils.html

I had hoped that this might happen some day.
I will be watching this