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Active elliptic - practical implementation

Posted 20th April 2013 at 09:33 AM by abraxalito

Here's the first channel under construction on 2mm pitch double-sided proto board. The opamps in this instance are AD8014 in SOT23-5 packages, hence the choice of the 2mm pitch board. Power supplies will go on another board to be attached to the reverse side.
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What is dynamics?

Posted 5th March 2013 at 03:02 AM by abraxalito
Updated 11th March 2013 at 06:35 AM by abraxalito

Fascinating discussion going on about the nature of 'dynamics' over on this thread : https://www.diyaudio.com/forums/multi...nger-what.html

Pano writes (post 1174):

There is a consistency across several decades and cultures that high efficiency speakers sound more dynamic than low efficiency. That's a common subjective assessment, so we might ask "why?"

I'm not going to chip in on that thread because I have bigger fish to fry, but ISTM they're all barking up the wrong tree. That's because the question itself isn't quite posed correctly even though its a great start. Nobody listens to speakers alone, they're always powered by amplifiers. The answer to dynamics lies in amplifiers, not speakers. Put another way 'Its the electronics, stupid!'.

Higher efficiency speakers tax amplifiers (here meaning their power supplies in the main) much less - so there's no way to do an apples-apples comparison...
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Nvidia wants a divorce from TSMC?

Posted 18th July 2012 at 03:08 AM by abraxalito

This article is a fascinating peep behind the curtain of the current economics of semiconductor production through the eyes of a major IP player - Nvidia. More evidence that Moore's Law is grinding to a screeching halt I suggest.

Nvidia deeply unhappy with TSMC, claims 20nm essentially worthless | ExtremeTech
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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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New scope - update

Posted 25th November 2010 at 02:36 AM by abraxalito

The Tekway is still working well and survived the 35oC temperatures of Hangzhou's summer despite having no internal fan. That is, apart from its CMOS store of the date/time, which for some reason now thinks the year is 2011.

Someone on the EEVBlog just posted this - I haven't read it thoroughly yet but I intend to find out if I can upgrade to 200MHz. Looks promising

Upgrading DST1102B to 200MHz bandwidth
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How low can you go? - part II

Posted 31st August 2010 at 03:34 AM by abraxalito
Updated 1st September 2010 at 04:23 AM by abraxalito

Here are the schematics - the original output stage and the modified one.

On the first player I bought, I did all those mods in one hit. The third pic shows what they looked like - I took out some of the redundant connectors (guessing the same board is used in players which have more features like component video outputs) to make space for the electrolytics. Having replaced the board (just two screws, one on the rear and another in the base), then I listened. The improvement in bass performance brought about by increasing the value of the coupling caps was noticeable in listening - the cello became more full-bodied - and also on a frequency response plot I made using Audacity. I felt (but can't quite describe) that the soundstaging has improved - music feels more interesting to listen to somehow. I week or so later, I went out and bought a second one (at 99RMB, who's counting?) to remind myself of the original sound. On listening for the first time to a CD I'd just bought...
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How low can you go?

Posted 26th July 2010 at 06:46 AM by abraxalito
Updated 31st August 2010 at 04:28 AM by abraxalito

The prices of DVD players just keep on going down here. Yesterday I bought my very first 99RMB [that's under $15] model in Carrefour. I couldn't wait to get home to see how it sounded.

First up I listened to one of my favourite BIS recordings - Mozart 40 in a version for piano, flute and strings. The sound really wasn't as bad as I'd expected - the cello sounded really 'reedy' rather than full-bodied and the flute was akin to a sopranino recorder in its higher register with very little bloom. But there was a fair approximation to a soundstage and really quite decent dynamics, not at all 'bitstream'.

Rebecca Pidgeon's 'Spanish Harlem' is the test disc I use to check for sibilance (it has lots of 's' sounds), and sure enough there was some but definitely not terrible considering the price.

This undoubtedly had potential for the price - I wondered if it could be improved. Inside almost all the functions are integrated on the MediaTek chip (although it...
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Tweaking electronics sound quality in active speakers

Posted 24th May 2010 at 12:39 PM by abraxalito
Updated 25th May 2010 at 04:24 AM by abraxalito

My main listening system has been based on Fayou XPE active speakers for over six months now. I bought my first pair of Fayou speakers a year earlier than that, the lower-spec'd B2 models. The B2s are now my main PC speakers, connected to an Asus Essence ST. After getting the B2s, it was only a matter of hours before I had them open, poring over the implementation details. I noticed that the grounding to tweeter and bass/mid was shared so sliced into the board to give each unit its own dedicated ground path. I also tweaked the high current paths to the main PSU caps to ensure no impedances in common with the audio signal grounds. After these mods, the sound was highly enjoyable.

When I first heard the XPEs I considered them not to be quite as good sounding as my (tweaked) B2s, but given their superior amplification and bass/mid driver, figured they were ripe for hot-rodding. Their construction also suits tweaking much better as all the electronics is easily accessible on the...
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