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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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HEC part II

Posted 17th June 2010 at 05:07 AM by abraxalito
Updated 8th September 2011 at 03:04 AM by abraxalito

Here's a pic of the underside of the DAC before I started hacking tracks. Bottom left area is where the digital circuits are, with ground plane. Top left are the analogue output filters. Right is the caps, rectifiers and regs of the power supplies - digital at the bottom and analogue at the top.

The AD1955 sits about the centre of this pic, and if you look closely you'll notice two small holes I drilled in the groundplane either side of it where I will later install the 10uF decouplers.

The second pic shows the component side, prior to any hacks - the 'virgin board' if you like, although sullied by the two small holes near the DAC chip. The analog supply is pin15, that's at top left.

Third, here's the meat of the digital circuitry and I've already added one decoupler to the AVDD (analogue positive supply). To the right of the 24.576 XTAL (not required) is the DIR9001 SPDIF receiver. The DIL chip is a multiplexer allowing both USB and SPDIF input...
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Towards a better DAC - introducing the HEC

Posted 14th June 2010 at 04:16 AM by abraxalito
Updated 8th September 2011 at 03:05 AM by abraxalito

Doug Self's comprehensive work on power amplifiers has been an inspiration to me over a number of years. In it, he coined the notion of the 'blameless amp' as one which was beyond reproach, measurements-wise. So I pondered over running with the notion of 'blameless DAC' along the same lines. Initially this sounded attractive, even though not entirely original. Google found a reference to it already here on diyaudio but could not show me the actual posting.

I decided on reflection that the 'blameless DAC' would be not such a good idea. That's partly because for me, measurements are not the goal of audio design. Enjoyable sound is what does it for me, not vanishingly low THD figures. So a 'blameless DAC' could only be blameless if measurements are God, so to speak. For someone like me for whom auditory experience is all, I decided I'd need another term for my DAC project.

I've settled instead on the term 'highly evolved converter' or HEC for short. This recognises...
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New scope...

Posted 2nd June 2010 at 04:59 AM by abraxalito
Updated 5th March 2012 at 03:52 AM by abraxalito

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Bought this (well not quite this one, mine has Chinese text on the panel) little puppy yesterday as my old UNI-T was just getting too frustrating to use. In particular its triggering ability is almost useless, giving way too much jitter. That added to the trig level encoder being majorly unreliable (its just over a year old) and lots of apparently self-induced noise on the trace meant I decided to bite the bullet. And boy I'm glad I did - its like getting a new pair of HD800s to replace my aged Sony CD3000s, everything is much clearer.... (and no, I haven't made that particular upgrade yet).

About six months ago I first noticed the younger sibling of this scope in a shop window in the local electronics market. I was blown away - a widescreen scope? That screen was drop dead gorgeous! This pic really doesn't do it justice so hopefully I'll post up one of my own pics soon.

Having been immediately...
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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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