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Old

Another incredibly cheap Taobao toy

Posted 19th July 2015 at 10:00 AM by abraxalito
Updated 10th August 2015 at 10:44 AM by abraxalito (Listening report added; chip pinout added)

When browsing Taobao I can't resist the temptation to try the very cheap stuff. This little TFcard player really takes the biscuit for the lowest price of a digital audio source - 9.9rmb. So I ordered up three, I might just order more soon.

First powering up I tried some FLAC files, these don't work but wav and mp3 work fine and it even finds files below the root directory. Power supply is nominally 12V but its using an EF fed by a zener diode, not an IC reg so almost anything from 6V will probably work. I haven't managed to find the technical blurb for the chip so far so a little reverse engineering was needed. It incorporates a 3.3V regulator to power the IR receiver and the TFcard - I have fitted an additional regulator for the first mod because I wondered if the low-level noise I was hearing was due to interference from the flash card's power draw. Turns out no as when playing .wav files this noise disappears.

Incidentally the 9.9rmb cost includes the remote...
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Old

Bargain beaut - headphone amp

Posted 2nd June 2015 at 05:44 AM by abraxalito
Updated 9th July 2015 at 09:43 AM by abraxalito

When I found this on Taobao a few days ago I could not believe the price wasn't a mistake, or that it was just for the case with nothing inside. But it turned out to be real, so I ordered one - it arrived just now so I'm taking it apart before having a listen. The case oozes quality and the volume control feels silky smooth.

Here - 莱曼(lehmann) 耳放 莱曼构架的好声耳放,全铝机箱,一体耳放-淘宝网

When I've had a listen (gotta search for my 1/4" adapter) I'll get into modding.... Incidentally for those on 110V, it does have a mains voltage selector switch. Amazing.

I traced out the circuit (still haven't listened) and found its pretty much as shown on the Taobao page. 78/79 15V regulators feed BD139/140s and a TL072 sits between the volume pot and the discrete OPS. This stage resembles a diamond, but instead of the more familiar current sources to the rails, it has 1500ohm resistors. LTSpicing this arrangement (schematic shown) reveals its...
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Old

New .wav player from Aune looks very interesting

Posted 11th November 2014 at 01:26 AM by abraxalito
Updated 15th November 2014 at 09:27 AM by abraxalito

Thanks to jambul for alerting me to this one - 赵宇为作品 - Aune M1 便携式播放器测评报告 [Soomal·数码多] (link is in Chinese but its mainly for the pics).

Notice that although its using the PCM1793 chip the D/A and analog circuits are all on a daughter board. This gives rise to the possibility of engineering a daughter board with a much better DAC chip (think TDA1387) and improved head-amp...

Street price here is around 800rmb (80, $130) so I shall be ordering one to have a play.

Update - looks like I'm rather slow to catch on, Taobao already has somebody's alternative DAC-AMP card, which appears to be selling fairly well, here : http://item.taobao.com/item.htm?spm=...cket=13#detail

I've now placed the order for the M1, hopefully it'll arrive tomorrow and then I'll follow Dave (EEVBlog)'s advice : 'don't turn it on, take it apart'. The main question I want an answer to is how...
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Old

The coolest Taobao SD card player yet

Posted 10th December 2013 at 03:50 AM by abraxalito
Updated 21st December 2013 at 12:48 PM by abraxalito

This one rocks - it plays FLAC, WAV and mp3s. The DAC is WM8740 (not so hot) but the designer has taken the power supply very seriously. Just check out all those caps and TDK noise filter on the PCB on the right Power comes from a lithium battery behind, so its portable but there's no case - there are acrylic front and rear panels screwed on to the PCB spacers. Two 3.5mm jacks provide headphone and line out.

Its using STM32F407 to do the decoding which is a first for ARM in this sphere and the design is configured that there's an I2S link between the two PCBs. So in theory anyone could design a better sounding DAC and replace that bottom PCB whilst keeping the UI. Which I may just do.... Price is 568rmb (just under $100).

Update - I was a little curious about the PSU so I've pulled out all of those SMT 220uF caps to get a closer look. The block filter's a Murata (not TDK) BNX024 which looks like a wrong choice of part primarily because its rated for 15A. Hence...
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Old

NXP's innovation in smart phone sound - any implication for the high-end?

Posted 2nd August 2012 at 05:13 AM by abraxalito

EET seems to be on a run of interesting articles of late - and here's the latest, about NXP's latest digital amp for smartphone speakers:

Achieving loud, rich sound from micro speakers

So yeah, smartphones are a long way from the high-end you say, so why talk about this at all? Well one sentence at the end caused me to pause and wonder how long before this kind of technology gets used where sound quality (rather than quantity) is paramount. I quote:

This leap in performance illustrates an important design trend. The days of stand-alone amplifiers and converters designed in isolation have gone.

The writer has put his finger on a major reason why the high-end of audio is a relatively stagnant pool for innovation. Pretty much everything's designed in isolation - players, amps, speakers. What if those days really are coming to an end, not just in smartphones but in quality audio too? Smartphones have the volume so there's economic...
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Old

New mobile phone

Posted 6th July 2011 at 05:50 AM by abraxalito
Updated 8th September 2011 at 03:08 AM by abraxalito

My trusty HTC Touch Pro2 kept dialling my last caller last week without my permission so I decided it was overdue for retirement. Can't say as I've ever really bonded with this phone - mainly due to the pants Windows Mobile 6.1.

Last Sunday I went into the Meizu shop and snapped up their M9 to replace it with. This is the first phone (out of 8 I think) I have bought based primarily on the OS (Android) rather than the hardware. That's evidence for the disruptive marketing behaviour of Google in the mobile space. Android wasn't quite available when I upgraded to the HTC around 2 years ago. Now they're claiming around 0.5million activations each day.

One interesting facility in the network menu settings is:

3G networks - turn off to save battery life and stabilize signal

I'd heard that running 3G soaked up juice but this 'stabilize signal' is a first on me. Its quite something when a new technology has the facility to disable it...
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Old

How low can you go in active speakers?

Posted 11th December 2010 at 11:54 PM by abraxalito
Updated 5th March 2012 at 02:57 AM by abraxalito

On one of my regular pilgrimages to the computer plaza a couple of days ago, I noticed these little puppies. The price apparently was a shade over $80 the pair so I was indeed very curious. A quick peek around the back showed they were not using a standard speaker cable, rather a custom 4-way umbilical between the two boxes. Whenever I see this, my heart misses a beat because what floats my boat is genuine active speakers, not just powered ones which still sport passive crossovers.

Click the image to open in full size.

Not wishing to ask to disassemble the powered unit on the spot (and doubtless be turned down) I went back home to do some online research. I was pleased to discover these were indeed true actives, and what's more they're powered by TDA8947 chip amps. I'd not come across this part before but its cool at least on paper because its 4 channels in one package - they're using two...
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Old

New scope...

Posted 2nd June 2010 at 04:59 AM by abraxalito
Updated 5th March 2012 at 02:52 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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