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Triton One speaker unveiled at CES

Posted 17th January 2014 at 03:45 AM by abraxalito
Updated 17th January 2014 at 03:57 AM by abraxalito

Just for a change from DACs, here's a speaker which caught my eye.

http://www.avsforum.com/t/1511825/go...ne-at-ces-2014

Now how much of its improved SQ over rivals three or more times the price is going to be down to the active bass section offloading the most PSU-draining signals from the driving poweramp? The comments about the scale of the soundstage do reflect the kinds of improvements I've been getting by reducing LF noise in my DAC, so the reduced LF noise from the poweramp from having a more benign load to drive could indeed be key. 92dB efficiency certainly helps a lot in reducing poweramp PSU stress.

That article says this speaker is 'sure to shake up the industry'. Really? What do you guys think?
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Old

Stereophile's measurements of dCS Vivaldi DAC

Posted 9th January 2014 at 03:59 PM by abraxalito

John Atkinson's 'WOW!' (more than once) to his measurement results from the Vivaldi DAC prompted me to have a closer look at how it does for noise modulation.

The AP's FFTs shown don't come with details about the number of points in the FFTs, so noise estimates are a tiny bit tricky. However there is enough detail to make some reasonable estimates.

I've attached the plot from which I'm making my estimates - if anyone notices I've made a slip-up, please do comment and correct me.

The red line shows white noise at peak level of -4dBfs. I generated white noise in Audacity at this level to compare - with the maximum 16k point FFT and BH windowing, I got the same level of noise as on this plot - -42dBfs in 22kHz bandwidth. That suggests to me that the FFT shown has 64k points.

Another way to estimate the noise is by looking at the difference between the blue plot (19.1kHz, 0dBfs) grass and the red. To my eye, the difference in level is 76dBr...
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Old

Ozone beta-build listening

Posted 8th January 2014 at 06:18 AM by abraxalito
Updated 8th January 2014 at 07:15 AM by abraxalito

I've had the beta build Ozone (no input stage yet, fed from my QA550 via the I2S transcoder to down-convert to 32fs) playing out 24/7 for a few days now.

Overall I'm very happy with how it sounds, just a minor gripe about sibilance on some operatic vocals which I'd like to understand better. On the upside the jump-factor (read dynamics) and soundstage stability (holographic on the right disks) are about the best yet. I'm using a couple of Decca double CDs for this - 'La Traviata' and "La Boheme'. They're about the most transparent sounding and demanding disks I have. Demanding in the sense that they have lots of emotional drama which should positively engage my attention if the DAC's really up to snuff. I never much enjoyed opera until I got into building my own NOS DACs, but now I really enjoy my dramatic fixes and these two recordings are really top of the pile. They're about 50 years old but so far I've not found anything newer which touches them (not that I've looked...
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Old

Ultimate SQ DAC

Posted 27th December 2013 at 07:08 AM by abraxalito
Updated 30th December 2013 at 01:52 AM by abraxalito

Inspired by this thread http://www.diyaudio.com/forums/digit...-new-post.html
I've been giving a little thought for how to move beyond the 'Ozone' to a DAC able to handle more than 16bit inputs and up to 96kHz input rate. The target being 20bits and 120dB SNR (non-A weighted). The OP in that thread preferred a more marketable 'ultimate' DAC (with 192k and potentially 384k capability, along with DSD) - aims which to my way of seeing clearly conflict with a DAC having any pretentions to ultimacy.

The simplest solution - building on the digital part I already have - would be to add more TDA1545As in parallel and with a Cortex M4 direct the data to the respective chips. What's unclear though is how low the noise will go when the extra chips are added. From the DS, an A-weighted SNR is quoted of 101dB (typ) with 2mA, however this is a static noise (code = 0) and hence may well not translate to the noise achieved with bits toggling....
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Old

The coolest Taobao SD card player yet

Posted 10th December 2013 at 04:50 AM by abraxalito
Updated 21st December 2013 at 01:48 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

Next generation active speaker electronics

Posted 3rd December 2013 at 05:12 AM by abraxalito
Updated 18th December 2013 at 02:59 PM by abraxalito

I'd like to be sure that my amp and the passive XOs in my speakers aren't significantly the bottleneck in the sound I'm getting from my DAC prototypes. To get a second reference point I'm starting to build a passive line-level crossover. Here's a pic of it taking shape - its using AD605s because I have plenty to hand and they're cheap and capable of being subjectively transparent with the right power arrangements. The pot core inductors are implementing LR4 XOs in balanced. Using the AD605s with their low input resistance and noise allows manageable inductor sizes for the XO - the largest being 9mH for a 3.5kHz crossover frequency.

Ah - I forgot to mention how I propose to do the transformation from normal (2V) line levels to the 70ohm impedance/20mV paradigm at the AD605 inputs. I shall be winding a pair of ferrite-cored step down transformers with centre-tapped secondaries Lots of turns to look forward to with 0.1mm or perhaps finer wire as I'd like to get at least 5H...
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Old

Analog stage for Ozone DAC

Posted 28th November 2013 at 11:55 PM by abraxalito
Updated 12th December 2013 at 07:53 AM by abraxalito

A few weeks ago I built an almost completely passive analog output stage for my DAC/filter front-end and found it sounded noticeably quieter than my active ones which have been using AD605 and AD8129. The only active component in the experimental stage was a single emitter follower buffer run in classA - voltage amplification was achieved by a much higher than usual I/V resistor and passive filter specially designed for the higher impedance.

The comparison left me rather puzzled as to what was clouding the active stages. It turns out it was inadequate power supply decoupling - the fix is an abundance of ceramic capacitors soldered across the top of the chip.

On the AD605, the feedback resistor in low gain mode is a relatively low 820ohms which presents something of a challenge. Also I'm using an inverting stage following with a similar value input resistor. While the low combined values don"t present any significant challenge to the output stage itself (which...
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Old

TI marches steadily down the road to oblivion

Posted 23rd October 2013 at 01:20 AM by abraxalito

But hey, its stock is 30% up on the year!

http://www.testosteronepit.com/home/...verpriced.html

Wolf is a little bit too polite in his analysis of TI's woes - #1 is crappy strategic thinking.
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Prototype stereo balanced passive filter for Ozone

Posted 14th October 2013 at 07:57 AM by abraxalito
Updated 27th November 2013 at 02:42 AM by abraxalito

Here's my first stab at an affordable yet screened passive filter using off-the-shelf inductors. Its a 17th order quasi-Chebyshev using 8 equal valued series L and 9 shunt caps achieving slightly better than 50dB rejection at 24.1kHz.

Update - this might be the first and last filter I build with these Coilcraft inductors. (If anyone's interested, the part no. is LPS6235-335). Reason being - on trying to order more, the price got hiked more than 100%. Originally these were attractive because on Taobao there was a source selling well below the manufacturer's list, but that seems to have dried up. At the list price in USD, there are other alternatives potentially better value. However none with the same inductance (3.3mH). The key feature is the Q - the Coilcrafts have a Q around 40 at 20kHz - this is very hard to beat in such a small package. As a reference, my pot-core hand-wound inductors have a Q about 160 but they're huge in comparison, so these tiny inductors are actually...
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Old

Introducing the Ozone DAC platform

Posted 9th October 2013 at 12:51 PM by abraxalito

The time has come to talk about the overall aim of my DAC developments - a modular DAC platform for DIYers and audio systems integrators. By this word 'platform' I mean this isn't going to be presented as a single end-to-end design that you can order up from a friendly reseller. Nor is this an 'open source' design, although it is open to anyone to use or adapt with no restrictions. Rather this is a DIYer's DAC architecture a series of interconnected modules that are subsystems from which an audiophile grade DAC can be assembled.

When I say 'audiophile grade' what I mean is this is a design optimized for aural satisfaction, not for the numbers. To be even more specific, its been optimized to give the highest perceived dynamics (within the limitations of the chosen DAC chip) rather than the lowest THD+N and flattest FR. If you're looking for ODAC-type measurements, feel free to move along now That's not to say measurements have been ignored, rather they're very much in the...
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