diyAudio - DAC design and development
Go Back   Home > Forums > Blogs > abraxalito

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
DAC design and development Digital delights - getting the most from your DAC chips.

First transportable Ozone incarnation

Posted 27th April 2014 at 03:48 PM by abraxalito
Updated 28th April 2014 at 06:33 AM by abraxalito

I took this to the park this morning, it survived the journey in my backpack but it exposed a dodgy RCA connector. The case I used (temporarily) for it is a cylindrical tea carton - the red 'tower' behind. Battery power comes from 3 NiMH AA cells giving around 10hrs of listening.

I've just done a mental estimate of the BOM cost of this DAC (labour cost is way dominant, but this is DIY right?) and it turns out to be dominated by the cost of the caps in the top three tiers (the small black ones). These are real Japanese Rubycons, chosen for their diminutive height (16mm) vs the Chinese ones at 25mm height. So if you didn't mind adding 3cm to the overall neight you could build this with all Chinese caps and save a few dollars. As it is the total parts cost is under $30 including batteries. If you wanted S/PDIF input (currently its I2S) you'd add a couple more $.
Attached Thumbnails
Click image for larger version

Name:	towerofsong.JPG
Views:	407
Size:	523.6 KB
ID:	1283  
abraxalito's Avatar
diyAudio Member
Views 674 Comments 13 abraxalito is offline

Ozone Chebyshev filter

Posted 18th April 2014 at 03:39 AM by abraxalito

I've munged the earlier 8 inductor filters down to only 5 - this one is using off-the-shelf TDK inductors, SLF7045-681, albeit they need to be hand-selected to get the correct values as the production tolerance is 20%. X7R caps sound just fine, surprisingly

FR is -3dB at 17,8kHz with around 0.25dB of passband ripple.
Attached Thumbnails
Click image for larger version

Name:	Ozone 5th filter.png
Views:	335
Size:	9.6 KB
ID:	1270  
abraxalito's Avatar
diyAudio Member
Views 672 Comments 0 abraxalito is offline

Hexacap-based Ozone DAC

Posted 20th March 2014 at 04:18 AM by abraxalito
Updated 31st March 2014 at 02:07 AM by abraxalito

Here's my current bench lash-up DAC based on three hexacaps. Total capacitance of the order of 1.3F.

32fs EIAJ is fed in, balanced, from the left, the central hexacap feeds two TDA1545ATs. Filters are TDK inductor based, six stage balanced with X7R caps (gasp!). Caps in the centre provide the mid-rail power (2.5V) which the I/V resistors are fed from. The two hexacaps on the right power the post amps based on AD815ARBs, gain set roughly to 26dB with a little NOS droop correction. They're the postage-stamp sized boards roughly in the middle. Output is differential and fed to ferrite-cored transformers to convert to SE.

I'm blown away by the dynamics of this, given the right recording. Next up is an amp based on paralleling 8 or 10 AD815s. Each fed from its own hexacap, of course....

Update1 - the DAC supply has now been upgraded to two tiers of the 4700uFs, interconnected by six 1.5mm diameter solid copper wires. Capacitive reactance measures 2.5mohm...
Attached Thumbnails
Click image for larger version

Name:	P1010092.JPG
Views:	631
Size:	713.7 KB
ID:	1260  
abraxalito's Avatar
diyAudio Member
Views 896 Comments 16 abraxalito is offline

Adventures in low impedance power supplies

Posted 10th March 2014 at 09:01 AM by abraxalito
Updated 17th May 2014 at 04:52 AM by abraxalito

Here's my latest crazy project, intended to answer the question 'How low can you go?' in power supply impedance. No listening tests yet, I've just finished assembling this stack of hexagon capacitor arrays out of cheap electrolytics. Total capacitance of the top 4 tiers is comfortably above 1F. The top tier is designed for lowest ESR at HF using Nichicon 1500uFs, the next tier is a trade between ESR and uF. The last two are the highest capacitance density I could find (a total of 182 4700uFs). I've yet to connect the bottom two hexagons to the upper tiers but the top two are connected by wires running through the gaps between caps.

The whole is intended to push the limits of low frequency noise in powering a couple of TDA1545s which will sit on a small PCB supported on thick wires from the centre of the top tier. I am aiming to get a capacitive reactance (at 50Hz) at the DAC supply pins below 3mohm and ESR below 1.5mohm.

Update1 : connected the bottom two tiers...
Attached Thumbnails
Click image for larger version

Name:	wedding-cake.JPG
Views:	493
Size:	691.1 KB
ID:	1253   Click image for larger version

Name:	OST4700uF.jpg
Views:	190
Size:	171.7 KB
ID:	1254   Click image for larger version

Name:	5captier.JPG
Views:	323
Size:	673.4 KB
ID:	1255  
abraxalito's Avatar
diyAudio Member
Views 952 Comments 4 abraxalito is offline

Next generation Ozone analog stage - 'free radical'

Posted 25th January 2014 at 02:28 AM by abraxalito
Updated 6th February 2014 at 04:49 AM by abraxalito

Last night I finished building the second channel of my dual mono approach to DAC building which I've called 'free radical'. Here's a picture of the second channel's build just prior to adding all the crapacitors (cheap shanzai 'Sanyos' which measure extremely well). While building the second channel I was listening to the first in mono and that was a spur to quick completion

From left to right there's the AD605 with its top hat array of MLCCs - outputs are isolated via ferrite bead chokes from the AD8017 under its own pile of SMT ceramics. In between the two active stages are the capacitors associated with power supply reference voltage filtering. I realized from the previous build that as the AD605's gain is controlled by DC voltages, these voltages need to be low noise to ensure gain stability. Hence lots of RC filtering with those Nichicon and Rubycon low ESR lytics. I'm using BC817 transistors as low drop-out regulators and the reference voltages (2.5 and 5.7V) come...
Attached Thumbnails
Click image for larger version

Name:	free radical.JPG
Views:	353
Size:	672.2 KB
ID:	1229  
abraxalito's Avatar
diyAudio Member
Views 813 Comments 7 abraxalito is offline

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...
Attached Thumbnails
Click image for larger version

Name:	P1010081.JPG
Views:	226
Size:	261.7 KB
ID:	1208   Click image for larger version

Name:	AD605-internal.png
Views:	260
Size:	47.8 KB
ID:	1209  
abraxalito's Avatar
diyAudio Member
Views 699 Comments 6 abraxalito is offline

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
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....
abraxalito's Avatar
diyAudio Member
Views 925 Comments 2 abraxalito is offline

The coolest Taobao SD card player yet - now further improved

Posted 10th December 2013 at 04:50 AM by abraxalito
Updated 21st September 2015 at 04:23 AM 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...
Attached Thumbnails
Click image for larger version

Name:	P6050075.JPG
Views:	486
Size:	66.8 KB
ID:	1176   Click image for larger version

Name:	P6050076.JPG
Views:	481
Size:	79.9 KB
ID:	1177   Click image for larger version

Name:	P1010080.JPG
Views:	348
Size:	79.2 KB
ID:	1193   Click image for larger version

Name:	zshanmini.jpg
Views:	13
Size:	130.4 KB
ID:	1717   Click image for larger version

Name:	flacplayer-item_pic.jpg
Views:	22
Size:	395.1 KB
ID:	1718  

abraxalito's Avatar
diyAudio Member
Views 1375 Comments 17 abraxalito is offline

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...
abraxalito's Avatar
diyAudio Member
Views 723 Comments 6 abraxalito is offline

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...
Attached Thumbnails
Click image for larger version

Name:	stereo_TL-filt.png
Views:	365
Size:	532.5 KB
ID:	1155   Click image for larger version

Name:	P4270069.JPG
Views:	249
Size:	77.9 KB
ID:	1157   Click image for larger version

Name:	third-gen-filt.JPG
Views:	349
Size:	79.5 KB
ID:	1169   Click image for larger version

Name:	P5220072.JPG
Views:	176
Size:	76.4 KB
ID:	1172  
abraxalito's Avatar
diyAudio Member
Views 1153 Comments 17 abraxalito is offline
Hide this!Advertise here!

New To Site? Need Help?

All times are GMT. The time now is 09:56 AM.

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2015 DragonByte Technologies Ltd.
Copyright 1999-2015 diyAudio

Content Relevant URLs by vBSEO 3.3.2