diyAudio - View Profile: abraxalito
Go Back   Home > Forums > Members List

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

abraxalito abraxalito is offline

diyAudio Member

About Me

  • About abraxalito
    Biography
    Ex professional- and consumer audio designer. Prior to working in audio I was in embedded systems.
    Location
    Hangzhou - Marco Polo's 'most beautiful city'. 700yrs is a long time though...
    Interests
    Maximizing dynamics and soundstage depth for the least money with multibit DACs
    Occupation
    English teacher, disruptive innovator with ARM Cortex M-series
    Country
    United Kingdom
  • Signature
    "I really can't believe it," Clevinger exclaimed to Yossarian in a voice rising and falling in protest and wonder. "It's a complete reversion to primitive superstition." - Joseph Heller

Statistics

Total Posts
Blog
Wiki
General Information
  • Last Activity: Today 04:04 PM
  • Join Date: 19th September 2007

Friends

Showing Friends 1 to 9 of 9

Contact Info

Instant Messaging
Send an Instant Message to abraxalito Using...
Home Page
http://abraxalito.googlepages.com
This Page
http://www.diyaudio.com/forums/members/abraxalito.html

Blog

Latest Blog Entry

Posted 16th January 2015 at 12:55 AM by abraxalito Comments 4
Thanks to Matthieu (Malefoda) for the heads up on this. It looks distinctly like a DAC inspired by the DAC-AH - note not only the 8 DAC chips but also the PCB layout closely follows that design's. The price on Taobao is about half the AH (368rmb) so I shall be ordering up one or more to have a play. Matthieu found it on another website with prices in USD, here - http://www.cart100.com/Product/42124644877/.
Note there are two options here (blue, black) - the cheaper one is a kit of parts I believe, the more expensive ($84) the finished unit. Going on the translation of the Taobao page, the kit does not include the transformers, mains switch or the case.

Posted 12th January 2015 at 02:57 AM by abraxalito Comments 8
Last night the battery of my I2S source ran out so while it was on charge, I unboxed my last remaining Lite DAC-AH to have a listen to that, fed from my (mains powered) QA550 wav player. I'd bought 3 DAC-AHs a few years back when I was playing with them.

The differences between the stock DAC-AH and the Ozone Pagoda were apparent in the areas of soundstage depth, dynamics (especially at LF) and coarseness at higher levels. So this got me wondering what would be the lowest hanging fruit in terms of mods to it. My procedure before had been to implement everything I could think of before having a listen - this way its not possible to know which mods are the most effective ones and which can be omitted.

This time I'm going to be a bit more disciplined for the purposes of discovering which mods deliver the best bang for the buck. The first one I'm going to try is a passive LC filter between the DACs and the AD847s. Here's the schematic for it - its using the cheap and...

Posted 31st December 2014 at 08:36 AM by abraxalito Comments 4
Here's the 'Ozone desktop pagoda' DAC for 2015.

A single TDA1387 feeds a 3 inductor quasi-elliptic filter followed by AD8017s as buffer-amps. The large ferrite cores in the base do the bal-SE conversion. The power supply is 4 * AA NiMH cells which should in theory last for a whole day's music.

The design is really a 'MkII' version of the Ozone portable where the AD815 buffers have been replaced to allow a more compact construction and lower power draw without the constraint of being able to drive IEMs directly. Whereas the portable used a stack of 1387s due to the choice of 7mm TDK inductors, this one's using pot-core chokes giving a much higher working impedance and hence higher output levels from just the one DAC chip. The desktop footprint is about that of a CD.

Update : I found some bargain Jamicon caps on Taobao which give the tower more elegant proportions, as well as improving the supply impedance to the buffer-amps and giving more breathing...

Posted 15th November 2014 at 03:51 AM by abraxalito Comments 4
I'll outline here some thinking in choosing the major building blocks (aka ICs) for this card - any comments welcome as this progresses.

First up the DAC chip will be the TDA1387 initially. I don't know for sure that the output from the ARM/Xilinx card is I2S but I'm going to verify that fairly soon. There's nowhere near enough room for the passive shunt I've adopted previously so the bass performance probably is going to have to suffer. I shall pay considerable attention to the power supply arrangements though in an attempt to make up for the LF lack.

After the DAC, passive I/V will follow and then a filter using the TDK 7mm inductors I've used previously. I've slotted them into the gap between the PCB and the case and there's just enough height available. Since space is at a premium I'll experiment with a 3 inductor design - the stop band attenuation will suffer but probably I'll add a secondary LC filter at the output to make up for that somewhat. The secondary...

Posted 11th November 2014 at 02:26 AM by abraxalito Comments 2
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...
Recent Comments
I'll confirm when I...
Posted 25th January 2015 at 12:13 AM by abraxalito abraxalito is offline
Any idea what the usb...
Posted 24th January 2015 at 12:42 PM by lordearl lordearl is offline
Excellent, looking forward...
Posted 22nd January 2015 at 01:08 AM by abraxalito abraxalito is offline
And here I go, two pieces...
Posted 21st January 2015 at 01:48 PM by Malefoda Malefoda is offline
I replied by email....
Posted 13th January 2015 at 01:07 PM by abraxalito abraxalito is offline
Hide this!Advertise here!

New To Site? Need Help?

All times are GMT. The time now is 04:51 PM.


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