Go Back   Home > Forums > Blogs > abraxalito
Reload this Page Revisiting mods to the Lite DAC-AH

Rate this Entry

Revisiting mods to the Lite DAC-AH

Posted 12th January 2015 at 02:57 AM by abraxalito
Updated 12th January 2015 at 03:07 AM by abraxalito
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 tiny TDK 7mm inductors (the two values I have). I've put in realistic values based on measurement of dozens of samples, they tend to average a bit below their 'sticker' inductance. The thinking behind going firstly for the filter is that when I first experienced the results of an LC filter (I wrote about that on the WBF thread 'Digital that sounds like analog') the most apparent thing at the time was the soundstage improvement - it went 'holographic', something I'd never before experienced. So my hypothesis is that the filter gives a dramatic drop in the perceived noise floor. It also I suspect should improve dynamics because with this filter installed the image frequencies are going to be strongly suppressed (90dB+ rejection above 37kHz shows on LTSpice) and this should improve the IMD error noise.
Attached Thumbnails
Click image for larger version Name: DAC-AH-filter.jpg Views: 646 Size: 37.2 KB ID: 1521  
Views 1660 Comments 8
« New year, new DAC     Main     TDA1387 octal DAC looks like a good modding base »
Total Comments 8

Comments

  1. Old Comment
    DAC-AH is DAC based with TDA1543 and it's dac with active I/V AD847 ?

    is mean from the disscusion before passive filter can improving sound of the dac is it ?
    permalink
    Posted 12th January 2015 at 08:40 PM by oxoxbyx oxoxbyx is offline
  2. Old Comment
    abraxalito's Avatar
    You're right about the DAC chip, that's TDA1543 (there are 8 of them in parallel), but the I/V is passive then the AD847 is used as an amplifier. So I plan to put the filter after the passive I/V and before the amplifier.
    permalink
    Posted 12th January 2015 at 11:49 PM by abraxalito abraxalito is offline
  3. Old Comment
    abraxalito this is the lastest design your filter ? this filter can use in TDA1387 also ?
    permalink
    Posted 13th January 2015 at 05:33 AM by oxoxbyx oxoxbyx is offline
  4. Old Comment
    abraxalito's Avatar
    Its just a minor redesign of the filter I worked out for the Aune. The difference is the 160ohm working impedance which I chose to give the highest output level from the 8 paralleled TDA1543s.
    Yes you could use it with the TDA1387 but the output level will be rather low due to the 160R impedance. I'd recommend for a single TDA1387 using Fastron inductors (27mH) - that gives a much higher output level. You'll see in an earlier blog post I had a filter designed using Fastrons.
    If you need more help, just ask - glad to work on any new filter specification you might have.
    permalink
    Posted 13th January 2015 at 07:14 AM by abraxalito abraxalito is offline
    Updated 13th January 2015 at 07:19 AM by abraxalito (Corrected inductor value)
  5. Old Comment
    I really want to try your ozone dac, I really interest with it, I already found source TDA1387 here but I didn't find any source good inductor here such as fastron inductor.

    if didn't found a big inductor like 27mh can I just use 1 mh and with resistor ?
    permalink
    Posted 13th January 2015 at 08:30 AM by oxoxbyx oxoxbyx is offline
  6. Old Comment
    abraxalito's Avatar
    If you're limited by inductors, what's the biggest inductor you can get easily? Can you get the 1mH SLF7045s from TDK? Can you get the next size up (12mm) from TDK? They go up to 1.5mH. The bigger the inductor (in mH) the more voltage swing you can get out of the filter.
    If you can only get the 1mH SLF7045s I can design you a filter which uses them in series (say 5 in series for each element) and that'll give more output volts.

    I got your PM with the webshop links, will check them out and get back to you on here.
    permalink
    Posted 13th January 2015 at 08:38 AM by abraxalito abraxalito is offline
    Updated 13th January 2015 at 11:58 AM by abraxalito
  7. Old Comment
    I send you by pm because I don't want kind of advertise online shop
    permalink
    Posted 13th January 2015 at 11:57 AM by oxoxbyx oxoxbyx is offline
  8. Old Comment
    abraxalito's Avatar
    I replied by email. I've also found these - Magnetically shielded inductor 16 * 16MM (472) 4.7MH-in Diodes from Electronic Components & Supplies on Aliexpress.com | Alibaba Group

    a bit risky but they might work well. There's no technical data there, no idea of manufacturer. The size though is promising - bigger means more thick wire
    permalink
    Posted 13th January 2015 at 01:07 PM by abraxalito abraxalito is offline
 

New To Site? Need Help?
Copyright ©1999-2017 diyAudio