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Thread: The Ozone layer - modding the Lite DAC-AH

  1. #1
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    The Ozone layer - modding the Lite DAC-AH

    Here's a new thread for all the pictures I'm going to take to show in detail how you can transform your Lite DAC-AH into one of the world's most dynamic NOS DACs - Ozone

    Once you take off the lid of your DAC-AH (8 + type screws to remove) you'll see this within :

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    The PCB (to the left of the R-core transformer) divides logically into three areas, bottom to top. First the digital input receiver and digital power supplies. Moving upwards we have the DACs themselves and finally, at the top the output buffer stage with its own analog power supply.

    Getting the PCB out of the case turns out to be tricky by virtue of them having used hot-melt glue to secure the S/PDIF input connector. So you'll probably have to sacrifice this (its the lowest quality component in the whole box, so no big sacrifice there) in order to extract the board from its case. Remove all the + type screws securing the back panel and the torx-headed one on the optical input unit first. Also desolder the L,R phono output wires. There are three + type screws fixing the PCB to the bottom of the case.

    P.S. I also want to mention - because this is important - that you're seeing this development almost in real-time (just a few days behind) that there's some risk involved that the DAC (which works fine on top of my speaker) won't fit inside the case with the additional filters. Or that it won't fit without incurring some hum from the trafo. Just so as you know its not a total slam dunk at the outset and if you also want to follow along in real time there's that slight risk
    Last edited by opus111; 12-27-2012 at 09:13 PM.

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    Some progress to report...

    I finally finished winding and building the stereo pair of balanced filters which hopefully will fit within the form factor available inside the DAC-AH. The edges look a bit ragged because I had to take the shears to them to get the width the same as the available height inside the case. The underside is where the NP0 ceramic caps are mounted, along with some ferrite beads to enhance the attenuation beyond the SRF of the inductors.

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  3. #3
    WBF Founding Member/Member Sponsor FrantzM's Avatar
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    Hi
    Just trying to understand this. A part list would be useful. Are the ferrite part of the DAC or should they be purchased separately? I am interested, trying to get into DIY.
    Frantz
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    Yes a parts list will come along as the design progresses - I'm doing the design as I go along, based on the foundation of the DAC-AH. So to build this you'd first need to acquire a DAC-AH, then modify per my instructions with parts that I'll specify. I'll do a parts list of each aspect separately - the first (seems easiest) will be this filter, for which you'll need to purchase the cores and wind them yourself with enamelled copper wire (otherwise called magnet wire). The ferrites are also items to be bought separately though if anyone wants to make a kit of parts available commercially I'm more than willing to co-operate with them to facilitate this.

  5. #5
    WBF Founding Member/Member Sponsor FrantzM's Avatar
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    Quote Originally Posted by opus111 View Post
    Yes a parts list will come along as the design progresses - I'm doing the design as I go along, based on the foundation of the DAC-AH. So to build this you'd first need to acquire a DAC-AH, then modify per my instructions with parts that I'll specify. I'll do a parts list of each aspect separately - the first (seems easiest) will be this filter, for which you'll need to purchase the cores and wind them yourself with enamelled copper wire (otherwise called magnet wire). The ferrites are also items to be bought separately though if anyone wants to make a kit of parts available commercially I'm more than willing to co-operate with them to facilitate this.
    Maaan! Winding up my own ferrite cores inductors???!!?? Ok! Now a few questions: Wouldn't it be better to just acquire the DAC board (about $100 on e-Bay) without the PS and build one, improved of course and drop the whole thing in a boxr? Granted that increases the cost but if I am following, the results are to be world-class performance and sane person prices.
    Frantz
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    "For me, it is far better to grasp the Universe as it really is than to persist in delusion, however satisfying and reassuring."
    —Carl Sagan
    "Any intelligent fool can make things bigger, more complex, and more violent. It takes a touch of genius -- and a lot of courage -- to move in the opposite direction."
    — Albert Einstein.

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    Its certainly one option just to buy the PCB and mod that, yes. That's assuming you're comfortable sourcing your own trafo and case, along with the input/output connectors.

    In the much longer term I'll do a full PCB layout for this, and make those files available, but the route of starting off with the DAC-AH gets you a finished DAC more quickly

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    After an interesting diversion into chipampery, its about time now to reboot this thread with some serious DAC-AH modding. So here's what to do for improving the PSU noise performance in several easy stages. Firstly - bridge rectifiers produce RF noise as they switch so I'm adding snubbers to absorb this. A snubber is an RC network designed for noise suppression. Here the noise is relatively low in level so only a small resistor is required as a kind of 'noise sponge'. Each diode of the bridge (the red rectangle shows its location on the opposite side of the PCB) needs to have a snubber, so four in total for each of the two bridges. The bridge on the left is the analog supply and that on the right, the digital - the connections marked 'AC' come direct from individual windings on the DAC's R-core transformer.

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    Component values here are 47ohms for the resistors and 0.1uF/50V for the capacitors.

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    Postage stamp shunts

    Top flight sounding analog needs plenty of attention paying to power supply cleanliness - both in terms of filtering from 'external' noise and also from self-generated noise. Shunts are the solution which does the best job of both, giving in general a lower impedance than straightforward series regulators at lowish currents. For none-too-critical applications I'll use a TL431 - this gives an LF supply impedance below 0.4ohms. To do better needs a slightly more complex shunt, and here I'm building up some for the Ozone mods. I measured the first prototype as giving around 20mohm LF supply impedance.

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