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Thread: 230VAC DAC re-design for car-pc 12VDC.

  1. #1
    Aze
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    230VAC DAC re-design for car-pc 12VDC.

    Hi guys.

    I have made a lot of different car-pc and audio installs over the past years.
    I have always been pretty satisfied with the audio reproduction using some smaller USB powered DACs from various manufactures, and some middle-end component-systems and amplifiers.
    But now it has comed to a new era for me...I will make a new install/setup from scratch, containing everything needed to have the perfect audio reproduction. This time it will be a setup for the SQ and only SQ.
    I have ordered amplifiers, 3-way component-systems, middle-woofers and subwoofers. Everything will be running full active crossing, 2x 5ch amplifier for each door side, and 1 monoblock for the middle-woofers, and 1 monoblock for the subwoofers. The linesignal will be kept balanced all the way, and the car will be sound damped with 100Kgs of damping material.

    So basically everything was fine, but no chain is stronger than the weakest link, and I found that what I really needed was an USB DAC with a VERY accurate sound reproduction, and some top parametres. Another thing that was VERY important for me was that the DAC had a physical volume-knob, as what I misses the most in my previous car-ps setups, is the the opportunity to have a volume-knob controlling the volume. I love touchscreens, but I HATE adjusting the volume through one of those. Don't know why...for me a real high-end audio system just need to a volume-knob.
    Anyway...After some reading of tests and reviews I decided to to buy a USB DAC for home audio use, from a company called HLLY.
    After testing it in my home audio system I was SURE...This baby should spent the rest of it's life in my car...

    As for any other home audio equipment the DAC had to be powered by AC230/110V, and that was my first concern that need to be solved.
    I got the schematics from the manufacturer and did a few measurings in the PCB to find out which DC voltages was actually needed.
    First off, as a DAC contains an OP-AMP a so called "positive/negative supply" was needed.
    So instead of an ordinary gnd/positive PS what I needed was a PS having actually 3 output values: a virtual ground (0v) a negative voltage at -15VDC, and a positive voltage at +15VDC.
    With these 3 values I would be able to power the OP-AMP in the same way that the ordinary trafo, diode rectifer and caps would do it.
    Beside this POS/NEG PS I also needed 2 isolated DC voltages at 8,5V powering each a section of the digital blocks in the DAC.
    So the total need was actually 3 galvanic isolated power supplies, abel to take a DC12V and make it to: 1x 9V, 1x 9V, 1x +/-15V.

    I did a lot of research on this, and then I suddenly found a company called BCT that actually had EXACTLY what I needed...What a day!
    BCT makes a lot of different DC-DC converters and a complete series of isolated PWM types, including DUAL and single outputs. They had the exact type I needed, including the DUAL +/-15V type.
    A big plus is that the ripple actually seems to be smaller than if running from 230/110VAC through the diode rectifier. And the best part is that the devices takes 9-18VDC in, and still supplies a much stable output at the different needed voltages.

    Enough talk...here's some pictures for the upgrade. Now I can run the DAC directly from my car, still having all the features of it.
    As you can see the front-panel connectors has been extended (the bundle of blue wires). This is because the DAC is going to be placed in the trunk while the VFD and volume knob will be integrated in the centerdash.

    The first pictures is the original pictures from the manufactor...




































  2. #2
    MySQL Error soundman98's Avatar
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    i'm not gonna lie-- after seeing that hlly actually sent you the schematics for the dac, i was expecting to see you using a dac that was well over the $500 mark.. that is a nice suprise that it is only $320..

    still more then i would spend right now, but the cost is much more justifiable then some of these high-end audio dacs...

    it is great that hlly was willing to send you the schematics so you could work this out.. i'm bookmarking them for future reference just for that.

  3. #3
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    Agreed, thats a great thing to see, there are less and less companies these days who are willing to help the "amateur" hobbyist.

    The way I see it, by offering the schematics to let you use the equipment in a new way, surely there would be others who would look at buying your equipment to use as well.

    I believe it helps foster new sales, with no real backlash to the company. It voids the warranty, so its not going to cost them in returned or RMA parts, and people who otherwise wouldn't look at the gear on offer are suddenly buying the stuff.

    Thanks for putting up the info Aze, and that is some mighty fine looking modification!!

  4. #4
    FLAC PhilG's Avatar
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    I guess the only downside of offering schematics to the public these days is they end up in Shaghai being used to make a "similar" product for 19.95 on ebay....
    My 2007 Ford F350 Work Log located HERE

  5. #5
    Aze
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    Thank you guys for the comments.

    In regards to the schematic sharing, I don't think that there's any "company secrets" in this. What makes the audio quality is the used components.

    PhilG: Actually it is a private high audiophile guy that makes these DACs with the name of HLLY. So even if another company made a similar item, there wouldn't be able to take the price down.
    The included OP-AMPs, caps, coax/spdif decoders, trafo's, VFD volume control etc costs a lot of money, so there's no big advantage in copying this...

  6. #6
    FLAC PhilG's Avatar
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    That sounds like a great piece of equipment. I'm following this thread!
    My 2007 Ford F350 Work Log located HERE

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