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Thread: 8 Channel USB sound device for LaserBoy

  1. #11
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    Nope.

    You need a real computer with a DVD drive in it. You might also need a hard drive to transfer the ADAT data to, in the case that it needs to be inverted or the colors need to be realigned.

    James.

  2. #12
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    mixedgas is offline Creaky Old Award Winning Bastard Technologist
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    pangolin had access to the user bits in the ADATs raw datastream. Those don't exist in the sound card data.

    Steve

  3. #13
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    One of the cheapest and neatest ways to get ADAT data and actual audio signals on 8 outs too, is the Gina 24 card by Echo. All DAC (and two channels of ADC) are on the PCI card, appearing on a DB-25. Rare though, and not as cheap and available as C106-based USB cards and similar. Nice mods though, on those.

    James, I'm not sure what you needed to do to change that 3.3V scale with its 1.25V offset, but one way is as I use in the attached image. Most designs I've seen use two op-amp stages, so this is an improvement, and it's good for single supply use too. This circuit was for something else, but applies to lots of things. Might need to change value of gain setting resistance or offset input volts, but unlikely. Also, might need negative offset input volts, but will still work on single supply so long as output doesn't have to go negative.).

  4. #14
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    Talking

    This is the original design that I prototyped back in January of 2005.

    Note there is a zener for the -5VDC voltage reference for offset. The +/-12VDC comes from the PCI slot.


    Someone on the PL pointed out these nifty DC/DC converters. So that became part of the plan. The +5VDC from USB becomes +/-9VDC. Very handy magic!

    Then I got together with drlava and he suggested a fixed -5V regulator. So that's what comes on the pcb kit that we did.

    In order to fix the general design to work with 3.3VDC and a bit less output, I swithed out the fixed -5V regulator for an LM337 variable negative voltage regulator and a trim pot.

    Now I can set my gains to full and my offsets to middle and dial my offset voltage in on one trip pot, then tweak each channel with it's own offset pot.

    I wasn't getting all the way up to +5V on my color channels, so I put 47K in series with the 50K gain pot. This just about doubles the maximum gain of the channel.

    James.

  5. #15
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    Your schemo is very similar to the one Dean designed. What do the 1M resisters do for you?

    James.
    Last edited by James Lehman; 12-30-2008 at 11:23.

  6. #16
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    I like mine a bit better. More independence between gain and offset controls, and it preserves signal polarity, though I have used an offset tweak based on feeding the -ve input via a 10M resistor for very fine leverage to get fine adj of zero offset, here: http://www.photonlexicon.com/forums/...0845#post20845)
    When biasing over several volts instead of a few millivolts, I wanted a different way. I also wanted single supply operation, so no inversion of signal. So I used a non-inverting amp, which is fine for gains at or above 1. I used a passive averager with two 1M resistors, then gain of 2 on the result when using two inputs. (10M for input resistors is better if the environment is electrically silent). The circuit works for negative or dual rails too, if you supply them, and a negative DC offset input signal can be used at any time so long as output is in range of supply. That signal has to be stable but the supply can be anything so long as it's quiet and large enough. Being 'quiet' also means that the offset signal can be taken direct from the supply, so only a supply regulator is needed for good results. And sometimes a negative DC signal might be needed, but only a positive single rail supply, in which case I can tap whatever's there as it won't load it much. In short, this circuit is very compact and hugely adaptable to many and varied situations, so the layout can be modular and copied between designs with little extra work. Only change that might be needed is where the offset pot grounds to, might also be -ve supply, but this one was meant for broad tweaks for signals that peaked at zero, not crossed it.

    I like DC-DC convertors too, but they cost loads. At the end of the thread I linked to just now I posted a new version of that circuit (that no-one seems to care about, but never mind). In it I wanted isolation so I could have a common ground but a floating supply, and a high voltage to give full scale of >20W read on a meter using 1mV per mW. I needed 22V and enough negative to tweak the offset to zero accurately, and run it all on a 5V single rail supply. Because of the cost of the converter, I only use one if it satifies several things I can't do easily another way, but it's perfect for that meter circuit.
    Last edited by The_Doctor; 12-31-2008 at 01:55.

  7. #17
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    Talking The Annihil8or

    WOW! Look at what I just made!











    I call this The Annihil8or!

    This is an 8 channel LaserBoy Correction Amp, with a variable negative offset reference voltage and a lot of gain. This one has a tracks matrix patch block so you can rearrange the tracks any way you want on the analog side. Since the audio jacks and DC decoupling caps are still in place on the sound card, you can lift any paired signal lines out of the track matrix and use the jack for standard stereo audio! You can also lift the +5VDC from the USB connection and power it with a little wall wart! By default X, Y, R, G, & B are soldered in place, but the remaining 3 signals can be assigned to the 3 auxiliary color signal lines in the ILDA connector (or not). So you can use all 8 channels for laser signals. The red jumper is the safety interlock switch. There is a +5VDC (TTL level) shutter actuator on pin 13.



    In the process of making this, I think I may have found a cure for my Echo Layla woes.

    BTW, I don't think this one is for me. I'm pretty sure it belongs to someone else!

    I can't wait to make another one for myself!

    Start thinking about getting all those old ADAT tapes together for one last play. Once all that data gets to hard drive, it can be properly preserved.

    James.
    Last edited by James Lehman; 01-04-2009 at 23:01.

  8. #18
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    wow, that's some piece of work james!

    congrats!

    I'll have to send you some laser printer copper transfer pages for future projects, they work quite well

  9. #19
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    Quote Originally Posted by James Lehman View Post
    I think I may have found a cure for my Echo Layla woes.
    Was she a fickle mistress?

  10. #20
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    Actually, she flipped out just before she got to SELEM! For some reason, the ADAT pass-through is now inverted and Windows doesn't have the right codec to play multi channel waves anymore!

    James.

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