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Thread: The LaserBoy Thread

  1. #401
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    Quote Originally Posted by dchammonds View Post
    Yes, the summing circuit is pre-soundcard in and bears some similarity to what you would use for modified soundcard output.
    Interesting. I'd have expected the soundcard to have AC coupling capacitors in series to their A/D inputs. If they typically do not, then this is great news.
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  2. #402
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    Quote Originally Posted by lasermaster1977 View Post
    Interesting. I'd have expected the soundcard to have AC coupling capacitors in series to their A/D inputs. If they typically do not, then this is great news.
    Actually, they do have coupling caps on both ends, hence the need for external correction circuits.

  3. #403
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    Quote Originally Posted by dchammonds View Post
    Actually, they do have coupling caps on both ends, hence the need for external correction circuits.

    Soundcards can be modified to record bipolar DC
    The mod would removing the coupling capacitors on both ends, for recording to wav and playback? Adding DC to an AC soundcard signal isn't recording bipolar DC. I'm old, give me a break if I am dense.
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  4. #404
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    Quote Originally Posted by lasermaster1977 View Post
    The mod would removing the coupling capacitors on both ends, for recording to wav and playback? Adding DC to an AC soundcard signal isn't recording bipolar DC. I'm old, give me a break if I am dense.
    Soundcard DACs have a constant idling voltage (on both input and out) in the range of 1.5-2.5V, and can swing about +/-1.5v to either side of that when signals are present.
    The right correction amp at either end can compensate (when the coupling caps are bypassed) and provide true bipolar functionality.

  5. #405
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    Quote Originally Posted by lasermaster1977 View Post
    For James:
    I have some 15ips 1/4 track tape recordings of XY signals (no DC component) that I've converted to wav files that I'd like to try with Laserboy. My impression is that Laserboy has the ability to tweak the phase difference between the X and Y signals. Am I correct, James?
    I'm not sure what you mean. If you need to do some sample shifting, I would have to tweak my code a bit. But that's definitely possible. You can also add or delete samples from one channel or the other at the very beginning of a wave using Audacity.

    Also, the LaserBoy Correction Amp kit that I have would work as an input summing amp as well as an output summing amp, I think.
    Last edited by james; 12-31-2020 at 19:13.
    Creator of LaserBoy!
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  6. #406
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    Quote Originally Posted by dchammonds View Post
    Soundcard DACs have a constant idling voltage (on both input and out) in the range of 1.5-2.5V, and can swing about +/-1.5v to either side of that when signals are present.
    The right correction amp at either end can compensate (when the coupling caps are bypassed) and provide true bipolar functionality.
    Got it. With complete information (when the coupling caps are bypassed) the true meaning is revealed.

    Many thanks, dc.
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  7. #407
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    Quote Originally Posted by james View Post
    I'm not sure what you mean. If you need to do some sample shifting, I would have to tweak my code a bit. But that's definitely possible. You can also add or delete samples from one channel or the other at the very beginning of a wave using Audacity.

    Also, the LaserBoy Correction Amp kit that I have would work as an input summing amp as well as an output summing amp.
    Thanks James, summing amps I've been doing for 40 years.

    Here's what would be neat as a Laserboy feature although I'm not sure how many would find it useful. Idea: Laserboy "reads" a given analog 2 channel (X & Y signals) wav file and in the process of defining points per second and points per frame, etc. one could also specify a small phase-shift adjustment to be applied to either the X or Y channel during the conversion process. Plus or minus 45 degrees in 16 or 32-bit steps would be way cool, too.

    Example: We recorded laser shows on 4 track 1/4" tape at 15ips audio tape (we couldn't afford DAT or digital recorders), two tracks for music, two tracks for XY signals. When recording the XY signals this was typically done while viewing the playback heads in real-time so adjustments to the phase between the XY signals could correct for any head-alignment or head-wear that caused minor phase shifts. As the tapes were played over and over again, head wear could not be avoided, but azimuth head-alignment could help correct for minor unwanted phase shifting. After digitizing these XY tape signals to wav files, they have a minor, unwanted phase shifting that needs to be adjusted out so the X & Y channels playback with the desired 90 deg phase difference between them.
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  8. #408
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    Quote Originally Posted by james View Post

    Also, the LaserBoy Correction Amp kit that I have would work as an input summing amp as well as an output summing amp, I think.
    Not exactly, overall gain control is different unless you want an interactive adjustment nightmare.

  9. #409
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    Quote Originally Posted by james View Post
    I'm not sure what you mean. If you need to do some sample shifting, I would have to tweak my code a bit. But that's definitely possible. You can also add or delete samples from one channel or the other at the very beginning of a wave using Audacity.

    Also, the LaserBoy Correction Amp kit that I have would work as an input summing amp as well as an output summing amp, I think.
    I think adding or deleting samples from one channel or the other could be an equivalent way of achieving the same thing. I'll give it a try.
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  10. #410
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    Quote Originally Posted by lasermaster1977 View Post
    I think adding or deleting samples from one channel or the other could be an equivalent way of achieving the same thing. I'll give it a try.
    Well you can adjust for a time shift between the channels that way of 1/sample_rate seconds per sample.

    Currently LaserBoy allows you to do sample shifting on the import and the export of a multichannel wave between the scanners and the color mod signals. The color mod shifts are independent of each other. The default is to hold the color signals back 5 samples at 48KHz, but you can change that to whatever you need. The XY signals are locked together, but I can change that if you need this feature.

    When you export a frame set as a LaserBoy Formatted (time optimized) wave, the sample shifts between the channels are stored in the header of the wave, so when LB goes to open the wave again to populate the frame set memory, it knows how to unshift it so the colors match up with the vector art. This also works for importing unformatted multichannel waves like ADAT recordings.
    Creator of LaserBoy!
    LaserBoy is free and runs in Windows, MacOS and Linux (including Raspberry Pi!).
    Download LaserBoy!
    YouTube Tutorials
    Ask me about my LaserBoy Correction Amp Kit for sale!
    All software has a learning curve usually proportional to its capabilities and unique features. Pointing with a mouse is in no way easier than tapping a key.

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