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Thread: Odd Issue with CT-6215s, Galvo Guru Needed!

  1. #11
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    I wonder if the Cambridge amp simply has a lower input impedance than some of the other amps you've been using? Basically this would mean that a slightly noisy output on one of the DACs ends up being a problem for the Cambridge units but not for the other ones you have...

    Don't get me wrong; J4cbo makes a nice product, but it is priced to be affordable and with that comes the understanding that you might get a tiny bit of variation from one unit to the next. I think in this case the Cambridge amps were picking up the slightly elevated noise from the scan-speed clock in the DAC, whereas a cheaper scan amp might have well ignored it.

    As far as troubleshooting goes, if you think about it - the fact that the interference changed only when you changed scan speed suggests very strongly that the DAC was the source.

    Given how low the prices have fallen on used QM-2000 boards lately, you might want to consider picking one up as a "reference DAC" to be used when tuning scanners or troubleshooting projectors. Even though I own several different controllers, when I tune a set of scanners I *always* use the QM-2000 board's output.

    Not trying to be a huge Pango fan boy here; just pointing out that many commercial controllers have various issues related to noise or sample jitter, either of which can mask a more fundamental problem with the projector itself. But I've never had any reason to question the QM's output...

    Adam

  2. #12
    swamidog's Avatar
    swamidog is online now Jr. Woodchuckington Janitor III, Esq.
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    DK,

    Were you using an Etherdream I, or an etherdream II?

    Bill,

    Itís funny. When I was talking to David about this, I suggested showing you the video. Your support and knowledge (even on non-Pangolin issues) is a great benefit to the community.
    suppose you're thinkin' about a plate o' shrimp. Suddenly someone'll say, like, plate, or shrimp, or plate o' shrimp out of the blue, no explanation. No point in lookin' for one, either. It's all part of a cosmic unconciousness.

  3. #13
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    Quote Originally Posted by laserist View Post
    Any chance the soldering iron tip isn't isolated? If there's an AC or DC leakage current it might fry both the same way...
    Ack! That's scary, but I think it would have shown up before now.

    Quote Originally Posted by buffo View Post
    I wonder if the Cambridge amp simply has a lower input impedance than some of the other amps you've been using? Basically this would mean that a slightly noisy output on one of the DACs ends up being a problem for the Cambridge units but not for the other ones you have...
    .
    .
    As far as troubleshooting goes, if you think about it - the fact that the interference changed only when you changed scan speed suggests very strongly that the DAC was the source.
    Yeah, the timing of noticing the issue really had me thinking it was something I had done. I had a set of 6215s with the same amps on the same bench just a few months ago and those didn't exhibit the same behavior. I'm relieved however that the problem is abated by using a cable shorter than 75 feet or possibly just a better cable.

    Given how low the prices have fallen on used QM-2000 boards lately, you might want to consider picking one up as a "reference DAC" to be used when tuning scanners or troubleshooting projectors. Even though I own several different controllers, when I tune a set of scanners I *always* use the QM-2000 board's output.
    I have an FB3, and FB4 and Quickshow, but no QM2K.net controller. I think QS is limited 30Kpps though so that would have restricted testing on a 60K projector, but in hindsight, I should have tried it.

    Quote Originally Posted by swamidog View Post
    Were you using an Etherdream I, or an etherdream II?
    EDIIs initially than an EDI.

    Thanks again for all the input, guys!

    -David
    "Help, help, I'm being repressed!"

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