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Sound Blaster Gurgling From Digital CD-IN

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First post, by wiibur

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I've started using the digital output of my Sound Blaster CT4760 to capture my game audio, including digital CD audio through the card's digital CD-IN pins. It works really well and sounds very clean but sometimes when I insert a new disc I will get tons of gurgling noise from the digital CD-IN (see below youtube video for an example). Even if I eject the CD in the drive the sound remains and the computer needs to be rebooted to get it to stop. I am using the audigy_2_zs_drivers_for_sound_blaster_live_2.1.zip driver pack. I had a chance to try another optical drive but the issue still manifested itself, albeit not from inserting a new disc but in a different way.

I haven't used digital outputs very much before so I'm not sure if this is a coaxial cable issue, optical drive issue, a driver issue, or maybe something else. Does anyone have any ideas?

Video of the issue: https://www.youtube.com/watch?v=TDkcyWom_ZI

Reply 1 of 4, by wiibur

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The product manual shows a Digital Output Module connected to the rear digital mini-jack. I'm currently using an RCA to 3.5mm mono jack cable and this seems to tap the correct digital output signal. If I was using a stereo jack RCA cable I assume the card would expect digital input on the second/right speaker line.

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Reply 2 of 4, by wiibur

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I tried three optical drives and each one exhibited this issue in a different way, sometimes in-between cd tracks, sometimes after loading a disc, etc. I started trying different driver versions at this point and found ones that appear to have resolved the issue. They can be found here on vogonsdrivers.

Reply 3 of 4, by Cloudschatze

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wiibur wrote on 2023-06-21, 00:23:

If I was using a stereo jack RCA cable I assume the card would expect digital input on the second/right speaker line.

The CT4760's Digital Out mini-jack is strictly output only, and carries both the front and rear stereo channels at TTL voltage levels. The mentioned Digital Output Module (CT4801) provides an ideal, transformer-isolated pairing, but it's also an exceptionally uncommon part.

Straight-through, 3.5mm stereo-to-RCA cable connections were commonly recommended instead though, just with the aforementioned TTL caveat. The Sound Blaster Live! Book even provides the following illustration:

CT4760_DO.png

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