VOGONS


First post, by appiah4

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I was checking out a card for a fellow VOGONer:

Edison-Gold-16-D.jpg

Interestingly I noticed that FM music is extremely distorted on Line-Out but otherwise perfectly smooth on Speaker out.

What could be the cause? Is the distortion due to hooking it up straight to el cheapo headphones or TV audio in?

I sprayed the jack with contact cleaner but that solced nothing.

I did not test digital audio - what would be a good game for this?

Retronautics: A digital gallery of my retro computers, hardware and projects.

Reply 2 of 8, by mkarcher

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appiah4 wrote on 2020-06-06, 16:11:

Interestingly I noticed that FM music is extremely distorted on Line-Out but otherwise perfectly smooth on Speaker out.

What could be the cause? Is the distortion due to hooking it up straight to el cheapo headphones or TV audio in?

Line-out is designed to deliver some voltage to an amplifier, but line-out is not designed to push current through headphones. In technical terms, line-out is meant to drive a high-impedance device (around 10.000 Ohms), but el-cheapo headphones are anywhere between 8 and 32 Ohms. Depending on the sound card, connecting a low-impedance load to line-out can cause distortion.

Line-out should sound right if you connect it to a TV audio in, though. TV audio in is exactly that type of high-impedance device line-out is meant to be connected to.

A possible cause for bad sound at the line-out jack might be a damaged line-out jack or bad solder joints at the line-out jack. Another cause might be worn-out DC decoupling capacitors directly at the line-out jack (probably C3/C4, maybe C5/C6), speaker out uses C1/C2. Anything farther away from the line-out jack is also used by the speaker out signal path, so if speaker out is clean, the line level signal as generated on the sound card has to be clean, too.

Reply 3 of 8, by appiah4

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I tested this card on another PC and the Line Out was clean as a whistle there. For that testing, I routed the Line Out of the card to the Line In of my daily PC, and it was crisp clear. Why, I do not know..

Retronautics: A digital gallery of my retro computers, hardware and projects.

Reply 4 of 8, by chrismeyer6

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Is the power supply in the system with the distorted sound in good shape. It's probably a long shot but I've had similar issues in the past when a power supply had not so great power output

Reply 5 of 8, by appiah4

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chrismeyer6 wrote on 2020-06-22, 20:30:

Is the power supply in the system with the distorted sound in good shape. It's probably a long shot but I've had similar issues in the past when a power supply had not so great power output

It's an old AT PSU salvaged from a throwaway PC. The PSU in the PC that worked fine is NOS. That might be the cause..

Retronautics: A digital gallery of my retro computers, hardware and projects.

Reply 6 of 8, by gdjacobs

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appiah4 wrote on 2020-06-22, 20:18:

I tested this card on another PC and the Line Out was clean as a whistle there. For that testing, I routed the Line Out of the card to the Line In of my daily PC, and it was crisp clear. Why, I do not know..

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Sound card line inputs are high Z so the preamp isn't going to hit it's current limit and distort. Try feeding the line output through another line input device on a sound card, mixer, audio amplifier, mini system, or the like prior to going through your headphones.

All hail the Great Capacitor Brand Finder

Reply 7 of 8, by appiah4

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gdjacobs wrote on 2020-06-30, 15:39:
appiah4 wrote on 2020-06-22, 20:18:

I tested this card on another PC and the Line Out was clean as a whistle there. For that testing, I routed the Line Out of the card to the Line In of my daily PC, and it was crisp clear. Why, I do not know..

mkarcher +1

Sound card line inputs are high Z so the preamp isn't going to hit it's current limit and distort. Try feeding the line output through another line input device on a sound card, mixer, audio amplifier, mini system, or the like prior to going through your headphones.

Such a basic concept, but yes this is what it was.. Thanks for the clarification.

Retronautics: A digital gallery of my retro computers, hardware and projects.