Need help bypassing amplifier on ES1868F-based card \ VOGONS

Need help bypassing amplifier on ES1868F-based card

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First post, by megatog615

Posted on 2025-03-17, 07:28

megatog615 Offline

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I'm attempting to bypass this card's amplifier so it doesn't sound so terrible. At first I thought it would be straightforward, moving the resistors from R9 and R11 to R8 and R18 but that resulted in no audio output at all. I'm tempted to just desolder all of these SMD components around the amp chip and run a wire straight from pins 50 and 51 on the ES1868F to the output jack but I'd like a more elegant solution.

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Reply 1 of 7, by Tiido

Posted on 2025-03-17, 08:26

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I'm pretty sure you also need to disconnect the outputs of the amp chip before things begin to work correctly. Pins 1 and 3 are the outputs.

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Reply 2 of 7, by PcBytes

Posted on 2025-03-18, 17:59

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I'm kind of in the same boat but with a 1869F. The audio is horribly clipped no matter if Windows or DOS and I'd love to find a fix to that - even if it means disabling the amplifier.

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Reply 3 of 7, by megatog615

Posted on 2025-04-04, 16:54

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Tiido wrote on 2025-03-17, 08:26:

I'm pretty sure you also need to disconnect the outputs of the amp chip before things begin to work correctly. Pins 1 and 3 are the outputs.

I moved the resistors and cut pins 1 and 3 off the amplifier. ~~I only get right-channel mono sound. Descent setup puts right and center on the right and nothing comes out on the left. Should I just cut the amplifier off entirely?~~
EDIT: Turns out the 22k ohm resistor on that line was dead. I've fixed it and I get stereo sound now. HOWEVER, I think a 22k resistor is too much; the volume takes a big hit. I think since the whole amp circuit is bypassed I can take the 2.2k or the 220 ohm resistors and use them instead. I'll make a new post with my findings.

PcBytes wrote on 2025-03-18, 17:59:

I'm kind of in the same boat but with a 1869F. The audio is horribly clipped no matter if Windows or DOS and I'd love to find a fix to that - even if it means disabling the amplifier.

Are you sure your card doesn't have jumpers for that? If so you're in luck. Some of the 1868/1869 cards had jumpers to enable or bypass the amplifier. This cheap 1868F card of mine has the amp hard-wired.

Last edited by megatog615 on 2025-04-04, 19:04. Edited 2 times in total.

Reply 4 of 7, by PcBytes

Posted on 2025-04-04, 17:03

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megatog615 wrote on 2025-04-04, 16:54:
I moved the resistors and cut pins 1 and 3 off the amplifier. I only get right-channel mono sound. Descent setup puts right and […]
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Tiido wrote on 2025-03-17, 08:26:

I'm pretty sure you also need to disconnect the outputs of the amp chip before things begin to work correctly. Pins 1 and 3 are the outputs.

I moved the resistors and cut pins 1 and 3 off the amplifier. I only get right-channel mono sound. Descent setup puts right and center on the right and nothing comes out on the left. Should I just cut the amplifier off entirely?

PcBytes wrote on 2025-03-18, 17:59:

I'm kind of in the same boat but with a 1869F. The audio is horribly clipped no matter if Windows or DOS and I'd love to find a fix to that - even if it means disabling the amplifier.

Are you sure your card doesn't have jumpers for that? If so you're in luck. Some of the 1868/1869 cards had jumpers to enable or bypass the amplifier. This cheap 1868F card of mine has the amp hard-wired.

Mine didn't have jumpers either.

"Enter at your own peril, past the bolted door..."
Main PC: i5 3470, GB B75M-D3H, 16GB RAM, 2x1TB
98SE : P3 650, Soyo SY-6BA+IV, 384MB RAM, 80GB

Reply 5 of 7, by megatog615

Posted on 2025-04-04, 19:47

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Okay, through some quick testing I was able to figure out that the 2.2k resistors were the best for volume. Here's my (ugly) work. Ignore the lifted pad on R11, I don't know where that came from(he lied). I get stereo sound and the card is now poly-modded.

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Reply 6 of 7, by megatog615

Posted on 2025-04-04, 20:00

megatog615 Offline

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PcBytes wrote on 2025-04-04, 17:03:

megatog615 wrote on 2025-04-04, 16:54:
I moved the resistors and cut pins 1 and 3 off the amplifier. I only get right-channel mono sound. Descent setup puts right and […]
Show full quote

Tiido wrote on 2025-03-17, 08:26:

I'm pretty sure you also need to disconnect the outputs of the amp chip before things begin to work correctly. Pins 1 and 3 are the outputs.

I moved the resistors and cut pins 1 and 3 off the amplifier. I only get right-channel mono sound. Descent setup puts right and center on the right and nothing comes out on the left. Should I just cut the amplifier off entirely?

PcBytes wrote on 2025-03-18, 17:59:

I'm kind of in the same boat but with a 1869F. The audio is horribly clipped no matter if Windows or DOS and I'd love to find a fix to that - even if it means disabling the amplifier.

Are you sure your card doesn't have jumpers for that? If so you're in luck. Some of the 1868/1869 cards had jumpers to enable or bypass the amplifier. This cheap 1868F card of mine has the amp hard-wired.

Mine didn't have jumpers either.

What card is it?

Reply 7 of 7, by PcBytes

Posted on 2025-04-04, 20:18

PcBytes Offline

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Location: Bacau, Romania

megatog615 wrote on 2025-04-04, 20:00:

PcBytes wrote on 2025-04-04, 17:03:

megatog615 wrote on 2025-04-04, 16:54:

I moved the resistors and cut pins 1 and 3 off the amplifier. I only get right-channel mono sound. Descent setup puts right and center on the right and nothing comes out on the left. Should I just cut the amplifier off entirely?

Are you sure your card doesn't have jumpers for that? If so you're in luck. Some of the 1868/1869 cards had jumpers to enable or bypass the amplifier. This cheap 1868F card of mine has the amp hard-wired.

Mine didn't have jumpers either.

What card is it?

A noname card w/ no jumpers (or any way of adding them anywhere either.)

"Enter at your own peril, past the bolted door..."
Main PC: i5 3470, GB B75M-D3H, 16GB RAM, 2x1TB
98SE : P3 650, Soyo SY-6BA+IV, 384MB RAM, 80GB

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