VOGONS


First post, by appiah4

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I have been using a Zoltrix Audio Plus 6400 3D PnP (AV309) in my 5x86 system without issue - it is basically noise free with or without the speaker amplifier.

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Out of curiosity I replaced it with this Acer Magic S23A (CS4236B) card I had laying about, thinking it could be even better due to being more integrated. I also wanted to compare CS4289's OPL3 vs CS4386B's.

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However, this card is attrociously noisy. Not only is there a very high and very annoying high background noise, but it also picks up noise from all across the system - ISA Bus, PCI Bus, IDE activity, you name it.

This does not sound normal to me and I THINK it has to do with dried out caps, but wanted to ask your opinions first. Should I attempt a recap of this card, is this something normally known to be silent and well filtered?

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

Reply 2 of 12, by Tiido

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it essentially boils down to wrong design on the card. From what you described, it has grounding mistake and digital currents pass through the analog side which is what causes all the noises. There is no cure that makes sense to do (actual board modifications are necessary, probably on a significant scale).

T-04YBSC, a new YMF71x based sound card & Official VOGONS thread about it
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Reply 3 of 12, by appiah4

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Tiido wrote on 2021-04-20, 12:02:

it essentially boils down to wrong design on the card. From what you described, it has grounding mistake and digital currents pass through the analog side which is what causes all the noises. There is no cure that makes sense to do (actual board modifications are necessary, probably on a significant scale).

I see.. So it's not something that would have to do with dried up electrolytic filtering caps? Not worth trying a recap at all?

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

Reply 4 of 12, by weedeewee

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appiah4 wrote on 2021-04-20, 12:55:

I see.. So it's not something that would have to do with dried up electrolytic filtering caps? Not worth trying a recap at all?

I have no experience with the board,
it could very well have something to do with the capacitors being dry,
though consider that if the output capacitors are dry, you would hardly get any volume out of it.

Reply 5 of 12, by Tiido

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You can try to change some capacitors on the power rails as a test. It probably will have some improvement but most probably it won't reach the level of the other card.

T-04YBSC, a new YMF71x based sound card & Official VOGONS thread about it
Newly made 4MB 60ns 30pin SIMMs ~
mida sa loed ? nagunii aru ei saa 😜

Reply 6 of 12, by appiah4

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Tiido wrote on 2021-04-20, 13:56:

You can try to change some capacitors on the power rails as a test. It probably will have some improvement but most probably it won't reach the level of the other card.

Right... and which ones would those be? 😁

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

Reply 7 of 12, by weedeewee

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appiah4 wrote on 2021-04-20, 18:56:
Tiido wrote on 2021-04-20, 13:56:

You can try to change some capacitors on the power rails as a test. It probably will have some improvement but most probably it won't reach the level of the other card.

Right... and which ones would those be? 😁

Well.. you take your multimeter and measure which capacitor has a direct connection to one of the voltage rails, either 5v, -5v, 12v, -12v
Not sure if you should also do the gnd rail ... 😉

Reply 8 of 12, by appiah4

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weedeewee wrote on 2021-04-20, 19:00:
appiah4 wrote on 2021-04-20, 18:56:
Tiido wrote on 2021-04-20, 13:56:

You can try to change some capacitors on the power rails as a test. It probably will have some improvement but most probably it won't reach the level of the other card.

Right... and which ones would those be? 😁

Well.. you take your multimeter and measure which capacitor has a direct connection to one of the voltage rails, either 5v, -5v, 12v, -12v
Not sure if you should also do the gnd rail ... 😉

OK, time to dig out the ISA slot pinout 😁

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

Reply 10 of 12, by appiah4

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pc-sound-legacy wrote on 2021-04-27, 23:41:

I would set the jumpers to line out position. Sometimes the noise came from the amplifying circuity.

I've already done that, but it doesn't help. The noise is not amplifier related, it's basically VERY LOUD interference from the ISA Bus.

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

Reply 11 of 12, by orcish75

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appiah4 wrote on 2021-04-28, 08:01:

I've already done that, but it doesn't help. The noise is not amplifier related, it's basically VERY LOUD interference from the ISA Bus.

Unfortunately there's not much you can do about it. The board layout is very poor, there are many open ended traces going nowhere and not grounded or terminated. They're like many tiny antennas picking up every bit of EMI in your PC case and then transferring it into the analogue section of the card. I have one those cards as well as a couple of the CS4232/OPL3 variants and they're all very noisy.

Reply 12 of 12, by appiah4

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orcish75 wrote on 2021-04-29, 19:18:
appiah4 wrote on 2021-04-28, 08:01:

I've already done that, but it doesn't help. The noise is not amplifier related, it's basically VERY LOUD interference from the ISA Bus.

Unfortunately there's not much you can do about it. The board layout is very poor, there are many open ended traces going nowhere and not grounded or terminated. They're like many tiny antennas picking up every bit of EMI in your PC case and then transferring it into the analogue section of the card. I have one those cards as well as a couple of the CS4232/OPL3 variants and they're all very noisy.

That's what I feared. Thank you. 😀

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