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Soundcard PCB layout and layers ?

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MathWizard:
I have an old  soundcard here that used to have an intermittent distortion problem of some kind. It's full of caps, I'll have to check some of them later. Also at some point a little fuse on the 12V input got fried, IDK if it was me or while in the PC.

Today I'm going through datasheets for it. I just want too play around with it, see if I can find the cause and fix it, and then see what a BusPirate makes of it. See if I can "hack it up" (LOL I bet kool kids say that)

1) It's PCI-e x1, has digital audio in/out, and 7.1ch output. How many layers would such a thing be? I see the #6,8, even 10 ?
Here's some spec's
https://www.guru3d.com/articles-pages/auzentech-x-fi-forte-7-1-soundcard-review-|-test,3.html


There are via's everywhere, linear regulators on the top, with little else. On the bottom there's all the digital chips, buck converters, op-amps, output caps/etc

2) And in the end, what about the chips on it like the this  24-bit 192 kHz Stereo ADC
https://www.cirrus.com/pubs/proDatasheet/WM8782_v4.8.pdf
I don't really have any ADC, how general purpose is such a thing ? If your voltages and frequency are close to audio properties, I bet someone could do a lot with it. I have a lot of analog stuff to learn 1st tho. But I can't wait to start trying something with ADC's and ram chips, etc

Whales:
Depends what you mean by "intermittent distortion". 

Distortion that cuts in and out arbitrarily? Likely to be a bad connection somewhere.  Parts within the soundcard, connectors to the outstide world or in the outside world (speakers, cables, etc).  EDIT: pay attention to the grounding jumper on the corner of the card too.

Distortion that's always there and does not sound like clipping: could be the caps.  EDIT: the caps are an unlikely cause of problems in general unless this card has been run in a hot environment for a long period of time.

Extra noise that's always there, even when sound is not playing?  Not distortion, instead that's interference from other components.

You need to be able to reproduce the problem if you want to get to the cause, otherwise you will have to remake half the card (and still may not fix the problem).

Whales:
To answer your questions:

Layers: probably not more than 4.  There's no need for super-high density in an audio card, not worth the cost unless you need it.

ADC: yes ADCs are used a lot beyond just audio cards.  It looks like this one supports I2S, a simple and standard interface.

Be wary however that the "24 bit" claim is not necessarily valid in practice, most often the last several bits are not visible/useful/distinguishable form noise or other forms of error.  Also the card might only be useful for AC coupled operation (have not had a proper look, but I saw mention of internal amplifiers).

MathWizard:
This had distortion year's ago, I don't remember exactly how it would start, or how often, maybe a few times a month?

I want to say I fried the fuse trying to power it up out of the PC, but IDK, I should remember either situation, since I'm good like that. So far I've only found the 12V rail on the linear reg. side. No sign of any damage tho. I have a bench PSU, at some point I want to power up the soundcard w/o the PC.

I tried counting the layers with a microscope, but I'm not used to multy-L PCBs at all, so IDK.

It only has +12 and 3.3V in from the mobo. I need to continue with the datasheet searches.

magic:

--- Quote from: MathWizard on March 24, 2020, 11:29:57 pm ---I want to power up the soundcard w/o the PC.

--- End quote ---
What would be the point of that? You aren't going to interface anything easily with PCIe anyway.

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