[LAU] Crackles in audio - how to troubleshoot ? Tim's TEST RESULTS:

termtech termtech at rogers.com
Fri Aug 26 17:13:49 UTC 2016

On Friday, August 26, 2016 5:04:12 AM EDT jonetsu at teksavvy.com wrote:
> On Thu, 25 Aug 2016 18:19:17 -0400
> termtech <termtech at rogers.com> wrote:
> Hi,
> > Is this a new or replacement PC?
> Neither.  I have this one for a few years now.
> > Go to this site:
> > http://onlinetonegenerator.com
> > 
> >  and input a high frequency of say 15000Hz, so that you don't
> >  hear the tone so much as any noise that may accompany it.
> There is no noise at all, at the moment.  The problem is not steady.
> It can happen suddenly.  

OK. Make sure you try some of the following:

Turn off any SpeedStep or Cool n' Quiet BIOS settings.
These are CPU clock throttling mechanisms that ARE well
 known to produce pops and clicks (but not the digital noise
 I mentioned). Turning them off or adjusting them is known to 
 solve many cases of clicks and pops.

I found some tools in Linux for handy speed settings
 such as a neat 'indicator-cpufreq' taskbar icon where
 you can adjust the throttling mechanisms.
You get 'performance' 'on demand' 'power save' modes etc.
 as well as a dozen or so specific CPU frequencies to choose from.

Unfortunately it doesn't seem to work.
No matter what I choose doesn't seem to affect anything.
	"grep -E '^model name|^cpu MHz' /proc/cpuinfo"
 shows no change in the CPU cores' frequencies.
(SpeedStep is currently enabled.)

Speaking of which, I also tried adjusting the card's 
 interrupt CPU affinity settings (on interrupt #20) :
	sudo echo [desired CPU bit pattern] > "/proc/irq/20/smp_affinity"
	"cat /proc/irq/20/smp_affinity"

No change in noise.

> I have linked somehow to the use of Bitwig
> although from your comments I now start to veer off towards the 10101LT
> capacitors.
> One thing: with a tone say of 1500HZ generated from the above web page,
> there is crackling as soon as the volume slider is moved from left to
> right repeatedly.  No crackling otherwise.

Hm, well in my case, when the digital noise is present, simply moving
 the mouse around, across borders and so on, affects the noise.

The volume slider thing may be normal, possibly just the way the site works,
 not seamlessly switching volumes.

(I mention in another post this MB is shared video memory, so 
 I tried a video card, but no luck.)

> Compensating for audio variations could involve capacitors I think.  If
> they start to fail then shaking the volume slider could produce noise,
> could it ?

Mm, as I say that could just be the site and the volume slider making pops. 

If weak capacitors are involved you'd likely get some kind of noise 
 with any operation, even just playing a sound.

> > So, today I brought the card to my dealer and we tried it on
> > 
> >  another i5 PC, having a much better Asus MB.
> It"s also an Asus board in this machine.  I always get Asus since some
> time.

Yeah, one of the best. Love 'em.

> > Believe me if there was something I could do to make it work
> > 
> >  I would do it and report back. I was contemplating replacing the
> >  electrolytic capacitors on the card just in case. You'd be surprised
> > 
> > just how weak caps can be, allowing digital ripple on supply lines
> > etc. It's possible that may help.
> > But given that the card works OK elsewhere, and I don't want to waste
> > 
> >  any more time on this, I am just going for the replacement PC
> > 
> > instead.
> Replacing the capacitors could be something to do.  Are they easy to
> get ?  How many of these are on the card ?

You should be adept at soldering and have a good iron.
This is a double sided (likely multi-layered) board so the iron needs to
 be good and not lose heat quickly to surrounding copper, metal etc.
You'll likely want de-soldering braided wick, or a de-soldering pump,
 to remove the solder from the holes, although luckily with caps having 
 just two legs you can sometimes get away with just pushing the 
 two legs of the new capacitor through the solder-filled holes one at a time.

As for the actual caps, I can't look now 'cause it's installed, but I did 
 of course see cheap non-Japanese caps in there (never a good thing).

In particular, you'll want to start with the largest ones, near the
 7805 +5V voltage regulator. Good power bypassing is a crucial start.

I wouldn't worry too much about all the other small ones,
 most of them are signal decoupling caps and if bad you would likely
 get steady clipping or weak signals instead of digital noise or 
 infrequent (non-clipping-related) pops.
Still, some of the smaller caps can be power supply bypass caps
 so eventually you may have to make your way to them.

As a repair tech, I have dealt with thousands of noisy situations like this.
Bad converter bits, weak data buses, noisy supply lines... Seen it all.
Anyone who has ever brought a hand close to a CD player's sensitive 
 optical pickup cable will know the noise that is produced.
That's sort of, kind of, the digital noise I'm getting.
I suspect that if I open this PC's case and start touching the 1010 card 
 with my fingers, providing some extra capacitance and conductance, 
 something would snap into place - it is that close to functioning fully 
 properly. I hate being defeated by crap like this so I am thinking of trying 
 that when I get a chance. I hate when stuff has to be discarded.
I may just hook up my oscilloscope to try and find out what's going on.
It may reveal bad caps...

* Insider's tip: Freeze spray is your best friend!
Get a can of it, or use an upside down can of compressed air 
 (it makes freeze spray when upside down).
Spray the capacitors, semiconductors, even the copper traces on the board,
 to reveal bad caps, bad semiconductors, bad traces etc.
Then watch for the symptoms to appear or disappear.
Guaranteed to easily reveal bad caps in virtually ALL situations.
(The chemical electrolyte heats up / cools down.)
The inverse is also helpful: Heat the top of the metal cans of the
 capacitors with the soldering iron tip and watch for changes.
I may try it and report back...

> OTOH, I was at the music store recently and upon mentioning 1010LT the
> remarks went on about age and who is older.  Maybe it could be time to
> upgrade to a newer card.  Maybe.  I have no idea on what's on the
> market that plays very well for Linux.  I'll start another thread.

Yeah exactly, I am (or was) searching for possible replacements
 so I am curious what is out there, good to start a thread on this.
Seemed there's not much comparable to this card, new products
 out there seem to start in the hundreds of dollars :-(

Particularly USB devices I'd like to know how well they perform,
 latency etc.


> Cheers.

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