Change the hard drive.

This damned problem!!! I have faced it too...
In the couple of cases I had I swapped PSUs... the problem either disappeared or the noise became more faint...
IMHO this is due to old parts and poor shielding designs of the era... try and change the psu, it might get better DK!

Good old analogue technology. Just change parts until it's better 😀

If the source are voltage fluctuations then change the PSU, but
Usually I build my older computers this way that the soundcards are put into the last ISA slots. If you have a free ISA slot, leave it between the soundcards and the other ISA cards.
If this does not help, mirror the cards in the slots and try the other end of the bus. This is often more difficult since this area is mostly blocked for longer cards.

Some shielding may help. It might even work if you plug a non used card between the soundcards and the rest.

Mau1wurf1977 wrote:

Good old analogue technology. Just change parts until it's better 😀

I was hoping someone could point me in the right direction rather than have me pull the whole thing apart and rebuild from scratch 😜

If the source are voltage fluctuations then change the PSU, but Usually I build my older computers this way that the soundcards […]
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If the source are voltage fluctuations then change the PSU, but
Usually I build my older computers this way that the soundcards are put into the last ISA slots. If you have a free ISA slot, leave it between the soundcards and the other ISA cards.
If this does not help, mirror the cards in the slots and try the other end of the bus. This is often more difficult since this area is mostly blocked for longer cards.

Some shielding may help. It might even work if you plug a non used card between the soundcards and the rest.

The sound card is already in the ISA slot that is most distant from the PSU and hard drive.
The LAPC-I is right next to it.

Swapping the PSU made no difference. Admittedly its another old AT PSU but its not like new ones are easy to come by...

I think skard is on the right track. Unplugging the hard drive and booting from floppy still has some noise but it seems greatly reduced. Removing the hard drive from the case so its electrically isolated (except for the power cable) doesn't make a difference either.

So I removed the drive and plugged in a CF card with IDE adapter. I can STILL hear the computer thinking noise, particularly when accessing the disk.

I wonder if using an 80-wire IDE cable would be of any benefit...

caps and coils make those noises

cdoublejj wrote:

caps and coils make those noises

Coils, maybe, but not capacitors. At least, there's no reason they should.

Well short of replacing every cap and coil in the whole system, that doesn't really help me much.

I was fiddling last night and just about rebuilt the whole thing with spare parts and the noise still occurs. I guess its just one of those idiosyncrasies of computers of the era. I probably never noticed back in the 90's because I was using those crappy unpowered paper cone speakers that came bundled with sound blasters, and now that I'm using quality headphones and amplified speakers the noise is a lot more noticable.

The other thing of course is to use a different card. The AWE64 GOLD should give you good results and goes well with your LAPC-I.

You'll lose OPL3, but at least the sound should be clearer.

The Media Vision PAS16 has very good shielding. It does have a hiss of it's own, but it's more a Hi-Fi hiss like from a record and it's constant regardless of what's going on. I didn't get any "computer thinking" noises on that card though.

Comes with an OPL3 chip and Sound Blaster 2.0 compatibility.

Actually, I think Keropi had the right idea with the PSU. A bit of Googling suggests the problem even happens with much newer computers: I work with one that, at times, whines at a slightly different pitch when I scroll a window up and down.

Silly question, perhaps, but can you still hear the sound even if you take the sound card out entirely? Or what if you run the PSU on its own with only, say, a CD-ROM drive plugged into it to provide a variable load?

Maybe you can try clamping down the PSU more securely. I guess if you're feeling really adventurous, you can open the PSU right up and see if you can pinpoint the exact component (and clamp it down more securely), but that's kind of risky.

Ah yes, but that's the kind of whine that you hear coming from the computer, not through the speakers. Video cards also have this issue and in general the higher powered your gear is (the more amps you are pulling), the louder.

In many cases enabling Vsync reduces or removes this whine as it limits the power draw somewhat.

EDIT:

There are CF card adapters (I use such a model) that plug directly into the IDE port. So no IDE cable at all.

Mau1wurf1977 wrote:

The other thing of course is to use a different card. The AWE64 GOLD should give you good results and goes well with your LAPC-I.

You'll lose OPL3, but at least the sound should be clearer.

I don't want to lose OPL3 because a lot of the games I'm playing are FM-only.

Plus I need a Sony CDROM interface. Unless I go out and buy a new optical drive which I'd really rather not.

Was really hoping to keep the SB Pro to keep the build's aesthetics but it seems there's no real solution save for swapping out the sound card.

Silly question, perhaps, but can you still hear the sound even if you take the sound card out entirely? Or what if you run the PSU on its own with only, say, a CD-ROM drive plugged into it to provide a variable load?

No its definitely coming through the speakers. If I remove the speakers/headphones there's no noise, or if I turn the speakers off the noise stops.

I've tried a new PSU with no change.

I've also tried new IO controller, video card and hard drive. I've also disconnected all floppies and CDROM with no change.

I had this Sound Blaster 16 variant picking up static. I could reduce it significantly by placing a bunch of electrical wire (thin wire, insulated, wrapped up like a coil) on the right part of the sound card. I could not grasp the logic of it much, like when I moved the bunch of wire just a little the noise came back.

DonutKing wrote:

No its definitely coming through the speakers. If I remove the speakers/headphones there's no noise, or if I turn the speakers off the noise stops.

I see...

In that case, can you be certain that the noise is originating from the sound card and not within the speakers/headphones? If it's not within the sound card, maybe you can put some RF filter chokes on your audio cables.

I suppose if you get really desperate, you can look into some kind of post-processing solution (like a second cheap computer?) that will cut out the specific frequency of the whine.

DonutKing wrote:

I don't want to lose OPL3 because a lot of the games I'm playing are FM-only.

Plus I need a Sony CDROM interface. Unless I go out and buy a new optical drive which I'd really rather not.

Was really hoping to keep the SB Pro to keep the build's aesthetics but it seems there's no real solution save for swapping out the sound card.

You can try using both cards. Configure the SB Pro with "off" values and the AWE64 GOLD will sit at the usual 220/5/1/5 or 220/7/1/5.

Then if you want FM + speech you use the SB Pro 2.0 and if you want MIDI + speech you use the LAPC-1 and the AWE64 GOLD.

FM will play out of both cards, though it should be possible to disable FM on the AWE64 GOLD. But when I tried this I had issues with some games not detecting the AWE64 GOLD as Sound Blaster anymore...

Bumping this thread for it still very relevant.

I acquired a SBPro2 CT1600 (069237) and it has the same thinking noise but mine sounds like high pitched whine that changes in pitch.
The thinking noise is coming from the YMF262+YAC512 part of the card BEFORE the mixer chip.
When I lower the FM volume to 0 using the mixer software the noise is completely gone, making the SBPro2 very silent card.

Further investigation of this matter came to show that a PWM controller of the CPU/BUS on the Motherboard somehow injects noise, but I don't know whether it is on Ground, 5V or 12V but it surely reaches the SBPro2 through one of these.

Here is a picture of the problematic area:

* Red circled SMT CAP is temperature sensitive and changes the noise pitch when I put my finger on it.
* Green arrow points to a PWM controller KA3843B, the red circled cap is in its RT/CT network responsible for the frequency and duty cycle.
* Blue arrow is the CPU voltage jumpers.

Here is how it sounds:

0 to 6 seconds, Volume wheel at zero.
7 to 12, Wheel at full (FM mixer volume zero).
12 to 16, FM mixer volume full.
16 to 26, Touching with my finger the red circled cap.
26 to 31, FM mixer to zero.
31 to end, Wheel to zero.

Unlike the YMF719 that I regularly use, the SBPro2 interacts with the motherboard somehow and picks the slightest change in voltage, hence CPU/BUS thinking noises.
I tried filtering the noise by attaching a small ceramic caps to the ISA slot on-the-fly between 5V and GND where the YMF262 takes its power from, but to no avail, the thinking noises are still there.

So, the thinking noises come from the Motherboard/CPU/BUS and affect the YMF262 part of the SBPro2 but NOT the PCM part of it, the PCM part is actually as silent as my Yamaha YMF719...
BTW, all the PCM DAC part of the SBPro2 take 5V power from a TO92 regulator (MC78L05) on board, NOT from the 5V that the YMF262 take power from which is straight from the motherboard.
Strange isn't it? 😕

I know further investigation can actually solve the issue.
Can someone try to zero the FM volume of the SBPro mixer and report if the thinking noises are gone?

EDIT:
Here is a sample of Doom gameplay using my CT1600 with FM completely disabled via SBPVOL TSR software after the game starts.
Track is normalized to -0.1 dbFS Peak, self noise is -79dbFS RMS, the card can be considered very quiet for an ISA card especially when knowing that 8bit is only 48db.
The SBPro2 is actually a very quiet ISA card if there is no interference!

Interesting discussion. Although this may not be relevant to the complainants here, but I also have similar issues with mouse movement and the "thinking sound" which I isolated to my KVM. As I am not going to do without my KVM, I have learned to live with it. It is only noticeable when the speaker volume knob is turned up quite a bit and there is nothing being played through the speakers.

I have had comparable issues on even my newest PC (with a Sound Blaster ZxR), at least it sounds basically the same.

I use two sets of speakers in combination with audio switches, Quadral Rondo Aktiv (for the main rig, WinXP & DOSBox machine and the PC I'm doing my office related tasks on) and Canton Plus Media 3 (for all my retro PCs).

The first time I noticed those sounds was when, years ago, I connected the former main rig and the former office PC to an audio switch. All of a sudden I could hear the mouse movements on the main rig and there was a constant whining or whatever you want to call that, changing pitch with e.g. cpu load.

When I started setting up more then one retro PC (using a KVM switch with audio) that too gave me those noises.

The solution that worked for me is this: http://www.palmer-germany.com/pro/en/PLI-03-L … annel-PLI03.htm

Expensive, yes, but now I don't have any noise at all. I use several of those boxes. Whenever I encounter a problem like that, I order another one, hook it up in between line out and audio switch and I'm fine.

I think you hit the nail on the head, the "thinking noises" may very well be due to the fact that the YMF262 doesn't take it's supply voltage from the 7805. I'll check my Aztech and TB Tropez+ cards and see if the 7805 on them supplies the YMF262, as these are my quietest cards and don't have "thinking noises".

Most 7805s have a ripple rejection ratio of around 70-80dB, which will significantly reduce any ripple that may be introduced into the YMF262.