Hissing and whistling in the STe audio output

[BlankVector]

Here is the abominable sound of the left channel of my STe (right channel is not much better).
This is the sound just after reset, and booting the Faith demo. Typical example of floppy loading.

I have quickly recorded the left speaker, then normalized the wave. This is exactly what I hear when I turn the volume (not so) up. Of course I have bad speakers with some white noise, but it is completely negligible compared to that STe internal mess.

Note that the microphone was very close to the speaker, the actual floppy motor noise can't be heard. But floppy parasites are strong as hell, you can easily recognize track steps in the last part.

I also provide Audacity analysis.

There is a peak around 14700 Hz, certainly the hi-pitched constant noise I always hear, regardless to floppy activity. I don't know if that could be related to the 15 KHz video signal.

[exxos]

yikes that is bad indeed.

Wrap the floppy power cable through a core like this...

fc.jpg

.. likely you will have to flick out the cables from the connector and wrap around the core about 3 times and put back in the connector. Put a low ESR 1,000uf as close to the motherboard end of the 5V floppy power cable as possible.. also place a 1,000uf across the floppy side of the cable...

That *should* help clamp a lot of noise issues...

Its actually the same idea as used on car radios.. I had to do the same on my vans radio, as the alternator was causing noise in the my speakers, plus things like the indicators was causing clicks and pops.. when I used the idea as mentioned above, all problems vanished. It's a really common problem and common solution.

[Paulo P]

Hmm, that's interesting.
OK, I will record my "mess". Directly from STe audio output by cable, no microphone, no speakers, just directly to line input on my soundcard. Then I will normalize the wave and put it here.
It looks that my motherboard is fully recapped (pictures are here: viewtopic.php?f=41&t=569), so I think this problem wouldn't be solved. :(

[Paulo P]

Here is a normalized sample from my STe audio output recorded directly by audio cable. So, what do you think? Thanks very much.

[troed]

Here is a normalized sample from my STe audio output recorded directly by audio cable. So, what do you think? Thanks very much.

You have an enormous peak at 2600Hz, just as I do. Then you have one at 15.x kHz which is interference from the video output.

The 2600Hz peak is really interesting.

[Paulo P]

Here is a normalized sample from my STe audio output recorded directly by audio cable. So, what do you think? Thanks very much.

You have an enormous peak at 2600Hz, just as I do. Then you have one at 15.x kHz which is interference from the video output.

The 2600Hz peak is really interesting.

Maybe a motherboard recap would help...

[exxos]

If anyone has a bad motherboard to loan me for a while which has these faults, then I could look into it myself. None of my boards as yet have suffered anything like what you guys are seeing :shrug:

[Paulo P]

If anyone has a bad motherboard to loan me for a while which has these faults, then I could look into it myself. None of my boards as yet have suffered anything like what you guys are seeing :shrug:

That's very interesting to me. I have one more STe at home and it has the same problem. :O

[exxos]

That's very interesting to me. I have one more STe at home and it has the same problem. :O

Send me the MB on its own and I will take a look at it..

[troed]

Analyzed a third sound capture from a video that had been uploaded to youtube. The same ~2600Hz peak and harmonics is found there, so I'm beginning to become quite certain that this is indeed the well-known "STE high pitched whine".

As to the cause ... well. I don't think it's age related (I remember it from way back when the machines were new) and it's also something that's common to different machines doing different things.

ste_high_pitched_whine.png