Hi, are you sure it's the card ? As far as I know, the PAS16 had a very powerful amp.
Perhaps the actively powered speakers just can't handle the strong output of the PAS16, thus causing the distortion ?
Anyway. just a thought of mine.. Back in the 90s, when I used my PAS16 almost daily, audio technology was different (Sine vs PMPO).

Jo22 wrote:

Hi, are you sure it's the card ? As far as I know, the PAS16 had a very powerful amp.
Perhaps the actively powered speakers just can't handle the strong output of the PAS16, thus causing the distortion ?
Anyway. just a thought of mine.. Back in the 90s, when I used my PAS16 almost daily, audio technology was different (Sine vs PMPO).

Could be. I am using Klipsch Pro media 2,1 speakers.
Yes, They are powered speakers.

What speakers would you recommend to use with this MV-PAS16 sound card ?
DO I need to use some cheap non-powered passive speakers ?

Could be something as simple as a dirty output connector (or the card is just quite noisy).

If you have some other speaker or even some stout headphones, just try those and compare. If the popping is still there at the same volume, it's probably not your speakers' input stage that's clipping. The first step in troubleshooting is trying to eliminate variables. So, swap out that half of the signal chain and see whether the problem remains.

If you can narrow it down to the card being at fault, there are a few likely suspects. Agreed the output connectors could be one of the problems. I had to replace the jacks on my PAS16 because they were corroded. Another member here posted a picture of an Ebay auction recently and they were also corroded. Chances are good that yours might be as well. Seems to be susceptible to that.

I haven't traced the audio path, but on mine, there were two large capacitors near the audio outputs that looked like they were probably output DC-blocking caps. I replaced those trying to troubleshoot a problem of my own making, but your issue could be caused by bad caps as well.

Finally, the problem of my own making was a bad ground. The PAS uses the bracket for an audio ground. Make sure yours is secured well to the card and your case. Without the bracket, you will not get much of a signal out of the card, and what you do get will sound awful.

Sound fine with my headphones so it must be a problem with my powered klipsch pro media 2.1 speakers.
I will try some other speakers tomorrow.

Problem is probably that you are overloading the preamp of the powered speakers. Question is: why would you want to do that?
These old cards have such a powerful amp on board because they're meant to be used with headphones and non-powered speakers. You're not supposed to turn it all the way up when you connect another amplifier to it.

This is something I've been curious about for a while. Why DID so many sound cards have cheesy speaker amps in them? I can't recall ever once seeing anyone with non-amplified speakers attached to their computer. Was that common in the circles any of you ran in?

Headphones are another matter. Not that it's terribly convenient to have the headphone jack on the other side of the desk... but... a line-level stage should be enough to drive headphones provided it's capable of sourcing enough current. A reasonably stout op-amp will do that, and it's 100% compatible with high-impedance line inputs as well .... as evidenced by about any mobile audio device.

SirNickity wrote:

This is something I've been curious about for a while. Why DID so many sound cards have cheesy speaker amps in them? I can't recall ever once seeing anyone with non-amplified speakers attached to their computer. Was that common in the circles any of you ran in?

I think it was.
The late 80s/early 90s had this thing called 'Walkman speakers'. The lower-end models were non-amplified. Walkmen had enough oomph to use them without an amp.
On my Sound Blaster Pro 2, I used a set of Sony speakers, which I still use to this day.
You can see them in many of my YouTube videos, because they're so convenient to use, just like headphones. Just plug them in, no extra leads, no batteries or anything.
Here's one example: https://www.youtube.com/watch?v=m_pCHSqQmKs

There are some non-powered desktop speakers still available from HP and Dell. I tried some cheap speakers from logitech and I did not get any distortion or poping sound. However the sound quality was not good with these cheap speakers.

When our family computer finally got a Sound Blaster Pro, we got some little powered speakers for it too. You could run them in passive mode just by turning them off, but it was anemic, so I rarely did.

All the pack-in speakers I came across were non-powered, so I suspect that they were more common than not in the ISA sound card era. Of course my friends and I promptly dug up overpowered amps and whatever speakers we could find (the bigger the better) and cranked it - also not a good recipe for sound quality.

The Sound Blaster Pro actually has a notch on its volume wheel (I believe it was somewhere between 4 and 5). This notch indicates the recommended setting when using the output as a line-out.
Later cards such as the GUS had separate line-out and headphone outputs.

Is there any way to eliminate the signal power boost coming from the MV-PAS16 ?
I found this webpage and diagram but I am not an electronics engineer so I don’t know exactly how to interpret it.
https://electronicsforu.com/electronics-proje … dio-amplifier-2

What if I build a PCB board with some components and maybe resistors or some other components to eliminate the signal boost so it wont damage my powered speakers ? I can use wire traces to connect the components on the back of the PCB board.

I can connect the PCB board between the MV-PAS16 and my powered speakers.

There's no need for all that. It's very unlikely you'll damage your speakers. They'll clip when you drive the input buffer amp beyond its rails, but unless the input voltage is high enough to cause excessive current somewhere, it'll survive the ordeal. Just sounds terrible, so turn it down.

If you're dead set on it, add a resistor in-line on the hot (that is, the signal -- not ground) output lead. Experiment with values. The value you need depends on the input impedance of the speakers' amp, and how much you want to attenuate. You can also add a resistor between hot and ground (on the speaker side of the series resistor) to pad it more.

Series:

1out > ---/\/\/\--- > in

Padded:

1out > ---/\/\/\--+-- > in
2                 >
3                 <
4                 |
5                Gnd

I would start with a series resistor between 100R and 1K. (Higher values = more attenuation.) Parallel resistor, if you use one, from 10K to 1K (lower values = more attenuation.)

I don't remember off the top of my head if there are jumpers to disable or bypass the onboard amp -- and if there are, they're not always documented very well. Someone's figured it out though, I'm sure.