Stereo Tool

I've read the help section thoroughly and learned quite a bit about ST (Vers 7.24). I'll try 7.3 when I get a better sound card in my off-line test computer. But, there are some things on various pages that I don't find explained...

Under AGC, Compressor and Bass Boost are bars marked "Difference". What do they do?
What does the "Oversampled limiting and clipping" do under 'Advanced Clipper'? I'm using the processor on the air and this is not turned on. Yet.

Under Composite Clipping are "Clip demodulated peaks", "Also low frequencies" and "Multipath clipper". I can't find them explained. There is also a box marked "Level". It is at 200%. Level of what?

Sorry for all these questions but I'm enjoying tweaking ST and want to get the most out of it.

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Hi!

Difference button is for listening what the particular filter is doing to the audio, it kinda subtracts the filters output with the actual audio before it or something like that

Oversampled limiting and clipping means that the audio coming to the clipper will be limited and clipped while it's oversampled, which means that the signal going to the clipper is oversampled to higher samplerate (or to a higher bit depth, HELP?!). Anyway, it's there to make the clipping and limiting more accurate and better quality since the clipper will have more "space" to do it's magic.

Composite clipper is black magic to the radio industry at this moment so.... Maybe Hans will fill the missing details as a alchemist wizard.

That rules out selecting the 'difference' button while my station is on the air

Thanks for the explanation. And now, we will see who's next!

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Sorry for not responding sooner, I have been extremely busy with the IBC last week.

Diff -> correct

Oversampled -> Close. Say you have sample values 2, 10, 10, 2. Then if you double the sample rate, you'll get something like: 2 6 10 12 10 6 2. If you clip at level 10 without oversampling, then the peak to 12 would be completely invisible and hence not be clipped - the analog output signal would still contain this peak. Oversampled clipping works at 4x the sampling frequency to remove almost (except the last 1% or so) all these between-sample spikes. It's not enabled by default because it takes more CPU load and it hurts the audio quality a bit more, because more peaks get clipped. But if you have a sound card or other output that cannot handle these between-sample spikes, or if you're going to resample the audio afterwards, you really need to turn it on.

For FM you always need 4x oversampling to stay within legal limits, so this checkbox is disabled when you're using FM output.

"Also low frequencies" - use composite clipping instead of traditional clipping on lows. Probably has very little effect, but does increase CPU load. Theoretically it should be better though.

"Multipath clipper" is an experimental feature comparable to Stokkemask clipping, except that it works identically on all frequencies (Stokkemask has more effect on the extremes at +/- 75 kHz). Since you found that Stokkemask helps for these high frequency issues (other post), I would be really curious if you could also test:
- Different levels of Multipath Clipper (that's what the 200% slider is for)
- Single sideband stereo, all 3 modes (skip "Extreme", it's only there for some theoretical reasons but it causes issues).

Regarding to stereo, multipath, etc.. i found that stokke is best to use if you need to choose from SSB, multipath clipper, or stokke.
- SSB do almost nothing in my tests and it hurts audio, compatibility problems... Many Sony tuners does not like it, especially Sony car radios
- Multipath clipper kinda helps but it hurt audio a lot.
- Stokke does not hurt audio much, it is compatible with many tuners and actually super bad tuners likes it. RF is perfect.

If Stokke can be even better that would be huge +.

I cannot promise anything there - but I will definitely try (chances are that I'll need more CPU processing power to do it though).

Right now I check once at the start if there's a Stokkemask issue, and if so, I enable the filter - I need to use it multiple times for each sample though. And I don't look at in-between results to see if it's still needed. I can add that - but the analysis is expensive.

I didn't think we used stokkemast in the usa..Never saw it used.doesn't it affect your stereo separation?

It does. Less so if you increase that slider. If it improves the reception it might be worth it - there's a reason why it's recommended by the ITU.

I've had it turned on for a couple of weeks and don't think any decrease in separation is bad. I have the "small overshoots" at 5dB and don't hear any multipath. And I agree with Bojcha's conclusions above. That's also what I found when I tried the multipath clipper and SSB.

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