Stereo Tool
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Stereo Tool 6.10
https://forums.stereotool.com/viewtopic.php?t=3065		 Page 17 of 213
Author:  eldoradofm [ Thu Mar 24, 2011 3:57 pm ]
Post subject:  Re: Stereo Tool 6.10
@Hans I've did a test with your assymetric filtering from the calibrate menu. I'm testing now with audio until 18,5 kHz wich sounds awesome on FM without problems with the RDS. I think it's a must have before you upload your test file from the processing day.
Hmm, i do see the overshoot problem you were talking about. If you could fix that it's perfect.
Author:  Bojcha [ Thu Mar 24, 2011 4:08 pm ]
Post subject:  Re: Stereo Tool 6.10
what assymetric filtering from the calibrate menu ?
Author:  eldoradofm [ Thu Mar 24, 2011 5:25 pm ]
Post subject:  Re: Stereo Tool 6.10
Selecting Similar, but only using 23-38 KHz stereo signal.

What Leaf does is allowing highs until 17,5 kHz so you get 38-17,5 = 20,5 kHz. So plenty of protection for the pilot tone. But when you don't do asymetric filtering you also get 38+17,5 = 55,5 kHz which get's in the way of the RDS signal. So what he does is filtering on 20,5 kHz on one side and at 38+16=54 kHz on the oder side. But you could also filter everything from 38 kHz upward.
Author:  Bojcha [ Thu Mar 24, 2011 5:43 pm ]
Post subject:  Re: Stereo Tool 6.10
I know what you talking about, but i don't know how you done that in ST [?]
Author:  Luke [ Thu Mar 24, 2011 6:55 pm ]
Post subject:  Re: Stereo Tool 6.10
Quote:
Selecting Similar, but only using 23-38 KHz stereo signal.

What Leaf does is allowing highs until 17,5 kHz so you get 38-17,5 = 20,5 kHz. So plenty of protection for the pilot tone. But when you don't do asymetric filtering you also get 38+17,5 = 55,5 kHz which get's in the way of the RDS signal. So what he does is filtering on 20,5 kHz on one side and at 38+16=54 kHz on the oder side. But you could also filter everything from 38 kHz upward.

To be honest I don't understand the need for that.
It looks nice on a spectrum analyzer but adds nothing for 99.9% of the users. Have you seen what kind of filtering you have in a FM-tuner?
If you set the filter to 15.5KHz it is more than sufficient.
Author:  eldoradofm [ Thu Mar 24, 2011 7:01 pm ]
Post subject:  Re: Stereo Tool 6.10
I can clearly hear the difference between 16 kHz filtering or higher with my Sony ST-SB920 tuner.
I think there are a lot more tuners where you can hear this difference. But yes it depends on the filtering used in the tuners.
Author:  Luke [ Thu Mar 24, 2011 7:42 pm ]
Post subject:  Re: Stereo Tool 6.10
Quote:
I can clearly hear the difference between 16 kHz filtering or higher with my Sony ST-SB920 tuner.
I think there are a lot more tuners where you can hear this difference. But yes it depends on the filtering used in the tuners.
You must still have really good hearing. When I see the spec from your tuner ST-SB920 30Hz-15KHz (+0.3/-0.7dB) not to bad at all. Maybe you can do a sweep and see what is left at 16 and 17KHz.
I have a modified st-sa5es and I can't hear the difference anymore if I shift from 15.5 to 17KHz :-(
Author:  eldoradofm [ Fri Mar 25, 2011 1:50 am ]
Post subject:  Re: Stereo Tool 6.10
This is measured from the audio output from the tuner. I did a sweep from 30 Hz till 20 kHz and used a LPF of 16 KHz and one of 18,5 KHz in stereo tool.
It's about 10 dB's down at 17,5 KHz and 15 dB at 18 kHz compared too the flat line.

Attachments:
Meting.PNG
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Author:  Brian [ Fri Mar 25, 2011 2:58 am ]
Post subject:  Re: Stereo Tool 6.10
@Hans - HPF "Order" is not being saved in the DSP version. It apparently defaults to 6. No entry in the STS files for it.
Author:  hvz [ Fri Mar 25, 2011 3:52 am ]
Post subject:  Re: Stereo Tool 6.10
@Brian: I know, I was waiting for feedback to see if this feature is useful first.

@eldoradofm: I'm wondering if Leif's idea really works. Somehow, an FM receiver needs to filter out the RDS signal (which is very close to the stereo signal). Now the question is: Do receivers filter out frequencies above approx. 54.5 kHz before stereo decoding, or do they first decode the stereo and then remove the sounds above approx. 17.5 kHz (54.5-38)?

If the latter is the case, this feature is useless...
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