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Sound quality web vs. FM? Why so hard for FM?
https://forums.stereotool.com/viewtopic.php?t=33490		 Page 1 of 2
Author:  baldrick_nz [ Fri Feb 03, 2023 5:14 am ]
Post subject:  Sound quality web vs. FM? Why so hard for FM?
Hi all,

Why is it that it seems much easier to get a pleasing sound when processing for web, but is so much more difficult doing the same for FM?

I'm using our wired network to get audio from our playout PC to TX PC, using VLC and ogg (500k) at the playout PC, receiving using the built in VLC plugin in ST standalone at the TX. I've tried using flac encoder in VLC, but this seems to muddy things more.

It just seems whatever FM preset is used it's not as clear, more muffled than it's web counterpart - particularly with regard to vocals (4000-7000k).
I'm aware of the 16k limit for the stereo pilot signal, but I'm a bit unsure how this would affect the over driven sound all round?

If someone could provide some clarification, that would be awesome. Are some TXs better than others in this area, if so which ones? I'm currently using an Aareff TX.

Cheers,
Baldrick
Author:  Bojcha [ Fri Feb 03, 2023 7:23 am ]
Post subject:  Re: Sound quality web vs. FM? Why so hard for FM?
You probably doing something wrong and we dont know what.
Transmitter, not calibrated, some weird settings or setup inside MPX line, not disabled internal strereo-coder.. Soundcard/ST samplerate or soundcard itself. Cables.. etc.

16kHz is not problem you probably don't even hear beyond that.
Author:  xristostsilis [ Fri Feb 03, 2023 7:47 am ]
Post subject:  Re: Sound quality web vs. FM? Why so hard for FM?
As bojcha said you need first to check your sample rates across the whole broadcasting chain. Then you have to play the game of calibration. Sometimes this one is an easy task if you have a good exciter, however it might be a nightmare if your exciter is not good. You need to check the YouTube videos from Hans that explain how to calibrate an fm radio station.

You actually need an analyser to see what's going on with your station. it's not an easy task like streaming as you where saying.

At your position I would not use ogg or Flac streaming and process at the tx site. you better go with micro mpx and some hifiberry sound card that I would calibrate first. :)

with micro mpx you forget about sample rates and most of the problems
Author:  baldrick_nz [ Fri Feb 03, 2023 9:42 am ]
Post subject:  Re: Sound quality web vs. FM? Why so hard for FM?
Thanks for the replies guys. Much appreciated.

My TX only has power, PPL unlock, PPL locked and Drive Power LEDs, no meter of any description. It had a stereo coder inbuilt, but it was disconnected in favour of MPX which works fine.

https://www.aareff.com/en/fm-transmitter/1-watt/ (1W is the maximum allowable for LPFM in NZ)

I've seen the video Hans put out, but the meter he used I can't find, borrow or beg from anyone locally. C19 has meant a redirection of finances away from the station (it's just me running it) so to buy one is out of the question, at least for the foreseeable future. Same goes for MicroMPX, sadly.

As for sample rates, the playout PC transfers audio over the network to the TX PC at 48k/ogg. From there, the TX makes it 192k to allow for RDS.

It sounds like it's probably more to do with the TX, or calibration of, and maybe a better lead between the TX PC and the DAC (a Scarlett 2i2, used as a sound card for the PC) might also help. It's just a cheap RCA to RCA with a RCA-6.5mm tip at the DAC.

Hopefully things will improve financially soon and I'll be able to buy a better TX and the gear to calibrate it, but until then we're not on air and I can just listen over the network or while I'm out and about in the meantime.
Author:  Bojcha [ Fri Feb 03, 2023 9:47 am ]
Post subject:  Re: Sound quality web vs. FM? Why so hard for FM?
It's transmitter.
Author:  baldrick_nz [ Fri Feb 03, 2023 9:51 am ]
Post subject:  Re: Sound quality web vs. FM? Why so hard for FM?
Quote:
It's transmitter.
Thanks. Yeah, I might see if I can improve on the wiring from the MPX input to the connector. I notice if that moves away from the metal box, it dulls the sound too.

Did you mean the TX is crap, generally speaking? Are you familiar with them?
Author:  Bojcha [ Fri Feb 03, 2023 10:02 am ]
Post subject:  Re: Sound quality web vs. FM? Why so hard for FM?
Sure you can check cables and connectors but something in transmitter is probably wrong.

If you can, play PinkNoise for about 20 seconds, use only Clipper!, attach some good tuner on other PC and record that, then upload here.
Author:  baldrick_nz [ Fri Feb 03, 2023 10:04 am ]
Post subject:  Re: Sound quality web vs. FM? Why so hard for FM?
Quote:
Sure you can check cables and connectors but something in transmitter is probably wrong.

If you can, play PinkNoise for about 20 seconds, attach some good tuner on other PC and record that, then upload here.
Pink noise? I've head of white noise. Same thing?
Author:  Bojcha [ Fri Feb 03, 2023 10:08 am ]
Post subject:  Re: Sound quality web vs. FM? Why so hard for FM?
Quote:
Quote:
Sure you can check cables and connectors but something in transmitter is probably wrong.

If you can, play PinkNoise for about 20 seconds, attach some good tuner on other PC and record that, then upload here.
Pink noise? I've head of white noise. Same thing?
Eh there is 3 basic "noises" White, pink and brown. So, pink.
Author:  baldrick_nz [ Fri Feb 03, 2023 10:39 am ]
Post subject:  Re: Sound quality web vs. FM? Why so hard for FM?
Quote:
Quote:
Quote:
Sure you can check cables and connectors but something in transmitter is probably wrong.

If you can, play PinkNoise for about 20 seconds, attach some good tuner on other PC and record that, then upload here.
Pink noise? I've head of white noise. Same thing?
Eh there is 3 basic "noises" White, pink and brown. So, pink.
OK, I'll sort that tomorrow. Got a bit late now. I replaced the single wire MPX with a short length of RG58 earthing the braid to the chassis of the TX. Seems to have made a decent improvement in the fidelity stakes, but yeah I'll try your idea tomorrow.

Thanks for persevering with me!
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