Digital MPX Forum – Claesson Edwards Audio Forum

This topic has 161 replies, 18 voices, and was last updated 13 years, 5 months ago by yorkie98.

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October 27, 2009 at 5:37 pm #529

rocco123456
Member

Hello…Leif….!!!
Hello…. boys……!!
I think we could speak about digital mpx …in this new topic…..
I hope that we can make a new standard….. what about "D-MPX"….???????

Write your comments……and impressions….!!!!!

Thank you…
Rocco….

October 28, 2009 at 1:46 am #8671

Leif
Keymaster

This might be a good time to mention that there is an undocumented digital MPX output in BBP. It’s always fed before tilt/eq calibration, and can work in parallel with the standard MPX output — but you have to hack the ini file to turn it on.

I’ve used it to feed a pipeline with digital mpx, while feeding a sound card with tilt-corrected mpx, so that i could look at it in mpxtool.

To use it:
* Open the I/O settings
* Select the device you want to use for DMPX in the normal MPX output. Press TEST, and then stop the test.
* Don’t close the I/O settings.
* Edit breakawaybroadcast.ini with notepad
* Search for TestMpxOutput
* Rename TestMpxOutput to DMpxOutput
* Make a copy of the DMpxOutput section and rename it TestDMpxOutput
* Save the file
* Go back to the I/O settings, select your normal MPX output.
* Press TEST again. You should see them both working.

If you want to turn off the DMPX output again, edit the ini file, and rename the DMpxOutput and TestDMpxOutput sections to something else, for example NoDMpxOutput, NoTestDMpxOutput .

Please note that the ONLY difference between MPX and DMPX outputs in BBP is that DMPX is unaffected by Tilt and PEQ!

Also please note that this undocumented feature is not an official feature, is not part of BBP ASIO, and is subject to change at any time.

Best,
///Leif

October 28, 2009 at 7:50 pm #8672

rocco123456
Member

Hello Leif…!!!
Thank you for support…
My dream is this……:

PC(BPP+Airomate)>>>>>>>>>Coaxial Output(D-MPX)(no tilt-no correction)>>>>>>>>>>>Digital Radio LINK…Transmitter>>>>>>>>>>>Digital Radio Link Receiver(D-MPX Output)>>>>>>>DSS FM TRANSMITTER with (D-MPX)input……And then ON AIR WITH ABSOLUTE BEST QUALITY LOUDNESS AND NO OVERSHOOT…..

What ABOUT….???????????????????????????????????????

THANK…
ROCCO……

October 28, 2009 at 8:42 pm #8673

Boki
Member

hi Rocco,
Now you only need solution for link 🙂 .. and yes.. DMPX Transmitter.

October 28, 2009 at 11:02 pm #8674

rocco123456
Member

For the link…. i’m working… and i have a good and open source solution…but i’m still working….
For D-mpx transmitter… i’m not expert…. but all of you yes…and so…. the solution is near..!!!

Rocco….

October 29, 2009 at 4:25 pm #8675

JesseG
Member

As far as the transmitter, I think all you’re talking about is a D-Class switching amplifier. 😉 Not sure how that would be beneficial to the sound, but I wouldn’t be surprised if a lot of the solid-state transmitters already have that topology. It’s efficient and cheap.

October 29, 2009 at 6:25 pm #8676

rocco123456
Member

sorry…. we are talking about "D-MPX" like as "Digital – MPX"…. for a superbus quality of fm sound….!!!!!!!!

November 1, 2009 at 10:23 pm #8677

JesseG
Member

Call me crazy, but eventually the signal has to be turned into analog to become electro-magnetic in nature and amplified for the antenna, etc, etc… And I was under the impression that’s what the DDS exciter sigmacom is working on does. Gets the digital signal as far down the path as will ever be possible within the FM design, and delivers a signal higher quality than any known method we currently have.

Am I wrong?

November 2, 2009 at 12:45 am #8678

sigmacom
Member

[quote author=”JesseG”]Call me crazy, but eventually the signal has to be turned into analog to become electro-magnetic in nature and amplified for the antenna, etc, etc… And I was under the impression that’s what the DDS exciter sigmacom is working on does. Gets the digital signal as far down the path as will ever be possible within the FM design, and delivers a signal higher quality than any known method we currently have.

Am I wrong?[/quote]

No JesseG, you’re not wrong… 🙂

Even the digital modulation schemes like QPSK, QAM etc, become "analog" on air. The difference from FM, is that they have specific and discrete "analog" states.
The QPSK modulation for example, has only four and predefined discrete states (phase variation), while FM can have infinite states. Thus, the QPSK receiver cannot be easily confused and misinterpret between these 4 states, plus the use of error-correction techniques that elevate the fidelity of the transmitted information.

The "infinite possible states of FM modulation", luckily for us, is reduced down to ~16.8 million different states for a 24-bit audio sample. My DDS can accurately represend ~4.3 billion different states on air, and with extra programming + H/W can go up to ~18 quintillion states. The audio samples may arrive at a rate of 48.000 samples/sec per channel, but the DDS updates the output frequency at a rate of 540.000 times/sec. If I didn’t had the internal MPX encoder, it could go >1.000.000 times/sec.

So, about the ‘on air’ representation accuracy of the incoming digital audio, I think we’re good… 🙂

November 2, 2009 at 1:30 am #8679

Leif
Keymaster

I love those numbers! Man I can’t wait to hear this thing.

///Leif

November 7, 2009 at 10:19 pm #8680

rocco123456
Member

Hello Boys…Hello Leif….!!!
Any news about Digital MPX Transmitter prototype…?????
Honever… i’im working on a spdif-qpsk converter…and qpsk-spdif converter…..to convert analogic link in digital link….

Thank you…

Rocco..

Look at http://www.elber.it/en/schede-fm-audio- … .php?id=31

November 8, 2009 at 1:50 pm #8681

sigmacom
Member

[quote author=”rocco123456″]Hello Boys…Hello Leif….!!!
Any news about Digital MPX Transmitter prototype…?????
Honever… i’im working on a spdif-qpsk converter…and qpsk-spdif converter…..to convert analogic link in digital link….

Thank you…

Rocco..

Look at http://www.elber.it/en/schede-fm-audio- … .php?id=31[/quote]
At the end of this week, maybe beggining/mid of next week, it will be completed.

Beside the D-MPX input, will also have analog MPX input, as some people requested.
I disagree with that, and I suggest to use D-MPX of course…

About your digital STL project, I’d love it if you use 64 or 256-QAM and reduce occupied BW.
That kind of STL is in my next plans, if you can do it, I would like to co-operate! 🙂

November 8, 2009 at 4:18 pm #8682

camclone
Member

Gooooooooooood news!

As soon as the prototype with analogue MPX imput is tested well , make some youtube videos with " screenshots" of mesurments!!

sigmacom you will become rich with this box! ( and the 192 KHz SPIF links of course!! )

November 8, 2009 at 10:30 pm #8683

yorkie98
Participant

[quote author=”sigmacom”]
Beside the D-MPX input, will also have analog MPX input, as some people requested.
I disagree with that, and I suggest to use D-MPX of course…
[/quote]

Sigmacom, which standards of digital input are you planning to include? Optical SPDIF, Coaxial SPDIF, AES/EBU?
To please everyone, you will most likely need all 3 but I would suggest that consumer optical would be the most commonly used.

Really looking forward to trying the prototype.. 😀

November 9, 2009 at 12:25 am #8684

sigmacom
Member

[quote author=”yorkie98″]Sigmacom, which standards of digital input are you planning to include? Optical SPDIF, Coaxial SPDIF, AES/EBU?
To please everyone, you will most likely need all 3 but I would suggest that consumer optical would be the most commonly used.

Really looking forward to trying the prototype.. 😀[/quote]
Well, it seems you’re lucky! 🙂 It provides:
– 1 digital electrical interface: XLR connector (selectable Unbal.75 / Bal.110 Ohm)
– 1 analog electrical interface: XLR connector (selectable Unbal.75 / Bal.110 Ohm)
– 1 optical interface: F05 connector (Toshlink – 5 mm)

It recognize AES3 and S/PDIF at any input (electrical or optical) up to 192k.
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