Stereo Encoder

David Crespo · Post by **David Crespo** » Thu Mar 17, 2022 8:38 am

Hello, I am currently using a "Pira" stereo encoder which works quite well. I am starting a new project but what I have found is quite expensive.
I have seen these and wanted to know if anyone has tried them, and if they are similar in terms of sound quality to those of "Pira"
Thanks and regards!!
https://www.enigma-shop.com/component/h ... -broadcast

Albert H · Post by **Albert H** » Thu Mar 17, 2022 1:22 pm

No. It's a pretty crude switching coder, with pretty rudimentary audio filtering. Where do you intend to do your stereo coding - at the input end of a link or in a main rig?

David Crespo · Post by **David Crespo** » Thu Mar 17, 2022 5:51 pm

Hello Albert, it is for a main rig

David Crespo · Post by **David Crespo** » Thu Mar 17, 2022 7:15 pm

And what do you think about this one: https://www.a****f.com/es/kit-coder-ste ... ansmitter/
For some reason it hides part of the link but it is the veronica encoder

yellowbeard · Post by **yellowbeard** » Thu Mar 17, 2022 8:04 pm

The name is hidden because that company gets slagged off so much on here, really badly and deeply, so admin made it a swear word to stop him suing. As far as I know you can call them cunts but you can't call them by their registered name.

Don't buy it will be the consensus.
https://www.hf-electronics.nl/Webwinkel ... udget.html
There is that same encoder for cheaper, Netherlands for the win!

David Crespo · Post by **David Crespo** » Thu Mar 17, 2022 10:17 pm

yellowbeard wrote: ↑Thu Mar 17, 2022 8:04 pm The name is hidden because that company gets slagged off so much on here, really badly and deeply, so admin made it a swear word to stop him suing. As far as I know you can call them cunts but you can't call them by their registered name. Don't buy it will be the consensus.
https://www.hf-electronics.nl/Webwinkel ... udget.html
There is that same encoder for cheaper, Netherlands for the win!

OK, lol I didn't know that. Shipping costs are very high here, it is better to buy enigma at least for me.

Krakatoa · Post by **Krakatoa** » Thu Mar 17, 2022 11:36 pm

The Enigma stereo coder is an SMD version of the "SPI stereo coder" that's been around the internet for ages... here is some info: https://www.fluxfm.nu/3-mtr-info-sales/ ... index.html
As Albert said, it is basic 38khz switch mode coder, will sound just fine to the ears, but the output spectrum is not as clean as the Pira (that uses oversampling techniques).

sinus trouble · Post by **sinus trouble** » Fri Mar 18, 2022 12:12 am

Krakatoa wrote: ↑Thu Mar 17, 2022 11:36 pm As Albert said, it is basic 38khz switch mode coder, will sound just fine to the ears, but the output spectrum is not as clean as the Pira (that uses oversampling techniques).

I totally agree with Krakatoa!

The Enigma/SPI coder will do the job! However if you feel brave and have the relevant skills to build the PIRA coder? Go for that!

Its not really expensive but will take up a lot of labour time!

I believe the PIRA coder also supports RDS sync which is an extra bonus!

David Crespo · Post by **David Crespo** » Fri Mar 18, 2022 9:19 am

Hello, thanks for the information. I bought the Pira for €30 already assembled a few years ago, now it is worth double or more.
I'm not capable of doing it from scratch, I can assemble a kit, but my knowledge doesn't go any further.
Thanks!!

David Crespo · Post by **David Crespo** » Fri Mar 18, 2022 10:01 am

I have found another one, the NRG pro 3, how is it compared to the Pira?
https://www.ebay.es/itm/224857914635?_t ... 0667.m2042

Albert H · Post by **Albert H** » Sat Mar 19, 2022 2:27 am

David - that's another very simple, crude coder. I re-worked the design a few years ago, to guarantee that the channels would always be the right way 'round (unlike the A**R*F job further up this page). I also added mono / stereo switching. Again, it's a very basic coder, and doesn't have much filtering.

If you're going to put it with the main rig, the cheap 'n' simple switching types will be OK - you really don't want to give away an expensive one!

What are you using for your audio source? If you're using an MP3 player, you should filter off any audio above 15 kHz to prevent aliasing and the nasty distortion that causes. You could prepare and edit your programmes using "Audacity" and use the filtering facilities built into that software.

David Crespo · Post by **David Crespo** » Sat Mar 19, 2022 7:52 am

If I use mp3 from the computer with stereo tools that have filtering. I would use the encoder from estero tools but I have many meters of cable to the transmitter and it doesn't work well.
I think I'll try to buy the pira which is the one with the best sound quality, thanks for the advice!!!

mikroman · Post by **mikroman** » Sat Mar 19, 2022 2:57 pm

do you have the ability to place a PC with a stereo tool near the transmitter? It is the cheapest and highest quality solution for you.

David Crespo · Post by **David Crespo** » Sat Mar 19, 2022 6:38 pm

I can't, I have the PC at home, the transmitter on the terrace and there are more than 20 meters of cable, I've already tried it and it doesn't work with that much cable.

mikroman · Post by **mikroman** » Sat Mar 19, 2022 9:03 pm

note that pira and other cheap stereo generators have unbalanced audio inputs. There is a good chance in your case that you will experience a groud loop problem. be sure to do a studio-tx wire connection test/modulation test before.

David Crespo · Post by **David Crespo** » Sat Mar 19, 2022 10:37 pm

Yes, I have already tried it. I am currently using it like this and I have no problems, I guess it is not the best thing to have so many meters of cable, but it works fine for me.

Albert H · Post by **Albert H** » Sun Mar 20, 2022 11:30 pm

A couple of useful tricks you could try:

(1) Amplify the composite multiplex output from "Stereo Tool" with a TDA2020 amplifier running form (say) 30V supply. Scale your modulation so that there's (say) 20V p-p of the multiplex running down the cable. At the transmitter end, use a passive resistive attenuator to "scale down" the MPX signal to the level required for the transmitter. The high level of the MPX will be much greater than that of any hum picked up on the way, so that hum won't significantly appear at the transmitter end. Also the low output impedance of the TDA2020 will be reflected in low values for the passive attenuator, so that the capacitance of the cable won't significantly affect the high frequency content, allowing a good quality stereo signal through!

(2) Use a Raspberry Pi 3B+ at the transmitter end, running Stereo Tool into the rig. At your studio end, just send your stereo audio to the Raspberry Pi using something like BUTT (Broadcast Using This Tool). If you have wi-fi, the Raspberry Pi can pick up your studio output wirelessly!

David Crespo · Post by **David Crespo** » Mon Mar 21, 2022 5:33 pm

Good ideas Albert, I'll try to amplify the signal. I also thought about leaving the amp on the deck and leaving the transmitter in my studio.

Albert H · Post by **Albert H** » Tue Mar 22, 2022 1:39 am

A physical separation between the audio and the RF parts is usually sensible

rigmo · Post by **rigmo** » Sun Dec 31, 2023 5:08 pm

DAVID III 3 https://www.qsl.net/yo4hfu/DAVIDE_CLONE.html
https://mirror.unpad.ac.id/orari/librar ... o-encoder/

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