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Author Topic: Stereocoder design  (Read 3706 times)

Stereocoder design
« on: June 08, 2024, 12:49:28 am »
Design for a stereocoder.
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Re: Stereocoder design
« Reply #1 on: June 08, 2024, 03:15:33 pm »
NRG stereo coder
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Re: Stereocoder design
« Reply #2 on: August 13, 2024, 09:56:05 pm »
Quote from: Dave on June 08, 2024, 12:49:28 am
Design for a stereocoder.

That's an oldie!  It's a truly horrible design, and will have lots of "unwanted" outputs!

If you're looking for a really good, easily built stsreo coder, I'll put one up here shortly.
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Re: Stereocoder design
« Reply #3 on: August 15, 2024, 06:19:41 pm »
Look forward to seeing it
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Re: Stereocoder design
« Reply #4 on: August 18, 2025, 02:23:38 am »
Sorry for the delay - here it is:


This was one I designed for NRG back in about 1999.  Both the subcarrier and the pilot generation are oversampled for purity.  The distortion is very low, the stereo image is fabulous, and the harmonic products are well suppressed.  It's about as good as you can get with cheap CMOS and a couple of NE5532 low noise dual op-amps.  The supply used an external "wall wart" providing low voltage AC to the board.  This is half-wave rectified - either way, to derive +/- 15V.  A couple of resistive droppers and zener clamps provide +/- 7.5V for the logic ICs.

There were jumpers on the board to select 50µs or 75µs pre-emphasis, and we used passive Toko 15 kHz lowpass filter modules to make certain that no audio content would interfere with the 19 kHz pilot (or cause aliasing products).  Those filters were originally designed for use in tape recorders to prevent  the tape bias signal beating with the 19 kHz pilot if you were recording from the radio!
« Last Edit: August 18, 2025, 02:35:32 am by Albert H »
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Re: Stereocoder design
« Reply #5 on: August 18, 2025, 10:58:56 am »
Hi Albert,
i did copy the NRG Pro 4 coder and get some PCB's printed and populated the board but it didnt work. ive probably messed something up as im getting 12v on MPX output. i put it to 1 side for the minute. ill get some pictures uploaded of it when im at home. maybe you might spot something or point me in the right direction to get her working.

cheers

Ben
« Last Edit: October 02, 2025, 07:00:30 am by MonTaylor »
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Re: Stereocoder design
« Reply #6 on: August 28, 2025, 07:28:20 am »
here is my build
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Re: Stereocoder design
« Reply #7 on: October 14, 2025, 01:13:19 am »
At first glance, your board looks about right, but I can't see what you've done with the tracks!

Make sure that you have the right supply voltages in the right places - all the op-amps are supplied with +/- 12V, and the logic ICs with +/-7.5V.  That's the very first thing to check.  If the supply voltages are wrong, it's not going to work!
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Re: Stereocoder design
« Reply #8 on: October 29, 2025, 06:56:05 am »
its working now. i found a fault on the pcb on IC2. 2 cut traces and a jumper wire and its working as intended
« Last Edit: October 29, 2025, 07:01:07 am by MonTaylor »
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Re: Stereocoder design
« Reply #9 on: November 02, 2025, 08:56:15 am »
Good it works .
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Re: Stereocoder design
« Reply #10 on: November 05, 2025, 09:14:15 pm »
Quote from: MonTaylor on August 28, 2025, 07:28:20 am
here is my build
Hi
Do you shere gerber
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Re: Stereocoder design
« Reply #11 on: November 06, 2025, 08:07:46 am »
If Albert is happy for me to share i will post them up. the files were the originals converted from x1 to 274x with a little tidying up, hench the mistake on the pcb. it is fixed now on the gerbers.
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Re: Stereocoder design
« Reply #12 on: November 06, 2025, 08:54:28 am »
Quote from: MonTaylor on November 06, 2025, 08:07:46 am
If Albert is happy for me to share i will post them up. the files were the originals converted from x1 to 274x with a little tidying up, hench the mistake on the pcb. it is fixed now on the gerbers.
Wher you get this 19khz filter?  do you heve datasheat?
I ask for gerber if is possible get to start meke my drawing with gyrator-based elliptical filter insteadd  coil inductor hard to find it...

It's much easier to start from your work than from scratch. I'm ready to trade. I hope you understands me.
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Re: Stereocoder design
« Reply #13 on: November 06, 2025, 10:45:05 am »
here is the data sheet for the 19khz filter
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Re: Stereocoder design
« Reply #14 on: November 06, 2025, 03:31:15 pm »
Quote from: MonTaylor on November 06, 2025, 08:07:46 am
If Albert is happy for me to share i will post them up. the files were the originals converted from x1 to 274x with a little tidying up, hench the mistake on the pcb. it is fixed now on the gerbers.

Go ahead - post away!  I can also put up an easy-to-build 15 kHz LPF pair to replace the unobtanium Toko filter.  I'll sort out the notes and post shortly.
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