Radio Builders
Radio Discussion => Technical Corner => Topic started by: Dave on June 08, 2024, 12:49:28 am
-
I designed a replacement for the 15kHz filters in the Pro IV, using op-amps with gyrators emulating inductors. It was published some years ago in EDN. I'll dig it out and post it here.
is this it?
https://www.edn.com/brick-wall-lowpass-audio-filter-needs-no-tuning/
-
Stereo coder Pro 8x Sample
http://radioinitiation.chez-alice.fr/english/stereo%20coder%20pro/stereo%20coder%20pro.html
-
i would like to see that mate
-
That's not too bad as a simple passive filter. However, you're going to have to get the inductors to better than 2% accuracy channel-to-channel, and the capacitors should be better than that, if you want a reliable stereo image. Also, don't install it too close to a mains transformer, or you'll get the dreaded hum!
I designed a replacement for the 15kHz filters in the Pro IV, using op-amps with gyrators emulating inductors. It was published some years ago in EDN. I'll dig it out and post it here. I designed a PCB for it that was designed to fit above the Pro IV coder PCB. I'll put that up too. It's a single-sided board, and it sounded significantly better than the passive Toko BLR filter. It also suppresses out-of-band signals better than the Toko jobs.
I'll post it in the next day or so.
-
Can be something like this .
-
Thanks sir , valuable.
-
cheers Albert for the design work. Here it is all bundled together with the original docs and modification to the filter
[attachmini=1]
-
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.
-
here is the data sheet for the 19khz filter
-
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.
-
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.
-
here is my build
Hi
Do you shere gerber
-
Good it works .
-
its working now. i found a fault on the pcb on IC2. 2 cut traces and a jumper wire and its working as intended
-
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!
-
here is my build
-
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
-
Sorry for the delay - here it is:
(https://www.radiobuilders.co.uk/proxy.php?request=http%3A%2F%2F%5Battachimg%3D1%5D&hash=91acb2c49ddfd8df310a8dbe05996104ae24d045)
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!
-
Look forward to seeing it
-
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.
-
NRG stereo coder
-
Design for a stereocoder.