Also want to thank you back for taking up on a project where I left off. I always appreciate input on my ideas and designs and always look forward to hearing from others who give them a go. You're always welcome to contact me through PM or email. I have been quite busy lately with other things so I may not get back right away. All I ask for with the information I give out is credit where due, and credit to those who I took ideas from myself which I give due. I have always been in this for the hobby aspect and realize how incredibly useful it is that information and schematics are freely available to people wanting to take to that hot soldering iron themselves and build an idea
As you know I used your circuit as a learning exercise for Kicad and Freecad. When I first posted I did not know how to use them both. I will say I was impressed with the results.
Let me thank you, for the availability of your circuit. I had a little advantage learning the programs as the first cad system I trained on, was in 1989.. lol I had to chuckle when I was laying out the LM3914 circuit. It was the test circuit I used to learn on that first cad program. (Daisy/Cadnetix, I remember our company paid over 400 grand for that cad system)
To make it clear I am a pcb layout designer and passionate radio hobbyist, not an Eng or Tech, they were my customers
Anywho when I assigned footprints to the schematic, The most concern I have for accuracy is the capacitors. I believe all of the values are available in the 200mil ceramic packages that I’ve assigned to most of them. At this point if I was to build this circuit, I would be kitting the caps and adjusting the footprints to suit. Can you tell me more about the power circuit? I want to redo the placement, Is the power transistor a good choice? Do they get hot?
As a seasoned pcb layout guy, I have a high level of confidence in the kicad database. If the schematic and the footprints assigned are correct and if my placement is ok, it should work on power up.
Anyone feel free to comment good or bad. This is the stage where corrections or improvements on my layout must be considered and made.
Cheers All
Hello how are you! I am interested in sending to manufacture the pcb. Would you have the Gerber files to be able to send to the factory?
As you know I used your circuit as a learning exercise for Kicad and Freecad. When I first posted I did not know how to use them both. I will say I was impressed with the results.
Let me thank you, for the availability of your circuit. I had a little advantage learning the programs as the first cad system I trained on, was in 1989.. lol I had to chuckle when I was laying out the LM3914 circuit. It was the test circuit I used to learn on that first cad program. (Daisy/Cadnetix, I remember our company paid over 400 grand for that cad system)
To make it clear I am a pcb layout designer and passionate radio hobbyist, not an Eng or Tech, they were my customers
Anywho when I assigned footprints to the schematic, The most concern I have for accuracy is the capacitors. I believe all of the values are available in the 200mil ceramic packages that I’ve assigned to most of them. At this point if I was to build this circuit, I would be kitting the caps and adjusting the footprints to suit. Can you tell me more about the power circuit? I want to redo the placement, Is the power transistor a good choice? Do they get hot?
As a seasoned pcb layout guy, I have a high level of confidence in the kicad database. If the schematic and the footprints assigned are correct and if my placement is ok, it should work on power up.
Anyone feel free to comment good or bad. This is the stage where corrections or improvements on my layout must be considered and made.
Cheers All
Hello how are you! I am interested in sending to manufacture the pcb. Would you have the Gerber files to be able to send to the factory?
Thank you very much!
Hey ya sure pm me and I'll send you a drawing package with the gerbers
I don't know how I didn't notice this before but the VU LED driver IC I used was a LM3914. There is a mistake in the schematic listing it as "LM3904" but I think most people would have noticed the mistake if they built that part of the circuit which is optional but highly desirable because who doesn't like blinky lights?
It would be better to use a LM3915 or LM3916 since they measure logarithmically which makes them better suited for proper VU meter drivers, but the LM3914 I used is fine too and has wider availability. Any of those should be interchangeable and pinout is the same I believe.
I did carefully select the color of the LEDs to represent where expansion (green) and compression (yellow) happens so that might need changing if anyone chooses to build the VU circuits to this project and uses a log based meter chip instead of linear.
Have you done any further work on the processor? If the Gerbers are available for the PCB layout, I'd like to get some of them made. Can you let me know about the Gerber files?
My FM stereo processor has ground to a halt at present, because I'm having great trouble getting the MN3007 delay lines to go fast enough. I'm thinking of changing to another BBD if I can find a shorter one that's easily available. Some of the MN3007s I bought worked fine, but others wouldn't play ball at all!
The whole problem is that I need a delay time of around 300 - 500 µs, which allows a "zero-attack time" limiter. It also overcomes the problem of overshoot (because I'm using three bands) and the results sound fabulous - transparent limiting without distortion, pumping or over-deviation! It seems to work well with any kind of programme material - even "classical" orchestral music. I sum the audio to drive the sidechain, and use common control voltages for each channel in each band, so that the stereo image remains coherent at all levels.
I'm looking forward to trying out your AM processor.... Please send me the Gerbers or post them on here!
Have you done any further work on the processor? If the Gerbers are available for the PCB layout, I'd like to get some of them made. Can you let me know about the Gerber files?
My FM stereo processor has ground to a halt at present, because I'm having great trouble getting the MN3007 delay lines to go fast enough. I'm thinking of changing to another BBD if I can find a shorter one that's easily available. Some of the MN3007s I bought worked fine, but others wouldn't play ball at all!
The whole problem is that I need a delay time of around 300 - 500 µs, which allows a "zero-attack time" limiter. It also overcomes the problem of overshoot (because I'm using three bands) and the results sound fabulous - transparent limiting without distortion, pumping or over-deviation! It seems to work well with any kind of programme material - even "classical" orchestral music. I sum the audio to drive the sidechain, and use common control voltages for each channel in each band, so that the stereo image remains coherent at all levels.
I'm looking forward to trying out your AM processor.... Please send me the Gerbers or post them on here!
I do not have PCB layout files but fkawee did excellent work trying to convert my schematics to the files you are asking for and as far as I know they still download fine.
As far as the project itself it's the finalized version as far as I'm concerned. I have no plans to improve on the build since it works perfectly fine for the application and after a few years of use has proved to withstand the test of time along with good audio reports on par with other triband broadcast processors of similar analog design.
The only thing I'd consider in the future is possibly making a stereo version for FM use by changing values for the pre-emphasis and removing the asymmetric clipping ability along with tying the left and right channels AGC levels together to remove stereo "platform shifting". This of course would be fairly easy to do, or even simpler if anyone wanted to use stereo AM broadcasting since the pre-emphasis is already set for that purpose so the brick wall filtering would need no component value changes.
Your design premises utilizing delay lines to limit/hard compress before the audio has a chance to overshoot is by far a more elegant way to design something like this but has a drawback where the DJ is listening to the live feed and can give a slight phase shift in audio in their monitors. At that point it really comes down to how much is tolerable if going that route. Many of the later broadcast processors used your technique with that slight caveat but it's nowhere near as bad as digital processors where the delay is unbearable.
A lot of this comes down to personal preference. Some people do like the older technique of soft clipping and then hard limiting or phase adjusting/subtracting the final brick wall filter "ringing" peaks to reduce them to within the regular fully modulated range like my processor and many others in the earlier eras did. This gives the benefit of little altercation in the finalized audio timing and the rare peaks after filtering are subtle enough once tamed that people would be hard pressed to ever hear it doing its job without watching a modulation overdrive light, whereas the delayed limiters will always have that slight phase difference that may be audible if live feed listening while on-air. Then there is the whole hair pulling thoughts of where to place the limiters and how since all brick wall filtering will cause overshoots (especially after applying pre-emphases) no matter what you do. It's the nature of the beast. Either limit, clip, filter, <> and then phase adjust and subtract overshoots, or filter and then time delay hard limit to adjust for overshoot (which I question if it would punch holes in the audio upon transients?). Either method has their benefits and complexity, and that's not even getting into AGC and multiband compression, or even deeper features like audio expansion to quiet the noise floor of vinyl and tape materials, which all come before the final limiter and filtering as discussed anyway.
I am very curious how far you got along in your design though and what thoughts you have to offer. You are more than welcome to start a new thread to discuss your project if you decide to continue with it. My personal advice would be to work on the last stages first. Get the brick wall filtering, any clipping and overshoot compensation, and pre-emphasis figured out first, then backtrack and design the multiband compressor and AGC stages and whatever else you want to throw at it.
Hello how are you! I am interested in sending to manufacture the pcb. Would you have the Gerber files to be able to send to the factory?
Thank you very much!
Hey ya sure pm me and I'll send you a drawing package with the gerbers
I did just notice one small error after this thread was brought back up.
The "virtual rail power supply splitter" section from my schematic in your file has the negative input of the OP Amps tied to the base of the transistors whereas they should be connected to the Emitters of the NPN TIP41C and PNP TIP42C transistors as shown in my original schematic. The reason for this is because the OP Amp senses the current across the 1 ohm resistors to keep the reference ground constant throughout the entire circuit.
Of course this entire circuit can be bypassed if using a dual rail power supply which is easily found or built for "+" and "-" 12 to 15vdc with a 0vdc ground reference. I used a single 30vdc "wall wort" to rail splitter circuit to provide me +15 and -15vdc for convenience but this is purely optional.
Hey ya sure pm me and I'll send you a drawing package with the gerbers
I did just notice one small error after this thread was brought back up.
The "virtual rail power supply splitter" section from my schematic in your file has the negative input of the OP Amps tied to the base of the transistors whereas they should be connected to the Emitters of the NPN TIP41C and PNP TIP42C transistors as shown in my original schematic. The reason for this is because the OP Amp senses the current across the 1 ohm resistors to keep the reference ground constant throughout the entire circuit.
Of course this entire circuit can be bypassed if using a dual rail power supply which is easily found or built for "+" and "-" 12 to 15vdc with a 0vdc ground reference. I used a single 30vdc "wall wort" to rail splitter circuit to provide me +15 and -15vdc for convenience but this is purely optional.
Hello Kage Thanks for the review :-) I corrected the error on the schematic and updated the pcb. I initially designed the pcb without the power supply splitter because I didn't notice the circuit until I started on the display board. Frankly I'd rather just remove it from the pcb. I left it on as you can just bypass it.
I have created a zipped drawing package that has all the required files and documents to create both the processor and display pcbs. The files size is 3megs. The zipped file for the processor fabrication files only is over 1meg. I have attached the assembly "page" (cool) for the processor board. just double klick and it should open in your browser. I guess I can email the zipped file to anyone that would like a copy of it. If you have the latest copy of Kicad, I can send the database as well.
Hello All. I can send the complete file set (gerbers kicad database etc) too anyone who wants it. Send me a pm with a email address then I can send them to you. Cheers all.