First schematic... No direct view, large image.. i.imgur.com/vQ023dK.png (edit: many corrections since this schematic, don't use, only left here for reference, updated one posted below)
Also want to give credit to boomerthedog.net for the RFI low pass filter they used in their C-QUAM stereo circuit which I utilized within my setup before stereo to mono mixing.
I think the circuit is pretty damn tight at this point but I may reversion it a few times so don't jump the gun yet. Spent the better half of 4 hours drawing the damn thing but beer was had and kicking back actually listening to it.
Added in an Asymmetry IN/OUT toggle too because why the hell not. It simply shorts out the OP Amps positive input bias if in off position, otherwise everything rides on DC bias above or below 100% depending on an internal control position in the final clipper stage which is built to force asym. peaking.
Power supply is becoming a pain in the ass. The whole circuit powers fine as is with as little as 200ma at 24vdc using a virtual ground supply, but I am aiming to add LED VU meters with 10 LEDs for low, mid, and high, and possibly even output level. Kind of forgot how fast MA adds up from small LEDs. They may take 30ma individually but multiply that by 10 and then again by 4 and that's far over my original plan to use a 500ma 24 wallwart power supply. Might have to build them for dot mode instead of bar graph mode. Dot mode is kind of cool anyway and will set my project apart from others for the cool blinky lights lol. Best of all it will be beyond power efficient. Worst drag on the supply is the output buffer stage if it actually has to push something, but I've never seen any line-level equipment actually need serious push, usually 1v p-p at line level over hundreds of feet of wire works fine without issue in my experience, not like we are talking composite video or something.
EDIT: I just noticed the scaling on the image compressed some part numbers removing the dot like in 2.2k resistor it shows 2 2k. Re-uploaded with edited image. Don't mind the OP Amp power and pinouts, it's generic but I didn't order each dual OP Amp pinouts yet and isn't important anyway, especially if people use quad OP Amps instead. Pinout for the SSM2164 can be added later and the THAT corporation alternative has slightly different pinouts but is compatible. I'll edit later and if requested I can split the schematic sections into printable pages which might be easier to read. I'll upload the .SCH file soon when I finalize the schematic. As is right now everything looks correct but I'm going to triple check later to make any last correction. Also plan on adding an extra schematic for LED VU metering, clipping indicator LED, and overdrive LED as an accessory feature.
Hopefully youtube doesn't mute the audio because I used some Butthole Surfurs to play through the processor audible in the background. Showing the 10x3 LED VU meters I built showing the low, mid, high expansion/compression bands in operation. Part way through I switched them from dot mode to bar mode to show the difference in looks. Think I am prefering the dot mode because it's unique and saves power supply milliamps.
Super simple to add actually except the point to point wiring of the VU meter chips but there are premade PCB kits online for those chips. They wire right in where I showed on my schematic but require a few add-on components like a diode and capacitor to rectify the audio and smooth out the VU movement. I will add the schematic to the metering soon since there's little to it.
It's one thing hearing ones own project, but blinky lights sure add to the visual
WOW, that's intimidating. What is the part number of those Op-Amps? RC4558? So that's what all the unlabeled ICs are?
It looks good, but I have limited knowledge in this area.
I could try to make a PCB, but it would take a while and I've got other stuff right now.
Let me know when it's completely done.
Yes all the OP Amps are the same. Any of the common OP Amps will work in the 4558 family. Other pin compatible chips may work fine too but since this is for AM use and not audiophile HIFI stuff I find the RC4558, JRC4558, or the KIA4558 are perfectly fine and extremely low on noise. Quad OP Amps can be used too, and in some places in my circuit I used a few but that's up to the designer. I just used what OP Amps I had laying around that were convenient and socketed all of them so if I wanted I could replace them later with lower noise types.
The only oddball part in the whole circuit is the Analog Devices SSM2164 VCA (quad voltage controlled amplifier). THAT corporation makes their own copy of the chip too if people can't find the now hard to find previous brand. Everything else is generic, diodes are all 1N4148 and JFETs can be any common small signal type. I even kept all the outside user adjustable potentiometers 10kohm so people can buy a bulk pack of the same value and be set. Internal pots may not be so easy to find, like that random 3k internal drive adj. but 2k will work fine.
Don't worry about the PCB unless you really want to take that on. I would appreciate it but I realize the amount of work would be a lot of volunteer time.
This project for me is kind of a do all end all to my studies into audio broadcasting processing and aided me with understanding the structure of audio processing and multiband compression and so on. It was a wrap for me, taking what I know from music production to my RF fun with pirate radio and hobby broadcasting and trying to fit it all into a once size fits all. I was inspired by Dorrough and Texar which is obvious from the circuits if you look into their older designs, and Orban with overshoot filtering. I have odd hobbies and goals what can I say?
Not finished with this thread yet though. Next post will be a built box all control labeled and whatever. The least fun part of the project for me, but got to pretty it up for any potential future owner. It will drive my station for a few years at least though.
One thing I really hope people take in mind here is that even though that schematic looks intimidating, and trust me I am proud it does considering the R&D I put into it over 5 months of time for the sake of learning without pay, it's my wish that people can pick it apart and use what bits of it they can for their own circuits. No one said a schematic has to be built exactly, constructing projects involves a lot of picking bits out of other peoples things, everyone is free to do so to mine. I welcome it, just hope people will give credit where do.
And just for fun before I get it all painted and knobs put on and control labels...
Next video/pic will be finished unit with some audio samples.
Honestly I am happy I am almost finished with this project. It was nothing short of exhausting to research and design and took me around five months with an hour here and there dedicated to soldering it up. It was like a never ending impossible puzzle in some respects. Think my next project will be something simple that takes me at most a night or two, like an ESR capacitor meter or something which I can use on my bench.
It was discussed before. I just don't have the time right now to design a PCB for it and writing up the instructions along with principals of operation would be a bit exhaustive. Maybe sometime down the road I'll reconsider it.
The schematics and info are freely available for anyone to use though and released as public domain for those tempted to build their own. For me it was more fun to design the circuitry and see it work when completed, I certainly wouldn't expect kits to sell for more than the PCB and maybe included parts would be worth along with a little pocket cash considering the modern options available with PC based audio processors so there really isn't any money in it given the niche market.
It was discussed before. I just don't have the time right now to design a PCB for it and writing up the instructions along with principals of operation would be a bit exhaustive. Maybe sometime down the road I'll reconsider it.
The schematics and info are freely available for anyone to use though and released as public domain for those tempted to build their own. For me it was more fun to design the circuitry and see it work when completed, I certainly wouldn't expect kits to sell for more than the PCB and maybe included parts would be worth along with a little pocket cash considering the modern options available with PC based audio processors so there really isn't any money in it given the niche market.
Hello Guys, new member here. Is there any interest in getting this circuit on a pcb?. About myself I was a professional PCB layout designer who is at this time not working. Always wanted to checkout Kicad as a pcb layout tool for two reasons, one: it is free, two: it is in collaboration with Freecad 3D which is also free. Both programs I found to be pretty darn good, being it is open source. Anyways this circuit is cool and I though it would be a good project to learn how to use Kicad. So far I have already created a schematic of this circuit and am quite pleased with the software. Now I am at the next step of the pcb layout process, and that is footprint assignment. At this time the schematic can be easily modified to change out op-amps assign smt or through hole etc... What I have to do is define which op-amps to use and it's footprint. For instance the NSRC filter, it would seem to be ideal for a quad package op-amp . Same problem about footprints for those darn capacitors. Back in the day the engineers (my customers) would give me a data package with the all the special information on the parts. I though if there is interest maybe I can get help from you guys to nail down the package information of the parts. I used to have a workshop but everything is in storage. This means I can't try to build or test it. This project is mostly a learning exercise for me, but it would really be cool to do it right and help you guys along. Every thing I do on Kicad will be available to all. Like I said I have the schematic created on Kicad. Not sure how to share it. Kage do you have any thoughts on this?
Hello Guys, new member here. Is there any interest in getting this circuit on a pcb?. About myself I was a professional PCB layout designer who is at this time not working. Always wanted to checkout Kicad as a pcb layout tool for two reasons, one: it is free, two: it is in collaboration with Freecad 3D which is also free. Both programs I found to be pretty darn good, being it is open source. Anyways this circuit is cool and I though it would be a good project to learn how to use Kicad. So far I have already created a schematic of this circuit and am quite pleased with the software. Now I am at the next step of the pcb layout process, and that is footprint assignment. At this time the schematic can be easily modified to change out op-amps assign smt or through hole etc... What I have to do is define which op-amps to use and it's footprint. For instance the NSRC filter, it would seem to be ideal for a quad package op-amp . Same problem about footprints for those darn capacitors. Back in the day the engineers (my customers) would give me a data package with the all the special information on the parts. I though if there is interest maybe I can get help from you guys to nail down the package information of the parts. I used to have a workshop but everything is in storage. This means I can't try to build or test it. This project is mostly a learning exercise for me, but it would really be cool to do it right and help you guys along. Every thing I do on Kicad will be available to all. Like I said I have the schematic created on Kicad. Not sure how to share it. Kage do you have any thoughts on this?
I told Kage a while back that I might help him with this, but it's likely not going to happen. I'm working on my own FM TX now and I don't really have time for this, so it's great you took this up instead.
Since you have the skills. I was wondering if you have any experience with really small packages like the QFN24? No matter what I do, I can't reliably attach it to my TX board. I want to get some kind of module that it's soldered to, so I can easily install it onto my board. Is this something you could do? The main challenge is finding a company that will charge less to attach just one chip to the module.
Thanks. And I don't mean to hijack this. If you want to focus on Kage's processor instead, that's understandable. He put a lot more work into this processor.
Hello Guys, new member here. Is there any interest in getting this circuit on a pcb?. About myself I was a professional PCB layout designer who is at this time not working. Always wanted to checkout Kicad as a pcb layout tool for two reasons, one: it is free, two: it is in collaboration with Freecad 3D which is also free. Both programs I found to be pretty darn good, being it is open source. Anyways this circuit is cool and I though it would be a good project to learn how to use Kicad. So far I have already created a schematic of this circuit and am quite pleased with the software. Now I am at the next step of the pcb layout process, and that is footprint assignment. At this time the schematic can be easily modified to change out op-amps assign smt or through hole etc... What I have to do is define which op-amps to use and it's footprint. For instance the NSRC filter, it would seem to be ideal for a quad package op-amp . Same problem about footprints for those darn capacitors. Back in the day the engineers (my customers) would give me a data package with the all the special information on the parts. I though if there is interest maybe I can get help from you guys to nail down the package information of the parts. I used to have a workshop but everything is in storage. This means I can't try to build or test it. This project is mostly a learning exercise for me, but it would really be cool to do it right and help you guys along. Every thing I do on Kicad will be available to all. Like I said I have the schematic created on Kicad. Not sure how to share it. Kage do you have any thoughts on this?
I told Kage a while back that I might help him with this, but it's likely not going to happen. I'm working on my own FM TX now and I don't really have time for this, so it's great you took this up instead.
Since you have the skills. I was wondering if you have any experience with really small packages like the QFN24? No matter what I do, I can't reliably attach it to my TX board. I want to get some kind of module that it's soldered to, so I can easily install it onto my board. Is this something you could do? The main challenge is finding a company that will charge less to attach just one chip to the module.
Thanks. And I don't mean to hijack this. If you want to focus on Kage's processor instead, that's understandable. He put a lot more work into this processor.
Do you mean an adaptor? Something like this? link At my old job with my old toolsets, about a couple hours. Kicad probably has a QFN24 footprint to make it easier.
In my opinion, it is probably better to have your chip mounted directly on your pcb.
I told Kage a while back that I might help him with this, but it's likely not going to happen. I'm working on my own FM TX now and I don't really have time for this, so it's great you took this up instead.
Since you have the skills. I was wondering if you have any experience with really small packages like the QFN24? No matter what I do, I can't reliably attach it to my TX board. I want to get some kind of module that it's soldered to, so I can easily install it onto my board. Is this something you could do? The main challenge is finding a company that will charge less to attach just one chip to the module.
Thanks. And I don't mean to hijack this. If you want to focus on Kage's processor instead, that's understandable. He put a lot more work into this processor.
Do you mean an adaptor? Something like this? link At my old job with my old toolsets, about a couple hours. Kicad probably has a QFN24 footprint to make it easier.
In my opinion, it is probably better to have your chip mounted directly on your pcb.
Mostly yes, but it could be compressed a bit cause not all pins are used and I'd probably include the crystal on it.
You're right, I'd rather have it on the actual PCB, but it's so hard to solder even after watching tutorials I can't duplicate their ease.
I'm going to try to find another assembly company. The ones I contacted before said they couldn't use this chip and that I'd have to ship it to them in China cause it's rare and the coat would be higher. I'll keep trying. I just wish there was a more elegant solution.
Do you mean an adaptor? Something like this? link At my old job with my old toolsets, about a couple hours. Kicad probably has a QFN24 footprint to make it easier.
In my opinion, it is probably better to have your chip mounted directly on your pcb.
Mostly yes, but it could be compressed a bit cause not all pins are used and I'd probably include the crystal on it.
You're right, I'd rather have it on the actual PCB, but it's so hard to solder even after watching tutorials I can't duplicate their ease.
I'm going to try to find another assembly company. The ones I contacted before said they couldn't use this chip and that I'd have to ship it to them in China cause it's rare and the coat would be higher. I'll keep trying. I just wish there was a more elegant solution.
Not this exact chip, but something like this:
I Feel your pain. At my old job, I was able to wander over to the assembly dept. and sweet talk the girls into soldering the difficult chips for me. Surface mount sucks for the average hobbyist. I miss those resources.
Hello Guys. I'm having a lot of fun using kicad. I have attached a pdf file of the schematic created in kicad. Please take a look and tell me if I have made any errors translating Kage's schematic. I have attached footprints to all the components. I used the Mouser website to find capacitor datasheets to assign footprints. link
So far I am in the preliminary placement of the components. I have all the components grouped into their own blocks. Next I have to try to condense the circuits while ensuring a good signal flow. Cheers All