Where is your sense of adventure, just need these
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And some tweezers..
If clearly seeing the SMD components was the only issue you might be correct. It may surprise you to know that as your muscles and nervous system ages your fine muscle control significantly deteriorates. So you can mount your magnifying headgear and flood your workspace with light, but you may then be seeing the tip of your soldering iron wandering around in a path larger than the SMD component you are trying to solder. Getting old is a b***h...but it beats all of the known alternatives!
I used to offer the Modulus-286 with only the SMDs populated for a reasonable price. People either bought the bare boards or the fully assembled ones. So I stopped offering the partially assembled ones.
You mean LME49720. That's an option in theory. Last I looked at splitting the two halves of an LME49720 between channels, I reached the conclusion that the layout wasn't up to my standards.
Also, while it is likely possible to connect the dots of a stereo LM3886 with a 2-layer board, for good performance you really need a 4-layer board. Those are about 3x the cost of a 2-layer board. Once you start doing the math you'll quickly realize that the board won't sell.
As for the bridge/parallel, I suggest reading my latest addition to the Taming the LM3886 series, Output Power. Paralleling is an option. Bridging is not - at least not if you want to be able to power a 4 Ω speaker.
I'd somehow missed that the LME49720 is still available in DIP. I thought it was SMD only by now. In that case, one solution would be to just use one half of it and terminate the other half so it doesn't chatter. A more elegant solution would be to use the OPA1611 and rework the compensation circuits. The OPA1611 is SMD only, though (SOIC-8).
Would one SOIC-8 on an otherwise all-leaded board be a show stopper for those without the motor control to reliably solder SMDs?
Tom
Are you able to solder SOICs?
So the solution is to train my kids to solder SMD?
Well. With the number of kids you have, if you get all of them trained properly you'd have some pretty serious manufacturing capability on your hands. Who needs Foxconn when we have Bill Shurv.
Tom
That's certainly a valid question to ask. From a business perspective - which I have to take as I chose to make Neurochrome my only source of income - I think it's also important to look at the demographic data. Who actually builds stuff anymore? I bet it's mostly the baby boomers and older Gen X'ers. I'm a young Gen X'er and must reluctantly admit that I just can't see the colour bands of resistors as well as I used to; never mind reading the markings on 0805 or 0603 components. So if I want a large serviceable available market, I should keep making leaded boards thereby allowing my builders to actually be able to see the parts.
The problem with that is that leaded parts are going away and the more exciting new parts are all SMD. Some, such as voltage regulators and references, are not human solderable. At some point the choice becomes performance vs solderability. Given my value-add, I will choose performance in that case.
So I think we'll just have to accept that with a few exceptions DIY will start with a pre-assembled or partially assembled board that the builder then completes. If I can help nudge the field in that direction, I'd be stoked, especially if builders will accept that assembly costs money.
Many complete their Modulus-286 builds without a hitch, but some do struggle a bit, resulting in more product support being needed for the SMD build than the leaded build. While I will always support my products, I would prefer that every build is a successful one and I think starting with a preassembled module or partially assembled board would increase the odds of success.
Tom
So according to Wiki an SOIC has 1/2mm wide leads on a 1-1/4mm pitch. My only attempt at SMC soldering was a successful repair of an eBay DAC that had two components (a cap and a resistor) switched in position. It was that exercise that led me to conclude that I had no business soldering SMC components. So I've never tried an SOIC but I'm pretty sure the results would be substandard. Fortunately I have a working amp with Mod 86 and Parallel 86 so I don't plan to build any more amps! Oh and we skipped the kid thing so no help there either.
I could've sworn I came across this in one of the Neurochrome amp build threads, but I can't find it anymore.
Three questions:
1) Of the four kinds of wiring, being mains input, DC power, line-level analog, and speaker out, which ones can be kept somewhat close to each other and which ones need maximum separation?
2) For chassis wiring from the panel RCA jacks to the line level inputs, is normal twisted-pair acceptable or should shielded cable be used?
3) If shielded cable is recommended for the chassis line level wiring in some or all situations, should it be coaxial or will shielded twisted-pair work (assuming shield connected only at the board ground)? Pros/cons of each?
Three questions:
1) Of the four kinds of wiring, being mains input, DC power, line-level analog, and speaker out, which ones can be kept somewhat close to each other and which ones need maximum separation?
2) For chassis wiring from the panel RCA jacks to the line level inputs, is normal twisted-pair acceptable or should shielded cable be used?
3) If shielded cable is recommended for the chassis line level wiring in some or all situations, should it be coaxial or will shielded twisted-pair work (assuming shield connected only at the board ground)? Pros/cons of each?
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any wire with a changing current will emit EMI. If you can pair that wire with another that returns the changing current to the source and couple these two wires together then the emitted EMI is much reduced at longer distances.
For low level signal wires susceptable to interference, any loop in a sensitive circuit will operate as an aerial and will pick up EMI. Again close coupling of the Signal and Return wires/traces will minimise the pick up of EMI
Some here will only use coaxial for signal wiring. I have found that a twisted pair for internal wiring works well for my builds. I have also found that twisted pair works well for unbalanced interconnects over a few metres. Few do this and they always use coaxial
Coaxial with the core carrying the Flow signal/current and the screen/shield carrying the Return signal/current. The screen/shield is NOT a ground. It is part of the signal circuit and MUST remain close coupled to the Signal Flow wire all the way from Source to Receiver.
You can use a screened twisted pair (stp) for signal connections. The Flow and Return are the signal circuit and need to remain close coupled from Source to Receiver.
The screen/shield of the stp is a true shield and is connected to the Enclosure/Chassis, preferably at both ends to maximise the screening to the highest frequencies. We all use mobile phones and WiFi. They emit very high frequency EMI. Protect your systems from their deleterious effects.
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If clearly seeing the SMD components was the only issue you might be correct. It may surprise you to know that as your muscles and nervous system ages your fine muscle control significantly deteriorates. So you can mount your magnifying headgear and flood your workspace with light, but you may then be seeing the tip of your soldering iron wandering around in a path larger than the SMD component you are trying to solder. Getting old is a b***h...but it beats all of the known alternatives!
I'm getting there too..
Some tips I use.
Make a firm support for the PCB, you need both hands for the solder (sodder) ing.
Use a rest/steady for the hand holding the soldering iron, as sign writers.
Hold your breath at the critical moment to prevent diaphragm movements transferring to your work.
Buy a couple of SMD practice boards, available for peanuts.
Enjoy the fruits of your labours.
I'm getting there too..
Some tips I use.
Make a firm support for the PCB, you need both hands for the solder (sodder) ing.
Use a rest/steady for the hand holding the soldering iron, as sign writers.
Hold your breath at the critical moment to prevent diaphragm movements transferring to your work.
Buy a couple of SMD practice boards, available for peanuts.
Enjoy the fruits of your labours.
More advice from a 67 yr-old:
No coffee on the morning that you'll be working on this.
Extra coffee, and perhaps Metamucil, the next morning to, um, catch up.
Or, check out iancanada's smd assembly how-to. Solder paste and the kitchen oven.
DocumentDownload/SMDtutorial.md at master * iancanada/DocumentDownload * GitHub
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I've been doing something similar with a (purpose-bought) skillet and my cooking range (aka stovetop). I've only done it a few times, but I did it by feel and simply watching the solder paste flow. Results were surprisingly good, although I think Ian's method sounds easier and less error-prone. My only concern: do any of the fumes that come off of molten solder---particularly lead-based solder---stick to the interior of the oven in any way? In other words, does Ian's method "pollute" the oven to make it eventually unsuitable for actually cooking food?
I suppose I could allay these fears by purchasing a dedicated toaster oven.
Thanks for the quick response Andrew.
My mistake - I meant to say signal return, not ground. Bad habit, I suppose.
I plan to use insulated RCA jacks whose barrels are not bonded to the chassis. Because of this, I'm not sure that I can connect the shield of STP at both ends inside the chassis (where would the "outside" end connect to?).
SMD
Soldering smd by hand can be difficult, specially the very small. But there are some alternatives, although you still have to place the parts on the board. Some of these alternatives are not cheap...
Hope this helps:
1) The low $ investment oven path: DocumentDownload/SMDtutorial.md at master * iancanada/DocumentDownload * GitHub
2) The high $ investment oven path: Whizoo.com if you want to buy a ready-to-assemble kit or there's also several open source projects and diy from scratch projects on the web.
3) Hot air gun (aka "smd rework station"): Aoyue 968A+ 4 in 1 Digital Hot Air Rework and or similar. There are cheaper ones with just the hot air. Have to be Chinese made, as ones from Hakko and the like are very expensive.
4) If you have to rework a soldered board, this works good to protect the stuff around the part(s) you need to remove with hot air: https://www.techspray.com/wondermask-p-peelable-solder-mask-2
5) This helps if you need to remove parts using a soldering iron: Chip Quik -
6) A cheap diy part holder: http://www.frantone.com/designwritings/design_writings5.html#hold
7) You need some kind of magnification to both:
a) put small parts on board
b) if mounting anything with many tightly spaced legs, to check for no solder or solder bridges after you solder.
You can use cheap head magnifiers, low magnification stereo microscopes (less than 10x is probably the best) or usb microscopes.
8) Use leaded solder paste, it requires less heating!
Soldering smd by hand can be difficult, specially the very small. But there are some alternatives, although you still have to place the parts on the board. Some of these alternatives are not cheap...
Hope this helps:
1) The low $ investment oven path: DocumentDownload/SMDtutorial.md at master * iancanada/DocumentDownload * GitHub
2) The high $ investment oven path: Whizoo.com if you want to buy a ready-to-assemble kit or there's also several open source projects and diy from scratch projects on the web.
3) Hot air gun (aka "smd rework station"): Aoyue 968A+ 4 in 1 Digital Hot Air Rework and or similar. There are cheaper ones with just the hot air. Have to be Chinese made, as ones from Hakko and the like are very expensive.
4) If you have to rework a soldered board, this works good to protect the stuff around the part(s) you need to remove with hot air: https://www.techspray.com/wondermask-p-peelable-solder-mask-2
5) This helps if you need to remove parts using a soldering iron: Chip Quik -
6) A cheap diy part holder: http://www.frantone.com/designwritings/design_writings5.html#hold
7) You need some kind of magnification to both:
a) put small parts on board
b) if mounting anything with many tightly spaced legs, to check for no solder or solder bridges after you solder.
You can use cheap head magnifiers, low magnification stereo microscopes (less than 10x is probably the best) or usb microscopes.
8) Use leaded solder paste, it requires less heating!
I use solder flux and normal solder to attach smd parts. If you can tack down on lead you can usually get the rest lined up okay. I have used solder paste, but the hot air station can sometimes release small components that are near by. Frustrating.
Also, mount them one at a time. They will move, guarantied.
-Chris
Also, mount them one at a time. They will move, guarantied.
-Chris
I reached 43 a month ago and find that my eyes aren't what they used to be. Telling the colour bands on resistors apart (especially brown/red/orange) requires much more light than it used to. Being able to resolve the markings on 0805 resistors while also keeping them in focus is becoming more of an issue.
I can still reliably solder 0805 and some smaller parts. I can do 0603 by hand still, but wouldn't want to solder those every day all day without a microscope.
Will do.
Tom
Keep the primary wires on the transformer (so all the mains wiring) tightly coupled.
Keep the secondary wires on the transformer tightly coupled.
Keep the wires between the power supply and the MOD86 tightly coupled.
Keep the output connections tightly coupled.
Some interpret "tightly coupled" as twisted or braided, but with heavier gauge wire I find bundling the wires tightly with wire ties to work better.
Either will work. A cable with two conductors and a shield will provide some shielding against capacitively coupled signals. Sadly, most of what you have to worry about in audio is inductively coupled signals (from mains transformers), so shielding isn't as effective inside the enclosure as many assume.
Outside the enclosure I would use shielded cable to minimize the ground impedance and to provide shielding against RF signals.
Shielded twisted pair is better.
Tom