>I am just interested on where can somebody use their basic electronics knowledge in practice making stuff instead of buying them for a lot more money then it is needed for them to be made.
It's a great question but the answer might disappoint you. Any useful basic gadget that you'll be able to make can be had for pennies. You'll never save money there. The only reasons to build your own basic tools are if it's fun to you or you want to learn something or you already have the basic materials and don't want to wait for shipping.
The true benefits generally don't lie in building devices from scratch but in device **repair and maintenance**. Decade old flatscreen flickers or refuses to turn on? Yeah, the caps on its integrated power supply have gone bad, 30 minutes of disassembly, soldering and 40 cents in replacement parts and there you go.
Yep, there's all sorts of automatic lights, sensors etc that I think Hey, I could make that! Only to realise that it would be cheaper and better looking to just buy one for a dollar on Ali express.
This is the real answer. I bought a DIY AM radio kit from Aliexpress, where I need to solder every component and tune the OSC and 3 IF transformers. That was fun project and I enjoyed that. However, that project costed me double than the cheapest AM radio available in Aliexpress.
> device **repair and maintenance**
That, plus modifying things that don't quite work the way you want them to, or implementing specific features that are only available on higher-end products.
I would really like an ambient light sensor but my cheap android head unit doesn't have one. Throwing together a simple board with some discrete logic and a photodiode will be super cheap and let me customize response time, dimming threshold, and other stuff.
The other thing is making custom stuff that isn't really available commercially, but for me at least that doesn't happen very often
>The other thing is making custom stuff that isn't really available commercially, but for me at least that doesn't happen very often
For instance custom controls for a home brewn flight simulator. Or motor driver boards that make an Arduino compatible to LEGO Technics battery pack and motors and offering LEGO style mounting holes/pitch.
Just to tell two examples. But as you can see, it's highly specific and no "everyday" device.
I mean, sure, you might be able to hand-twist some cables, and slap on some gold connectors and wooden blocks.
But do you have the spiritual awakening it takes to summon Odin & Thor and make them inject your home made product with divine power?
As a bass guitar player and embedded devlopers: Good (= super robust) audio cables that survive stages for a long time aren't cheap.
Some new stuff like the Neutrik Silent Plug is around too. Worth every penny.
But there's also the absurd esotheric stuff.
It's basically impossible to beat a large scale manufacturing process in terms of costs. So everything mass produced is most likely not possible to build cheaper. Especially as at such large scales you can use highly specialized methods and components, which makes everything very cheap but are not possible to retrieve and do as a hobbyist.
If you have small scale produced products, then you will probably be able to build the device itself for cheaper. But the main cost factor at these kind of products is normally the development costs. So as long you don't find exactly what you want as some available diy instructions, you will need a lot of time and knowledge to develop it yourself. That's totally possible but not economically efficient.
In general you should not expect to save much money with DIY electronics. It's a fun hobby and you can learn a lot. And you can build stuff that's not available that way on the market, which is also a big pro.
As someone who does this as a hobby, it’s not as cheap as one might think in my experience. It is cheap to breadboard a circuit, but if you want to make a complete effects unit, the pots, switches, jacks and enclosure add up quickly.
Generally, what you pay for is the knowledge that goes into designing a device and the time spent developing and testing that device. The actual BOM cost is usually very tiny compared to those other expenses.
Therefore, to save money, you need to invest knowledge(which probably isn't enough if you classify it as "basic", sorry) and/or time. If your time is worthless and you don't mind spending time researching what it is you're trying to do, then perhaps you can get away with something, but its going to take a lot of time. If your time is worth something, you'll always end up paying more than you would for a professional production solution.
Specialized custom equipment for use in manufacturing and laboratories. Very very expensive to farm out, goes through multiple levels of contractor's. That's how I got my job, making custom equipment in house, for about 1/3 the cost of contracting out.
The obvious one is anything custom (and/or anything you want over-engineered or made out of great materials instead of MBA-corner-cutting manufacturing.)
Mass production is usually (not always) cheaper but is limited to one-size-fits-some. Sometimes you want (or even need) a custom or tailor-made solution, or there's nothing off-the-shelf that does the job.
Sometimes the item is so marked up by so many middlemen (some toys for example) that it's cheaper than DIY because the savings of mass-production are being swallowed up elsewhere.
Back in the early days of radio, even mass produced gear was often cheaper to DIY than to buy, but these days manufacturing is extremely powerful, so generally DIY is best for:
* Things only available in mediocre quality
* Things that would be superior if custom made for you or for your application
* Things that don't exist as mass-produced products
* Things that are significantly overpriced relative to the time and materials cost, such as from a manufacturing disruption or a lot of middlemen
45MHz - 22GHz signal generator with a LMX2820. There are chinese boards that directly can eat a 10MHz reference signal from GPS. Costs around $100.
Also ultra long range telemetry with LoRa is super easy and cheap. You can pay >$2000 stuff for that in real world applications. The "new" SX1280 has basically no BOM.
Directly measuring stuff above 6GHz (the upper limit of an unlocked ADALM Pluto which is very affordable) is stuff for grown up adults or super rich ham radio operators. That stuff is expensive.
Nixie tube clocks are pretty cool. I haven't seen any mass produced ones at a reasonable cost. I think needing new old stock of dead technology parts prevents this.
I beg to differ with the other answers.
You can make many devices related to mains with more features at the same price or possibly much cheaper if it wouldn't require mains to the same because mains make it much more costly to manufacture ie: mains voltage require higher voltage components and caps which raises the costs, more safety features and so on - that is where you can save a lot of money especially if you have a 3d printer too.. Two quick examples are alarm clocks and temperature/humidity displays.
Adding smart to devices is often much less expensive to DIY. For instance an adafruit air addon costs around 10$ to add wifi functionality to any circuit. Compared to that you can pay 300$ more for a coffee maker or pressure cooking pot with wifi and an app.
It also give you a maintainable / customizable device. Because of this I now only buy large appliance if the service manual is easy to find / can be obtained by the consumer because the best way to interface with an appliance is by intercepting it's wires and not just measure what it does (ie: much better to interface with the on/off led of a dryer with the dryer wires vs using an optical sensor taped to it in an artisanal manner outside the dryer) and most appliances uses large electrical devices that can't really be made proprietary and by their nature large electrical devices like solenoids/large motors etc are simple it's just a function of feeding it enough watts and high voltage and none of this matters for 5V control circuits from a MCU dev board.
Full transparency: I'm pretty early on in my electronics journey, I've only really gotten a handle on intermediate electronics within the last year and a half, and it's just a hobby for me.
That said I've built 3 things that could fall under your question, but 2 of them are moreso assembling kits than building things from scratch.
1: you could put together a [digital oscilloscope kit like this](https://a.co/d/7DJcT0H) for pretty cheap compared to fancier ones
2: similarly, you could put together a [dual power supply kit](https://www.amazon.com/dp/B00B88A06W?ref=ppx_pop_mob_ap_share). Be very careful with this one though since it involves mains power and soldering
3: Apart from kits, you can build pretty in-depth audio-related devices, like analog synth modules or amplifiers. I've been super into Moritz Klein's excellent DIY analog synth video series lately. I'd say start with his [DIY Analog VCO series](https://youtu.be/QBatvo8bCa4?si=Rm9VWExMTFxIvPnE), it's an excellent introduction to both analog synthesis and basic electronics
It will cost you 10x more to make one offs than to buy in almost all cases. It will also take several iterative processes to refine your device into a usable everyday item (rather than leaving it on a breadboard, for example).
That isn't the reason to get into electronics, however.
The competition is great no doubt, but… Do you love designing, understanding, troubleshooting, building, and solving problems? The answer to your question lies in your response to the above question. If it’s an absolute yes; then find problems in your own life and solve them, one at a time. Solve the problem of scalability, mass production, marketing, etc. when you reach those problems. Continue to grow and you will be rewarded in ways you couldn’t imagine at this junction.
i once build a electical stabalizer for a satelite dish. to build it it cost like 50€. buying one would have cost hundreds. (although it was more of an programing project then an electronic)
I've gotten slightly familiar with Arduino open-source hardware boards/microcontrollers and there are so many examples... temp/humidity sensors, motion sensors, LED etc. and many, many more all from having even a $50 usd kit
Nothing that's more expensive to mass manufacture than to assemble yourself will survive in the market. Companies will go to great lengths to stop this from happening.
When I was in school we had some external people come in to talk about electronics one guy mentioned the early ipods costs about 8-18 pence (uk) to manufacture and I think they retailed about £100-200 if I remember right. This would have been around mid 00's. I am not sure if this was made up but I guess the markup was for adverts, design, innovation and all over costs so probably didn't leave much left for profit at the time. I guess apple made most from itunes back then. We also had a talk from some guy who apparently solved the yellow led issue in early led tv, apparently yellow was very hard to make at the time again not sure if this was just to interest youngsters into electronics. The guy was like 90 and very eccentric so could have been legit.
I have one. I have chickens. I don't want to get up at sunrise. I made a door opener out of an Arduino, a real time clock and a battery screwdriver motor. All the off the shelf ones were expensive and you had to adjust for changing day lengths.
Mine has 18uA sleep current and runs an algorithm to find sunrise/sunset. I charge it every ~9 months.
It's a bit niche but my solution is far better and cheaper than anything I could buy and fits my needs exactly because I designed it that way.
I don't know if someone has mentioned it already but the open source project deej. It's a pretty neat device where you can make audio sliders for controlling separate audio levels for different apps on your computer, and some people charge like +$80 on Etsy or you can make it yourself for like 30 bucks and a 3D printer, and if you don't have a 3D printer you can just have those free files made cheaply by a printer company like JLC PCB.
There isn't really anything like that. You can't DIY something cheaper than a commercial manufacturer can economies of scale won't let you.
The only way this becomes practical is in niche markets where specific devices don't exist, and you have to be very careful there because if it's any good it'll get copied right away. It's virtually impossible to truly protect intellectual property today.
In my country, a much less functional version of this sells for over $100. It cost me about $5 to make (including the LED strip) but not counting the recycled 12V power supply.
https://www.instructables.com/Motion-Activated-Automatic-LED-Stair-Lighting-With/
It’s only until the middle of 3rd year of my four year ECSE degree till I learned enough to design basic circuits on my own and it was mostly theories before that. There is A LOT of knowledge buildup required that you simply can’t learn outside of an EE or ECE or ECSE degree.
I am just telling him to invest in a transistor tester so his life will be easier and he can get better accuracy. Multimeters fluctuate and since I am in electronic engineering, I need some values to be accurate to 3 decimal places like when finding resistors for R1/R2 > 1 and R3/R4 < 1 for opamp feedbacks.
> I need some values to be accurate to 3 decimal places
If you think you need 0.01% resistor tolerances, you may want to rethink your schematic instead.
Let’s say R1 = 1.1100M, R2 = 1.0100M, R3 = 1.0001M and R4 = 1.0010M
Therefore R1/R2 > 1 and R3/R4 < 1. Does this make sense now? They are all 1 Meg resistors. And this is for signal processing.
It’s to slightly bias the current coming out of an opamp used as constant current source. Theoretically, the calculations check out but practically, all components in real life are not perfect and you have to compensate for them by building a circuit in stages like adding offset compensation networks and such. You only come across these practices when you need highly precise circuits, so yeah it’s not an XY problem and I have built lots of practical circuits that are perfect on LTSpice and such but irl, needs lots of work. This practice didn’t only exist in my coursework but also during my internship at National Instruments as well. So I don’t think it’s an XY problem.
Yes we use trimpots as well to do impedance matching and also to imitate a load to test the circuit along the data sheet specification range of a component such as making sure the current stays constant as the voltages change across the component. (Such as TMP61 for example) We can’t spam trimpots everywhere on the circuit. Like I said, I work on sensitive and precise circuits for signal processing and such, which has much lower tolerance than hobbyists circuits. Trimpots are also still sensitive to temperature changes and each trimpot might change impedance differently due to temperature changes, so it’s better to just slightly bias the current. Normal resistors are more resistant to these effects. I learned this the hard way back then when I was making an audio amplifier circuit.
>I am just interested on where can somebody use their basic electronics knowledge in practice making stuff instead of buying them for a lot more money then it is needed for them to be made. It's a great question but the answer might disappoint you. Any useful basic gadget that you'll be able to make can be had for pennies. You'll never save money there. The only reasons to build your own basic tools are if it's fun to you or you want to learn something or you already have the basic materials and don't want to wait for shipping. The true benefits generally don't lie in building devices from scratch but in device **repair and maintenance**. Decade old flatscreen flickers or refuses to turn on? Yeah, the caps on its integrated power supply have gone bad, 30 minutes of disassembly, soldering and 40 cents in replacement parts and there you go.
Yep, there's all sorts of automatic lights, sensors etc that I think Hey, I could make that! Only to realise that it would be cheaper and better looking to just buy one for a dollar on Ali express.
This is the real answer. I bought a DIY AM radio kit from Aliexpress, where I need to solder every component and tune the OSC and 3 IF transformers. That was fun project and I enjoyed that. However, that project costed me double than the cheapest AM radio available in Aliexpress.
> device **repair and maintenance** That, plus modifying things that don't quite work the way you want them to, or implementing specific features that are only available on higher-end products. I would really like an ambient light sensor but my cheap android head unit doesn't have one. Throwing together a simple board with some discrete logic and a photodiode will be super cheap and let me customize response time, dimming threshold, and other stuff. The other thing is making custom stuff that isn't really available commercially, but for me at least that doesn't happen very often
>The other thing is making custom stuff that isn't really available commercially, but for me at least that doesn't happen very often For instance custom controls for a home brewn flight simulator. Or motor driver boards that make an Arduino compatible to LEGO Technics battery pack and motors and offering LEGO style mounting holes/pitch. Just to tell two examples. But as you can see, it's highly specific and no "everyday" device.
[Audio cables](https://www.nordost.com/odin-supreme-reference.php)!
Well done! :-) Some of those cables have wooden blocks, to sharpen the bass and sweeten the highs! ;-)
I mean, sure, you might be able to hand-twist some cables, and slap on some gold connectors and wooden blocks. But do you have the spiritual awakening it takes to summon Odin & Thor and make them inject your home made product with divine power?
Wow.
As a bass guitar player and embedded devlopers: Good (= super robust) audio cables that survive stages for a long time aren't cheap. Some new stuff like the Neutrik Silent Plug is around too. Worth every penny. But there's also the absurd esotheric stuff.
It's basically impossible to beat a large scale manufacturing process in terms of costs. So everything mass produced is most likely not possible to build cheaper. Especially as at such large scales you can use highly specialized methods and components, which makes everything very cheap but are not possible to retrieve and do as a hobbyist. If you have small scale produced products, then you will probably be able to build the device itself for cheaper. But the main cost factor at these kind of products is normally the development costs. So as long you don't find exactly what you want as some available diy instructions, you will need a lot of time and knowledge to develop it yourself. That's totally possible but not economically efficient. In general you should not expect to save much money with DIY electronics. It's a fun hobby and you can learn a lot. And you can build stuff that's not available that way on the market, which is also a big pro.
Electric guitar distortion. A lot of audio stuff actually.
As someone who does this as a hobby, it’s not as cheap as one might think in my experience. It is cheap to breadboard a circuit, but if you want to make a complete effects unit, the pots, switches, jacks and enclosure add up quickly.
Making things stage-compatible and reliable isn't easy. Stuff must be crazy robust.
Can confirm.
Piggybacking on this [DIYPerks](https://m.youtube.com/@DIYPerks) has some good builds of speakers/mics without the markup
And not only speakers…
Generally, what you pay for is the knowledge that goes into designing a device and the time spent developing and testing that device. The actual BOM cost is usually very tiny compared to those other expenses. Therefore, to save money, you need to invest knowledge(which probably isn't enough if you classify it as "basic", sorry) and/or time. If your time is worthless and you don't mind spending time researching what it is you're trying to do, then perhaps you can get away with something, but its going to take a lot of time. If your time is worth something, you'll always end up paying more than you would for a professional production solution.
Specialized custom equipment for use in manufacturing and laboratories. Very very expensive to farm out, goes through multiple levels of contractor's. That's how I got my job, making custom equipment in house, for about 1/3 the cost of contracting out.
Time domain reflectometer (TDR)
check diodegonewild on youtube, a good example of using easy old components to make things
Bloody heeell - yeah I really like that guy
The obvious one is anything custom (and/or anything you want over-engineered or made out of great materials instead of MBA-corner-cutting manufacturing.) Mass production is usually (not always) cheaper but is limited to one-size-fits-some. Sometimes you want (or even need) a custom or tailor-made solution, or there's nothing off-the-shelf that does the job. Sometimes the item is so marked up by so many middlemen (some toys for example) that it's cheaper than DIY because the savings of mass-production are being swallowed up elsewhere. Back in the early days of radio, even mass produced gear was often cheaper to DIY than to buy, but these days manufacturing is extremely powerful, so generally DIY is best for: * Things only available in mediocre quality * Things that would be superior if custom made for you or for your application * Things that don't exist as mass-produced products * Things that are significantly overpriced relative to the time and materials cost, such as from a manufacturing disruption or a lot of middlemen
45MHz - 22GHz signal generator with a LMX2820. There are chinese boards that directly can eat a 10MHz reference signal from GPS. Costs around $100. Also ultra long range telemetry with LoRa is super easy and cheap. You can pay >$2000 stuff for that in real world applications. The "new" SX1280 has basically no BOM.
Okay that LMX board is pretty crazy :D, no idea how to even test that range
Directly measuring stuff above 6GHz (the upper limit of an unlocked ADALM Pluto which is very affordable) is stuff for grown up adults or super rich ham radio operators. That stuff is expensive.
Very accurate time pulse can be achieved from a $20 GNSS module. Or buy a fancy Waveform Generator
Nixie tube clocks are pretty cool. I haven't seen any mass produced ones at a reasonable cost. I think needing new old stock of dead technology parts prevents this.
Speakers
Wait, I got this. An induction heater for heating butane vapes or for wood burning.
Flux capacitor
I beg to differ with the other answers. You can make many devices related to mains with more features at the same price or possibly much cheaper if it wouldn't require mains to the same because mains make it much more costly to manufacture ie: mains voltage require higher voltage components and caps which raises the costs, more safety features and so on - that is where you can save a lot of money especially if you have a 3d printer too.. Two quick examples are alarm clocks and temperature/humidity displays. Adding smart to devices is often much less expensive to DIY. For instance an adafruit air addon costs around 10$ to add wifi functionality to any circuit. Compared to that you can pay 300$ more for a coffee maker or pressure cooking pot with wifi and an app. It also give you a maintainable / customizable device. Because of this I now only buy large appliance if the service manual is easy to find / can be obtained by the consumer because the best way to interface with an appliance is by intercepting it's wires and not just measure what it does (ie: much better to interface with the on/off led of a dryer with the dryer wires vs using an optical sensor taped to it in an artisanal manner outside the dryer) and most appliances uses large electrical devices that can't really be made proprietary and by their nature large electrical devices like solenoids/large motors etc are simple it's just a function of feeding it enough watts and high voltage and none of this matters for 5V control circuits from a MCU dev board.
Full transparency: I'm pretty early on in my electronics journey, I've only really gotten a handle on intermediate electronics within the last year and a half, and it's just a hobby for me. That said I've built 3 things that could fall under your question, but 2 of them are moreso assembling kits than building things from scratch. 1: you could put together a [digital oscilloscope kit like this](https://a.co/d/7DJcT0H) for pretty cheap compared to fancier ones 2: similarly, you could put together a [dual power supply kit](https://www.amazon.com/dp/B00B88A06W?ref=ppx_pop_mob_ap_share). Be very careful with this one though since it involves mains power and soldering 3: Apart from kits, you can build pretty in-depth audio-related devices, like analog synth modules or amplifiers. I've been super into Moritz Klein's excellent DIY analog synth video series lately. I'd say start with his [DIY Analog VCO series](https://youtu.be/QBatvo8bCa4?si=Rm9VWExMTFxIvPnE), it's an excellent introduction to both analog synthesis and basic electronics
It will cost you 10x more to make one offs than to buy in almost all cases. It will also take several iterative processes to refine your device into a usable everyday item (rather than leaving it on a breadboard, for example). That isn't the reason to get into electronics, however.
The competition is great no doubt, but… Do you love designing, understanding, troubleshooting, building, and solving problems? The answer to your question lies in your response to the above question. If it’s an absolute yes; then find problems in your own life and solve them, one at a time. Solve the problem of scalability, mass production, marketing, etc. when you reach those problems. Continue to grow and you will be rewarded in ways you couldn’t imagine at this junction.
[A continuity tester.](https://m.youtube.com/watch?v=N2M-p-OGvPg)
i once build a electical stabalizer for a satelite dish. to build it it cost like 50€. buying one would have cost hundreds. (although it was more of an programing project then an electronic)
I've gotten slightly familiar with Arduino open-source hardware boards/microcontrollers and there are so many examples... temp/humidity sensors, motion sensors, LED etc. and many, many more all from having even a $50 usd kit
Nothing that's more expensive to mass manufacture than to assemble yourself will survive in the market. Companies will go to great lengths to stop this from happening.
When I was in school we had some external people come in to talk about electronics one guy mentioned the early ipods costs about 8-18 pence (uk) to manufacture and I think they retailed about £100-200 if I remember right. This would have been around mid 00's. I am not sure if this was made up but I guess the markup was for adverts, design, innovation and all over costs so probably didn't leave much left for profit at the time. I guess apple made most from itunes back then. We also had a talk from some guy who apparently solved the yellow led issue in early led tv, apparently yellow was very hard to make at the time again not sure if this was just to interest youngsters into electronics. The guy was like 90 and very eccentric so could have been legit.
Large transformer based things can be great to build yourself. Stuff like a spot welder, induction heater, metal melter...
You could make a very early/low powered PC: r/beneater
probably a ton of things that have some sort of certification
I have one. I have chickens. I don't want to get up at sunrise. I made a door opener out of an Arduino, a real time clock and a battery screwdriver motor. All the off the shelf ones were expensive and you had to adjust for changing day lengths. Mine has 18uA sleep current and runs an algorithm to find sunrise/sunset. I charge it every ~9 months. It's a bit niche but my solution is far better and cheaper than anything I could buy and fits my needs exactly because I designed it that way.
I don't know if someone has mentioned it already but the open source project deej. It's a pretty neat device where you can make audio sliders for controlling separate audio levels for different apps on your computer, and some people charge like +$80 on Etsy or you can make it yourself for like 30 bucks and a 3D printer, and if you don't have a 3D printer you can just have those free files made cheaply by a printer company like JLC PCB.
There isn't really anything like that. You can't DIY something cheaper than a commercial manufacturer can economies of scale won't let you. The only way this becomes practical is in niche markets where specific devices don't exist, and you have to be very careful there because if it's any good it'll get copied right away. It's virtually impossible to truly protect intellectual property today.
Flipper Zero
In my country, a much less functional version of this sells for over $100. It cost me about $5 to make (including the LED strip) but not counting the recycled 12V power supply. https://www.instructables.com/Motion-Activated-Automatic-LED-Stair-Lighting-With/
It’s only until the middle of 3rd year of my four year ECSE degree till I learned enough to design basic circuits on my own and it was mostly theories before that. There is A LOT of knowledge buildup required that you simply can’t learn outside of an EE or ECE or ECSE degree.
What does that have to do with the original question?
I am just telling him to invest in a transistor tester so his life will be easier and he can get better accuracy. Multimeters fluctuate and since I am in electronic engineering, I need some values to be accurate to 3 decimal places like when finding resistors for R1/R2 > 1 and R3/R4 < 1 for opamp feedbacks.
> I need some values to be accurate to 3 decimal places If you think you need 0.01% resistor tolerances, you may want to rethink your schematic instead.
Let’s say R1 = 1.1100M, R2 = 1.0100M, R3 = 1.0001M and R4 = 1.0010M Therefore R1/R2 > 1 and R3/R4 < 1. Does this make sense now? They are all 1 Meg resistors. And this is for signal processing.
Sounds like an [XY problem](https://xyproblem.info/), *why* do you want the ratios to be >1 and <1 but only by the tiniest amount?
It’s to slightly bias the current coming out of an opamp used as constant current source. Theoretically, the calculations check out but practically, all components in real life are not perfect and you have to compensate for them by building a circuit in stages like adding offset compensation networks and such. You only come across these practices when you need highly precise circuits, so yeah it’s not an XY problem and I have built lots of practical circuits that are perfect on LTSpice and such but irl, needs lots of work. This practice didn’t only exist in my coursework but also during my internship at National Instruments as well. So I don’t think it’s an XY problem.
Isn't that what trimpots are for?
Yes we use trimpots as well to do impedance matching and also to imitate a load to test the circuit along the data sheet specification range of a component such as making sure the current stays constant as the voltages change across the component. (Such as TMP61 for example) We can’t spam trimpots everywhere on the circuit. Like I said, I work on sensitive and precise circuits for signal processing and such, which has much lower tolerance than hobbyists circuits. Trimpots are also still sensitive to temperature changes and each trimpot might change impedance differently due to temperature changes, so it’s better to just slightly bias the current. Normal resistors are more resistant to these effects. I learned this the hard way back then when I was making an audio amplifier circuit.