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In this article, we'll introduce the fundamental concepts of direct FM generation and examine a key FM modulation circuit: the reactance modulator.

The problem: I share a long driveway with my neighbor who runs an Airbnb and I’m tired of telling the guests to slow down. This device monitors the car speed, takes a photo of the car if it exceeds a set point, uploads the photo and data to a server and emails several people automatically. It’s powered by a solar panel with battery. submitted by /u/nutstobutts [link] [comments]

Just finished my first PCB! It's a TTL clock using mostly 74LS90 ICs. Didn't expect it to work on the first try :3 submitted by /u/SuperSuperCat [link] [comments]

submitted by /u/Kustekk [link] [comments]

I have just started looking and playing with electronic abt 2 months ago .I have also made a power bank and few other plug n play devices with the help of Arduino . Now I am looking for a new project suggestions to explore more electrical components, thanks Btw here's the link to this project working https://drive.google.com/file/d/19qMVNdBbIMH3ztrHKshNMicb7OIMiIwN/view?usp=drivesdk submitted by /u/in_for_de_mony [link] [comments]

He told me there was a wiring mistake and then he sent me the second picture. It tracks time from a gps and it's awesome! It works perfectly and I love it! submitted by /u/llapizz [link] [comments]

Today I successfully milled my first PCB and soldered ESP32-WROOM-32 on it. Next step: Upload a sketch. submitted by /u/Big_Lack_ [link] [comments]

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Hi again =D Big thanks to everyone here for the feedback and encouragement on my very first PCB! I took all that advice, went back to the drawing board, and I’m excited to share the second revision—this one includes a bunch of improvements based on suggestions from my previous post. The design files are up on my GitHub if you’d like to dig into the details, and I’ve also included some gallery shots above (hopefully a bit more presentable this time). Honest feedback is always welcome—it really helps me level up as a beginner. Technical Overview Project: Mainboard for a Bluetooth-controlled RC car Tooling: Designed in KiCAD 9 Form factor: 4 mounting holes, 4 copper layers F.Cu → signal layer (traces, routing) In1.Cu → +5V power plane In2.Cu → GND power plane B.Cu → secondary signal layer Assembly: Through-hole (all components except battery holders) Core MCU: Arduino Nano Features Dual DC motor control (L293D IC) Servo motor control Rear status LEDs (brake, reverse, turn signals—modeled after real cars) LED blinking logic (555 timer in monostable mode + 74HC00 NAND gate) Bluetooth communication via HC-05 module Audio signals: 2 piezo buzzers (horn + alarm) Power source: two 18650 Li-ion cells (7.4V) regulated through a 7805 submitted by /u/Practical-Friend-960 [link] [comments]

I've been wanting to make a card that has the usually hidden SMBus and JTAG signals in a PCIe slot available to the user. I've also made 3.3V, 5V and 12V rails available. If you want to checkout the project go checkout the github. submitted by /u/SuperCookieGaming [link] [comments]

I wanted to put together a minimal LED flasher circuit using only a few components. No microcontrollers, no 555 timer, just good old analog behavior. Parts used: 1 × BC547 transistor 1 × 1000µF capacitor 1 × 1k resistor 1 × LED How it works: The capacitor charges slowly through the resistor. Once it hits a threshold voltage, the transistor conducts and lights the LED briefly. Then the cap discharges and the process repeats, it creates a satisfying blink loop. It starts flashing after a short delay and just keeps going. I’d love to hear ideas on how to iterate on this, different values, transistor types, or ways to expand it? I posted a short 30s demo in the top comment if you'd like to see it in action. submitted by /u/ftuncer59 [link] [comments]

Behind the foundational and advanced radar textbooks of our day stood the brilliant engineer and researcher Merrill Skolnik.

My first proper audio setup, discounting the GE Wildcat record player I had as a kid:

was a JVC PC-11 portable stereo system (thank goodness for Google Image Search to refresh my memory!), an example of which my (Catholic) high school chaplain owned, played (George Winston tapes, to be precise) in the background during weekly confession sessions, and acted as inspiration for my own subsequent acquisition, which made it through most of college:

Pretty slick setup: this was the pre-CD era, but the JVC PC-11 included an AM/FM tuner, five-band equalizer, cassette player, all (plus the speakers) detachable, and turntable inputs:

And for the purposes of today’s discussion, check out these modest specs:

• Output power: 2 x 15 W max.
  • DC fluctuation: < 0.05 % WRMS
• Speaker chassis diameter: 120 mm “High Ceramic” cone
  • Impedance: 6 Ohm
  • Efficiency: 90 dB / W / m

Nevertheless, it could fill my dorm-later-fraternity room with tunes discernible even over whatever party might have been going on at the time. Distorted? Mebbe. But discernible still.

Historical precedents

Even more “proper” was a Kenwood KA-4002 integrated amplifier (albeit with switch-selectable separate preamp outputs and main amp inputs, plus a separate mono output, no less!), apparently manufactured from 1970-1973, that I acquired at around that same time. I vaguely recall that my dad might have bought it for me used from a co-worker of his? The JVC PC-11 eventually died: I vaguely recall—again—that the cassette deck locked up, plus the pressboard-construction speaker enclosures were getting beat up from my back-and-forth moves between the university campus in West Lafayette and my co-op sessions at Magnavox in Fort Wayne.

At that point, I pressed the KA-4002 into service, along with speakers and other discretes whose identities I no longer recall (though I remember a 10-band equalizer with a bouncing red multi-LED display!). It eventually also met its demise, complete with an acrid “magic smoke” release if I recall correctly, but only after serving me faithfully for a remarkably long time, including, at the end, acting as a power amplifier for a passive subwoofer. Again, check out the modest specs:

• Continuous power (at THD)
  • 8 Ohm: 2×18 W (RMS, 20Hz…20Khz, 0.05% THD), 2x 24W (8 Ohm, 1Khz)
  • 4 Ohm: 2×33 W

A modern (and even more modest) successor

I reminisced about both of these past personal case studies when I saw on Reddit last November that audio equipment manufacturer Schiit (who I’ve mentioned before) was doing a $99 (vs $149 MSRP) last-call sellout of its Rekkr 2W/channel amplifier. The Rekkr product page is no longer live on the manufacturer’s website, but here’s a January 2, 2025, snapshot courtesy of the Internet Archive. Stock photos (still active on Schiit’s web server as I type this) to start:

Yes, it really is that small:

and came in both black and—briefly—silver patina options:

Now for a peek at the internals:

For those of you still scratching your head at that earlier 2W/channel power output spec, allow me to reassure you that it’s not a typo. More precisely:

• Stereo, 8 Ohms: 2W RMS per channel
• Stereo, 4 Ohms: 3W RMS per channel
• Mono, 8 Ohms: 4W RMS

That last one’s particularly interesting to me; hold that thought. For now, here’s a visual hint:

More:

• Frequency Response: 20Hz-20KHz, ±0.01dB, 3Hz-500KHz, ±3dB
• THD: <0.001%, 20Hz-20KHz, at 1V RMS into 8 ohms 
• IMD: <0.001%, CCIR, at 1V RMS into 8 ohms
• SNR: >120dB, A-weighted, referenced to full output 
• Damping Factor: >100 into 8 ohms, 20-20kHz
• Gain: 4 (12dB)
• Input Sensitivity: AKA Rated Output (Vrms)/Rated Gain. Or, 4/4. You do the math.
• Input Impedance: 20k ohms SE
• Crosstalk: >80dB, 20-20kHz
• Inputs: L/R RCA jacks for stereo input, switch for mono input on R jack
• Topology: fully discrete, fully complementary current feedback, no capacitors in the signal path
• Oversight: over-current and over-temperature sensors with relay shutdown for faults
• Power Supply: 6VAC, 2A wall-wart, 12,000µF filter capacitance, plus boosted, regulated supply to input, voltage gain, and driver stages
• Power Consumption: 12W maximum 
• Size: 5” x 3.5” x 1.25”
• Weight: 1 lbs.

And here’s a link to the Audio Precision APx report PDF (also still active as I write these words; if not by the time you read them, you can get to it from the Internet Archive product page cache).

Target usage details

How on earth did Schiit rationalize the development and (even more notably) subsequent productization of such a seemingly underpowered product? Here’s the intro to company co-founder (and chief analog design engineer) Jason Stoddard’s “Less Power, More Better” post at the Head-fi forum, which accompanied the public unveil of Rekkr (and its Gjallarhorn “big brother”, which is still in the product line) on February 23, 2023:

And so now there’s Gjallarhorn and Rekkr, and a whole bunch of people saying, “I don’t care I can get a Class D widget with like 100,000 watts that’s the size of a matchbook for $4, why are you making these crazy low-power antique-technology things?”

Let’s start with the TL;DR:

• Because they don’t hiss like a demon cat, drilling slowly into your synapses and draining your soul.
• Because let’s face it, how much power do you need for desktop speakers?
• Because, reaaaaaally let’s face it, how do your neighbors feel about 100,000 watts if you share walls with them?
• Because these little suckers probably get a lot louder than you think.
• Because they sound really, really good.

In short: less powah. Moar better.

A new idea, yes. But maybe one you can get behind.

These next few paragraphs from his post were especially resonant for me, as you’ll understand now that I’ve shared my own personal low-power audio amplifier heritage with you:

A Billion Years Ago…I had a compact Realistic receiver that did 10 watts per channel into 8 ohms. Together with some tiny Minimus-7 speakers, it sounded pretty darn good. And it got fairly stupidly loud, enough that my parents really regretted me getting into music.

Think about that a bit: 10 watts into 4” 2-way speakers that were probably, what, 85dB efficient at best (in other words, they don’t make much sound for the watts you put in). Bass cranked almost all the way up…loud enough to piss off your shared-wall neighbors…that 10 watts did fine.

Somehow this antique receiver and speakers burrowed its way into the back of my mind and sat there for, like, 40 years. Because I always enjoyed the way it sounded. And I tried to replicate the experience over and over again.

I commend the full post to your attention, but for now, I’ll dive into detail on a few of Jason’s overview points. First off, what did he mean by “Because they don’t hiss like a demon cat, drilling slowly into your synapses and draining your soul”? He was contrasting Rekkr’s Class AB approach to what alternative noisier (he believed, at least, and at least at the time) Class D amplifiers exhibit. My personal take: he might have been right about Class D a few years ago, especially in the near-field configurations he’s specifically advocating for Rekkr, but no longer. More on that in a follow-up post to come.

Usage requirements

Speaking of near-field, let’s attempt to quantify his comment, “Because let’s face it, how much power do you need for desktop speakers?” Near-field translates to (among other things) “close proximity”, i.e., speakers located 5 feet (1.5 meters) or less away from the listener. Why’s this important? It’s because sound intensity follows the inverse square law: doubling the distance from a sound source reduces the intensity to one-quarter of its original value (said another way: the sound level will be down by 6 dB). There’s a handy online calculator (along with others) for ascertaining sound level variance versus distance on Crown Audio’s System Design Tools webpage. And to my earlier comments: near-field speaker configurations are conveniently-for-Jason also most likely to result in listener-discernible amplifier-generated “hiss”.

Directly above that calculator is another one we’re going to focus on most today, titled “Amplifier Power Required”. Note that sound level is a function of multiple factors:

• Distance (already discussed)
• Speaker sensitivity, which indicates how efficiently a speaker converts electrical power into sound. It’s measured in decibels at a specific distance (usually 1 meter) from the speaker when 1 watt of power is applied. The higher the sensitivity (which for any single- or multi-transducer setup also varies with frequency; the spec’d value is an average), the louder it will sound for a particular connected-amplifier power output. Or said, another way, the higher the sensitivity the less power is needed to hit a given sound level.
• And, of course, the amplifier’s per-channel power output capability (optionally also allowing for headroom to prevent clipping caused by sound level “peaking”). This is in part dependent on the speaker impedance load that the amplifier is connected to (lower impedance = higher output power). Reference, for example, the earlier Rekker specs.

Crown Audio’s “How Much Amplifier Power Do I Need?” essay provides an excellent review of these factors, along with their relevance to different kinds of music and listening environments. I’ll only offer one caution: the company’s business model particularly focuses on live sound venue setups, so although the essay concepts remain relevant for the home, you’ll need to tweak the specifics a bit. For now, let’s plug the following values into the online calculator:

• Distance: 1.5 meters
• Desired sound level: 85 dBSPL
• Speaker sensitivity: 85 dB (at 8 ohms)
• Headroom: 3 dB

The calculated result? The required per-channel amplifier power is only 4W (per channel for a stereo setup). Decrease the speaker-to-listener distance, and/or the peak sound level (and/or associated headroom), and/or increase the speaker sensitivity, and the per-channel amplifier power requirements further plummet.

To wit, trust me when I tell you that I didn’t proactively twiddle with the input values to come up with any particular calculator output end result. In fact, they actually overshoot those of the setup I’m planning on hooking up shortly after completing this preparatory write-up. It’s based on a set of Audioengine P4 passive speakers:

rated at 88-dB sensitivity and 4-ohm nominal impedance. Their likely normal distance to me will be more like 3 feet, not 5 feet, i.e., 1.5 meters (but we’ll stick with 5 feet for now). And when Jason postulates about how “neighbors feel about 100,000 watts if you share walls with them”, in my case, that’s my wife, who I doubt will long tolerate 85 dB (or even close) sound levels spreading from my office throughout the rest of the house. That said, try this data set:

• Distance: 1.5 meters
• Desired sound level: 85 dBSPL
• Speaker sensitivity: 88 dB (at 4 ohms)
• Headroom: 3 dB

And you’ll discover that the result, 2W/channel, is less than the 3W/channel (4 ohm) output power capabilities of a single Rekkr. To confirm or deny the calculator claim, I’m going to try out this single-amp configuration first. And then, since I happen to have a pair (two pairs, actually, both black and silver sets) and it’s so easy to configure them in monoblock mode (the user manual is here on Schiit’s site, for all the implementation details), I’ll try ‘em that way, too. Stand by for results to come in a follow-up post (or a few) soon.

Is bigger always better?

As is often the case with my writeups, my motivation here wasn’t just to tell you about a diminutive audio amplifier that seemingly punches above its weight. And it also wasn’t just to quantify for you that, in fact, at least for its target usage scenarios, Rekkr’s weight was exactly right. It was to use this case study as an example of a bigger-picture situation: that in the absence of in-depth understanding to the contrary, consumers are always going to assume that “bigger numbers are always better”…even if those bigger (power output, in this case) numbers come with bigger price tags, and/or require housing product in bigger (and heavier) form factors, and/or have bigger associated distortion specs, and/or…you get my drift.

I strongly suspect that many of you, whether you’re in the audio industry or another, regularly struggle with “crazy numbers-for-sake-of-numbers, power-nervosa specsmanship” (see below for the verbiage reference) demands from your target customers and/or your own company’s marketing, sales, corporate execs and others, often motivated by your competitors’ statements and new-product actions. I’d love to hear more about the specifics of your various situations and how you deal with them. Please sound off with your thoughts in the comments; your fellow readers and I look forward to reading and responding to them. Thank you in advance!

Jason delves into this understandably frustrating dichotomy at the tail-end of his February 2023 post, which I’ll reproduce in full in closing, preceded by the reality-check calibrating contents of a subsequent post he made last November when word of the Rekkr discontinuation became known to the community: “Rule 1 of all business: don’t make what people don’t buy.”

The “less power, more better” manifesto

Now, some people are still not convinced. They want more power. And that’s fine. Maybe I’ll stack two Vidar transformers in a Tyr chassis and do a 300WPC stereo amp. Probably not, because it would also require a panic fan, and I hate fans, but after last year’s ordering debacle, we got lots of Vidar transformers to play with.

But I’d say, keep an open mind. You might be surprised.

We’re sooooooo conditioned to want more, more, mooore, moaaarrr! that I think sometimes we lose perspective, like I did when I started this amp adventure. And that can quickly devolve into venerating something that can produce huge power above everything else—even if we don’t need that power.

I mean, here’s the thing. I’ve had desktop systems for ages. A lot of them used a 60W integrated amp—first the Sumo Antares prototype, then the Ragnarok, then the Rag 2. And each of them had a common denominator: I never used even a fraction of those amp’s output power.

And yeah, I’ve also had desktop systems based on powered monitors. Including ones that like to brag they have like 1000W for the woofer and 50,000W for the tweeter and that sounds like 10,000,000W and etc. (Well, maybe a bit of hyperbole there, but you know what I mean: powered monitors with a bunch of watts and claims of hitting 1XXdB at 1 meter and other silly numbers.

And each time, those mega-powered systems were used once for that circus trick of huge output—then turned down for use at regular listening levels.

Because, you know, yeah, they go loud, but Rina’s yelling at me from the other room.

And each time, those mega-powered systems didn’t last long on the desktop—their infernal hisssssssssssssssssssssss drove me bonkers, and I went back to passive.

So, yeah, something used for a party trick once (but then annoys the neighbors) with the added bonus of the unrelenting hiss of a demonic cat drilling its way into your ears…yeah, no thanks, not for me.

Aside: and yes, I know, there are pros that have legit uses for such monitors, and people who don’t have to worry about neighbors. Not dissing those. Just asking: do you really need it? Can you use it? Or is it just crazy numbers-for-sake-of-numbers, power-nervosa specsmanship?​

Sooooo…maybe it’s time to recalibrate.

To sit back, and think, “Do I really need power for the sake of power?”

Yes. I know. It’s a challenging idea.

But maybe, just maybe, it’s time for something less power, more better.

 —Brian Dipert is the Editor-in-Chief of the Edge AI and Vision Alliance, and a Senior Analyst at BDTI and Editor-in-Chief of InsideDSP, the company’s online newsletter.

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The post Audio amplifiers: How much power (and at what tradeoffs) is really required? appeared first on EDN.

This project came about because I wanted to experiment with my new oscilloscope but had no way to generate the needed signals. So, I decided to put something together myself. Right now, it can produce: RS232 serial output I²C signal output Positive and negative runt pulses Burst pulses Classic waveform generators: Sine, Triangle, Sawtooth Amplitude modulation (AM) wave patterns The hardware-specific parts are kept separate from the hardware-independent parts, so it should be relatively easy to adapt this for a different microcontroller or DAC. I also designed a PCB for it — my first ever! Routing the traces was a bit tricky, but it was a fun learning experience. Feedback and suggestions are always welcome. https://github.com/coderarjob/ScopeTester submitted by /u/arjobmukherjee [link] [comments]

submitted by /u/DropMysterious1673 [link] [comments]

submitted by /u/SubhajitBarman [link] [comments]

A small microphone I designed for Hack Club's Highway to Hardware program! Still needs some modifications to work properly for daily use - but still incredibly happy it works! The build was supported by Hack Club, a not-for-profit for supporting teenagers to create and build hardware and software! All the design files are available on Github at: https://github.com/ConfusedHello/USB-Mic submitted by /u/ConfusedHornPlayer [link] [comments]

The new 3.3 V, four-channel hybrid redrivers may promote HDMI signal integrity for high-fidelity video transmission.

I found a 24v led strip but because I didn't have anything to control it, I decided to make a pcb to do so! It's very overpowered for what I currently use it for, but because of the way it's designed and the psu, i could maybe power 50 meters! Everything including firmware is open source at https://github.com/espcaa/led-system submitted by /u/espcaaa [link] [comments]