You're correct.
The TDA2004 and its siblings are mediocre amps designed for cars.
Road noise masks their issues.
I built a "cheap and dirty" preamp designed to be very small. It all fit in a small router case that was only 1" high. It was designed to work off an external DC source of 12-30 volts. I employed a "brute force" R-L-C filter on a small board with the barrel connector. Even the ground is isolated by a resistor and inductor.
This unit performs just fine from a 20 volt laptop supply. The whole thing is a compromise because I built it with specific constraints in mind (size, cost = 0, work from switching supply) and it's not as good as my traditional preamp. I built it as an exercise but it works fine and is very handy for quick testing various builds. In fact, it's better than most (all but 2!) preamps I've seen in consumer grade receivers.
I also have an everyday use headphone amp that is powered by a switching supply. I know it's heresy to purists, but I wanted the challenge of ironing out the kinks and I succeeded.
I think a switching supply is a logical choice for a power amp, where its smaller size and higher efficiency have the biggest payback. Switching supplies aren't inherently bad. The designer just has to know how to handle them.
I tried to fix a Fender mixer-amp with a SMPS power supply, The thing would make odd blips and other noises at odd times. I though I had it fixed by correcting ground straps at one point but the problem eventually returned. Yes avoid SMPS if possible.
SMPS supplies traditionally use small, low Mfd caps for filtering the high frequency component from the SM transformer.
330, 470uf are typical values, and when heavily loaded, show that high frequency component in the output.
You can't hear the 50-100Khz ripple, but it does interact with audio in strange ways, such as odd noises, blips, clicking, etc.
Face it, SMPS supplies are nothing more than a "cheap and dirty" answer to manufacturers designs.
It costs way less to make an SMPS than using a big, heavy transformer in a traditional design.
About every piece of consumer as well as pro gear is running on switchmode supplies. Not the same types and levels of quality of supplies, but on neither end have I recognised "odd noises, blips, clicking, etc". All the Crown, LabGruppen, QSC, ... amps I've used in the last 10 years were dead silent without any odd noises. Yesterday I hooked up my dbx DSP to a 113dB/W/m horn system. No "odd noises, blips, clicking, etc" despite the switchmode supply. What am I doing wrong?
This may be true, consumer electronics go that way. But concluding from your single bad experience that all smps are crap just shows you do not have a clue how to build good smps.
That assumption is ignorant, incorrect and uncalled for.
Because I've been in the Service Business professionally for 45 years now and have serviced thousands of consumer audio/video products though the years!
You assume I've only a "single experience?
So bite down on THAT one now!
I ought to know what I'm talking about, although some of you on the internet fail to know my credentials.
Considering the lots of people who did experience excellent results with SMPS feeding audio circuitry including my humble person the ignorance is solely on your side. 😉
You insist on arguing your point, fine.
Which to me doesn't mean crap.
I don't care about your "experience", because it surely doesn't amount to mine.
And with that, it's time to block you.
Goodbye.
smps work really well if you filter it with a 10uh 10A inductor and 2200 / 35v capacitor.
a 0.1uf ceramic should also be placed across the 2200uf .
a 0.1uf ceramic should also be placed across the 2200uf .
Filtering a SMPS is not a simple matter of adding a inductor and capacitor at the output, unfortunately. Your suggestion does help, of course, but the SMPS is a true RF power circuit. To build it properly, instrumentation and some experience and/or a good template to copy are a necessity. If you don't have them, you risk placing a RF oscillator next to the sensitive analog circuits, and this would ruin any design. This is why, on a DIY perspective, I believe that the suggestion to avoid SMPS is a good one unless good RF instrumentation is at hand or a commercial, certified power supply with guaranteed full specifications is used (not cheap).
Filtering at the input is equally important, if not more important, than filtering at the output. One of my recent design mistakes was a microprocessor control device with a small (10W) SMPS circuit. To lower the electromagnetic interference and increase efficency of the SMPS flyback converter, I specified a comparatively new controller chip with quasi-resonant operation mode. First prototype worked perfectly, it seemed at first. But when we tested EMI on the measurement chamber, limits were exceeded by almost 20dB - this design was a failure. Turned out that there was a mistake on the PCB traces, and that the controller chip was not behaving properly when the output load was low. As result, we had to redesign the SMPS from scratch.
Equipment servicing is one of my jobs and therefore I fully understand why wiseoldtech does have such a bad opinion about SMPS technology. The endless stream of devices with faulty SMPS that come on my service bench speaks for itself: when the products had a traditional transformer based power supply, faults in this area were less common and also cheaper/faster to fix. But there is a catch, due to the nature of the service business. The service technician sees the bad designs every day, even when they bear a Big Brand Name, but it rarely sees the good designs that simply works. The bulk of the cheap misbehaving SMPS aptly described by wiseoldtech at post #24 are the result of a "bean counter" decision (hint: even Expensive Big Brand Names hire "bean counters") or are designs from a past era, when EMI compliance was not so important, power semiconductors were not optimized for the job, and there was widespread ignorance on how to place a SMPS next to a sensitive analog circuit safely.
My professional design experience is about comparatively expensive devices that aren't selected on a cost basis alone. On this context, the traditional transformer based power supply is vanishing because, let's face it, the behaviour is very far from ideal. The burden on space and weight is already something that many applications cannot tolerate. Due to the way the capacitors are charging, they draw a highly distorted current waveform and therefore they wreak havoc on the supply circuits and are increasingly banned by regulations. The icing on the cake is the comparatively low efficiency. A high quality equipment manufacturer would love to keep manufacturing traditional power supplies. The transformer and the generic power semiconductors are coming from places like China at low prices, the design is a no-brainer, and the dependability is proven. To design a quality SMPS you need fancy semiconductors from leading manifacturers, expensive custom wound transformer, high-grade capacitors, maybe a custom shielding, and above all a real R&D department - unless you don't mind faking the latest regulations compliance and have the product sitting on someone service bench at regular pace. This high quality SMPS power supply will cost more than the transformer based one, not less.
Filtering at the input is equally important, if not more important, than filtering at the output. One of my recent design mistakes was a microprocessor control device with a small (10W) SMPS circuit. To lower the electromagnetic interference and increase efficency of the SMPS flyback converter, I specified a comparatively new controller chip with quasi-resonant operation mode. First prototype worked perfectly, it seemed at first. But when we tested EMI on the measurement chamber, limits were exceeded by almost 20dB - this design was a failure. Turned out that there was a mistake on the PCB traces, and that the controller chip was not behaving properly when the output load was low. As result, we had to redesign the SMPS from scratch.
Equipment servicing is one of my jobs and therefore I fully understand why wiseoldtech does have such a bad opinion about SMPS technology. The endless stream of devices with faulty SMPS that come on my service bench speaks for itself: when the products had a traditional transformer based power supply, faults in this area were less common and also cheaper/faster to fix. But there is a catch, due to the nature of the service business. The service technician sees the bad designs every day, even when they bear a Big Brand Name, but it rarely sees the good designs that simply works. The bulk of the cheap misbehaving SMPS aptly described by wiseoldtech at post #24 are the result of a "bean counter" decision (hint: even Expensive Big Brand Names hire "bean counters") or are designs from a past era, when EMI compliance was not so important, power semiconductors were not optimized for the job, and there was widespread ignorance on how to place a SMPS next to a sensitive analog circuit safely.
My professional design experience is about comparatively expensive devices that aren't selected on a cost basis alone. On this context, the traditional transformer based power supply is vanishing because, let's face it, the behaviour is very far from ideal. The burden on space and weight is already something that many applications cannot tolerate. Due to the way the capacitors are charging, they draw a highly distorted current waveform and therefore they wreak havoc on the supply circuits and are increasingly banned by regulations. The icing on the cake is the comparatively low efficiency. A high quality equipment manufacturer would love to keep manufacturing traditional power supplies. The transformer and the generic power semiconductors are coming from places like China at low prices, the design is a no-brainer, and the dependability is proven. To design a quality SMPS you need fancy semiconductors from leading manifacturers, expensive custom wound transformer, high-grade capacitors, maybe a custom shielding, and above all a real R&D department - unless you don't mind faking the latest regulations compliance and have the product sitting on someone service bench at regular pace. This high quality SMPS power supply will cost more than the transformer based one, not less.
Thank you.
You summed it up quite nicely.
28 years ago, when I started work at the last Service Shop that I was at, the owner there asked me "what do you know about "chopper supplies?" - meaning SMPS supplies.
Even though he was a long time experienced service tech himself, he explained that SMPS troubleshooting was clearly not his favorite job.
VCR's, TV's, among other consumer products, were starting to come into the shop with failed supplies in droves.
And I soon experienced this as well, as you mentioned, the flow was endless.
Sure, it helped to "keep us in business", but the time involved troubleshooting the various different designs made our other work pile up, and this annoyed the customers involved.
Occasionally, the customer got tired of the wait, and took their equipment to another shop.
Service info was sometimes not available, because the unit was "too new", barely out of warranty, and the manufacturer didn't yet offer the needed information.
All this turned a healthy Repair Business into a headache to work for.
Added stress, which is not good to have when performing service of anthing.
After years of this, my mind was made up, I just didn't like anything built with an SMPS supply, plain and simple.
So that snotty assumption by an earlier poster on here about "my one bad experience" was utterly wrong and uncalled for.
I never had the same problems, naturally, with traditional power supplies, and the reliability of those products of course was much better.
How does it not? Why does it not?
And what is your experience? 45 years of not understanding switch mode supplies?
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