Same question can be asked for a traditional power supply. The rectifier is a switching noise factory too. The rectifier in a traditional power supply emits tons of 120 Hz + harmonics, which is clearly audible if it gets into sensitive circuits. A well-designed SMPS on the other hand emits switching noise that's well above the audio band, thus, inaudible if it gets into anything. Also, modern switchers use spread spectrum clocking, which 'smears' the switching noise such that it falls below the noise floor.
Tom
Hi
exactly! I still have not heard a good explanation from the trafo apologets why noise located in a inaudible frequency range way way out of the hearing range should play a more prominent role than the noise generated well within the audible range.
While it is quite easy to verify 100/120Hz+ artifacts with an FFT from an audio analyzer in probabely the majority of all trafo-supplied devices, its much harder to verify switcher artifacts within 20-20k.
Sometimes it sounds like a rather weird discrimination between good in-band trafo noise and bad out-of-band switcher noise.
I'd say I'd be happy about every bit of noise within the audible band less that I don't need to cope with.
jauu
Calvin
ps. how nice would it be for us audiots if the line frequency weren't at 50/60Hz but 50k/60k 😉
exactly! I still have not heard a good explanation from the trafo apologets why noise located in a inaudible frequency range way way out of the hearing range should play a more prominent role than the noise generated well within the audible range.
While it is quite easy to verify 100/120Hz+ artifacts with an FFT from an audio analyzer in probabely the majority of all trafo-supplied devices, its much harder to verify switcher artifacts within 20-20k.
Sometimes it sounds like a rather weird discrimination between good in-band trafo noise and bad out-of-band switcher noise.
I'd say I'd be happy about every bit of noise within the audible band less that I don't need to cope with.
jauu
Calvin
ps. how nice would it be for us audiots if the line frequency weren't at 50/60Hz but 50k/60k 😉
Small detail many ignore or dismiss:
50 Hz wavelength is 6000 km, so a 1/4 wave antenna is 1500 km long. (roughly 1000 miles)
500 kHz (in the band of "favorite" SMPS frequencies) wavelength is 600m; perfect 100% efficiency 1/4 wave radiating antenna is 150m.
Of course, no wiring inside an SMPS is 150m long, nobody is claiming that, but please think which one has a 10000 times easier job of radiating interference around.
The one with the higher frequency because the radiated power is a function of frequency...I doubt your unshielded tube guitar amplifier in drive mode can pick-up your neighbour mains, but i'm pretty sure it can pick-up his cell phone when called although his mains runs at about 10 000 times more power than his cell phone!
Hello. When I started this post I had the question about the benefits of using a switched source in audio devices.
After seeing that there is already a phono preamplifier with this source (Cambridge Alva Duo) and reading the different opinions in this publication, I have started looking for information on the subject.
Well, I have convinced myself that if the switched source is well built it has its benefits when using it in audio.
Calvin's explanation is very good.
I have a Denon DPN800NE network player. It felt very light and suspected that its source could be switching.
Searching on the internet, trust me that it is so.
The Rotel RB-1572 amplifier is class D and its source is switched.
I was convinced that these sources have their advantages.
Greetings
After seeing that there is already a phono preamplifier with this source (Cambridge Alva Duo) and reading the different opinions in this publication, I have started looking for information on the subject.
Well, I have convinced myself that if the switched source is well built it has its benefits when using it in audio.
Calvin's explanation is very good.
I have a Denon DPN800NE network player. It felt very light and suspected that its source could be switching.
Searching on the internet, trust me that it is so.
The Rotel RB-1572 amplifier is class D and its source is switched.
I was convinced that these sources have their advantages.
Greetings
All fine and good. But the rectifier does not emit at 50/60 Hz. It emits at much higher frequencies, especially if it's a fast rectifier with a hard reverse recovery profile. I write at some length about that here: https://neurochrome.com/pages/rectification-snubbers
You can also read Benchmark Media's take on it here: https://benchmarkmedia.com/blogs/ap...audio-myth-switching-power-supplies-are-noisy
I highly recommend watching the video near the bottom of that page. Here's a direct link to the video:
I've made similar observations in my designs. The data are hard to argue with. 🙂
Tom
What if it's not a rectifier with a hard reverse recovery profile? It looks like everybody forgot the 2.2...10nf capacitors in parallel with the diodes in the bridge...Nakamichi used high frequency soft reverse recovery diodes with no capacitor shunting the bridge in their preamps since the 80's ...I think they first did it in a Nelson Pass design for phono preamps .I can accept that one of the best recording machine, the Studer A80..827 was supplied mainly by switching amplifiers but that was a 100kg equipment with tons of circuitry and very power hungry...Sony did it the same with their receivers since the 90's using resonant converters powering everything including the phono preamp , but nobody rulled out the use of linear supplies in low power circuits yet...
A rectifier diode with a fast, soft recovery is best. But you still don't get around the switching. You also don't get around the fact that the charging pulses through the rectifier are very high bandwidth. They can reach hundreds of ampere if you go bonkers with the supply capacitance like many DIYers do. High supply capacitance -> low conduction angle -> high charging current pulses. That's physics...
A well-designed snubber will help some. At least it reduces the frequency of the EMI emitted by the rectifier. But it doesn't eliminate the charging pulses. Also, just slapping capacitors on the diode bridge is generally not the best. You can see my article on Rectification & Snubbers. I linked to it two posts back.
Anecdotal evidence makes for good dinner conversation. But take a look at the data presented in Benchmark's video.
Tom
A well-designed snubber will help some. At least it reduces the frequency of the EMI emitted by the rectifier. But it doesn't eliminate the charging pulses. Also, just slapping capacitors on the diode bridge is generally not the best. You can see my article on Rectification & Snubbers. I linked to it two posts back.
Anecdotal evidence makes for good dinner conversation. But take a look at the data presented in Benchmark's video.
Tom
I don't give a f....k on useless overlyexpensive Benchmark equipment or theories.There are LITERRALY BILLIONS audio preamplifiers built by hundreds IF NOT THOUSANDS of companies over a hundred years which DON'T exhibit any f...g audible diode switching noise.Here's DIYAUDIO, not DIY Siemens medical xray or Geiger counter detectors ...and i used to service Siemens medical equipment a decade ago yet i can't remember reading Benchmak papers on how to lower detector's and switching noise in 100kWatts 250kV Xray or MRI equipment power supplies so that those 300 chips on their boards still allow you for good CT scans... Do you know what the instantaneous power per scanning pulse of such machine is? Only a few tens of MegaWatts...Its electronics component only weight about 2...300 kg.
78xx/79xx regulators are wonderful and cheap and easy to use (though you still need to pay attention) but they have flaws, like output impedance that rises dramatically with frequency in the audio band. A good shunt reg or "super reg" is better for circuits like phono stages. I have never tried one of Jan Didden's Silent Switchers.
Hi,
tomchr: That's physics ...
Dreamth: I don't give a f...k
Well, that tells a lot .... doesn't it? 😉
jauu
Calvin
tomchr: That's physics ...
Dreamth: I don't give a f...k
Well, that tells a lot .... doesn't it? 😉
jauu
Calvin
Hi,
... skipped on social chemistry? lol
Maybe due to the language barrier, but the tone of Your reply appeared quite harsh, not to say inappropriate.
jauu
Calvin
... skipped on social chemistry? lol
Maybe due to the language barrier, but the tone of Your reply appeared quite harsh, not to say inappropriate.
jauu
Calvin
Hello. I finally found another example of a switched source in a phono preamplifier.
IFI ZEN PHONO.
And the reviews and measurements are excellent.
https://www.soundstagenetwork.com/i...reamplifier-measurements&catid=414&Itemid=547.
Calvin was right.
IFI ZEN PHONO.
And the reviews and measurements are excellent.
https://www.soundstagenetwork.com/i...reamplifier-measurements&catid=414&Itemid=547.
Calvin was right.
If there is low frequency jitter on the clock of a switch-mode power supply there would also be low frequency components below the switch frequency aliased into the supply's output. I seriously doubt that precision clocks and output transistor linearisation are on the top of the agenda for switch-mode power supply designers.
I'm not for or against linear (which still have 'switch spikes' due to the diodes in the rectifiers) or switch-mode. Either has to be designed and implemented correctly to prevent noise from being induced into an associated circuit whether directly or by EMI; the noise mechanisms just manifest in different ways.
I'm not for or against linear (which still have 'switch spikes' due to the diodes in the rectifiers) or switch-mode. Either has to be designed and implemented correctly to prevent noise from being induced into an associated circuit whether directly or by EMI; the noise mechanisms just manifest in different ways.
