Fosi's New Linear Power Supply

[solderdude]

I couldn't deal with them. Both amplifiers have balanced inputs. LFPS is still noisy.

To put this wonderful measured difference in a practical perspective ...

Suppose you dial the volume of the 1kHz tone all the way up to a screamingly LOUD 130dB SPL.
In that case you would immediately cover your ears.
Still it represents 0dBFS in a recording with peaks so the absolute hearing threshold is valid.

Yep, measurable but absolutely inaudible hum.
And for the 2kHz and 3kHz components I have not even drawn in auditory masking which would make those 2 distortion components absolutely inaudible as well.
The blue line is absolute hearing threshold for young folks in total silence and with acclimatization to absolute quiet.
Imagine trying to hear those harmonics which are barely detectable when the 1kHz tone would not be there while hearing an unbelievable screamingly loud 1kHz tone (which would distort a lot anyway at 130dB SPL (while covering your ears as you would be thinking you are dying when this was suddenly turned on while acclimatized to silence for a while.

If music would be playing the average SPL would be in the neighborhood of 110-120dB SPL which is more than uncomfortable loud.

Nothing to worry about. Absolutely inaudible in reality.
This is what you get when you combine measurements with (young adult) human hearing thresholds and puts things in perspective.
Besides the real world noise floor would drown the spikes you see anyway.

Measurements can go magnitudes lower,deeper and further than any human ear ever can.

 

[Mike123]

Yep, measurable but absolutely inaudible hum.

I wrote this that there are audible and measurable distortions. I don't dispute that measurable differences are not audible in my case. This is where the pleasure of good engineering comes into play. Just like the DAC with SINAD 123 is more technically advanced than the DAC with SINAD 121, although from a listening point of view they are equal. But Amir gives better scores and is higher in the ranking table . Although the advantage of the blue graph is that the problem of being heard or not heard can be completely discarded. Because the problem is not even measured. However, the problem with LF PS is that the slightest errors in design lead to the fact that these harmonics are not only measurable, but also perfectly audible. And in my experience there are many more than one such examples.

 

[xanalog]

...
I should be doin' somethin' far more useful than I am right this minute, though... ...

Ohhh, noooo!

We may be part of the gigless crowd, but we are in giggles.

 

[xanalog]

Latter part of the thread for FOSI ZA-3 Amp Review had a reply that FOSI now offers a DC Power Filter.
I was chastised when asking for relevant test result data for the "filter", over-and-above the following 'specs' offered at FOSI website:

Specifications
Power Input
AC: 115V / 230V
Note:
115V setting supports 100–120V input
230V setting supports 220–240V input
Power Output
DC 1: 12V / 15V (Rated Power: 20W)
DC 2: 12V / 5V (Rated Power: 15W)
USB: 5V / 1A (Rated Power: 5W)
Operating Temperature
-20 ~ 40°C (-4°F ~ 104°F)
Temperature Rise Test
Temperature rise of 25°C (77°F) at full load

Oddly enough, I was contacted by FOSI peeps; asking for what type of data would be 'relevant'.

In the case of this FOSI LPS, I don't think --besides their "0.1mV ripple" spec-- nothing else is provided that is relevant or meaningful.
I am having second thoughts about where the new FOSI-mindset is heading.

 

[fpitas]

I am having second thoughts about where the new FOSI-mindset is heading

Grab that cash with both hands and make a stash?

Seriously...I doubt that 1 out of 10,000 people would benefit from that data. But you would hope they'd still supply it (pun intended).

 

[xanalog]

Seriously...I doubt that 1 out of 10,000 people

LOL:
We must be the 1 out of 10,000 people who ask for objective and relevant data.
I don't mind being the odd-man out. I am sure you don't either!

ADD: I was not asking FOSI for stringent MIL-STD-220 (filter insertion-loss) or MIL-STD-461 (conducted-emission) type tests.
I further think that no engineer (who professes to be an 'engineer') would not have done some 'relevant' measurements to pitch the product to mgmt/mktg.
Perhaps, their data does not support that their LPS is any better (less noisier) than a SMPS.

 

[fpitas]

LOL:
We must be the 1 out of 10,000 people who ask for objective and relevant data.
I don't mind being the odd-man out. I am sure you don't either!

ADD: I was not asking FOSI for stringent MIL-STD-220 (filter insertion-loss) or MIL-STD-461 (conducted-emission) type tests.
I further think that no engineer (who professes to be an 'engineer') would not have done some 'relevant' measurements to pitch the product to mgmt/mktg.
Perhaps, their data does not support that their LPS is any better (less noisier) than a SMPS.

Also, I doubt the filter accomplishes anything, practically speaking.

 

[xanalog]

Imagine the possibilities, if there was substantial data?

>> in combo with 2x >>

We could be down to KTB levels of noise-free!

 

[DLloyd]

I ordered one five days ago to power my Fosi ZH3 and Raspberry Pi 4 (which runs piCorePlayer).

 

[RandomEar]

I ordered one five days ago to power my Fosi ZH3 and Raspberry Pi 4 (which runs piCorePlayer).

This supply is not suitable for a Pi 4. Specs say 5 V @ 1 A for the Fosi, so 5 W max. The Pi uses about 3 W in idle and about 7 W peak without any peripherals connected. If anything is plugged into the USB ports, that needs additional power.

The official recommendation is to use a 5 V 3 A supply on the Pi 4. For good reason. This Fosi supply may be good enough to boot it, but your Pi may randomly crash under load.

 

[voodooless]

your Pi may randomly crash under load.

Well, at least it makes a difference then

 

[DLloyd]

This supply is not suitable for a Pi 4. Specs say 5 V @ 1 A for the Fosi, so 5 W max. The Pi uses about 3 W in idle and about 7 W peak without any peripherals connected. If anything is plugged into the USB ports, that needs additional power.

The official recommendation is to use a 5 V 3 A supply on the Pi 4. For good reason. This Fosi supply may be good enough to boot it, but your Pi may randomly crash under load.

I don't plan to use the 5V USB output. The switchable outputs are 12V/15V at 20W and 12V/5V at 15W.

 

[AgarWave]

The distinction is which output is being used. Fosi lists DC1 as 12/15 V, 20 W, but DC2 as selectable 12/5 V, 15 W. At the 5 V setting, 15 W corresponds to 3 A, so DC2 is at least nominally in the Pi 4’s recommended 5 V / 3 A range. The 5 V / 1 A USB output is the one that is clearly undersized.

Two cautions remain: do not feed the Pi from either 12 V setting, and use a correctly wired cable/adapter that delivers 5 V to USB-C with low enough voltage drop under load. I would also check the Pi’s undervoltage/throttling flag during a CPU-plus-USB load test before calling the setup stable. That verifies the actual voltage at the Pi, which matters more here than whether the supply is linear.

 

[babadono]

I have replaced the mains transformer, diodes, filter cap linear PS in several pieces of equipment with +/-24 volts from Meanwell SMPS. No more background hum in the room. That noise drives me nuts.

 

[DLloyd]

 

[DLloyd]

So the PSU20 arrived from China and I have been using it for a few days now. Just like the ZH3 it is well made and solid, and also runs on the warm side. Does my system sound better? Categorically yes...

 

[Bleib]

I don't think it makes any difference at all (ZH3 is already way beyond human hearing), but everyone decides on their own

 

[Flaesh]

>>

Sorry, but why are these wonderful rays blue and not orange?? I don't want blue . (I have five V3s, I use them all at the same time daily and with quite good success; , it's hardly accuse me of disloyalty to the brand))
And all these LEDs on amplifiers and power supplies would do well to be made orange instead of vulgar blue and green. It doesn't bother me (almost) at all, I rarely see them; but these blue rays filled the cup to overflowing

 

[xanalog]

Imagine if I put up a "ForSale" ad that I have "InternalCombustionEngine vehicles" for sale... and people started ordering them because of the word ICE.
Wow!

 

[SanojS]

I think the use case for this is where people have 2-3 of these types of small boxes and don't want 3 large external bricks and 3 cables going to power wall socket. Then it makes sense. Like you have a streamer, a Fosi DAC and a Fosi preamp. Then it would be neat!
Price is OK for a linear 40W box and I would happily pay that to clean up the power plug spaghetti.