Fosi Audio Box X5 Phono Preamp Review

[steve f]

Guys, after reading this thread I decided to go for X5 and it sounds great to me, but I have an issue with provided power unit, it makes a buzzing sound when not in use and stays hot even though X5 is off. Is it common issue? Any fix or should I return it? Thanks

Something is wrong. Mine works fine.

 

[DeadBeatAnon]

Guys, after reading this thread I decided to go for X5 and it sounds great to me, but I have an issue with provided power unit, it makes a buzzing sound when not in use and stays hot even though X5 is off. Is it common issue? Any fix or should I return it? Thanks

No, that X5 shouldn't be running hot. Even when in use, the X5 is cool to the touch. Does your turntable have a ground cable, and did you connect it to the X5 grounding screw? The fact that your X5 stays hot when not in use is alarming. It's now a fire hazard. Return it.

 

[shivver]

No, that X5 shouldn't be running hot. Even when in use, the X5 is cool to the touch. Does your turntable have a ground cable, and did you connect it to the X5 grounding screw? The fact that your X5 stays hot when not in use is alarming. It's now a fire hazard. Return it.

It's not X5 that runs hot but the power brick. It's strange that it gets hot if the Fosi X5 is off.
I will play with the cables again, maybe it will help.

 

[nagster]

Guys, after reading this thread I decided to go for X5 and it sounds great to me, but I have an issue with provided power unit, it makes a buzzing sound when not in use and stays hot even though X5 is off. Is it common issue? Any fix or should I return it? Thanks

First, if the AC adapter is too hot to touch, unplug it from the outlet immediately.
Mechanical noises or overheating may indicate a malfunction in the Box X5. However, it could also be caused by a DC component or significant waveform distortion in your room's main power supply.
This can easily happen if hair dryers, electric heaters, dimmers, etc., are being used nearby. Especially if the noise or vibration level changes depending on the time of day, it's highly likely that the quality of your main power supply is the cause.

I measured the power consumption of the Fosi Audio Box X5's AC adapter. I measured the power consumption both with the unit connected and without the unit connected.
As a simple simulation, I superimposed a DC voltage.

I listened to the sound of the Box X5's AC adapter.
When the DC voltage was 0V, I could faintly hear a "pooo" sound when I pressed the adapter against my ear.
When the DC voltage was 5V, I could hear a "boogie" sound even when I was about 50 cm away from the adapter.
These are inputs from a power source with very low distortion. I suspect that the waveform distortion would be much greater with input from a wall outlet.

 

[nagster]

I measured the temperature of the AC adapter for the Fosi Audio Box X5. For comparison, I also placed it next to the AC adapter for a Schiit Midgard and another AC adapter I had lying around.

Fosi Audio Box X5 Phono Preamp Review

If we default the capacitance to 0pF and have 4 levels of adjustment, with the first level being+50, the second level being+50, the third level being+50, and the fourth level being+50, then you can get five levels of adjustment: 0/50/100/150/200pF. What do you think? Actually, if you'd you'd...

www.audiosciencereview.com

 

[Jake71]

The FFT plot says dBrA, does that mean you used A-weighting for this measurement?

 

[Jimi Floyd]

The FFT plot says dBrA, does that mean you used A-weighting for this measurement?

Of course not, but that's a very good question.

 

[Jake71]

Of course not, but that's a very good question.

Then what does the A stand for? Usually dBrA means dB relative to the test tone with A-weighting.

 

[NTK]

Then what does the A stand for? Usually dBrA means dB relative to the test tone with A-weighting.

The "A" in "dBrA" means the reference testing level used was the input level for the AP analyzer channel A.

https://www.eetimes.com/introduction-to-the-six-basic-audio-measurements-part-1/

 

[Jake71]

The "A" in "dBrA" means the reference testing level used was the input level for the AP analyzer channel A.

https://www.eetimes.com/introduction-to-the-six-basic-audio-measurements-part-1/

Thanks. I wonder why they did it like that. Will it show dBrAB if you use both channels? Very strange, but thanks for clarifying because the FFT plot doesn't look like A-weighting was applied.

 

[Boltman92124]

Thank Amir for the great review. We hope everyone will enjoy the Box X5.

Here are the links for purchase：
Fosi Audio site: https://fosiaudio.com/products/box-x5-phono-preamp

Do you have the input capacitance for this unit? Pretty much a mandatory spec to publish before purchase.

 

[nagster]

Will it show dBrAB if you use both channels? Very strange,

APx offers two types of variable input references—dBrA and dBrB—with freely configurable levels (e.g., Vrms).
Therefore, to accurately interpret plots using dBrA or dBrB axes, you need to know both the configured input reference level and the actual input signal level.
Incidentally, there is also a variable output reference setting, designated as dBrG (Generator).
The link below provides an explanation excerpted from the APx User's Guide.

Review and Measurements of Purifi 1ET400A Amplifier

I got a question regarding this results that I will appreciate some feedback: The High frequency peak is still only -20db from the main music that sits on 0 ? Isn't that basically means that we spend 0.1W for each Audio level we product - and that is literally being dissipated on the tweeter ...

www.audiosciencereview.com

 

[nagster]

Do you have the input capacitance for this unit? Pretty much a mandatory spec to publish before purchase.

The link below contains data measured by a user; it might be better than nothing.

Fosi Audio Box X5 Phono Preamp Review

There we have it, again. 240uV (10Hz ...22kHz) noise with cartridge, but only 28uV with AP as source, about 18dB worse and SINAD would take a similar hit. ... Finally strict on topic, see below. But here are some blank numbers from my LTSpice simulation at 20°C, as we are dealing with thermal...

www.audiosciencereview.com

 

[Boltman92124]

The link below contains data measured by a user; it might be better than nothing.

Fosi Audio Box X5 Phono Preamp Review

There we have it, again. 240uV (10Hz ...22kHz) noise with cartridge, but only 28uV with AP as source, about 18dB worse and SINAD would take a similar hit. ... Finally strict on topic, see below. But here are some blank numbers from my LTSpice simulation at 20°C, as we are dealing with thermal...

www.audiosciencereview.com

Thanks!> Looks pretty high on the Pf. Will induce that AT HF rise and cut-off above 8khz I think.

 

[Jim T]

Thank you for your review Amir. Superb performance and price.

I have both an amplifier and a receiver with a phone input, but would still plug in the Fosi Audio Box X5 instead because I don't really trust that inputs one on my vintage HiFi is that good.

I just bought a Denon PMA 600 and am using the Fosi X5 instead of the internal phono preamp. The internal premap is of utility use only. The X5 is a killer phono stage.

 

[Boltman92124]

For a few bucks more a Schiit Mani 2 is far superior. Adjustable input capacitance is one of many reasons. Made, supported and serviced in the US the clincher. $150.

 

[Ropeburn]

For a few bucks more a Schiit Mani 2 is far superior. Adjustable input capacitance is one of many reasons. Made, supported and serviced in the US the clincher. $150.

That doesn't have the appeal you think it has outside the US. Not generally, and these days even less.

 

[AaronJ]

For a few bucks more a Schiit Mani 2 is far superior. Adjustable input capacitance is one of many reasons. Made, supported and serviced in the US the clincher. $150.

Well there’s also the $17 S&H that’s so comically high for a <1 lb device it’s like an as-seen-on-tv product, the untenable wall wart (Fosi X5 uses a floor wart), and the knowledge that you’re supporting that goofy owner and his “crazy uncle” shtick.

 

[Boltman92124]

That doesn't have the appeal you think it has outside the US. Not generally, and these days even less.

You can't even get a Fosi product serviced in the US. Even under warranty. It's a paper weight if it breaks.

 

[Boltman92124]

Well there’s also the $17 S&H that’s so comically high for a <1 lb device it’s like an as-seen-on-tv product, the untenable wall wart (Fosi X5 uses a floor wart), and the knowledge that you’re supporting that goofy owner and his “crazy uncle” shtick.

That crazy uncle has been selling audio products like the Mani for over 40 years. I'll give Fosi some credit though, it's the only ChiFi product I've bought that didn't break in two years.(T20 tube amp).