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Fosi Audio Box X5 Phono Preamp Review

Rate this phono stage:

  • 1. Poor (headless panther)

    Votes: 4 2.0%
  • 2. Not terrible (postman panther)

    Votes: 8 4.0%
  • 3. Fine (happy panther)

    Votes: 35 17.5%
  • 4. Great (golfing panther)

    Votes: 153 76.5%

  • Total voters
    200
It would be interesting to compare with the Boulder 2108, a slightly more expensive offer for phono preamps. The Fosi might have a better SINAD! Thank you Amir for showing us how to get SOTA at bargain prices!
 

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Maybe the same mental process as smoking. It is killing you but you like it.
I could easily believe that physically engaging with the medium makes you pay more attention to it. Really, how you can avoid it? You laid out quite a few things that force it to happen.

And there is reason to believe that paying closer attention to what you are listening to makes it sound better.

As we know, placebo effect can overcome reason pretty easily, it happens all the time. So maybe vinyl really does sound better in the end? ;)
 
if it can be essentially intended for use on mm cartdrige....it would be good to indicate the input capacitance... ??? ( impedance in mc?)
just there my little regret on a machine of this type and range absence of this adjustment with some capacitance values see a very low one ( , it remains possible to add more...the opposite is not true)
perhaps for the futur x6...
;-)
Dont understand what's your regret.
 
What I really would like ... a "pro" version with balanced output :)
 
Considering my turntable has rumble at about -70 this is very nice and even MC is good enough. Looks like a good deal. Any idea about MM input capacitance?
Edit: And for MC it would be nice to have options for 50/100/200/400/1000Ohm range. I'd happily pay double or triple with both adjustments included.
I dont know much about phono stage, could you please explain what is MM input capacitance?

Also why need to have options for 50/100/200/400/1000Ohm for MC?
 
What I really would like ... a "pro" version with balanced output :)
Next version in 6 months will add few functions. You can buy this one and you will scratch your head in 6 months to know if the upgrade bla bla bla.

At least we know at @Fosi Audio they pay attention to our wishes and want to bring us some fun.
 
This looks impressive for the money. Good job. @Fosi Audio: maybe you could consider adding a second, slightly more expensive version with a switchable high-pass around 30 Hz and a switchable LF cross-feed for noise reduction around 80 - 120 Hz?
Why do you need a high pass filter around 30Hz, usually a HPF is about 80Hz.
 
Highpass filter for phono cartridges are around 20Hz, to suppress cartridge/arm resonance whis is typically around 10Hz. Without suppression, high rumble will cause intermodulation distortion and stresses the amp and speakers which are desperately trying to reproduce 10Hz. In worst scenario woofer's coil will burn before amplifier's fuse or relay shuts.

Capacitance affects spl response (total and high freq resonance), and MC cartridges can be very different, as well as the thin wires from cartridge to preamp.
 
Highpass filter for phono cartridges are around 20Hz, to suppress cartridge/arm resonance whis is typically around 10Hz. Without suppression, high rumble will cause intermodulation distortion and stresses the amp and speakers which are desperately trying to reproduce 10Hz. In worst scenario woofer's coil will burn before amplifier's fuse or relay shuts.

Capacitance affects spl response (total and high freq resonance), and MC cartridges can be very different, as well as the thin wires from cartridge to preamp.
From what I understand, this Fosi lacks a rumble filter? Why? A design flaw? Does that mean that in practice it has a bigger problem with distortion than the measurements here indicate?
 
It is lot of fun but you have to spend some money in this. A nice turntable, a good cartridge, a phono preamp.

Then comes the cleaning brush. Add a new mat, a protractor, an ultrasound cleaning machine, and the records. Don't forget these little bubble levels and the cartridge weight gauge.

Every 20 minutes you need to move because it is time to listen to B side or another record.

Yes, not comfortable, expansive and the quality is far below what you can have with some inexpensive DAC.

Maybe the same mental process as smoking. It is killing you but you like it.
Not forgetting the cost of new vinyl :)
 
The printing on the rear side has typos, the gain unit is "dB", not "DB".

For the given price, aming at the entry level market, the simple circuit design is OK. Elaborated rumble filters as well as load switching options are not to be expected. MM loading will sure be the standard 47k. Capacitance is not as standardized and should be stated in the manual/specs.

@Fosi Audio : And that's where my real concerns are: There is no real datasheet, the specs given on the website are a joke, totally incomplete.
I would never give my money to a company that isn't able to provide even the most basic specs in a proper PDF datasheet as that shows either incompetence or a don't care attidude.
EDIT: Now I see that a PDF manual/datasheet is hidden under the "what's in the box" section which is plain silly. And that hidden PDF is still incomplete and most likely incorrect, stating a 10kOhm output impedance. Are you kidding us?
 
It is lot of fun but you have to spend some money in this. A nice turntable, a good cartridge, a phono preamp.

Then comes the cleaning brush. Add a new mat, a protractor, an ultrasound cleaning machine, and the records. Don't forget these little bubble levels and the cartridge weight gauge.

Every 20 minutes you need to move because it is time to listen to B side or another record.

Yes, not comfortable, expansive and the quality is far below what you can have with some inexpensive DAC.

Maybe the same mental process as smoking. It is killing you but you like it.
Agreed ... except two bits ... the 'quality' bit I would just add 'measured', because a good vinyl set up can act as a reminder of 'what we actually hear' (well below DAC measurements), quality of source (even of digital transfer) ...

and getting up to turn the record over is good for you, so definitely improves life expectancy in my book (or here's hoping) :D
 
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The printing on the rear side has typos, the gain unit is "dB", not "DB".

For the given price, aming at the entry level market, the simple circuit design is OK. Elaborated rumble filters as well as load switching options are not to be expected. MM loading will sure be the standard 47k. Capacitance is not as standardized and should be stated in the manual/specs.

@Fosi Audio : And that's where my real concerns are: There is no real datasheet, the specs given on the website are a joke, totally incomplete.
I would never give my money to a company that isn't able to provide even the most basic specs in a proper PDF datasheet as that shows either incompetence or a don't care attidude.
EDIT: Now I see that a PDF manual/datasheet is hidden under the "what's in the box" section which is plain silly. And that hidden PDF is still incomplete and most likely incorrect, stating a 10kOhm output impedance. Are you kidding us?
what a friendly comment....
 
I STILL want to see measurements of actual vinyl playback. I WANT TO KNOW THE ACTUAL PLAYBACK SINAD from a test disc!
For a pivoted arm there is a distortion dominance from the tracking error (except the 2 null regions), then from the cartridge itself. Noise is usually led by the turntable rumble and arm/cartridge resonance in the bass region. Playing a test disc one could hardly spot distortion and noise from any phono stage.
 
I STILL want to see measurements of actual vinyl playback. I WANT TO KNOW THE ACTUAL PLAYBACK SINAD from a test disc!
While doing that sounds nice in theory, in practice that opens a "can of worms". What cartridge, which stylus profile, what turntable, which test record, how many times do you play the rest record before tossing it, etc. Significantly changing the test protocols basically invalidates previous results. While the testing routine may not be "perfect", it does provide "value".
 
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