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Fosi Audio Box X5 Phono Preamp Review

Rate this phono stage:

  • 1. Poor (headless panther)

    Votes: 5 2.2%
  • 2. Not terrible (postman panther)

    Votes: 8 3.5%
  • 3. Fine (happy panther)

    Votes: 39 17.3%
  • 4. Great (golfing panther)

    Votes: 174 77.0%

  • Total voters
    226
Which cart are you using?
The Fosi sounds towards the bright side, at least with AT carts of the VM series and tends to brighten my M75 Shure too.

I think this could be due to capacitance, the lower the brighter is the sound, and I guess this box has a pretty low value.
 
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Which cart are you using?
The Fosi sounds towards the bright side, at least with AT carts of the VM series and tends to brighten my M75 Shure too.

I think this could be due to capacitance, the lower the brighter is the sound, and I guess this box has a pretty low value.
Not quite, as with subjective evaluation lowering the L versus C resonance with increasing C, damped by R, would increase the perceptibility, making the „sound“ brighter.

I was just about to write a little spread sheet for evaluating the infamous equivalent input noise current from noise output with two different input generator resistors. Not only that it was pretty useless considering the surface noise of even the best, new records. But I also wonder if there is a real desire to replace the mysteries, that keep the topic of optimizing vinyl playback alive. There‘s so much ‚character‘, from imperfections, in the vinyl technology, one has to embrace it with true love, not strangle it with cold hearted analysis. Keep on!

❤️
 
Not quite, as with subjective evaluation lowering the L versus C resonance with increasing C, damped by R, would increase the perceptibility, making the „sound“ brighter.

Not quite... :)

Here we're taliking about the contribution of the phono stage.
The cart, the tonearm, the mat, the platter, even the cable, whatever you want... All are the same.

I own the MX Vynl as said before, and this one has a switch for capacitance.

If I set the AT VM95 at 50pF sounds very close to the Fosi, towards the bright side.
If I set it at 200pF (as AT suggests) the same cart sounds fuller...

So my guess is that this Fosi has a low capacitance, for sure lower than 200pF
 
normally..that s the inverse...hihi
 
lowering the capacitance value attenuates the treble response....
 
Not a general rule at all... It depends from the "starting point".
Above some values trebles are rolled off.
;-)
(and it is constantly observed and measured... )
 

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And this is referred to what?
Measuring what?

;)
there is no shortage of literature on this subject...in a few clicks...
here hagerman...
but very well known... for decades...
 
You're not answering... What are you measuring here?
Which cart?

Any cart has a different response, so where you see a peak you could find a rolloff soon after...
The curve raises and moves back toward zero...
 
yes many times...standart mesureament...
there are tons of these measures right here...

sorry...find out...
 
If you wanted to experiment with the effect of capacitance on the phono input could you use a RCA "Y" adapter and connect one of these to the 2nd leg?


Temporarily, of course...
 
If you wanted to experiment with the effect of capacitance on the phono input could you use a RCA "Y" adapter and connect one of these to the 2nd leg?


Temporarily, of course...
This approach on y and "RCA plug" was marketed in the 70s ;-)

hence the interest of a minimum on the pre-phono side...see low capacitance cable...see shortcut just to help...

 

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yes many times...standart mesureament...
there are tons of these measures right here...

sorry...find out...

Low capacitance makes sound flatter, if the cart is on the bright side of the spectrum (and it is the case of the AT)... It will sound bright.
If you go above the "turning point" could make it sound "fuller" or rolled off (depending on the point of view).
At 200pF it is spot on.

Just as I described above... :)

Read again my message...My guess is that this Fosi has a low capacitance.
Did you measure it?
 
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Low capacitance makes sound flatter, if the cart is on the bright side of the spectrum (and it is the case of the AT)... It will sound bright.
If you go above the "turning point" could make it sound "fuller" or rolled off (depending on the point of view).
At 200pF it is spot on.

Just as I described above... :)

Read again my message...My guess is that this Fosi has a low capacitance.
Did you measure it?
no... perhaps if a version more complete and successful come..
(juste for fun..i have many prephono )


for you
Post in thread 'Phono Cartridge Response Measurement Script' https://audiosciencereview.com/foru...esponse-measurement-script.41148/post-1461053

etc etc etc
 
Low capacitance makes sound flatter...
Wrong terminology. Lowering the capacitance causes the output to roll-off sooner. Every cartridge presents a unique load to the phono input. The RLC of this load can be 'tuned' by changing parallel Resistor & Capacitor values. There will be some combination where the combined values yield an optimally flat response. Go BELOW that capacitance and it will sound dull. Too much and it will sound too bright (harsh, sibilant).
 
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