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Fosi Audio SK-01 Headphone Amplifier Review

Rate this headphone amplifier:

  • 1. Poor (headless panther)

    Votes: 7 4.7%
  • 2. Not terrible (postman panther)

    Votes: 58 38.9%
  • 3. Fine (happy panther)

    Votes: 73 49.0%
  • 4. Great (golfing panther)

    Votes: 11 7.4%

  • Total voters
    149

paudio

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given the position of the headphone out and line/in-out/USB ports, the orientation of the button descriptors seems very counter intuitive. so this has to be laid on its side to get to all inputs/outputs...?
I believe it's supposed to sit flat on a desk with I/O on the back and headphones at the front. You'd be high enough above it to read the descriptors
 

paudio

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1700424014436.jpeg


A picture from their Amazon page. What CD Player is that? Looks cool enough to tempt me to use CDs again
 

LTig

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Voted fine instead of not terrible due to the loudness and tone controls :) it makes the product so much better in practical use .
Me too. It's a steal for this low budget with tone controls and loudness, and as long as your headphone is not extremely power hungry it should be fine. There is more HD in the lows than I like but OTOH we humans are rather bad hearing HD in the lows, so fine with me. I'm sure nobody would be able to hear differences between this and a SOTA device as long as it doesn't clip.
 

dzerig

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I like this. Maybe something in a flat form factor for portable headphone use, slightly better performance, and it's own battery! Tone controls are a win!
 

pablolie

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I like this. Maybe something in a flat form factor for portable headphone use, slightly better performance, and it's own battery! Tone controls are a win!
IMHO tone controls -in 95% of cases- result in a criminally distorted sound picture if released into un-trained hands :-D. When tone controls were pervasive in amps, I remember I judged friends and acquaintances by how far they had boosted bass and treble. :)
 
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amirm

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Many headphones I test have flat bass response. A turn of the knob on this thing will fix that or you could use the loudness button. It won't be exact but much better than listening to a headphone with so much less bass.
 

pablolie

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Many headphones I test have flat bass response. A turn of the knob on this thing will fix that or you could use the loudness button. It won't be exact but much better than listening to a headphone with so much less bass.
Are we talking Grado? :-D
 
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amirm

amirm

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This one says 18.3V??
Fosi SK-01 Headphone Amplifier with tone control Power vs impedance measurement.png
That's old bug in graphing library AP uses. The cursor shows the wrong value unless you gab it and move it back and forth. I usually do that but here, it is not visible at it is at the edge of the graph. If you look on X axis, you see that it barely goes above 6 volts so clearly nothing I am showing has 18.3 volts there.

As to detail, this amp triggered its protection very quickly before the AP got a chance to make more precise measurements. I can't think of a good fix for this situation in that measurement.
 

paudio

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Are the power output specs super overstated at 2400mW rms?

Also units like this are definitely high value but I've always wanted one of these that have analog controls for DSP based stuff. It's at least a 10x price difference. Nobody makes something for a few hundred with DSP based but analog controlled EQ

1700433962155.jpeg

(Meier Audio Corda Country)
 

GGroch

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Loundness functionality I think is a great feature to have. At least if you occasionally listen at low volume. It would have been even better if the Fosi Audio SK-01 had variable loudness, but that's perhaps too much to ask for the $80 it costs.
Agreed, variable like the old Yamaha receivers would have been nice. Note that Bass/Mid/Treble remain functional with loudness on, so you do have a good bit of tweaking available.

I bought one when they first became available and use it a good bit more than I expected. Amir is right about the nice appearance and build quality.
I have no IEMs, so it sounds fine to me on the headphones use, even Planars. I do listen softly.

There is an existing ASR thread on the SK01 here started by Djano

Note that the manual says the flashing blue light is not a clipping indicator. It flashes at 2V "to let you know if the volume is too high before wearing headphones....if the signal light is flashing, it is recommended you turn down the volume before wearing (plugging in) headphones, and then adjust the volume to your desired level". I have never had mine shut down....but again, I listen softly.



I'd like to see a version with a built in USB Dac....that would make for an even more useful Swiss Army Knife.
 
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dzerig

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IMHO tone controls -in 95% of cases- result in a criminally distorted sound picture if released into un-trained hands :-D. When tone controls were pervasive in amps, I remember I judged friends and acquaintances by how far they had boosted bass and treble. :)
I listen to a great deal of poorly recording, unprofessionally recorded tapes made live from the audience. Still, with the Schiit Loki for example, usually I make changes, listen to the result, and leave it flat because you are right.
 

staticV3

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Are the power output specs super overstated at 2400mW rms?
Oh yeah what's up with that @Fosi Audio ?

RMS 2400mW@32Ω according to your website, yet Amir's unit went into protection at barely over RMS 500mW@32Ω.
Was that expected?

(please don't tell us that 2400mW is like the combined output or single sine cycle or similar cheat methods)
 

paudio

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Oh yeah what's up with that @Fosi Audio ?

RMS 2400mW@32Ω according to your website, yet Amir's unit went into protection at barely over RMS 500mW@32Ω.
Was that expected?

(please don't tell us that 2400mW is like the combined output or single sine cycle or similar cheat methods)
Does this unit come with the USB power supply? I wonder what it was consuming peak for 500mW. 2400 is a lot more than 500.
 

Bruce Morgen

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Check again. I've had it for about 2 months and the headphone output is stronger than the line out I use for the amp! Overall, as a preamp with EQ controls it sounds incredibly good.

I guess we could confirm that by plugging headphones into "LINE OUT" and doing a volume comparison with the same headphones plugged into one of the designated headphone jacks.
 

Bruce Morgen

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Amir's unit went into protection
As explained elsewhere in this thread, this unit's "protect" circuit isn't triggered by clipping, but rather by (what Fosi has somehow decided is) excessive SPL for headphone users.
 

Bruce Morgen

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Does this unit come with the USB power supply? I wonder what it was consuming peak for 500mW. 2400 is a lot more than 500.
It only comes with a suitable USB cable -- you'll need to provide your own "wall wart" or similar 5VDC source. Moreover, it's possible -- and I'm only indicating a possibility -- that the charger is not the limiting factor and that any (typically very brief) musical peaks that could conceivably demand that supposed 2400mW can be handled by the battery.
 

Bruce Morgen

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FYI, this thing is typically priced in the low $60s and not anywhere near the $80 figure Amir noted in the review, which seems to be the MSRP. I could have bought one for under $60 from Fosi via eBay but decided to spend a little more and ordered one from Amazon.
 

paudio

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It only comes with a suitable USB cable -- you'll need to provide your own "wall wart" or similar 5VDC source. Moreover, it's possible -- and I'm only indicating a possibility -- that the charger is not the limiting factor and that any (typically very brief) musical peaks that could conceivably demand that supposed 2400mW can be handled by the battery.
It depends entirely upon the design.
 

Palladium

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I dunno about you all but I don't think its very portable when you at least need to hook a line-in from somewhere else.
 
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