• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required. There are daily reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!

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

Jimster480

Major Contributor
Joined
Jan 26, 2018
Messages
2,805
Likes
1,974
Location
Tampa Bay
Another product with Tone Controls!
If only you had time to test my Geshelli Archel3 Pro @amirm! I've really been loving the Tone controls on that amp...
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 agree, the layout is a bit weird.
 

GGroch

Major Contributor
Forum Donor
Joined
Apr 7, 2018
Messages
1,059
Likes
2,046
Location
Denver, Colorado
I agree, the layout is a bit weird.
You say bit weird I say unusually convenient :)

Similar to the Schiit Fulla/Hel gamer DAC/amps, it's layout is designed for quick access to top mounted controls on a table/desktop next to your laptop/keyboard/source.

It's size is similarly small, with the added benefit of optional battery power. One wire in, one wire out.

If it is on your right side the logos for the three buttons would be clearly visible. On the left, you would need to learn what they did. I can still do that. If I forget I will blame senility not the SK01.

Not all amps should not look like this. It is sweet to have choices.
 

Jimster480

Major Contributor
Joined
Jan 26, 2018
Messages
2,805
Likes
1,974
Location
Tampa Bay
You say bit weird I say unusually convenient :)

Similar to the Schiit Fulla/Hel gamer DAC/amps, it's layout is designed for quick access to top mounted controls on a table/desktop next to your laptop/keyboard/source.

It's size is similarly small, with the added benefit of optional battery power. One wire in, one wire out.

If it is on your right side the logos for the three buttons would be clearly visible. On the left, you would need to learn what they did. I can still do that. If I forget I will blame senility not the SK01.

Not all amps should not look like this. It is sweet to have choices.
The question is though; who is it for? Since it doesn't have a DAC; how many people need a portable AMP only like this?
 

GGroch

Major Contributor
Forum Donor
Joined
Apr 7, 2018
Messages
1,059
Likes
2,046
Location
Denver, Colorado
The question is though; who is it for? Since it doesn't have a DAC; how many people need a portable AMP only like this?
Yep, my earlier post on this thread said I wish it had a USB DAC, but to be honest I think that is the ASR techie in me talking.

Most digital sources have decent DACs built into them. My main PC has a sound card, my mini PC and laptop have good internal DACS with terrible speakers and tiny amps that will not drive most headphones. CD players and streamers have decent audio outs as a rule. None have external tone controls or physical volume knobs.

In my case, I do not hear a significant difference when I plug the SKO1 directly into my PCs compared to running it through an external DAC 1st. Certainly YMMV a lot.

I was surprised Fosi sent an SK01 to Amir as it does not seemed targeted at our demographic. They will sell a lot more V3s to ASR folks.
 

ZolaIII

Major Contributor
Joined
Jul 28, 2019
Messages
3,867
Likes
2,285
As much as I am for variable equal loudness normalisation this is not it. Implemting it on headphones it has it's chelanges. Before all measuring the SPL to match and enable it and then regulating the voltage volume steps to corelate. So we won't have good accurate implementation of it for headphones any time soon, eventually if some of the bigger names implement it directly to some of their wireless models which I think they should in order to protect the hearing of their users. In such case not so hard to achieve (when you take in consideration processing power of even TWS modern SoC).
I woted this not terrible and even that much for the effort.
 

ocinn

Senior Member
Joined
Sep 14, 2022
Messages
358
Likes
886
Location
Los Angeles, CA
Feel free to enlighten me but I genuinely don’t understand why cheap headphone amplifiers exist. I can’t think of a target market.

Even outside of that point, skip a couple fast food meals out, save up $30 and buy a Magni Heretic or another one of the million actually high performance headphone amps on the market.

IEM users don’t need the power, and the biggest benefits are from flawless channel matching and low noise, which this doesn’t have.

Mid-range headphone users would likely purchase all-in-one DAC/HP amp boxes, which there are many models available for not really all that much more $ than this, and would absolutely demolish this in every important metric.

And lastly, High end headphone users are not buying $80, 85 SINAD headphone amps with bad current limiting and numerous technical flaws.

The battery power feature makes no sense as this isn’t even remotely portable. 3 band eq is about as good as none, imo ( @amirm would be nice to see the filter-centers and Q, in the future).

And “loudness” filtering was invented to combat fletcher-Munson for low level listening (background music, nighttime/non disturbance)….. problems which are completely made irrelevant by, you guessed it, wearing headphones!

I guess… entry level vinyl users could get use out of it? But then again, every single entry level vinyl user I know, the types that would be in the market for an $80 headphone amp, are using integrated/AVR amplifiers that already have a headphone amp that is completely competent to drive their entry level headphones if needed.
 

Jimster480

Major Contributor
Joined
Jan 26, 2018
Messages
2,805
Likes
1,974
Location
Tampa Bay
Yep, my earlier post on this thread said I wish it had a USB DAC, but to be honest I think that is the ASR techie in me talking.

Most digital sources have decent DACs built into them. My main PC has a sound card, my mini PC and laptop have good internal DACS with terrible speakers and tiny amps that will not drive most headphones. CD players and streamers have decent audio outs as a rule. None have external tone controls or physical volume knobs.

In my case, I do not hear a significant difference when I plug the SKO1 directly into my PCs compared to running it through an external DAC 1st. Certainly YMMV a lot.

I was surprised Fosi sent an SK01 to Amir as it does not seemed targeted at our demographic. They will sell a lot more V3s to ASR folks.
Yea with a USB DAC It would be much better especially for the laptop market. My Nitro5 for example has an atrocious headphone output.... then again so does my Alienware M15 R5.. However my Lenovo Ideapad Slim 7 Carbon w/ Dolby Atmos has a great headphone output (not sure on the power output but it drives several of my easier headphones great) is really clean. So with that laptop I suppose I could use something like the SK-01 if I wanted to try to power one of my Planars... but based on @amirms testing; it wouldn't actually be great for my planars.... so again I kind of wonder if there is a market big enough to sustain this product.
I certainly wouldn't want to use this product with a trash output source just to amplify poor sound and it doesn't really offer enough power to run heavier headphones. On top of that the actual performance of the amp isn't really good enough. I've got a little headphone Amp + DAC that even has the ability to have external power which can actually drive my planars and it costs the same or less than this product.

I offered it to Amir for testing but he didn't want it... o well. It is actually really great in my own personal testing. I spent a couple hours A/B with my actual gear and its transparent in most everything and the things it wasn't transparent in might have been due to the amp stage or something... really not sure but definitely quite good.
 

TonyJZX

Major Contributor
Joined
Aug 20, 2021
Messages
1,846
Likes
1,758
the novel way we've seen this being used is it being zip tied to the central gas monitor arm on a desk

to me these things dont make sense since you also need a dac but maybe some guys like to hook it up to the 3.5mm on their smartphones
 

Leiker535

Active Member
Joined
Jul 7, 2020
Messages
253
Likes
311
Feel free to enlighten me but I genuinely don’t understand why cheap headphone amplifiers exist. I can’t think of a target market.

Even outside of that point, skip a couple fast food meals out, save up $30 and buy a Magni Heretic or another one of the million actually high performance headphone amps on the market.

IEM users don’t need the power, and the biggest benefits are from flawless channel matching and low noise, which this doesn’t have.

Mid-range headphone users would likely purchase all-in-one DAC/HP amp boxes, which there are many models available for not really all that much more $ than this, and would absolutely demolish this in every important metric.

And lastly, High end headphone users are not buying $80, 85 SINAD headphone amps with bad current limiting and numerous technical flaws.

The battery power feature makes no sense as this isn’t even remotely portable. 3 band eq is about as good as none, imo ( @amirm would be nice to see the filter-centers and Q, in the future).

And “loudness” filtering was invented to combat fletcher-Munson for low level listening (background music, nighttime/non disturbance)….. problems which are completely made irrelevant by, you guessed it, wearing headphones!

I guess… entry level vinyl users could get use out of it? But then again, every single entry level vinyl user I know, the types that would be in the market for an $80 headphone amp, are using integrated/AVR amplifiers that already have a headphone amp that is completely competent to drive their entry level headphones if needed.
You underestimate the impact of currency exchange and taxes in international imports. What you said is true for the restricted NA and maybe European market, but not for the rest of the world.

Fosi/Ayima/Aoshida/Nobsound mainly sells in marketplaces like Alibaba, which caters to buyers outside those regions, and where an additional 30$ makes the difference between buying the product or not buying anything at all. Not to mention that some countries and regions have importing quotas and taxes that are relative to the FOB. For instance, in Brazil, where I live, anything over 50 dollars has a 90% importing tax to promote the internal market; anything below that only pays 20% or less.

In this context, you either buy something like this from a chinese marketplace or pay literally 5x for said magni heresy because it's american.
 

paudio

Active Member
Joined
Sep 18, 2021
Messages
283
Likes
161
the novel way we've seen this being used is it being zip tied to the central gas monitor arm on a desk

to me these things dont make sense since you also need a dac but maybe some guys like to hook it up to the 3.5mm on their smartphones
$10 apple dac dongle would work fine with this
 

paudio

Active Member
Joined
Sep 18, 2021
Messages
283
Likes
161
Yea I mean the dongle has good SINAD performance (better than this Amp)
Personally I use the dongle exclusively as it gets loud enough even for my Aeon 2 Noire on my PC by a large amount even with EQ. I've got very sensitive hearing. This device's noise floor may bother me and so I just use APO/Peace. What I would like is analog controls for digital EQ like the Corda Country. I've yet to pull the trigger on one though. It's a lot of money. It would be sick if someone built something with the guts of a Qudelix 5K but with analog controls for the graphic EQ.
 

Jimster480

Major Contributor
Joined
Jan 26, 2018
Messages
2,805
Likes
1,974
Location
Tampa Bay
Personally I use the dongle exclusively as it gets loud enough even for my Aeon 2 Noire on my PC by a large amount even with EQ. I've got very sensitive hearing. This device's noise floor may bother me and so I just use APO/Peace. What I would like is analog controls for digital EQ like the Corda Country. I've yet to pull the trigger on one though. It's a lot of money. It would be sick if someone built something with the guts of a Qudelix 5K but with analog controls for the graphic EQ.
Personally I enjoy the Geshelli Archel3 Pro. They recently came out with it and it has tone control like this amp does. Performance should be much better though as Geshelli actually has an analyzer and designs products with it. It has become my main amp as I barely turn my THX AAA 789 on now after 6 years of listening to it prior to the arrival of this Geshelli.
 

Bruce Morgen

Addicted to Fun and Learning
Forum Donor
Joined
Aug 3, 2019
Messages
829
Likes
1,176
Personally I enjoy the Geshelli Archel3 Pro. They recently came out with it and it has tone control like this amp does. Performance should be much better though as Geshelli actually has an analyzer and designs products with it. It has become my main amp as I barely turn my THX AAA 789 on now after 6 years of listening to it prior to the arrival of this Geshelli.
Nice -- but way larger and more expensive than the product nominally under discussion, sort of like sharing ones enjoyment of a Benchmark AHB-2 in an Aiyima A07 review thread. I personally have an appropriate use case for this Fosi gizmo, but if it carried a mid-three-figures USD price tag like that Geshelli I'd pass on it, just as I passed on the clearly better-performing -- but also bigger/costlier -- THX unit a few years back.
 

m8o

Senior Member
Forum Donor
Joined
Jan 28, 2019
Messages
348
Likes
223
Wow... utility and decent mid-fi at a low-fi price.
 

Jimster480

Major Contributor
Joined
Jan 26, 2018
Messages
2,805
Likes
1,974
Location
Tampa Bay
Nice -- but way larger and more expensive than the product nominally under discussion, sort of like sharing ones enjoyment of a Benchmark AHB-2 in an Aiyima A07 review thread. I personally have an appropriate use case for this Fosi gizmo, but if it carried a mid-three-figures USD price tag like that Geshelli I'd pass on it, just as I passed on the clearly better-performing -- but also bigger/costlier -- THX unit a few years back.
For some reason my initial response here didn't get posted.
However I only mentioned the Geshelli because it has Tone controls like this Amp and it is one of the VERY FEW Amps that have tone controls. The other one I know about costs around $9k.
 

Bruce Morgen

Addicted to Fun and Learning
Forum Donor
Joined
Aug 3, 2019
Messages
829
Likes
1,176
Loudness curves normally depend on volume pot setting. In this review we see only measurement at one position.
I'm pretty sure that would require an old-fashioned volume pot with an extra terminal connected to a tap on the resistive element -- and even then it frequently wouldn't work as per a curve, if only due to differences in transducer sensitivity. Using this device as sort of a crude, defeatable -- it will be connected via tape monitor loop -- EQ in my system, the volume knob would be a level set rather than a volume control since I control overall volume with the seven-gang motorized pot of my Yamaha DSR-100 Pro, which is further along in the signal chain.
 

pma

Major Contributor
Joined
Feb 23, 2019
Messages
4,515
Likes
10,539
Location
Prague
I'm pretty sure that would require an old-fashioned volume pot with an extra terminal connected to a tap on the resistive element -- and even then it frequently wouldn't work as per a curve, if only due to differences in transducer sensitivity.
Exactly, however, without level dependence of the frequency responses there is no attempt of "loudness control", just the empty label.
 
Top Bottom