SK01 Headphone Amplifier Equalizer Preamp with Bass Midrange Treble Tone Control and Loudness Compensation Portable Class A Analog Amp with 3.5mm 6.35mm Jacks

I bought this to add life and depth to a portable cd player that works great but sounds a little flat, and struggles to drive higher-impedance headphones. This works perfectly, adds a lot more power/volume and the tone controls give a good range of eq. The "loudness" button is also very useful at low volume, the sound quality of my cd player is greatly improved with this little device. Couldn't be happier with it. Also does the same for phone/tablet. Build quality is excellent, feels very solid and durable. Small enough to put in your pocket, if a little heavy.

I use headphones when listening to videos on the internet and have a good quality set of headphones for that purpose. That being said, my computer motherboard's output was not adequate to drive the headphones well enough. This wee headphone amplifier gives my headphones that extra bit of power to improve the volume with dedicated controls to boost the treble, midrange and bass to suit my taste. A really nice bit of kit for a bargain price. Highly recommended for my type of application. Five stars.

Fosi SK01 delivers on many fronts, with its versatility. The sound quality is very smooth too. I've used it with my bass heavy Soundcore boom plus 2 Bluetooth speaker, it literally tames the bass, and the ability to also increase/decrease midrange and treble frequencies too makes the speaker sound stupendously awesome, and a joy to listen too ! Results are also very good on my mobile phone, TV and DJ controller. Not so good on my laptop, but that's purely because the laptop manufacturer has skimped on quality audio components, having said that it still sounds great, but with less oomph. All the knobs, buttons and inputs/outputs just work like they should, and my Sennheiser headphones have come alive too. No need to have the volume up too loud either as it delivers great audio quality. Battery life is dependent on how hard you use it, but satisfying all the same. The warning indicator light above the treble knob will flash when the battery power is running low, and show red when you're charging it up. When fully charged, the red light will go out. You can continue to use it when it's charging, but I think it's best to make it charge undisturbed, to prolong the overall longevity of the battery life. The light below the volume knob will flash faster when the volume is too loud, another nice touch My lower quality music files are also enhanced by the Fosi SK01, as I take advantage of the ample frequency ranges provided to tailor and boost the sound where ever it is needed. The sleek rectangular shape is aesthetically pleasing to look at and solidly built, the bottom of the knobs are almost seamless against the main body of the amp, which eliminates dust getting inside I'm not a headphone amp connoisseur so can't compare, and no doubt there are brilliant premium models out there, costing mega bucks ! But Fosi Audio have come up with a winner, that covers many bases, delivering real quality at a price point that doesn't break the bank. One more point… I wish it had Bluetooth capability, to combine with my Bluetooth speaker, to eliminate using leads connecting them together, when I'm out in the public domain. Overall, though, a very well-thought-out product that deserves the accolades and positivity lavished upon it. Well done Fosi Audio 💯 🔥🔥🔥🔥🔥🔥😁

The SK01 work really well, and I like the fact that there are tone controls on the unit. Although they are very basic, for most people it will work find without having to use extra equalising s/w or h/w etc. The unit I have does seem to suffer from just the tiniest amount of noise, but this is barely noticeable when in use.

I have been using the headphone amp for getting on a year, i cannot fault it! It easily drives my sennheiser hd600 and 650, ideal if you require a little more bass or treble, the loudness button is super for supplying bass and treble at low volumes, i have also found that while using loudness, the eq knobs can still be used for adjusting to preference. If you need a headphone amp you wont regret buying this!

I like this device, my only criticism is that because there is a rechargeable battery on board the device needs to be switched off when not in use. I would prefer the on/off switch to be separated from the volume control. Turning this thing on and off every day will probably lead to unnecessary and premature wear of the volume control resistive track. That aside, the first thing I noticed, was how well the item is made. It is beautifully engineered and the feel of the controls inspire confidence. The range of the tone controls from plus to minus allows the user to adjust the sound just as you would wish. I am impressed by the dynamic range of the amplifier. I have fitted this FOSI audio SK01 to my active speakers because they don't have tone controls and the result has transformed my listening experience. I am planning to buy another SK01 to be used as an interface between my mp3 player and headphones.

It is a good addition to what I have. Giving a way to tune not only the bass and treble but also on the mid. The price is acceptable considering that it is a cleaning-sounding amp and powerful, too. Able to drive my HD650 effortlessly. I always perfer these volume knobs than the key-presses and these work very well. A happy purchase overall.

An excellent well made piece of kit. Did what it said on the tin plus.

I’m using the Fosi Audio SK01 together with the Fosi Audio DS2 and my Beyerdynamic DT 770 Pro 80 Ohm, and the combination sounds fantastic. The SK01 has more than enough power to drive my 80 ohm headphones with ease. The sound is clean, dynamic, and detailed. Bass has great punch and control, guitars sound clear and energetic, and vocals are natural without being recessed. It really brings my music to life. The tone controls are a big advantage. I can slightly boost the bass when I want more energy, or adjust the treble for extra clarity depending on the recording. It’s simple but very effective. Build quality is solid, the knobs feel smooth, and it looks great on the desk. For the price, the performance is impressive. If you’re building a budget-friendly but high-quality wired headphone setup, the Fosi Audio SK01 is absolutely worth it.

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Tengo varios amplificadores de auriculares, entre ellos alguno de sobremesa, con componentes discretos y en clase A y algún otro de triodos single ended. Pero desde que tengo éste, no he vuelto a usar ninguno de los otros. La versatilidad de poder ecualizar graves, medios y agudos y aplicar loudness (que por cierto está muy bien logrado) hacen que sin importar que cascos utilice, siembre encuentro el balance tonal adecuado. Muy contento con él.

Customer support:- I should mention this that initial product i received had tone button issues. Whenever I pressed it noise occurred. I thought it was fine as it only happened when music was playing. Later on it added channel imbalances also when pressed. So i emailed fosi support about this and they asked for a video of issue that i was having so that they can understand what issue was. Later support team sent a new replacement unit from china and i got it within 3 weeks. And new one is super good and no problems whatsoever. Initially i was very skeptical about what to do when fosi products start having issues. But after having to talk to guys with fosi support team, I am happy with their response and kind support. I really like their fosi za3 amp so waiting for their newly launched zd3 dac to arrive in india and then buy both as fosi have value for money products. Build of sk-01 is super nice. All metal and feels cold. Knobs rotation is quite nice. Even after using for months its good and no paint chipping off anywhere. Terminations:- Has a line in port at back with a line out mentioned below it which is actually a pre-out as volume can be controlled on this one and a 3.5mm and one 6.35mm port at front. The only thing I really think it should have had is a balanced 4.4mm out so that i could connect my good iems/headphones. Still 6.35mm and 3.5mm are implemented good and they are sturdy. Sound:- I would say if u got some headphones or iems that have some tonal imbalances, this fixes that. Also no noise is audible even on high gain. Some reviewers mentioned it having it a slight noise but thats on some really sensitive iems and u wont have those for casual listening. I got it to have more treble and bass gain for my sony wh1000xm4 headphones. Even though these headphones cost like 30k they arent good. People just don’t know how music should sound like and even me also didn’t knew. Recently I learned some audio professionals info and got to hear how music should sound like and i am impressed. Bought Kiwi ears Cadenza from headphonezone site india and it costs like 3k and still sounds way good that xm4. Now i regret not knowing about good audio quality products at such price exists for a long time. So used SK-01 to match clarity of those iems and since its a headphone its drivers are big, so bigger soundstage. Amp inside of it is nice as its way overpowering for most headphones. Its class a amp i think, not sure maybe check product description. Still it sounds good. Battery lasts around 5-6 hrs when fully charged. Bottom led in my opinion is not useful as it sucks battery power which instead can make device last more longer hrs. Final verdict:- Its a good product i would say for tone controls as aux port or usb c adapters are not that good in audio quality compared to external dacs and this sk-01 can add more power and tonal balances as per your need for any iems or headphones u got. Not only u can add but decrease tones also so do remember that. It can decrease harshness on some iems also. Plus its battery powered so portable. So maybe look into frequency graphs when buying next audio products as most audio professionals don’t like tone controls as they got high priced equipments which are neutral in tonality. Music is personal and for normal priced headphones or speakers or anything, this product is well value for money. Its clarity, build and versatility makes it a unique product that can be used with anything. Price is bit on higher side but u can get it for 7k using card discounts and at that price its good i would say. Not a product u must have but one that u can have for fixing tone controls and add in ur audio products arsenal.

Ich liebe das Ding. Habe es seit über einem Jahr in Gebrauch. Endlich mal ein guter Ausgang für Kaufentscheidungen anhand von Youtube und Rezensionen, klassische Hifi und Technik Magazine sind ja leider verschwunden. Eckdaten: - PC mit einem sehr guten Onboard Soundchip *schlagmichtot, hab ichgerade nicht exakt im Kopf* (man mag kaum glauben, auf wievielen Platinen noch der selbe `90er Adlib Chip sitzt) - Output: Sennheiser HD558 oder HD 490Pro Ergebnis: WUFF! Ich hatte ursprünglich nach einem kleinen Vorverstärker für den HD 490 gesucht, war mir aber nicht sicher, ob ich in dieser Konstellation überhaupt einen bräuchte. Ich will hier nicht mit Ohm um mich werfen und welche Quelle zu welchem Ausgabegerät, eigentlich bräuchte es ihn nicht. Aber, das Ding macht genau was es soll. Glasklar, und selbst dem HD558 ermöglicht es neue Spähren und Dynamik. (Kurzer Einschub: Ich bin kein Sennheiser Fanboy, bevorzuge aber diese glasklare und ausgewogene Wiedergabe in den Mitten und Höhen. Problem bei Sennheiser war immer, dass der Bass, besonders bei offenen Modellen extrem auf der Strecke blieb. daher der Kauf des SK01, eigentlich um einen kleinen Equlizer zwischenzuschalten. Der HD 490 hat das nicht nötig, aber auch der profitiert enorm.) Ergebniss: Wuff! Glasklar, ein deutlicher Zuwachs an Dynamik (ist natürlich stark abhängig vom Impedanz Bereich des Endgerätes), klein wie zwei aufeinandergestapelte Schokoriegel nur 5x so schwer + dass, das Ding nen Akku hat, habe ich erst vor Kurzem auf reisen im Hotelzimmer festgestellt: Handy->SK01->Kopfhörer: TRAUM! Für mich kein normaler Usecase, aber gut zu wissen. Aus meinem home Setup, auch nach Vergleichen mit diversen anderen Kophörern, nicht mehr weg zu denken. Würde das Ding immer wieder kaufen. Ich weiß, das war jetzt hier ein bisschen zu nischig, aber ich hoffe ich konnte dem ein oder anderen damit weiterhelfen.