Habe längere Zeit nach einem guten Verstärker gesucht, da ich gerne gute Musik vom Smartphone oder Tablet höre.Da ich einen guten und hochwertigen Sennheiser Kopfhörer benutze, ist dieser Verstärker für mich ideal.

This things is politically irreverant. For one, it apparently doesn't measure well in an era where other headphone amplifiers achieve technical perfection at really low costs. Worse yet, it has three(!) tone controls and a loudness EQ too. Heresy, heresy! We're supposed to just buy poor performing cables or overly dull or bright headphones to compensate for the general tone in our favorite recordings. It also has no DAC or balanced headphones support.I'm using this with a 70s Akai tape recorder. Just imagine how bad the headphone out is on that! Hooked the deck up to a 90s Onkyo reciever, and vast improvement but can still hear hiss and audible distortion through headphones. As limited as thsAnalog tape audio is an excellent rationale for tone controls by the way. Recordings may have been made on misaligned or dirty equipment, dubbed onto borderline defective tape stock, or just recorded and mastered with a casual and in some cases cavalier disregard for tonal balance. It's an aesthetic, yes, and if everything is already aestheticized, why not dial the aesthetic in to one's own preference thereof?

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.

9/11/2024 1242 Noon Hours EGMT {I corrected Date from Month 0 to 9}{update} Accidentally reviewed the Q4 DAC below, but also bought the FOSI SK01 Pre-Amplifier & it is "POWERFUL" in a small, compact, sturdy encasement. Together, or separately both are high-quality designs🫡! ...with a plethora of HiFi equipment & products on the market TODAY, & prices ranging from respectfully reasonable, to outrageously insane---it's difficult to hopefully make a decision that will actually enhance your listening pleasure, but this FOSI Q4 smoothly does exactly that, accompanied by individual Bass & individual Treble Control Knobs, that are incrementally calibrated; so that you feel each successful turn, along with hearing the enhancement each turn😃! The Q4 is a sweet little Box that performs a big job😉.GBJ😎

Solid build, dials feel good.The only pre-amp that I found that included mid tone adjustment.Good battery life.Loudness control is a nice option -- not too common with preamps.Size is good, fits in your hand. Can be mobile, not the smallest profile, but can take it with you.Descent power output, works well with my Sennheiser HD 600 and Hifiman Sundara headphones.Good price to feature ratio.Overall very pleased with my purchase of this amp.

Fosi SK-01 is an extremely well-constructed audio "enhancer" that has become almost indespensible in my different audio systems. Solid metal with some heft, the knobs fit tightly and move smoothly. A very slight adjustment is noticed almost immediately in the soundscape with the tone controls, the volume knob is slightly larger and provides easy access. I like the sound quality that the unit outputs and have used the SK-01 with various class D amps with only volume control - this unit is perfect for adding EQ adjustments. The tone defeat will bypass any EQ and play neutral, another feature that is really appreciated for my usage. The loudness button will bump certain frequencies and is a nice feature when playing at lower volumes. I have no complaints of this product and commend Fosi Audio for designing and bringing this device to the audio market. The 2500MaH battery will last me for several days if needed and the unit can run constant on USB 5V power. Also can work very nicely with phone/tablet/sound card as source and a usb "C" adapter with 3.5mm out will work perfectly as input source to the SK-01. There is a 3.5 headphone out, and also a 6.25" - I haven't used the SK-01 much with headphones but it has that option covered.. Great all-around device, I purchased another unit after 3 months of heavy use and I will probably always have one of these units on hand to modify an analog signal.

I wanted a spare headphone amp for my Sennheiser 6XX that I could just experiment around with, without the bulk. Got the Fosi SK01 for a discount price after reading reviews and was astounded by the quality and sound for the price. It doesn't have all the bells and whistle's but if bang for buck is what you are after, this is hard to beat. Outstanding!

Prodotto molto buono, ad un prezzo accessibile. Qualità superlativa del suono. Tutto secondo descrizione e specifiche del prodotto. Con questo acquisto ho potuto usufruire della mia cuffia Beyerdynamic DT 990 da 250 Ohm anche sull'uscita audio jack 3,5 dello smartphone Xiaomi Redmi Note 11 Pro+ 5G. Audio strabiliante. Prodotto consigliatissimo. Avevo scritto al supporto Fosi per consigli tecnici, e mi hanno risposto esaurientemente e presto. Fosi the best!

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.

All I wanted was to bring out the subtle sounds in the accompanying music mix without mushing up the vocalist's track. I use Moondrop Blessing in-ear-monitors (earbuds) ...https://www.amazon.com/gp/product/B0C1ZBTD2Vand a conventional CD player (KLIM Discover)...https://www.amazon.com/dp/B0BRXH9L84with an upgrade cable (GUCraftmans cable with two pin connectors to match the Moondrop Blessing earbuds)...https://www.amazon.com/gp/product/B08N6211FFI didn't want a DAC (Digital-to-Analog Converter) or a combo DAC & Amplifier because the DAC/Amplifiers require RCA inputs or OPTICAL inputs. My CD player has only one type of output: 3.5mm (for earphones).Instead, I just wanted a headphone amplifier that would sweeten the sound of my CDs. I wanted to use my CD's player's headphone output jack (standard 3.2mm headphone jack) to connect the CD player to the Headphone Amplifier's 3.2mm input. I would then plug in my earphones to the output headphone jack on the amplifier.This amplifier is special because you can adjust the sound by manually altering the tones for bass, mids, and treble. Or, by pressing a simple button, you can bypass all tone adjustments and just let the amplifier do all the work of adjusting the volume of the track. Even without the tonal adjustments disabled, music still sounds better than without the amplifier.There are two more adjustments that can be enabled or left alone. The manufacturer describes them as follows: "Diverse Capabilities: Instantly restore original sound with the one-click tone-defeating button (I explain that one above); Immerse yourself in music during the quiet hours using the loudness function; Tailor the gain level to accommodate headphones with various impedances through the gain level switch."The loudness function is a stumper for me. I hear no difference when I press the button. I am NOT very responsible when it comes to the volume streaming into my head through the earbuds. I like it loud. I imagine the loudness function is used to keep all sounds under a certain decibel. Or, enabling the function might make the quieter sounds louder, relative to surrounding sounds. It might a "limiter" of some sort.Your own headphones or speakers or in-ear-monitors should have their respective impedance ranges documented. But whether I set the amplifier gain control to 0 or to -10, I don't know which I should choose. Depending on the content on a particular CD, I choose either setting to determine which setting sounds best.The exact title of this amplifier is "Fosi Audio SK01 Headphone Amplifier Equalizer Preamp with Bass Midrange Treble Tone Control and Loudness Compensation Portable Class A Analog Amp for Electric Guitar Instrument with 3.5mm 6.35mm Jacks," but don't let the title throw you. Yes, an electric guitar player can use this amplifier to monitor his guitar-playing, but it can be used for just about anything that you would want to make louder and sweeter...like your collection of CDs!The Fosi Audio SK01: https://www.amazon.com/gp/product/B0CF1WL1V2