Fosi Audio P1 Tube Pre-Amplifier Mini Hi-Fi Stereo Buffer Preamp 6J1 Valve & Vacuum Pre-amp with Treble & Bass Tone Control for Home Theater System(with Power Supply)

This little preamp provides a great introduction into tube amplification, both the benefits and drawbacks of using tubes.First of all, as this is a preamp, it is very easy to set up direct A/B comparisons with commodity recording equipment (namely USB recording interfaces). Run a line out recording through the preamp, and again direct, match the output levels, and you now have a better insight into what these tubes are actually doing to the sound with A/B testing (preferably blind ABX testing).The good news - this preamp is pretty quiet and does a good job amplifying the signal coming in. I've had zero issues with noise including this in my playback chain. For a component containing tubes it is surprisingly quiet.The bad news (depending on your point of view) - the EQ knobs on this device affect the sound output far more than the tubes themselves. This is not a knock on the quality of the EQ, no, in fact, the EQ knobs are actually very useful given there is only a treble and a bass knob. In fact, the preamp is almost worth the price of the device given how well these work.The tubes themselves work as advertised. Sending a sine wave through the preamp, I definitely see way more second-order harmonic distortion through the preamp than through a direct output without the preamp. For instance, with a 440 kHz sine wave, I see the expected bump of 880 kHz at -30dB from the main signal. And there is noticeable compression running high-volume sounds through the preamp, particularly when running into the preamp at higher outputs. In short the expected effects of the tube (even order harmonics and compression) are measurable with sufficiently juiced inputs using relatively inexpensive measuring equipment.The real question is whether these effects are noticeable by your ears. For me at least the answer is yes, but the effect is pretty subtle, nowhere near what I was anticipating. For better or worse the stock tubes actually perform very well and have a good amount of headroom available before you notice any obvious changes in the sound. You kind of have to go out of your way to hear obvious changes, though, whether that be with bass-heavy music (Sublime's 40oz to Freedom works great for this) or by deliberately overdriving the inputs.A fun quantification of how this preamp affects sounds is to do a null test. First capture a recording of music played through the preamp tube, and then do the same exact source without the preamp tube. Line up both recordings *exactly* to the sample and to the same level, then invert the phase of one of them. Play them together and you'll get an exact audio representation of the difference between both input modes. This is more difficult than it sounds but if you do it you will hear the obvious distortions being introduced by the tubes. The interesting part is that they are both almost inaudible (unless you are carefully listening for them), and that even though these distortions sound not so great by themselves, when mixed into the output they can actually improve the sound of the music.OK, enough navel-gazing for now. Is this worth purchasing if you want to understand what "magical" tubes do? Absolutely. Is the effect going to be obvious? Probably not, unless you swap in tubes that are either busted or have very low headroom.Oh, and if you want to get an easy check for whether the tubes are actually in the signal path, grab a pencil and (gently) tap on each tube. As long as you don't have a fake you should hear the taps through your output speaker/headphones. There shouldn't be any ringing from the taps - that would indicate the tubes have gone bad and are microphonic - but you should be able to hear something with the volume up high enough. And the sound volume should increase gradually after a cold start like any self-respecting tube would.Speaking of tubes, I wish the silly LEDs under the tubes were not included. Even though this is just a preamp there is enough voltage running through the tubes to emit a slight glow after the tubes have warmed up. The red LEDs that turn on when powered up are *sort* of useful to make sure the device is working, but ultimately silly as it looks super fake compared to a real tube glow.

Primero, mi cadena de audio es gama de entrada, amplificador yamaha rs202, bocinas y sub polk y CD player onkio.El fosi p1 es de buena construcción y al prenderlo da buena pinta.La primera sesión de escucha, no noté diferencia en la mejora del audio, sin embargo, al irse calentando los bulbos se empieza a percibir el cambio.En la escucha de CD, la diferencia no es muy notoria, pero si le agrega calidez a discos qué tienen sonido plano.En donde si es muy notoria la mejora es la escucha de música por Internet (spotify, you tube, etc) le agrega viveza y una calidez perceptible.Lo que es destacado, es que potencia los bajos y les da una buena tersura, sorprende en este capitulo.El fosi p1 se calienta al tacto después de 30 min de uso, esto disminuye un poco al conectarlo a una regleta supresora de picos.En general, es buena opción para mejorar la escucha en equipos de gama baja y de entrada.No sé cuánto dure el equipo, ya que llevo 20 horas de prueba, pero si cambia el soniido conforme se queman los bulbitos.Mi opinión: no convierte tu equipo en high end, pero si lo mejora para disfrutar tu música

Mejora el sonido mucho no hace falta gastarse mas dinero

Prachtig product aan een zéér scherpe prijs. Thanks Amazon !!

Fosi audio has the best of the class preamp in the market and guess what there after sale service was also top notch. Changed my broken vaccum Tube without even asking any questions.