Fosi Audio P1 Tube Preamplifier Mini Hi-Fi Stereo Preamp 6K4 Valve Vacuum Pre-amp with Treble Bass Tone Control for Home Theater HiFi System(not for Turntable)

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.

I’ve been a Stereo Hi-Fi enthusiast since the mid-70s, and quality Hi-Fi equipment can be outrageously expensive. I was quite pleased to find this little device for under $50. I’ve already invested over $5000 in my sound system, but even so, the sound coming from my streaming audio source was less than satisfactory. It lacked the clean, crisp sound that you get from a vinyl record. My goal was to get the best sound from all my streaming music sources: Napster, Sirius XM, Amazon Music, and Music Choice on Xfinity. All of these music services are on my Dell computer using Windows 10. I am running a dedicated 50-foot cable to my stereo power amplifier. Without the Fosi preamp, my music was dull and lacked depth. The bass was muffled, and the vocals and instruments were a bit tinny. Before I connected the Fosi preamp to my sound system, I installed the GE 5654 tubes as recommended by other users. I was amazed at the transformation. I now get a clean crisp bass, rich vocals, and brilliant instruments. The music comes alive. The change was phenomenal. I highly recommend this little gadget for anyone who is a serious audiophile. One important note. If you don’t achieve great sound quality at first, you may need to make some volume adjustments on your software and devices. For example, my best sound came when I adjusted the volume settings on my computer; Windows volume setting at 90 and Napster volume setting at 5. It just takes a little time to find the right combination for your system. Also, I tinkered with the volume settings on the Fosi preamp and my stereo amplifier to achieve optimal sound. It took me about an hour to get it right, but you only need to do this once. Just play around with it. Even without making any volume adjustments, there still was significant improvement in the sound quality using the Fosi preamp. Pros: Price. Solid metal construction. Easy setup. Great sound. Cons: A little difficult to install the tubes.

Only have about 30-40 hours of listening on the unit. Installed nos GE 5654 tubes at turn on. My initial reaction is that this unit effects sound quality far more than the buffer it replaced, which failed. Took the edge off of high frequency issues with my analytical system that tends to be on the bright side along with my room which adds to the problem. I have some RCA nos 6AK5's I may swap in later if I detect any artifacts that I don't care for. The unit imparts a fleshier low mid-range/high bass which compliments my speakers nicely in addition to taming treble as noted. This would be a 5 star if it had a tone control defeat switch. Very happy with the unit. I do have some suggestions for FOSI though. 1. Supply the buffer with a tone control defeat switch. 2. Supply a SE edition with higher quality passive parts along with 1. noted above and keep the upgrade cost $20 to $30 more. You would knock the ball out of the park with this edition. This combination along with a good solid state pre-amp (if you need one) and solid state amp would give you some of the "tube magic" that many crave. Another interesting item that was not expected,is that Pandora jazz stations seem to place me a couple of rows closer to the performers and with a little bit of "air". Very unexpected but nice. One of the reasons for advocating for a tone control defeat switch is that my vinyl playback does not need tone shaping,however CD and streaming Pandora do need minor treble adjustments,down for cd's and a tad up for Pandora. Update 9-10-19 Now have 100 hours. Installed Voshkod tubes in place of GE 5654. About 40 hours on them. They are more dynamic than GE's but with a cooler presentatation. I really like them for jazz,however, like the 5654's for classical. Also have some RCA 6AK5's I may try in the future. The Fosi is a excellent piece of equipment.

I have all my music on Windows media player. I run that through an external digital to analogue convertor or Dac as it's known for those less in the know. This bypasses the inferior music chip in the computer to give superior analog sound and then straight into the rca on my 5.1av reciever. I was enjoying the sound but there was something lacking and I was constantly tweaking the sounds on the amp and equipment on the media player. So frustrating. Then I was hearing talk on cheap audio man channel on yt about preamps and how they can improve sound quality when added to the end of the chain into the amp it's self. He was reviewing this tube amp model. Check him out! I have no associations with him..I'm just a fan of the very informative channel as I'm no audiophile..but I know great sound when I hear it. At this price I was sold and I had nothing to lose. Anyway I've set it up and I'm blown away by the difference..it's night and day! Better presence, deeper richer lows mids and highs and crisp vocals. This is my first dive into preamps...even yt 320kb files are stunning! The unit is solid metal construction and doesn't feel cheap. In fact it's the opposite. I upgraded for the upgrade recommended tubes. The standard still come supplied. Vonnecyions are simple. I'm enjoying my music all over again. Beautiful product wow. Thank you Fosi for such an excellent product and cheap audio man for the review. Don't be misled by 'cheap' audio man. That's an understatement. His philosophy in.my opinion is that you don't have to spend huge bucks for great sound.

Pour le prix, c'est bluffant. j'ai un ampli transistors d'une grosse marque japonaise, vintage 80W, je ne voulais pas le changer car il fonctionne très bien, acheté pour une centaine d'euros. Et le changer pour quoi... j'ai cherché dans tous les sens, je ne peux pas avoir de garantie qu'une autre marque soit meilleure avec mes grosses enceintes colonnes 3 voies avec mon petit budget ridicule. Je n'ai pas le temps de tous les acheter pour les tester. Le son de mon ampli actuel restant superbe, très puissant, très détaillé, il s'avère quand même trop sec sur les morceaux de guitares saturées, rendant l'écoute fatigante sur le long terme. Ayant à l'esprit que dans un ampli intégré, souvent c'est le préampli qui pèche tandis que, dans un ampli intégré, c'est lui le plus important pour la qualité du son... Etant donné que la faveur des audiophiles allant plutôt sur les amplis à tubes, je me suis dit que choisir un préampli à tubes pour rentrer dans mon ampli transistors serait une bonne idée... Je n'ai effectivement pas les moyens d'acheter un ampli à tubes à 4000 euros, 50euros, ça me va bien. Eh bien bingo, ce petit préampli répond à mon cahier des charges. Le meilleur des deux mondes ! Le son est sacrément amélioré, c'est un plaisir. Il ne faut pas monter trop le son du fosi, à un tiers c'est bien, sinon il sature au delà. Testé avec d'autres tubes aussi, nickel. GENIAL BRAVO FOSI je recommande à tous ceux qui ont un ampli transistors un peu sec.

I bought the Fosi P1 and use it with 2 of their M02 mono/subwoofer amps, and I was very pleasantly surprised at the overall sound. I let the P1 and M02's warm up a bit for about 10 mins before beginning to listen. The sound was detailed and clear. After listening for about an hour,.the sound began to warm up. After about 3 hrs of continuous listening, the bass got deeper and more punchy. After about 5 hrs, LP after LP, the sound remained steady and consistent with the soundstage getting deeper. The sound was smooth and just flowed as good analog should. I did all my listening to my modded Audio Technica AT1240 turntable, Hana SL cartridge with Moon LPS110 v2 phono preamp and Klipsch RP160M speakers and 12 gauge multi-strand wire. Since the P1 has only 1 set of RCA inputs, my phono, laptop, cable box, and tape deck all go through my 20 yr old Great American Sound 5 way input switch box. The sound quality was warm and very lush. Great for jazz and other acoustic music. But, to compensate, for the added warmth, I adjusted out my speakers about an extra foot from the wall (now about 3' in total). However, the top end lost a bit of airiness and transparency. Fortunately, the bass and treble controls are of high quality but, as with all tone controls, should only be used judiciously. By leaving the bass "flat", and adding about 0.6 db of treble, the transparency returned with more realistic dynamics as well. That is where the tone settings will remain. I'm very satisfied with my new "small and compact" set up. Kudos to Fosi Audio for such high performing units. Update: After listening for about 40 hours, I realized that I can listen to my P1/M02 combo with the tone controls "flat". So as the stock tubes burned in, the quality of sound continued to improve. Anyways, as a result of the fine reviews of the 5654W, upgraded tubes from Fosi, I decided to order them. I have been listening to them for about 30 hrs now, and as good as the stock tubes are, these 5654W's have added an extra dimension of depth and clarity to the sound. Everything from the deep bass to vocals, to various instruments have tightened up, increasing the sense of rhythm and dynamics. Most enjoyable indeed!

旧AVｼｽﾃﾑに接続して使用。問題なし。

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