BT30D

Music is a huge and daily part of our lives. Because we don’t like to overdrive the living-room system just to also “light up” the kitchen area with sound, I’ve kept a small (homebrew) 18+18W amplifier and Minimus 77 speakers on top of our fridge for years. It was linked to the living-room system via a stereo audio isolation transformer, and a Bluetooth receiver with an audio switch. Unsightly, but it worked well and sounded nice. With a recent remodeling of the kitchen and living-room areas, a better-looking solution was required. With a 12x12 soffit running in an “L” shape above all of the kitchen cabinets, in-wall speakers were the obvious choice. We ordered a set of Dayton Audio ME625W in-wall 2-way units and as I will get into later, eventually added a Dayton Audio DCS165 subwoofer and quasi-matching grille, all via Amazon. (The Pyle and FOSI amplifiers mentioned here were also Amazon purchases.)My first choice for a new small amp to power this was the Pyle PFA540BT unit with built-in FM radio and Bluetooth features. That unit was bought as an open box from Amazon. While plenty loud, it had a subtle but definite grating midrange distortion once warmed up that I did not notice until it was outside of the return window. My bad, these new parts all sat around while we finished the other renovations. We all agreed it was annoying, even my kids. Additionally, the switch-mode power supply for that amp was so noisy (RF-wise) that the radio receiver only would pull in one station, with a local antenna from only a couple of miles away. The rest of the band was utterly swamped out. (No FCC cert logo visible on the PSU, now we know why).My second amp was a FOSI audio unit, the BT30D, which is much better. No radio, but BT and line in. As a plus, it’s a 2.1 system with a dedicated drive channel for a passive sub. It’s rated at 50+50+100w. It’s plenty loud, however be aware it ships with a switching power supply that can deliver only about half of that wattage. (24v x 4A = 96W). Ah, marketing.With the amp issue sorted, I was still disappointed that the in-walls did not have bass that matched the small mini-77’s that we had listened to for 10 years. Given the larger drivers and volume of trapped air behind the in-walls, I was a little surprised. Research on the FOSI website was not able to tell me if the FOSI unit has a fixed High Pass Filter on the L-R outputs or not, so I was not sure if it was the speakers, or the amp limiting the bass. Everything below about 120Hz was absent.The Pyle amp, which has no amplified sub output, sounded similar in the bass, and a third full-range analog amp I connected in also played with little bass. Conclusion is that it’s the speakers or the install environment, most likely the speakers, as the two are separated by a lot of insulation, preventing any phase cancelling behind the wall.As a result, the stout little Dayton Audio 6-1/2" sub driver was ordered and installed with a ¾” split-baffle as support in the corner of the soffit for best loading. Once set up and adjusted, we now have a system with some decent extension into the 50-100 Hz range and more than enough volume to fill the kitchen area while providing a nice stereo listening field for most of the room. I wish we had the space for a larger sub driver, but with the framing behind the 12x12 soffit, an 8” or 10” just wasn’t going to fit. The 6-1/2” sub is respectable but it’s being driven rather hard to make up for it’s lack of piston area. A second identical unit is being considered, to double the cone area and increase the efficiency, but at least for the moment it sounds nice at reasonable levels.(EDIT: a second identical sub went in, same baffle approach, as close as I could get it to the first, which helped a lot - a little more cone area to grab air - and they are not being driven so hard. The system as of March 2023 is still going strong and used daily - DSB)On balance, the FOSI amp has been very good and well-behaved. It runs a little warm, but for its size it’s punching well above its weight and the BT implementation sounds quite good. It must have a decent SBC buffer scheme, as we don’t experience any buffer under-run drop-outs over long term listening with any of the apple, android or Chromebooks attached. Bluetooth range has also been solid throughout the area. This is probably due to the external no-compromise BT antenna. The amp is small enough not to notice on top of the fridge, and looks pretty smart. I’d buy it again. I will be posting this same review on the Sub and In-Wall speakers pages as well, because it's kind of a system-level review of all the bits and pieces.

When our 12 year old Pioneer AV receiver in the master bedroom died recently, we needed to replace it ASAP. However, We did not want to spend the nearly $700 (right now anyway) on a new equivalent Pioneer or Denon AV receiver, since we (the wife and I) already have a large home theater system in the living room. We figured that since we already own several Fosi mini amplifier models of various configurations, for other purposes, we started looking for a Fosi mini amplifier in a 2.1 configuration to replace the Pioneer AV receiver with. That is when we came across this great little Fosi mini amplifier.We are now using this Fosi mini amplifier, along with an Anker 2 into 1 HDMI switch box. This Fosi/Anker setup replaced the Pioneer AV receiver for under $100. Granted, we lost the ARC capability of the Pioneer AV receiver, but such is life, I guess. The audio and video output of this setup both sound and look great. The rest of the setup (see photo) consists of a Sony 40 inch LED TV, Roku Ultra, Sony Blu-Ray player, Dayton Audio B652-Air bookshelf speakers, and a Pioneer SW-8, 8 inch active subwoofer. All of these individual components compliment each other very well, and work great together.This Fosi mini amplifier takes up a lot less room, and runs a lot cooler than the Pioneer AV receiver that it replaced, so that is a win in both cases. This Fosi mini amplifier is connected to the Sony TV through the TV's 3.5 mm AUX out/headphone jack, using a 3.5 mm to RCA adapter cable. This allows us to control the entire system volume with the TV or Roku remote, and we just leave this Fosi mini amplifier at around 3/4 volume all of the time (except when using a Bluetooth connection).This Fosi mini amplifier sounds great. However, it is nowhere near the "advertised" 200 watts of total output power. The provided power supply is 24 volts and 4.5 amps, which is 108 total watts of power available to the amplifier. Since an amplifier cannot "magically" output more power than it is supplied, divided evenly by 3 channels, that would make this a 36 (peak) watt per channel amplifier at full volume. However, since it looks like the single subwoofer channel has twice the adverised output power as the individual satellite speaker channels, that would put the subwoofer channel output around 54 (peak) watts and the satellite speaker channels at around 27 (peak) watts per channel. That would most likely put the RMS wattage ratings at about 40 watts for the subwoofer and 20 watts per channel for the satellites, depending on the efficiency of the D class amplifiers that Fosi is using in this mini amplifier. Also, if an "active" subwoofer is being used (the most likely scenario these days), then the wattage output of the RCA pre-out to the sub is a moot point, as it only provides a low voltage and low frequency (under 300hz) signal to the sub, and the sub's internal amplifier supplies all of the power, so a 1,000 watt plus subwoofer could be connected to this Fosi mini amplifier, if so desired, if a lot of bass is what a listener wants to hear.That all being said, this Fosi mini amplifier sounds great, and it can get loud, depending on the efficiency (db rating) of the satellite speakers being used. Any speaker over 90db is considered "efficient" when driven at 8 ohms. Also, having banana plug (5 way binding posts) and RCA connectors on a little amp like this makes the audio input and speaker output connections seem more high-end and very secure. This Fosi mini amplifier also has a very small footprint at 4-3/4 inches wide, by 4-1/4 inches deep, by 1-3/4 inches high. The control nobs protrude another 1/2 inch on the front. Therefore, this Fosi mini amplifier does not take up much space at all.The overall sound quality of this Fosi mini amplifier is very clear, with no hum or hissing whatsoever at any volume, or even with no volume present at all. The OP amps seem to be of high-quality, and sound good. Just make sure that all of the devices used with this Fosi mini amplifier are plugged into the same power strip, and are on the same electrical circuit ( this recommendation goes for any sound equipment, especially when using turntable phono preamps). This will prevent any 60hz ground-loop hum issues. This Fosi mini amplifier also works great for both music and movie audio. Being able to precisely control the tone and subwoofer output frequency are also great features of this Fosi mini amplifier. However, the full-range frequencies of the amplifier seem to always be sent to the satellite speakers no matter where the subwoofer frequency is set at on the amplifier. Therefore, It seems best to set the subwoofer at the maximum or LFE setting at the subwoofer itself, and set the amplifier subwoofer frequency control at about 80hz to 100 hz, depending on the low frequency capabilities of the satellite speakers being used. Then the gain can be set on the amplifier and/or subwoofer itself as the user desires. There are no markings on the Fosi mini amplifier for the subwoofer frequency and volume control nobs, so most of the fine tuning must be done by ear. However, the maximum subwoofer crossover frequency is 300hz, so 12 o' clock on the nob is around 150hz, I would assume. Also, since this Fosi mini amplifier is a 'D' type amplifier it plays a bit bright. leaving the treble setting nob around 1 o clock, and the bass setting nob around 3 o clock, seems to provide the best overall tone balance depending on the music or movies being played (just a suggested point of reference to start with, as user preferences will vary).The Blutooth feature of this Fosi mini amplifier works very well, and it connects to all of our Samsung Galaxy Smart Phones and Acer Nitro 5 laptops with no problem at all. The sound is clear (for Blutooth anyway), and the range is very good. However, there is no Bluetooth "pairing" button on this Fosi mini amplifier, so it is always searching for devices to connect to, which can be good or bad depending on the circumstances, and how close the neighbors live...lol. This always-on Bluetooth issue can be circumvented by turning the Fosi mini amplifier off when not in use. However, we leave the amplifier on all of the time so that it is already on when we use the TV, and we have had no problems with overzealous Bluetooth connectivity issues so far.Overall, we are very happy with this Fosi mini amplifier, just like with all of the other Fosi products that we own. Hopefully, we get the same longevity out of this Fosi mini amplifier as we have with all of the other Fosi products that we own. This Fosi mini amplifier sounds good, runs cool, and takes up very little room on our dresser (see photo). We leave it running 24/7 on 3/4 volume, and control the overall volume through the TV, and so far this Fosi mini amplifier has worked flawlessly in all aspects. Needless-to-say, I highly recommend this Fosi mini amplifier, and all of the other great Fosi products to anyone looking for a small but high-quality amplifier. Just be aware that while this amplifier sounds great, and can play loudly, it is nowhere near the advertised wattage Specs., and it is not going to blow the roof off of the house. That being said, pick up one of these great little Fosi mini amplifiers today. Have fun!

We had a Polk powered subwoofer which after 6yrs the amp started buzzin n humming. It sat along with 2 Orb Spkers for as many yrs. So, this little amp at a good price point put new life into the subwoofer that we made into a passive Sub, with two Orbs, and you got a Nice 2.1 stereo with line in and Bluetooth is simple, Perf, sound system. potentiometers are very smooth, precise, power output clean, adequate in watts for small room or outdoor portable sound system, and we "off grid" powered it! It draws minimal AC, from the power brick, 24v. super efficient. However beware when the amp is switched off, no prob, But if you unplug the Pwr brick the Amp will "discharged" resulting in aloud "Pow! from the Sub.Dang shame! Otherwise a nice system.

I was skeptical at first. I ordered anyway. Bluetooth connectivity is fast and stable. Audio is good enough for a inside room listening. I am very happy with the two out put for subwoofer. I am using both, one for my power subwoofer and the other one as a passive subwoofer. Su-bout is satisfactory. SUB frequency controller is helpful. All in all I am happy. As a hobby I also build high power audio amplifiers. So I know this Fosi Audio amplifier is very competitive.