Disclaimer:
Good morning, readers! Today we have in our hands the Fosi Audio MC331, a hybrid tube amplifier with a VU meter. Honestly, I had been hoping for a while to receive a similar product because I wanted to make my system with passive speakers leaner and simpler. The beginning of my hobby was born from my first PC system.
My old system initially consisted of an FX-AUDIO X6, FX-Audio Tube 01, and a Weiliang Audio TPA3116 (now Breeze Audio or BRZ hifi) and then evolved over time with various upgrades. The speakers are always the Schythe Kro Craft Rev.B. Finally, with the Fosi Audio MC331, the Kro Craft can express 100% of their potential.
The review, as always, will be completely unbiased, uninfluenced, and free of affiliate links.
I would like to remind you that I am just a person who enjoys trying out new items and listening to a lot of music; I am not an expert.
My opinions are obviously subjective.
Tech Specs:
- 2.0
- Input: RCA, Bluetooth, USB, Optical, Coaxial
- Output: Passive Speakers Output, Pre-Out, 3.5mm Headphone Output
- Chipset TPA3221+FS-2348B-2F (Fosi Audio Silicon)
- SNR: ≥100dB
- Dynamic Range: ≥ 00 dB
- THD ≤0.03%
- Terminal Impedance: 4-8Ω
- Max Output Power 105W × 2@ Ω
- Frequency Response 20Hz-20kHz (±1dB)
- Headphone Impedance: 32-300Ω
- Voltage Range: DC 19-24V
- Sampling Rate: USB: up to 24-bit/96 kHz
- OPT/COAX: up to 24-bit/96 kHz
- Bluetooth Connection Distance ≥10m
- Bluetooth Codecs: SBC, AAC
Packaging:
The Fosi Audio MC331 comes in the classic Fosi packaging, a little larger than usual; inside we find:
- Fosi Audio MC331
- BT antenna
- Remote control
- Power Supply 24V, 4.5A
- User Manual
- 2 GE JAN 5654W tubes
Unexpectedly, there is not a USB-to-type-C cable, but I have plenty, so it does not matter. Still, it would have been convenient to have one for the USB connection. Fortunately, they included some GE JAN brand tubes made in the USA instead of the typical Chinese tubes, and the package is complete. The power supply included is excellent and doesn’t need upgrades for the moment. Maybe out of curiosity in the future I will try a 24v 6A power supply. Usually the biggest difference is in the bass.
Build Quality:
It is known that Fosi Audio has raised the level of construction quality and nothing can be said about the choice of materials or the quality of assembly. The Fosi Audio MC331 presents itself as an amplifier with overall compact dimensions, an all-metal body painted black, and orange details as Fosi Audio wants. On the front, the thing that stands out the most is the VU meter that has that old-school charm that I like so much. We have a series of LEDs that indicate which input we’re using and headphone output, and then we have the tone knobs (very useful especially in my configuration).
We have the possibility of adjusting the treble and bass to our liking, while as regards the orange knob, it allows you to turn the MC331 on, off, and change the input used; obviously, turning the knob also adjusts the volume. On the upper part we have the tube housings that also have a protection to screw on top. The visual effect, as you can see from the photos, is very beautiful. On the back we have a good assortment of inputs. Starting from the left we find the USB input, BT antenna, optical input, coaxial, and RCA. Below we have, instead, speaker output (you can use banana terminals), a PreOut, and power input. It actually lacks an output for the SUB.
The feedback of the knobs is slightly lighter than others of larger dimensions but still of good quality. The VU meter is backlit with a very warm light that gives that vintage touch or flavor to the object. The audio tubes also have a slight illumination at the base.
First Impressions:
I have very little time at the moment; I actually have a move in the middle so I take advantage of it to already put other devices in the boxes and finally mount the Fosi Audio MC331, which takes the place of a Breeze Audio TPA3116 and an FX AUDIO DR07. As a first test, I connect it via USB to a very old Mac, which recognizes it immediately but somehow gives me a maximum output of 16-bit 48 kHz. Honestly, it should reach at least 24-bit 192 kHz, but considering how old the Mac is, it could be an incompatibility. In any case, I press play, and my speakers, with a particularly dark sound due to an overly aggressive tweeter filter, literally come to life. Already like this, the upgrade is evident; they are passive speakers that I have had since 2014 and I know them well.
Sound Signature & EQ:
Its sound quality is largely determined by the sound tubes you install, but it produces a fairly warm and detailed sound right out of the box. I have worked with tube-based products before and tried several models, including RTC, JAN, and VOSKOD. Of course, the options are limitless because the tones can be changed. Obviously, the result varies depending on your speakers.
Tubes Rolling:
GE JAN:
The differences are there and if I hear them with hard speakers, it means that with something more sensitive and refined, you could hear a lot more difference. I tried with the GE JAN 5654W included in the package and the result was already excellent as far as I’m concerned but it seemed to me that at low volume they were a bit grainy. I also tried the ones I own that are the same, thinking that maybe the ones included were not exactly first choice but the result was very similar.
Voskod (NOS):
Undoubtedly the most NOS I have, they have a clearly more analog sound than the modern ones, more suitable for classical genres but still excellent; perhaps they give a little more transparency and musicality to musical instruments. For the genres I listen to, the JAN tubes were better.
RTC (Mullard):
The RTC is the fullest, managing to be very clean even at low volume with nice round bass and lots of details in the highs. You then have to adjust the treble and bass to your liking but I got the best result with them and they are the ones I will use for the rest of the review and for my audio system.
Considerations after a week of use:
The Fosi Audio MC331, considering that it includes two products in one, actually 3—an amplifier, DAC, and tube preamplifier. It is a complete product, from my point of view, that allows you to save a lot of space on a desk. It is pleasant to look at; in use it is easy and intuitive.
With my Schythe Kro Craft Rev.B, it sounds remarkably good, although the speakers are undoubtedly improvable on the tweeter side. The mid-woofers are Hivi components and therefore of good quality.
The sound, thanks also to the possibility of adjusting the tones, is much more crystalline and seems to have completely different speakers. The VU meter is hypnotic and I could spend hours looking at it. The connection via BT is very stable in AAC and of excellent quality. No difference with the wired one. The remote control is super comfortable with complete control of everything because it allows use even on non-desktops, as I am using it but it could be implemented for home theater use coupled with a TV or external player. Yes, you are right; the sub output is missing but with the right speakers, listening is still pleasant.
Comparison:
I have never had a fancy setup; it has always been about getting the most out of your money. Just something affordable that sounds good. The image above displays my SMSL Sanskrit 10th with the Hivi Swans T200C, which is still in use today. The other one is made up of the Breeze Audio TPA3116 and the Schythe Kro craft REV. B. in conjunction with the FX-AUDIO X6 (which was later replaced by the DR07). I placed the Fosi Audio MC331 in the latter.
The true audiophile would probably want everything separate. I’ll start by saying that I have nothing directly comparable. If we take the products I had before individually, this one is clearly superior in everything: sound quality, functionality, versatility, and inputs. It is therefore difficult for me to say whether or not it is better than anything else, but I can tell you that rather than a cumbersome chain consisting of a DAC, tube preamp, and amplifier, this one does an excellent job and is superior to what I had before. It’s not just a question of tone control but of a sharper and clearer sound.
Conclusions:
Since my goal for the future is a minimal desk, I fully approve of this hybrid product that includes exactly what I was looking for to improve my desk. My advice is not to spend too much on replacing the sound tubes and, above all, if you are not looking for analog sound, do not pay too much for NOS tubes. Reading on the web, I found some users who complain about a problem that occurs at low volume so, as always, I recommend you read other reviews in addition to mine. I tried to replicate the problem and the only thing I noticed is that the sound at low volume seems less clean and clear (but I also have speakers that do not help). Honestly, I did not find anything obvious; my speakers are not efficient and need a lot of power even at low volumes but I did not notice any problem or, rather, nothing to highlight. Probably based on the configuration you have, the result changes. In my case there was an improvement on every front.
8.1/10
Pros:
- Compact Device – Desk space saver
- TPA3221 Pretty powerful
- Improved stage and details (in my setup)
- Refined sound
- Tubes seems to be working for real
- Tone knobs for easy EQ for Treble & Bass
- Remote
- Dedicated power supply
- VU Meter
Cons:
- More like a Tube buffer (not really a cons)
- Limited Dac built-in performance (but still sounding good to me)
- Not extra clear at low volume (but my speaker got pretty low sensitivity)
