Fosi Audio DA2120D

For $159 the DA2120D does a lot, so read on.

[Fosi DA2120D]
[Italian version here]

Product name: Fosi Audio DA2120D digital amplifier
Manufacturer: Fosi Audio - China
Approx. price: $159 USD
Reviewer: M.L. Gneier - TNT USA
Reviewed: September, 2023

Fosi Audio's description of this little amp is rather long: Fosi Audio DA2120D Bluetooth Audio Amplifiers 2.1 Channel Stereo 100W Power Amp USB Coaxial Optical AUX Remote Control. Yup, that's quite a mouthful. But, the fact is that the DA2120D really is all that. Though modest in appearance the D2120D is quite sophisticated. You can drive at as a digital amp through COAX, USB or optical inputs. Or, you can go Bluetooth. Or, if you're still stuck in the analog realm you can connect the Fosi to pretty much anything in the world using the 3.5mm stereo input Fosi labels AUX.

For my evaluation I primarily used USB and optical, Bluetooth (just to see how it sounded...not bad), and AUX (just to see how that sounded...not bad). The Fosi is small but it seems solidly put together. The power supply weighs nearly as much as the amp which explains the 100WPC rating. The unit powered on and off silently, always welcome but sometimes not the case when it comes to very inexpensive products like the Fosi. My initial impressions were extremely positive. The Fosi has an easy sound that's far better than one might expect possible for a product this inexpensive. Dynamics are especially good and there's plenty of dynamic swing. The top end was exceptionally smooth and musical but also significantly obscuring of fine detail.

After 10-20 hours of use I encountered a troubling problem. When being driven by any of the digital inputs (yes, I tried them all) the Fosi would emit a burst of varying durations that sounded almost like white noise. The first time it happened I suspected a loose connection since I had to pretty much move my entire system to get the Fosi into my rack. But, after checking everything I found no issues. I then suspected the source so I tried the COAX digital out from an old one-box CD player. After about an hour the same burst made its appearance. The burst was worrisome because it varied with volume so if it showed up while the volume was up my speakers got hit with a significantly wide-band load of energy. I was actually concerned for my tweeters. This, of course, led me to reduce the volume drastically during the rest of my evaluation.

I eventually emailed Fosi who indicated their awareness of the issue. My hope was that they'd have a solution or explanation but none was forthcoming. As I previously noted, this problem only happened while driving the Fosi from one of its digital inputs. Both AUX and Bluetooth functioned properly and without issue for the remainder of my time with the unit so the burst is obviously a fault in the Fosi's internal DAC.

So, is this burst a problem with the design of the DA2120D? Possibly. Is it a problem with assembly or quality control? Possibly. All I can say is that I swapped cables and sources in an effort to eliminate or reduce the burst without any increase or decrease in the rate or severity of occurence. This was an exceptionally disappointing outcome when you consider just how much Fosi accomplished with the D2120D. This is a very well-executed design in many ways. I'm sorry that Fosi couldn't have taken the time and effort to finish it off.

I have a lot of first hand experience with just how much effort is sometimes needed to rid a product of all of its operation gremlins. Mass-market companies get rid of gremlins first and concern themselves with how units sound later, if ever. High end companies do the opposite; they spend the lion's share of their time making a product sound as good as possible before going after gremlins. The problem with the Fosi DA2120D is that it's part mass-market product part new-era, high-end product. I'm sure Fosi has the ability to chase down the gremlins that had their way with the DA2120D. Here's hoping they take up the challenge and really finish the DA2120D. Now that's the Fosi DA2120D I would really love to hear.

Listen well but listen happy, my friends.

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