New Audio

 I love audio equipment and now that the house move (did I tell you about that?) is complete, I figured I would get myself a new stereo.  I picked up a pair of Polk T50 floor standing speakers and an a small (its so small!) class D stereo amplifier.

That amplifier is tiny!

The amplifier is a Fosi Audio DA2120C, bluetooth amplifier. I wanted BT on board because I like to stream music from Spotify via my phone sometimes.  But one of the things I noticed when looking for an amplifier is the disparity in tech specs.  So many manufactures just use peak rather than RMS for the power out. The issue here is that using peak can make a 10W amplifier look like a 1KW beast, and it plainly isn't.

This amplifier has an external power brick rated at 32V/5A. So in theory the maximum I can get out of the power brick is 32x5 or 160W.  The amplifier is advertised as 120+120W into 4Ohms, so 240W - obviously that is impossible, unless they are counting output as a short transient and using stored energy in the capacitors. However even if they do that, it is not sustained output.  If I assume the amplifier is perfect (it isn't of course) the max I can get out of the beast is ~160W or 80+80W.

The speakers are Polk T50s that I also purchased from Amazon. The speakers are rated 6 Ohm, and this will make a difference to the power that the amplifier can deliver.

Fosi, the manufacturer of the amplifier rather foolishly provide us with a list of the chips used in this amplifier. The power stage is a Texas instruments TAS5352A.  If you check the data sheet for that chip, you find a whole different set of specs:

Total Power Output (Bridge-Tied Load) 
 – 2×125W at 10% THD+N Into 4Ω 

 – 2×100W at 10% THD+N Into 6Ω

So we can see that into 6Ω under ideal conditions, I am looking at 100W per channel assuming the power supply can support that.  Now if you dig a little deeper into the data sheet, you will find that the power output figure is "Maximum power Output" which I think we can equate to near peak output (~90%). So what is the RMS output?

It depends but most likely somewhere about half the max value, so 50W RMS or there abouts.  I figure its actually a little lower because that initial 100W into 6Ω is at 10% distortion. Comfortably I think this little amp can run about 45W RMS per channel at a reasonable level of distortion. 

So how does it sound?  Actually it sounds pretty good with T50s.  They take some driving and perhaps I would have been better off spending 4x the amount the amplifier cost on a NAD or Denon, but I really didn't want to do that.  I may have to turn it up a fair way to get decent volume, especially when using the TOSlink from the TV, but honestly it does everything I need it to do in one very tiny package.

Despite its shortcomings, I am actually impressed.

Designed for Audio System

Chips: Cirrus CS8422 + Qualcomm QCC3008 + TI TAS5352A + TI TAS5508 + Cmedia CM6642

• THD: ≤ 0.01%
• SNR: ≥ 105dB
• Power Supply: 32V 5A
• System Supported: XP/W7/W8/W10/MAC/Linux
• Size: L180*W130*H38mm (7*5*1.5in)
• Supplied Accessories: DA2120C, 32V Power supply, AC cord, Remote control, USB cable, Optical cable, Bluetooth antenna, User manual