Tweak City Gizmo Class D Amplifier

Class D circuit seems to be the new favorite flavor for some. They are very inexpensive and provide outstanding sound quality for the price. Compared to other amplifier circuit topologies such as class A or Class AB, Class D is much more power efficient.

For such a small amplifier, this thing can push some power; this system can become way too loud for sitting in front of your system. We pushed this little power house to the end of it's volume fader and at about 35 the system starts becoming too loud for the front of a PC and you still have another 15 steps beyond that. Where does all this power come from? This amplifier is only 8" Deep x 2.5" High x 4.5" Wide! The power efficient Class D's they are truly something else!
These amps are usually very easy to mod also but more on that later…

Let's take a closer look at this amp:

The rosewood top blends well with the style of the ELT 's and modern living, media or computer rooms. This amplifier can be stuck in a cubby in most PC desks and you would never notice it is there. If you have never heard a good quality Class D amplifier, we recommend you try and audition one as they are very impressive and very cheap for their power ratings.

The controls are fully digital, starting from the left, we have Bass (-14 to +14)
STBY (Power), Mute, Master Volume (0 to 50) and finally Treble (-14 to 14).
In comparison many class D have simple controls such as simple power and volume. This model actually has many additional features to help with tuning your system sound usually unseen in amplifiers of this price point. Let's have a look at the back of this unit and see what we have for I/O:

We have right and left RCA inputs and the subwoofer output along with binding posts for connecting up speakers. These binding posts can take generic speaker wire or banana jacks plug in to the ends. There is also input for the 12 volt DC power supply which is included with the Gizmo.

Let's have a look at the specifications:

Specifications

• Output Connections: L/R channel speakers; Subwoofer out (RCA connection)
• Power Rating: 25WPC x 2 @ 4 ohms
• Class D amplifier
• Voltage: 110V/220V
• Shipping weight: 7 lbs (approx)
• Dimensions: 8"D x 2.5"H x 4.5"W

Additional Features:

• Digital Display
• Separate Bass and Treble Controls
• Subwoofer out
• Rosewood cap
• True 100 Hz crossover built-in
• Volume +/-, Mute, Standby and Bass/Treble controls

The subwoofer output is very unique features for a desktop amplifier in this price class. The Guru3D Audio Lab has a few Class D power amps and all except for the Gizmo are just plain 2 channel stereo output. The sub out is a great addition and we would like to see this on more desktop stereo amplifiers. 

A Note for Bass Setting: 
The Gizmo has an internal 100Hz crossover which filters bass out of the left and right signels and sends it to the sub out.  While this is optimal when you have a sub connected, when using just stereo speakers you will need to adjust the bass to compensate.  Start at the middle on the bass setting and adjust until your speakers sound balanced across the spectrum and not bass heavy nor bass shy.  There is really no magic number as some speakers have more bass then others.  Adjust until your speakers sound natural and balanced.