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Silver Member Username: JmloughreyFarmington, CT Post Number: 252 Registered: Jul-04 | What is the difference between a Class A/B amp and a Class D amp? |
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Gold Member Username: Jonathan_fGA USA Post Number: 1459 Registered: May-04 | I posted a reply to a similar thread not too long ago, it explains the technical side of a Class D amp: https://www.ecoustics.com/electronics/forum/car-audio/84609.html An A/B is analog, the signal is applied directly to a transistor rather than being converted to a binary signal. The transistors are biased accordingly(positive or negative) and connected to both the power supply and signal (RCA inputs), basically, a transistor works similar to a relay, it uses a small amount of current (the signal coming from the RCAs) to control a large amount of current (the power supply). When the signal dictates a positive wave, the positive biased transistor will receive the signal, and the transistor will "turn on", the signal will create current flow and electrons will flow (the signal dictates how strong the power) from the power supply through the transistor, resulting in a reproduction of the same signal with higher power. Simply put, when the signal is positive, the pos. transistor turns on and positively charged current flows from the power supply. Once the wave changes direction and goes negative, the neg. transistor turns on and negative current flows from the power supply. Same for the negative biased transistor, just reword it. A/B amps are much simpler in design compared to Class D, they offer less distortion and higher linearity, but are less efficient (around 50-60%, Class D is around 80%), producing more heat and requiring a larger amp. They are much more efficient than a Class A amp, although they have a tad more distortion, but have less distortion than a class B even at high volumes because they have an idle current, which keeps the transistors barely turned on so there isn't a delay when switching (transistors have to surpass their internal voltage, typically .7 volts in silicon doped transistors, before they amplify). If there wasn't an idle current, the signal would have to be strong enough to surpass .7 volts, so there would be a hole between 0V and .7 volts, and the transistor wouldn't be turned on, resulting in distortion in the signal because it wouldn't be produced anywhere from 0V to .7V. |