2. amps-preamps
  3. 187172-165308

Amplifier Specification questions

I understand the differences between different classes of amplifiers. Most common amplifiers are Class A/B. Does this mean that all class A/B amplifiers operate in Class A to some point then switch over to Class B when they hit a predefined threshold by the design of the manufacturer. Do some so-called Class A/B amps only operate in Class B? My power amp is designed to operate up to 18 watts Class A before changing class of operation. I assume this number is in 8 ohms. My amp is rated at 150 watts into 8 ohms and 300 into 4 ohms. Does this mean that Class A rating will double to 36 watts in 4 ohms or will it stay at 18 watts regardless. What's funny is I was thinking I needed more power because my meters were always pretty well deflected but after looking closer, I realized the meters were on the 5-WATT scale instead of the 150-WATT scale. I can't believe I never noticed that before.

willywonka

Showing 1 response by imhififan

imhififan's avatar
imhififan
2,129 posts
 

Interesting it does less class A into 4 ohms.

The amplifier bias current determine the output power of class A operation.

For example, an amplifier can provide up to 8 Watts of class A power @ 8 ohms load before it switch to class B operation, the current at the output is 1A (P = (I*R) * I ), if the output current over 1A it will switch to class B. Therefore @ 4 ohms load, the class A power is up to 4 Watts.

More to discover