Amplifier Volume Controls
Is an Amplifiers Volume Control really a Volume Control?
It is important for Audio Technicians to understand that power amplifier volume controls (level/gain controls) are actually “Input Sensitivity Controls” (also referred to as “Input Attenuators”). They are incorrectly referred to as amplifier “volume controls” and have nothing to do with the amplifier’s output stage. The input controls on power amplifiers essentially determine what “Input” level will cause the power amplifier to produce its full power, and they do not change any available output power the amplifier may have. It’s also a misconception that turning down the volume control on an amplifier can reduce the “Signal to Noise Ratio” and help a system’s “Dynamic Range.” This is not a valid point. All this info may sound confusing, but it’s the reality regarding the amplifiers misunderstood “volume control.”
Typical “Input Sensitivity” controls on a Power Amplifier.
Commonly and incorrectly referred to as “Volume” or “Gain” controls. This amplifier got it right and labelled their controls “ATTEN” (For Attenuator).
What happens when you send a signal that is too strong to an amplifier’s inputs? How do you know you’re “overdriving” the amplifier’s input? Clipping occurs, which is bad for the power amplifier and speakers. You really know you’re sending too much signal to the amplifier if the amplifier is turned all the way down and it’s still clipping. A few red lights intermittently here and there will be ok, but never keep the signal in a constant clipping state – the amplifier could be damaged, and you could end up with blown speakers.
What else can cause Clipping?
A couple other things that can cause Amplifier clipping.
- The amplifier cannot provide the needed power to the speakers connected to it, and is working way too hard.
- The speaker or speaker cable can be defective and have a possible short. Amplifiers do not like “short circuits.”
- Overheating – Heat is another main cause of amplifier clipping, when left too long in this state the amplifier usually goes to CLIP / Protection mode first, but can actually burn up over time. Keep your amplifiers well ventilated.
