# Understanding volume meter

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#### Dynam0

Hi guys newbie here, i would like to know if my head unit volume meter (which maxes out at volume 40) refers to maximun wattage per channel of the head unit.

It is rated at 40w x4 channel by the way.So abjusting the volume to 24 means that it is putting 24watts per channel?? If so, by abjusting the BASS BOOST,TREMBLE meaning it will put extra watts causing clipping??

#### Perry Babin

It may be able to determine when the head unit reaches clipping but you'd have to use a scope to know for certain. The meter could take the signal from any point in the circuit so using a scope would be the only way to know how useful it is.

#### The Lord Flashheart

Hi guys newbie here, i would like to know if my head unit volume meter (which maxes out at volume 40) refers to maximun wattage per channel of the head unit.

It is rated at 40w x4 channel by the way.So abjusting the volume to 24 means that it is putting 24watts per channel?? If so, by abjusting the BASS BOOST,TREMBLE meaning it will put extra watts causing clipping??

In fairly short terms, the higher you turn up the volume the more power the amplifier will potentially put out, limited by the amount of power it’s capable of and The speakers are capable of taking.

Is there a specific problem or is this a general question?

#### miniman82

Volume knobs seem to be graduated fairly arbitrarily IMO, but even if it did refer to 40wpc what Flashheart said above applies. I seriously doubt head units with 160w ratings, even if they achieved that sort of output they likely wouldn't last long if pushed hard. They lack heat sink surface area vs outboard power amps.

#### Perry Babin

I agree. The real (RMS) output power is essentially the battery voltage squared divided by the speaker load (4 ohms for most head units) divided by 2. For 14v of battery voltage it's (196/4)/2 or about 25w RMS and that is only if the output IC can drive to the rails (0v and 14v here).

There have been some head units that tried class D that could drive 2 ohms and there were (may still be) a few /media players (head units with no CD mechanism) that were class D that could produce more than the 25w.

#### miniman82

I just watched a video on a Sony unit that did 68w into a 2 ohm load, which is pretty impressive. But again, the heat that kind of power generates in a tight space like a dash can kill electronics in a hurry. I still have an older Alpine that makes a ton of heat just idling, I couldn't even use it in my Volvo it got so hot lol.

#### Perry Babin

There are class D ICs (like the IR4301, 5mm x 6mm) that don't even need a heatsink. Switching amplifiers change everything.

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