Fender's Peak Music Power = 2.2 RMS?

[jmaf]

I've been asked recently, by someone who found vintage Fender catalogs online, why Fender's Peak Music Power ratings on their 1970 or 1972 catalogs, for example, are nearly always 2.2 times the nominal RMS ratings. I couldn't reply. All I told him was that PMPO is not standard and that each manufacturer has its own idea of PMPO.

I'd like to have a better idea of this...I checked and indeed most PMPO are 2.2 times the RMS. Does anyone know why?

Is this some standard measurement that I am totally missing or is it something that Fender arrived at by its own methods?

Thanks very much in advance for any pointers.

[Steve Conner]

Hi jmaf

The peak value of an undistorted sine wave is 1.4 times the RMS. Power is voltage times current, so if voltage and current are both sine waves, then peak power is (1.4*1.4) = 2 times the measurement that we call "RMS power". This is also what used to be called "music power".

I don't know where the extra 0.2 comes from. It could be an allowance for sag. PMPO has got just ridiculous nowadays, you get "2000 watt PMPO" computer speakers that are actually about 25W RMS and couldn't produce 2000W if they were struck by lightning.

[jmaf]

Hi jmaf

The peak value of an undistorted sine wave is 1.4 times the RMS. Power is voltage times current, so if voltage and current are both sine waves, then peak power is (1.4*1.4) = 2 times the measurement that we call "RMS power". This is also what used to be called "music power".

I don't know where the extra 0.2 comes from. It could be an allowance for sag. PMPO has got just ridiculous nowadays, you get "2000 watt PMPO" computer speakers that are actually about 25W RMS and couldn't produce 2000W if they were struck by lightning.

Steve, thanks so much for the explanation. Funny that when I was asked, I mentioned the computer speakers example of PMPO.

Appreciate your reply.

[unparalleled]

Steve, thanks so much for the explanation. Funny that when I was asked, I mentioned the computer speakers example of PMPO.

Appreciate your reply.

I always thought PMPO meant "Punter's Meaningless Power Only".
The cruddier the product, the higher the number.