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Get behind inflated power ratings (1 Viewer)

bugmenot

Auditioning
Joined
Aug 3, 2007
Messages
12
Real Name
John Smith
I just discovered an easy and accurate way to get technical specs on budget level amplifiers; companies like Philips, RCA, store brands, even SONY's cheaper models. Audio equipment like this often has bogus power ratings, either measured at 10% distortion or even worse "dynamic music power" etc. Almost all of this cheap equipment uses IC amplifiers from a few major chip makers: PhilipsSemi, NXP, STMicro, NatlSemi etc. I opened the cases on some of my audio equipment (wait till warranty is over of course) and found the numbers on the power amp chips - easy to find, always touching the heat sink. Most of these chips have complete specs available on the web including graphs of power vs frequency & THD. It's a techonerd's dream!
Here's some cheap gear with the advertised power ratings and the true RMS power before clipping (taken from chip makers' graphs):

VR3 Car stereo "180 watts (4x45)" Actual RMS power: 16 watts x4 channels, 0.5% THD, 4 ohms, 20-20khz.

RCA stereo "50 watts x2 10%THD" Actual RMS: 30 Watts/ch @
 

Allan Jayne

Senior HTF Member
Joined
Nov 1, 1998
Messages
2,405
I thought that some standards for advertising audio amp power were established long ago. So people could find out before they bought the equipment.

Not exactly on topic but something like 30 years ago Consumer Reports once referred to a "300 watt console stereo" in a nice wood finish cabinet (2.0 system in today's HT terminology) that had 2 watts per channel according to their measurements. This was back in the discrete solid state component era and the power transistors, two per channel, were probably about the size and shape of pencil erasers and with a small metal heat sink fin clipped on each.
 

Leo Kerr

Screenwriter
Joined
May 10, 1999
Messages
1,698
stats have often been misreported. One of the other ways of inflating power vs distortion is, say, 20watts/channel @ 1kHz, 1 channel driven. As opposed to, say, 20watts/channel, 20-20kHz, 5 channels driven.

I've a (now old) book on PA systems from Yamaha, where one chapter near the end is "how those technical specs are lying to you." Everything in their perfectly normal sounding specs was lying, deceptive, or missing information, including the physical dimensions and weight!

Leo
 

chuckg

Supporting Actor
Joined
Apr 27, 2004
Messages
921
None of this is surprising. We even have an acronym for those advertised power ratings; "PPWHBL" which stands for "peak power when hit by lightning"

Unfortunately, no there are no real standards.
 

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