Fantastic new audio amp !
in [Design]
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From: Jim Thompson on 23 Nov 2009 09:59 On Mon, 23 Nov 2009 12:07:45 -0000, "christofire" <christofire(a)btinternet.com> wrote: [snip] > >You didn't spot the bit: 'In common use, the terms "RMS power" or "watts >RMS" are erroneously used to describe average power.' then? Or the >references: > >a.. The so called "RMS Power" >a.. Meaningless RMS Power - Why there is no such thing as 'RMS watts' or >'watts RMS' and never has been > >Unfortunately, the Wiki gnomes don't manage to weed out all the dross and >they've left in stuff like: 'The peak power of a sine wave of RMS value X is >?2*X; ' which is wrong for the same reason. > >Chris (a different one) > I was always fond of touting my amplifier as 400W CONTINUOUS RMS, as opposed to those nutcases who spout "music power" or "peak power" ;-) ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 |
From: ChrisQ on 23 Nov 2009 10:03 christofire wrote: > "ChrisQ" <meru(a)devnull.com> wrote in message > news:_wtOm.18019$492.10435(a)newsfe18.ams2... >> Tony wrote: >> >>> Not that this hasn't been done to death many times, but there's no such >>> thing as "rms >>> power", and the "rms value of a continuous sine wave" isn't really quite >>> explicit.enough >>> to be useful. >>> >> Sure there is and what's not explicit enough ?. An amplifier can be seen >> as a voltage generator and can have it's continuous power expressed in >> terms of rms value. >> >>> AFAIK the fictitious term "rms power" means something like V^2/R, where R >>> is the nominated >>> load resistance, and V is the RMS voltage of a sine wave that the amp can >>> be sustain into >>> such a load resistance without clipping. >>> >>> Cheers, Tony >> Fictitious ?. Ok, here's a wiki article on it: >> >> http://en.wikipedia.org/wiki/Audio_power > > > You didn't spot the bit: 'In common use, the terms "RMS power" or "watts > RMS" are erroneously used to describe average power.' then? Or the > references: > That was a bit of an own goal, but to be honest, just searched for an article as an explanation, without reading it in full :-(. Doesn't change the fact that rms measurement of power is just as valid and accurate for power as a true rms voltmeter is as valid as an average reading voltmeter, depending on what you are trying to measure. A true rms measurement takes into account waveform shape, whereas an average reading meter is calibrated for a given waveform shape, usually sine wave, at calibration time. It will be in error with anything else. Thus, a true rms measurement is more usefull in practice... Regards, Chris
From: Vladimir Vassilevsky on 23 Nov 2009 10:25 Jim Thompson wrote: > I was always fond of touting my amplifier as 400W CONTINUOUS RMS, as > opposed to those nutcases who spout "music power" or "peak power" ;-) Agreed. The real power, not bullshit power, tells a lot about the design. However, there is one more parameter: for how long the amp can sustain that power level undistorted. Vladimir Vassilevsky DSP and Mixed Signal Design Consultant http://www.abvolt.com
From: Jim Thompson on 23 Nov 2009 10:28 On Mon, 23 Nov 2009 09:25:10 -0600, Vladimir Vassilevsky <nospam(a)nowhere.com> wrote: > > >Jim Thompson wrote: > > >> I was always fond of touting my amplifier as 400W CONTINUOUS RMS, as >> opposed to those nutcases who spout "music power" or "peak power" ;-) > >Agreed. The real power, not bullshit power, tells a lot about the >design. However, there is one more parameter: for how long the amp can >sustain that power level undistorted. > > >Vladimir Vassilevsky >DSP and Mixed Signal Design Consultant >http://www.abvolt.com In my case "CONTINUOUS" meant exactly that ;-) ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 |
From: krw on 23 Nov 2009 12:51
On Mon, 23 Nov 2009 15:03:51 +0000, ChrisQ <meru(a)devnull.com> wrote: >christofire wrote: >> "ChrisQ" <meru(a)devnull.com> wrote in message >> news:_wtOm.18019$492.10435(a)newsfe18.ams2... >>> Tony wrote: >>> >>>> Not that this hasn't been done to death many times, but there's no such >>>> thing as "rms >>>> power", and the "rms value of a continuous sine wave" isn't really quite >>>> explicit.enough >>>> to be useful. >>>> >>> Sure there is and what's not explicit enough ?. An amplifier can be seen >>> as a voltage generator and can have it's continuous power expressed in >>> terms of rms value. >>> >>>> AFAIK the fictitious term "rms power" means something like V^2/R, where R >>>> is the nominated >>>> load resistance, and V is the RMS voltage of a sine wave that the amp can >>>> be sustain into >>>> such a load resistance without clipping. >>>> >>>> Cheers, Tony >>> Fictitious ?. Ok, here's a wiki article on it: >>> >>> http://en.wikipedia.org/wiki/Audio_power >> >> >> You didn't spot the bit: 'In common use, the terms "RMS power" or "watts >> RMS" are erroneously used to describe average power.' then? Or the >> references: >> > >That was a bit of an own goal, but to be honest, just searched for an >article as an explanation, without reading it in full :-(. > >Doesn't change the fact that rms measurement of power is just as valid >and accurate for power as a true rms voltmeter is as valid as an average >reading voltmeter, depending on what you are trying to measure. A true >rms measurement takes into account waveform shape, whereas an average >reading meter is calibrated for a given waveform shape, usually sine >wave, at calibration time. It will be in error with anything else. Thus, >a true rms measurement is more usefull in practice... No it isn't. RMS is valid for voltage and current because the square is useful for calculating power. The square, thus the root of the mean square, of power is meaningless. "Average" power says it all, regardless of waveform. Any other sort of power is bogus. |