Home |
Search |
Today's Posts |
|
Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
Reply |
|
|
LinkBack | Thread Tools | Display Modes |
#41
Posted to sci.electronics.repair
|
|||
|
|||
Measuring audio amp output power
On 8/2/2015 7:49 AM, Cursitor Doom wrote:
On Sat, 01 Aug 2015 18:29:58 -0700, Phil Allison wrote: ** A single sine wave is needed for audio power testing. Amplifier power ratings are based on the *rms* value of a sine wave - hence the misleading term "rms power". Well that would make sense with RMS being, IIRC, equivalent to the DC heating effect in a resistive load. RMS is an amplitude, e.g. 'volts RMS'. Phil's right that the term is in error, but there's so many lies and so much snake oil in the audio business that this minor absurdity seems a fairly small price to pay to clear away all the "peak intermittent music power" (PIMP) nonsense. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net |
#42
Posted to sci.electronics.repair
|
|||
|
|||
Measuring audio amp output power
On Sun, 02 Aug 2015 09:04:54 -0400, Phil Hobbs wrote:
RMS is an amplitude, e.g. 'volts RMS'. Yes, I recall 0.707 of the peak signal level. So for example if I set an amp to some arbitrary output and feed into an 8 ohm load and measure say 10V peak-to-peak on a scope, then I'm getting about 6.25W RMS out. Phil's right that the term is in error, but there's so many lies and so much snake oil in the audio business that this minor absurdity seems a fairly small price to pay to clear away all the "peak intermittent music power" (PIMP) nonsense. Fully agree with you on that! |
#43
Posted to sci.electronics.repair
|
|||
|
|||
Measuring audio amp output power
On Sun, 02 Aug 2015 13:29:38 +0000, Cursitor Doom wrote:
On Sun, 02 Aug 2015 09:04:54 -0400, Phil Hobbs wrote: RMS is an amplitude, e.g. 'volts RMS'. Yes, I recall 0.707 of the peak signal level. So for example if I set an amp to some arbitrary output and feed into an 8 ohm load and measure say 10V peak-to-peak on a scope, then I'm getting about 6.25W RMS out. Phil's right that the term is in error, but there's so many lies and so much snake oil in the audio business that this minor absurdity seems a fairly small price to pay to clear away all the "peak intermittent music power" (PIMP) nonsense. Fully agree with you on that! Should have put the 6.25W RMS in inverted commas, since there's no such thing as RMS power, of course. It's really all about *average* power. |
#44
Posted to sci.electronics.repair
|
|||
|
|||
Measuring audio amp output power
Cursitor Doom wrote:
RMS is an amplitude, e.g. 'volts RMS'. Yes, I recall 0.707 of the peak signal level. So for example if I set an amp to some arbitrary output and feed into an 8 ohm load and measure say 10V peak-to-peak on a scope, then I'm getting about 6.25W RMS out. ** The "peak" value is referenced to the zero line, so there are negative and positive ones. The "peak to peak" value has no polarity and is easier to read off a scope screen but to get the rms value of a sine wave one divides by 2.83 ( 2 x sq.rt 2) So in your example, that value is 3.54Vrms and the power is 1.56 watts. ..... Phil |
#45
Posted to sci.electronics.repair
|
|||
|
|||
Measuring audio amp output power
On Friday, July 31, 2015 at 8:42:40 AM UTC-7, MJC wrote:
In article , says... Most metallic conductors are Zero-Resistance at cryogenic temperatures. So, a wire-wound resistor may drop off to near-zero in liquid nitrogen. If only superconductors for liquid N2 temperatures (77K, -196C) were so common! Even at liquid He (4.22K, -270C) only a minority of metals make the transition. Superconducting transition is not the only misbehavior; carbon resistors have a semimetal/semiconductor transition, and turn high-resistance when cold, and metal-film resistors move VERY far from their nominal values when cold. Platinum film RTDs work because they have resistance accurately proportional to absolute temperatu resistance at 77k is about a quarter of that at room temperature. |
Reply |
|
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
Audio output transformer | Electronics Repair | |||
Very Odd Audio Common Mode Condition Started Just Before Midnight 12/31--Audio Feedback Oscillation through Power Line? | Electronics | |||
Adding speakers to tv with no audio output | Electronics Repair | |||
Audio and Video output from TV | Electronics | |||
Audio Voltage Output | Electronics |