when do amps give full power

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stevdart

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Posted: September 24, 2006 at 12:23 AM / IP Logged

greenbroncoguy, I wasn't talking about measuring amplifier output; instead, the method was meant as a way to compare voltage output at various volume levels. Use Ohm's Law to ballpark the power.

The AC voltage, which is relative to power, stays on a shallow curve until the very end, or highest volume levels. That's where the curve steepens upward as the voltage rises dramatically.

Steven Kephart wrote:

(at Adire we used a coil of wire submerged in water)

These are professional drivers on a closed course. Do not try this at home. when do amps give full power - Page 2 -- posted image.

Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

aznboi3644

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Posted: September 24, 2006 at 1:37 AM / IP Logged

How does a coil of wire submerged in water act as a dummy load??? I am curious...I've seem some non-inductive dummy loads on partsexpress.com

Steven Kephart

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Posted: September 24, 2006 at 2:25 AM / IP Logged

The coil produces a known resistance, and the water cools it down. I should mention it is insulated wire.

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aznboi3644

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Posted: September 24, 2006 at 2:47 AM / IP Logged

Ah icic...but does the impedance change with frequency still?

haemphyst

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Posted: September 24, 2006 at 9:07 AM / IP Logged

ANY load with a complex resistance (meaning inductive or capacitive) will present a dynamic resistance to a signal.

It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

DYohn

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Posted: September 24, 2006 at 9:57 AM / IP Logged

And don't forget, gentlemen, that there is a difference between average or sustained power and peak transient power. It is entirely possible that an amplifier delivering, say, 10-12 watts average may be called upon to deliver 100-200 watts for momentary transient peaks, so power headroom is a good thing. I don't mean to get the discussion off into slew rates and the like, just wanted to mention since most of this discussion so far has been about determining average power output.

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aznboi3644

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Posted: September 24, 2006 at 12:31 PM / IP Logged

Well...someone needs to make a sticky on how to measure an amplifiers rms output...I got a nice DMM for my birthday and wanna set my gain correctly...most of the threads here just tell people to use a DMM and a sine wave...nothing about the details and what to use and look for and how to really do it

DYohn

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Posted: September 24, 2006 at 1:07 PM / IP Logged

aznboi3644 wrote:

Some resources for you: http://www.bcae1.com/measpwr.htm, http://sound.westhost.com/power.htm

http://www.bcae1.com/gaincon2.htm

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Steven Kephart

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Posted: September 24, 2006 at 5:21 PM / IP Logged

aznboi3644 wrote:

Ah icic...but does the impedance change with frequency still?

To be honest, I don't fully know. I would guess that if it does, it would be VERY little. The DC resistance of the coil is fixed, as I believe the inductance would be since there isn't two magnetic fields working against eachother, and no changes in inductance from a moving coil around a fixed piece of steel. But I could be wrong, and have never asked. Maybe one of the Dave's could clear that up? If it does change, I would suspect it to be a linear change.

DYohn

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Posted: September 24, 2006 at 5:41 PM / IP Logged

Inductance in any wire goes down as frequency goes up (it's generally a logarithmic rate of change, not linear.) The amount of change is generally so small within the audio frequency band that it can be considered constant, however.

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