how to test actual wattage the amp is putting out

[frankiebones 10+ year member]

using a DMM, how can i do a bench test to see the actual wattage that my amp is putting out per channel? any formulas?

Click to read more...

 

[lincolnls 10+ year member]

using a DMM, how can i do a bench test to see the actual wattage that my amp is putting out per channel? any formulas?

ohms law

 

[Immacomputer 10+ year member]

To get an accurate result and to test like CEA (or how the company tests power output), you need a purely resistive load, a scope, and a very accurate true RMS ammeter and volt meter.

Multiplying RMS current times RMS voltage will NOT get you real power results but rather apparent power measured in volt amps (VA). You may see people doing this thinking it is correct but it is not. If you can calculate this value while keeping an impedance at or around DCR, it will give you a close value. If you cannot do this, your numbers will be greatly off.

 

[azbass 5,000+ posts]

or a clamp meeter thing-a-ma-bob

 

[n2audio 5,000+ posts]

using a DMM, how can i do a bench test to see the actual wattage that my amp is putting out per channel? any formulas?

w/o a scope to let you know when it starts clipping you can't get an accurate number.

 

[dirthog 10+ year member]

Always trying to learn. What is clipping?

 

[helotaxi 5,000+ posts]

Always trying to learn. What is clipping?

It's the limiting factor of what an amp can cleanly put out. The power supply rails are of a certain voltage. Try to exceed that voltage by turning up the gain too high or giving it too high an input signal voltage and the portion of the waveform that would be above and below the voltage rails gets "clipped" off. The resulting sound is generally characterized as harsh odd order distortion. The big problem with clipping is that the current that flows both through the amp and through the speaker can easily be more than either was designed for and can destroy one or both.

 

[Louisiana_CRX 5,000+ posts]

Does anyone like fluke or somebody make a DMM with a built in scope? or do you have to use the old fashion table top kind?

 

[Louisiana_CRX 5,000+ posts]

Ok ...I found one a Velleman 10Mhz Handheld personal scope...Does anyone know anything about this piece...It is carried by parts express?

 

[helotaxi 5,000+ posts]

Veleman (sp?) makes a pocket scope. Very limited resolution though. Not sure how well you could really see clipping with it.

Best way to test would honestly be to go to a shop that has all the gear and have them bench it for you.

Still not sure what the big deal is though about knowing how much power your amp can put into a purely resistive load...

 

[CBFryman2 5,000+ posts]

Current and voltage dont peak at the same time. This is why Apparent power and Actual power are different.

To get precise measurements you need a non inductave load capeable of handleing high power, an O-Scope, Clamp Amp Meter, and a DMM.

A good and cheap Non-Inductave load is a bunch of cremic 20w non inductave resistors wired to the desired load and then put in a bucket of distilled watter. Distilled is key because it isnt as conductive as tap water which has ions and impurities dissolved in it to make it a much better conductor.

 

[helotaxi 5,000+ posts]

Actually you want de-ionized water, not distilled. There is a difference.

Are you in Lake City, FL?

 

[Immacomputer 10+ year member]

Cooking oil will work.

 

[SPL140.2 5,000+ posts]

Ok ...I found one a Velleman 10Mhz Handheld personal scope...Does anyone know anything about this piece...It is carried by parts express?

I thought they banned you lol //content.invisioncic.com/y282845/emoticons/laugh.gif.48439b2acf2cfca21620f01e7f77d1e4.gif//content.invisioncic.com/y282845/emoticons/uhoh.gif.c07307dd22ee7e63e22fc8e9c614d1fd.gif//content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

egg

 

[ngsm13 5,000+ posts]

Hah.

Your not gonna do it with a DMM.

nG