Measuring amplifier output via meter.

 

Silver Member
Username: Invictuz

Seattle, Wa Usa

Post Number: 125
Registered: Jan-05
What tool would i use to measure amplifier output that would use a meter.

I have a multimeter and SP meter but want something that i can connect to the speaker outs and adjust the gain or freq and see the difference on the meter so i could then match several amps to the same reading...

what tool would do this?

or perhaps the multimeter will and i just need some direction on how (the 1 page manual doesnt appear to supply this info)

thanks in advance!

 

Gold Member
Username: Glasswolf

Wisteria, Lane USA

Post Number: 8599
Registered: Dec-03
oscilloscope
true RMS digital multimeter
non inductive leads
non inductive dummy load

those are the tools you'll need.
www.bcae1.com has a guide and an amplifier repair CD you can buy that walk you through the process.
 

Silver Member
Username: Invictuz

Seattle, Wa Usa

Post Number: 127
Registered: Jan-05
Thanks!
i thought my multimeter was missing something; I used it for wiring my subs but it does not have RMS measuring capability (only volts, amps and Ohms)... time for a trip to Home Depot...

i had a chance to buy an oldschool oscilloscope a few weeks ago at a garage sale for 10$...shoulda, coulda, woulda...

sorry for sounding NuB but what is a non-inductive dummy load; is that the same as a tone sweep? or test tone?

Reading site today; looks like a lot of really good info...similar to 12volt.

thanks again
 

Bronze Member
Username: Gpz1100

Post Number: 25
Registered: Jul-05
GW, don't most meters show RMS voltage (how is true rms different from RMS?).

When I stick my volt meter in the outlet, it shows 120 VAC. If it was a peak value it would be ~170 VAC.

A non reactive (non inductive/non capacitive) dummy load is one that's purely resistive. I can't think of one off hand that would not have some level of induction (if it's a heavy duty wirewound coil that would have a resistive component and an inductive one as well)
 

Gold Member
Username: Fishy

Tamarac Ft.Laud, FL USA

Post Number: 1468
Registered: Sep-04
dummy load = giant resistor
 

Gold Member
Username: Glasswolf

Wisteria, Lane USA

Post Number: 8611
Registered: Dec-03
a non raective load is a big resistor, but it's not "wound wire" as that would be inductive, like a speaker, which would affect the load.

basically you need a resistive load that can handle the heat/power of the amplifier to act like a speaker but give a constant 4 ohm load regardless of the frequency generated by the tone sweep.

GPz, no not all DMMs have RMS capability. Only the more expensive models. Yours does. Many radio shack specials do not. Most better Fluke models do. You just need to be sure it can read RMS on AC voltages. Otherwise you'll see zero volts on an AC wall outlet.
 

Gold Member
Username: Glasswolf

Wisteria, Lane USA

Post Number: 8612
Registered: Dec-03
you can build a non reactive load using a heat sink of adequate size, and an old hair dryer. unwind the heating element, and use it as straight wire, length determined by desired load.. then attach the heat spreader.
it'll get very hot but it works.. most of those hair driyers are rated for something like 1600+ watts
 

Silver Member
Username: Invictuz

Seattle, Wa Usa

Post Number: 128
Registered: Jan-05
Alot of good info from all thanks!

thats why i love this site!
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