How to get ur amp tested. or Where

 

Silver Member
Username: Bump05

CashMoney, 15 Hd3 USA

Post Number: 945
Registered: Aug-06
ey how or where can u get ur amp tested to see what it does @ impediences.
 

Silver Member
Username: Nickb4247

Post Number: 231
Registered: Dec-06
use a DMM(digital multimeter)
 

Gold Member
Username: Adddisorder

West palm, Florida

Post Number: 3360
Registered: Jan-06
^^NO


i think bcae1.com has a thing on it you need a clamp meter and an o-scope and stuff.

just call your audio shops and see if theyll do it
 

Silver Member
Username: Nickb4247

Post Number: 234
Registered: Dec-06
A DMM will read AC voltage output from an amp.
 

Silver Member
Username: Nickb4247

Post Number: 235
Registered: Dec-06
The only reason you need the o-scope is to make sure you arnt taking a reading while the amp is clipping.
 

Gold Member
Username: Adddisorder

West palm, Florida

Post Number: 3362
Registered: Jan-06
it still wont give you true output! and you wont know when its clipping without an o-scope so you cant determine the true max output
 

Silver Member
Username: Rob932

Post Number: 126
Registered: Feb-05
dmm will give you rms and o-scope will give peak
 

Gold Member
Username: Adddisorder

West palm, Florida

Post Number: 3363
Registered: Jan-06

quote:

dmm will give you rms and o-scope will give peak


no not magically and like i said befor their is still other stuff involved
 

Gold Member
Username: Adddisorder

West palm, Florida

Post Number: 3364
Registered: Jan-06
EQUIPMENT NEEDED TO MEASURE OUTPUT POWER
To accurately measure output power, you will need:
1.A regulated D.C. power supply capable of powering any amplifier that you need to test
2.A set of high power resistors. They must be rated to handle the power output of any amplifier which you need to test.
3.An oscilloscope to view the waveform.
4.Some sort of tone generator. A sine wave generator is a good choice but you may be able to get by with a CD player and a test tone disc.
5.A digital voltmeter capable of measuring A.C. voltage. A true RMS meter would be nice.

NOTE:This information is only to let you know how the test is done. If you have all of this equipment, you will probably already know how to make this test.

TEST EQUIPMENT SETUP

Connect the 12v power supply to the power wires on the amplifier.

Connect the power resistors (dummy loads) to all of the channels of the amplifier.

Set the gain controls for all channels of the amplifier to the same level. Either all of the way up or all of the way down will probably be the easiest. You can make fine gain adjustments at a later time.

Connect the tone (sine wave) generator to all of the amplifier channels. Turn the output level of the tone generator all of the way down.

Turn the power supply on. If it is adjustable, set it where you want it (12 volts, 13.8, 14.4 your choice).

Power the remote terminal of the amplifier.

Measure the output voltage of the D.C. power supply (it should be the same as before the amplifier was turned on).

Set all equalization to the off position and set all crossovers to full range.

Set the output frequency of the generator to any frequency that you want. I generally use 100hz. You should always use the same frequency or at least make note of the frequency used during the test.

Slowly increase the output of the tone generator until the output of the amplifier is approximately 2 volts A.C. Now set all of the gains to match the output of all of the channels.

Connect the oscilloscope to any channel (they should all be the same since you tweaked them).

Monitor the output voltage of the power supply, either with your volt meter or by the digital meters on the power supply. If the power supply doesn't have digital meters, use a digital multimeter.

Slowly increase the output of the tone generator while watching the oscilloscope. Increase the level until the top and/or bottom of the sine wave flattens out. Reduce the level until the wave is 'clean' again.

Now see if the power supply voltage has held to the preset value. Reduce the output level of the generator. If the D.C. voltage changed during the test, you must take this into account. A well regulated supply will have held the preset voltage.

Now connect the A.C. voltmeter to the output terminals of one channel. The channel connected to the scope would be a good choice.

Again Increase the level of the generator until just before the amplifier starts to clip. Make note of the voltage reading.

Turn the power supply off.

Quickly disconnect the dummy load of one channel and measure its exact resistance while it is still hot. The value of the resistor will change slightly as it heats up.

Now use the Ohm's law formula, P=E^2/R. If we found that the amplifier drove 35 volts A.C. across the resistor and the resistor had a D.C. resistance of 4.08 ohms, the amplifier produced 300.25 watts RMS.

P=35^2/4.08
P=1225/4.08
P=300.25 watts RMS

NOTE:
1.If the D.C. power supply does not hold its preset voltage, the power output will be lower than the amplifier is capable.
2.This test cannot be done using speakers in place of the dummy loads. The speakers will give you a false high reading at most frequencies.

Test Data:
The following data was taken in a test to show how calculating power when using the voltage across a speaker's terminals instead of the voltage across a non-reactive dummy load will result in false output data. The frequency is the test frequency. The voltage is the voltage that was measured across the terminals of the load (either speaker or dummy load). The power is the calculated power using the speaker's nominal impedance (4 ohms) and the voltage across the speaker's terminals at the various frequencies. The voltage across the dummy load will be virtually the same across the range of frequencies so only one voltage reading was necessary. The amplifier is capable of producing only 205 true watts (RMS power). When using a speaker, it appears to be able to produce as much as 376 watts (which it clearly is not capable of doing).

Frequency Voltage Power
35 33.7 284
40 35.86 321
45 35.53 315
50 37.19 346
55 38.0 361
60 38.8 376
65 38.5 371
70 35.88 322
75 33.2 276
Dummy Load 28.6 205


courtesy of bcae1.com
 

Silver Member
Username: Rob932

Post Number: 127
Registered: Feb-05
I know there is other stuff to do but most dmm's or at least everone i have ever used will give you the AC voltage in RMS and O-scopes will allow you to see the whole sine wave
 

Gold Member
Username: N2audio

Lawrence, Ks USA

Post Number: 1204
Registered: Mar-04
that's great Robbie, you can read voltage.

If the object is to see what the amp is capable of simply measuring voltage won't tell you a thing. You need to know WHERE the amp starts to clip which you can't do w/o a scope, or the procedure Mat posted from bcae1.

another option is to email one of the mods at carsound. They'll test it extensively for free as long as you pay for shipping.
 

Silver Member
Username: Rob932

Post Number: 128
Registered: Feb-05
yes i realize this and Matt is right i was actually agreeing with him someone said to use a dmm and matt said to use an o-scope i was simply clarifying for the other guy that was saying to use the dmm, that the dmm gives you RMS and the o-scope allows you to see the whole waveform and when it begins to clip.
 

Silver Member
Username: Nd4spd18

Post Number: 453
Registered: Jul-06
mat dope and optidriven are correct, nick and robbie are wrong. You CAN NOT bench test an amp without a scope.

The procedure posted above form bcae1.com is how to test the RMS output of an amplifier. A DMM alone will not tell you a damn thing about how much current an amp can produce.
 

Silver Member
Username: Rob932

Post Number: 129
Registered: Feb-05
I dont know why you keep saying im wrong when i agreed with matt but whatever
 

Silver Member
Username: Nd4spd18

Southeast PA

Post Number: 564
Registered: Jul-06
^^^^

You said a DMM shows RMS power output and a scope shows peak, that is wrong
 

Silver Member
Username: Rob932

Post Number: 130
Registered: Feb-05
whatever im not going to argue w/ you about it but im pretty sure DMM shows RMS and oscope shows peak to peak no matter WHAT you hook it up to. I might be wrong but thats just from my personal experience.
 

Silver Member
Username: Nd4spd18

Southeast PA

Post Number: 577
Registered: Jul-06
The procedure mat dope posted above is THE ONLY way to test the RMS power output of an amplifier.


*End Thread*
« Previous Thread Next Thread »



Main Forums

Today's Posts

Forum Help

Follow Us