using a dmm under 4 ohm load my amp does 45 volts a/c.

[stanky1219]

could i measure amps. then disconect the clamp and measure volts on the same tone? my dmm has a clamp on it.

 

[stanky1219]

my clamp said 2 amps? that doesnt sound right 45x2 is 90. only 90 watts?????

 

[smgreen20 10+ year member]

Your clamp is more then likely for AC not DC. You will need a DC clamp.

 

[stanky1219]

oh. someone on this thread said ac voltage x ac amps = wattage. and yes it only clamps ac , not dc.

 

[stanky1219]

its no biggie though. i know they arent clipping. the only reason i brought out the meter anyhow was to gain match them cuz they are pushing each coil of my sub temporarily till i get a sub amp thats worth a shit.

 

[Haunz 10+ year member]

It's been stated many times but I'll say it again, you CAN NOT accurately measure RMS power without a clamp meter.

Sure you can.. not much simpler then V^2/R (while using a dummy load anyway).. but you need a true RMS DMM at least..

Your clamp is more then likely for AC not DC. You will need a DC clamp.

WAT?

Dude, I'm not sure what meter you have... but all the cheap ones are set up the same way... they divide peak voltage by the square root of two, and are calibrated for 60Hz... You my friend are measuring the peak voltage divided by the square root of two, of some harmonic of your 50Hz fundamental tone; to which the meter is not calibrated...

I can pretty much guarantee you that the amps are running into distortion, and that they are really not putting out that amount of power....

 

[smgreen20 10+ year member]

Sure you can.. not much simpler then V^2/R (while using a dummy load anyway).. but you need a true RMS DMM at least..
WAT?

What?

The output side of the amp is AC, but its input side is DC. So, is why he needs a DC clamp meter. Not sure if that's what your "WAT?" means.......

And you're right, that's as simple as it gets, but... that was the simple part, it's much more complicated then just V^2/R. My PG ZPA0.5 will do 129VAC w/the gains cranked all the way up, but that doesn't mean it'll do 8,320 watts at 2 ohms..... You have to know the point at which the signal is starting to clip. You take that reading^2/R. You really don't even need to know the amperage that the amp is drawing, at that point you will also need to know the amps efficiency rating too.

To the OP, lets work this out again. In many reviews on the older MTX amps I've seen, they're under rated on average by 50%. In theory that 75 x 2 @ 4 ohms would be 300 x 1 @ 4 ohms, and at being under rated by 50%, that would equal 450 watts x 1 @ 4 ohms. So it is possible that you are getting that much out of each amp. 450w X 4 ohms = 1800, sq rt of 1800 = 42.42 vac of output on the speaker end of the amp. Me personally, I'd set each one to 40 vac even just for good measure. I would feel safe doing that if this was mine.

 

[stanky1219]

thats what i did. actually it was 41vac. but it sounds good to my ear and now my sub doesnt heat up like it did before i set the gains correctly.

 

[Haunz 10+ year member]

The output side of the amp is AC, but its input side is DC. So, is why he needs a DC clamp meter. Not sure if that's what your "WAT?" means..

WAT? means that you must be at minimum, mildly retarded... Why would you be measuring the current into an amp while you are trying to measure it's output power ?

The bottom line is that they are 325 watt amps (rated) on a good day with a favorable test... dynamic output IHF-202...

I think the same test conditions audiopipe uses... //content.invisioncic.com/y282845/emoticons/laugh.gif.48439b2acf2cfca21620f01e7f77d1e4.gif

 

[stanky1219]

either way 325 is great considering the sticker on the bottom says 150x1 @4ohms

 

[stanky1219]

all i know is the titan 1000 watt (Former amp i was running) was rated at 700@2 ohms and these kill it all day.

 

[roarzorz 10+ year member]

Your clamp is more then likely for AC not DC. You will need a DC clamp.

DC power has nothing to do with measuring an amplifier's output power which is always in AC. You measure the AC output voltage and clamp the AC current output.

 

[roarzorz 10+ year member]

Sure you can.. not much simpler then V^2/R (while using a dummy load anyway).. but you need a true RMS DMM at least..

Sorta true but erroneous when talking about in-car testing with reactive loads.

Dude, I'm not sure what meter you have... but all the cheap ones are set up the same way... they divide peak voltage by the square root of two, and are calibrated for 60Hz... You my friend are measuring the peak voltage divided by the square root of two, of some harmonic of your 50Hz fundamental tone; to which the meter is not calibrated...

The difference from 50hz to 60hz is extremely marginal at best.

 

[smgreen20 10+ year member]

Wow, we've got a few people here that don't understand. The amp runs off of DC voltage, that I'm sure you all know that, and what it outputs is AC voltage, that... some of you seem to know. If you don't know what the amp is putting out you can use the DC amperage that the amp is consuming (that's what the DC clamp is for) along with the efficiency and the AC voltage out to the speakers and a bit of math work and you can get a closely rough idea of how much power the amp is putting out. You still wont be able to tell if you're clipping though. Clamping the AC output on the amp isn't going to tell you any more then actually testing w/a DMM what the ACV is.

The best thing to do is to use an O-scope to see when the signal is starting to clip, back it off to where there is no clipping and then get your reading. Do the math and you'll find how much power the amp is putting out.

I'm no teacher and I have a hard time explaining it to others, but for background on me, I'm attending school for what started out to be Mechanical Engineering, that has now become my minor and Electrical Engineering is now my major, w/a 98% grade in my electronic courses.

 

[bubbagumper6 5,000+ posts]

Bottom line is, you need a scope. Any reading you take without one is irrelevant.