How do you "clamp" an amp?

[djtomczak 5]

I see people saying their rms "clamped" all the time, I'm curious to know what my Memphis is actually putting out. I have an amp probe and a dmm. How would I go about clamping my amp to see the power it is putting out?

[CrazyKenKid 64]

things you will need.

Power supply - this power supply should be able to hold a steady voltage for the entirety of your test and should be constantly monitored

load - a bank of resistors is ideal

oscilloscope - something that can handle the amount of power the amp should make

two multi-meter - a half decent one- one to monitor the A/c voltage and one to monitor the DC voltage

clamp-meter - to monitor the amperage going the load

tone generator - to generate a clean tone or sine wave

if you can follow me Dylan so far let me know and lets go from there!

and what is an amp probe? link? picture?

[Tirefryr 1,742]

I just screw it. Clamps can loosen.

[ssh 924]

I just screw it. Clamps can loosen.

Your not using cheap plastic clamps are you? The metal ones with some loctite work wonders.

[CrazyKenKid 64]

I just screw it. Clamps can loosen.

Your not using cheap plastic clamps are you? The metal ones with some loctite work wonders.

you guys are both wrong clamps blow and are ugly you should be using velcro!

[djtomczak 5]

things you will need.

Power supply - this power supply should be able to hold a steady voltage for the entirety of your test and should be constantly monitored

load - a bank of resistors is ideal

oscilloscope - something that can handle the amount of power the amp should make

two multi-meter - a half decent one- one to monitor the A/c voltage and one to monitor the DC voltage

clamp-meter - to monitor the amperage going the load

tone generator - to generate a clean tone or sine wave

if you can follow me Dylan so far let me know and lets go from there!

and what is an amp probe? link? picture?

Car charger work for power supply?

For the load wouldnt the subwoofer be the load?

Don't have an oscope

Fluke mm

fluke clamp meter

Test tone on a CD?

amp probe is clamp meter - fluke 376 i think is the one I have

[CrazyKenKid 64]

things you will need.

Power supply - this power supply should be able to hold a steady voltage for the entirety of your test and should be constantly monitored

load - a bank of resistors is ideal

oscilloscope - something that can handle the amount of power the amp should make

two multi-meter - a half decent one- one to monitor the A/c voltage and one to monitor the DC voltage

clamp-meter - to monitor the amperage going the load

tone generator - to generate a clean tone or sine wave

if you can follow me Dylan so far let me know and lets go from there!

and what is an amp probe? link? picture?

Car charger work for power supply?

For the load wouldnt the subwoofer be the load?

Don't have an oscope

Fluke mm

fluke clamp meter

Test tone on a CD?

amp probe is clamp meter - fluke 376 i think is the one I have

I would use a battery that is being charged by a car charger over just the charger. For example if your amp is rated at 1500 get a battery that can support at least 1500watts!

you would think that but resistors is what i say to use but in a pinch use a sub i guess lol!

oscope is used to tell us when the amp is clipping so we know where and when max power output is reached, look into borrowing one

test tone on a cd is fine as long as it is accurate and isn't like +3db or something crazy

now to clamp your amp simple:

hook your cd into your amp to play the tone repeatedly (ipod or cd player with a 3mm to rca converter or a head unit if you got one laying around)

hook the battery to the amp

hook a dmm up the battery

hook your sub up free air

hook your clamp meter on the positive lead going to the sub/load

hook your other dmm up to the output terminals on the amp to tell the A/C voltage

then take your stolen oscope and hook it up in parellel to the load

turn on the cd player

adjust gain until it starts to clip

read the numbers off of your dmm and current meter

do some math, you have voltage and current so do something with those to find power!

and report back and take lots of pictures lol! o and keep an eye on the battery voltage to make sure it stays constant! and if it drops record it!

the only thing wrong with a sub is when it heats, or temp in the room heats up, or as you change frequencies the impedance of the sub will changes this will lead to inaccuracies but for a daily kind a guy who want to try something for kicks do it up!

keeping in mind if you were profession the power supply and load would cost a lot of shinny pennies!

o and I think your subs should be free air? not sure how the box will effect the test. we will see if anyone else chimes in on this!

[djtomczak 5]

So multiply the Amps going through the positive to the subwoofers by the AC volts going to the subwoofer?

[CrazyKenKid 64]

Volts x Amps = Power! you are correct my man!

and yes all on the output side of the amp!

keeping in mind that the output of the amp is directly effected by the input voltage and load conditions! If your amp was rated at 14.4volt dc please try to keep 14.4 volts all test long!

[djtomczak 5]

Well 12.5 is what my charger can keep pretty solid. No idea what my amp was rated at, It's pretty old.

[CrazyKenKid 64]

nice! well one of the key things to get to look into borrowing is an oscope as that will tell us how much power the amp is outputting before it sends out a clipped signal to the sub. I guess you could call it a clean signal? and 12.5vdc that is weak! lol

[djtomczak 5]

It's only meant to charge the battery! There's a 16v start switch on the charger but I'm not going to send 16v to my new truck. Truck started I can hold 14.2

Edited January 31, 2012 by djtomczak

[CrazyKenKid 64]

do it up and report back! (once you get an oscope)

[djtomczak 5]

Will do! Don't have free time until Thursday though. I'll see about a video and pictures of my new install as well.

[CrazyKenKid 64]

nice! actually if you pop down to your local college and tell someone what you are doing I am sure they can help you out or even maybe want to she there class or whatever!

either that or pop over to your local car audio and ask if they have one you could borrow for a few minutes, I know my local car audio shop has one! but they think it is gold and never lend it out lol!

[djtomczak 5]

My local shop believes in adjusting by ear, I watched them do it today and he did a pretty good job!

[CrazyKenKid 64]

adjust by ear is the best way to go man!

[djtomczak 5]

I've always adjusted by ear, tried Dmm and turned out to be clipping still.

I'm lucky, Two of the top twelve retailers by mobile electronics magazine are in my area!

[Impious 1,476]

I see people saying their rms "clamped" all the time, I'm curious to know what my Memphis is actually putting out. I have an amp probe and a dmm. How would I go about clamping my amp to see the power it is putting out?

The first question is why you would want to "clamp" your amp to begin with? What are you hoping to find out and how will you use that information?

"Clamping" an amp in the manor it is most commonly performed provides little relevant or useful information. The reason the measurements aren't accurate are many....for one, you don't know the accuracy of the measuring equipment. Second, measuring power into a reactive load (i.e. your subwoofer) is not a simple Volts x Amps calculation. Third, you are not measuring distortion (even with an o-scope you are not measuring distortion, only when the wave begins to clip). That's just to name a few.

So all in all, the results of your measurement will be virtually useless and it will not tell you how much power your amplifier is "really" outputting.

About the only way to do that reliably is with a professional level bench test measurement system, which isn't cheap.

[djtomczak 5]

I see people saying their rms "clamped" all the time, I'm curious to know what my Memphis is actually putting out. I have an amp probe and a dmm. How would I go about clamping my amp to see the power it is putting out?

The first question is why you would want to "clamp" your amp? "Clamping" an amp in the manor it is most commonly performed provides little relevant or useful information. The reason the measurements aren't accurate are many....for one, you don't know the accuracy of the measuring equipment. Second, measuring power into a reactive load (i.e. your subwoofer) is not a simple Volts x Amps calculation. Third, you are not measuring distortion (even with an o-scope you are not measuring distortion, only when the wave begins to clip). That's just to name a few.

So all in all, the results of your measurement will be virtually useless and it will not tell you how much power your amplifier is "really" outputting.

About the only way to do that reliably is with a professional level bench test measurement system, which isn't cheap.

Why do people do it if it doesn't really show any useful information? I don't need an exact number I just want a ball park to see if it's putting out what it's claiming.

[Impious 1,476]

Why do people do it if it doesn't really show any useful information?

Monkey-see Monkey-Do

Happens a lot in this hobby. I could go on a pretty long rant about all of the useless or senseless things people do in this hobby.

I don't need an exact number I just want a ball park to see if it's putting out what it's claiming.

In all honesty, it doesn't really matter. Even if the amp is over rated by 25% you're not going to hear a difference. As long as you're not running one of those extremely low end amps which rate everything at PMPO or ILS, generally real power output is going to be close enough to rated to not make an audible difference. It's often nice to know just from a manufacturer reputability aspect.....sure, I'll put a little more faith into the general build/design quality and respect for a company if their 500w amp really outputs 500w. But if it only does 400w, you're not going to hear a difference. Unless you are chasing #'s on a meter, it really doesn't make that big of a difference.

But to actually measure the true output of an amplifier to the level of detail and accuracy required to compare it to the manufacturer's rated power is generally going to require a professional level measurement setup. A "clamp test" will do nothing of the sort.

[djtomczak 5]

Why do people do it if it doesn't really show any useful information?

Monkey-see Monkey-Do

Happens a lot in this hobby. I could go on a pretty long rant about all of the useless or senseless things people do in this hobby.

I don't need an exact number I just want a ball park to see if it's putting out what it's claiming.

In all honesty, it doesn't really matter. Even if the amp is over rated by 25% you're not going to hear a difference. As long as you're not running one of those extremely low end amps which rate everything at PMPO or ILS, generally real power output is going to be close enough to rated to not make an audible difference. It's often nice to know just from a manufacturer reputability aspect.....sure, I'll put a little more faith into the general build/design quality and respect for a company if their 500w amp really outputs 500w. But if it only does 400w, you're not going to hear a difference. Unless you are chasing #'s on a meter, it really doesn't make that big of a difference.

But to actually measure the true output of an amplifier to the level of detail and accuracy required to compare it to the manufacturer's rated power is generally going to require a professional level measurement setup. A "clamp test" will do nothing of the sort.

True^

[CrazyKenKid 64]

P.S. this is the guy who talked me out of wasting my time and doing a silly clamp test also! he is good people with a ton of knowledge!

Why do people do it if it doesn't really show any useful information?

Monkey-see Monkey-Do

Happens a lot in this hobby. I could go on a pretty long rant about all of the useless or senseless things people do in this hobby.

I don't need an exact number I just want a ball park to see if it's putting out what it's claiming.

In all honesty, it doesn't really matter. Even if the amp is over rated by 25% you're not going to hear a difference. As long as you're not running one of those extremely low end amps which rate everything at PMPO or ILS, generally real power output is going to be close enough to rated to not make an audible difference. It's often nice to know just from a manufacturer reputability aspect.....sure, I'll put a little more faith into the general build/design quality and respect for a company if their 500w amp really outputs 500w. But if it only does 400w, you're not going to hear a difference. Unless you are chasing #'s on a meter, it really doesn't make that big of a difference.

But to actually measure the true output of an amplifier to the level of detail and accuracy required to compare it to the manufacturer's rated power is generally going to require a professional level measurement setup. A "clamp test" will do nothing of the sort.

[RiottStarr 5]

Volts x amps = WATTS!......

Volts x Amps = Power! you are correct my man!

and yes all on the output side of the amp!

keeping in mind that the output of the amp is directly effected by the input voltage and load conditions! If your amp was rated at 14.4volt dc please try to keep 14.4 volts all test long!

[ssh 924]

Send the amp off to http://www.audiograph.se/