Benchtesting Amps

[KRD 10+ year member]

I want to learn how to do this. What equipment do I need. I have a DMM. What else? Thanks.

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[danteBirosel 5,000+ posts]

I suggest just using a DMM and a digital clamp meter. Benchtesting is a more critical test.

 

[Prowler573 5,000+ posts]

For starters you'll need a high amperage 12v power source (a car battery with a charger attached to it is a technically usable but not particularly advisable method of accomplishing this) which can prove somewhat pricey.

 

[squeak9798 5,000+ posts]

You'll atleast need an O-scope aswell, if you want to do it properly.

Otherwise you'll just be measuring the output without regard to distortion.

 

[danteBirosel 5,000+ posts]

^^ oooh forgot about that one. O-scope is a must!

 

[JimJ 5,000+ posts]

Having an oscilloscope helps too //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

Otherwise, you really don't know if you're under the clipping threshold or not.

 

[JimJ 5,000+ posts]

Edit - I hate you all.

//content.invisioncic.com/y282845/emoticons/tongue.gif.6130eb82179565f6db8d26d6001dcd24.gif

 

[netherland24 5,000+ posts]

and can bench an amp by sticking ur tumb on the top dead center, and then u have to get a themometer and check how hot it is, and then divide that # by 2/ then add about 3-4 0's too it depending on if it is a A/B or Mono amp.... that should get ya going

 

[KRD 10+ year member]

http://www.partsexpress.com/pe/pshowdetl.cfm?&DID=7&Partnumber=120-548

i have this power supply. I have a DMM and clamp meter.

 

[Phreaker 10+ year member]

http://www.partsexpress.com/pe/pshowdetl.cfm?&DID=7&Partnumber=120-548
i have this power supply. I have a DMM and clamp meter.

What do you want to do,bench the amp to see what it's putting out at a given impedence at 14.4v (car on) or at 12.5v (car off acc. on)?

If you want to find what the amp is pushing at say 1 ohm with a 14.4v power supply then just hook up the DMM and the Clamp meter.

I saw a thread the other day that explained how to use the DMM and Clamp meter.

I think you use the clamp meter on your amps power wire where it connects to the amp and it reads the Current or amperes.

I believe you set the DMM to AC volts.

If your subs are wired to your amp at 1 ohm cool but remember impedence rise from box so what you measure may not be a true 1 ohm impedence.

Take the reading from the calmp meter and the DMM at the same time.

Multiply the amperes by the volts

example 40v x 100amperes = 4000w

Do the same thing to find the amps output with 12.5 volts power supply by turning the car off and only having the ACC. on.

Remember also to have your HU's volume up to it's max unclipped volume when taking the readings.

The real way is to have a 14.4v power supply and a resistor something or other that is able to handle a certain amount of power at said ohm/impedence/resistance but GL finding or affording those.

Real bench is done with the o-scope aswell to know the threshold of clipping.

Here is some info I found on Benchtesting....

Well, the easiest thing to do is ...
Test tone

Multi-meter or voltmeter that reads AC voltage

Resistor in desired resistance (If you want to test @ 1 ohm, you need a 1 ohm resistor) that can handle the power.

Test the AC voltage at the resistor (i.e. 40 volts)

Plug it into Ohm's Law (Power = Voltage squared divided by resistance)

Power = 40*40/1

Power = 1600 watts

If you don't have access to resistors, you can use your subwoofer, but it's usually not quite as accurate, especially if the test tone you choose just happens to be at a very large impedance peak ...

Also I found this with 2 minutes of searching the web...Dummy Load 33 ohm 500 watt power resistor.

It says you can parallel four of them to make an 8 ohm 2000 watt audio amp load (actually 8.25 ohms).

They sell for about $15 shipped each....http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=270021303748&category=4664

 

[JimJ 5,000+ posts]

Impedance rise can be calculated with the clamp meter readings //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[Death By Bass 10+ year member]

well, that 22amp powersupply will be good for about 200watts of amplifier output power... //content.invisioncic.com/y282845/emoticons/tongue.gif.6130eb82179565f6db8d26d6001dcd24.gif

 

[Phreaker 10+ year member]

Impedance rise can be calculated with the clamp meter readings //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

Really...sweet,how do you do that?