Setting up an amp.

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Drock
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Setting up an amp.

Post by Drock »

Question for you guys,

my subs are 1600 rms, so if I add 6 subs that comes to 9200 watts total.

So that should be what I could safely play all day long right ?.

I clamped my amp last night and I'm set at 65v or .25gain.
For a total power of only 3200 rms from the amp at 25%.

So if I turn my amp gain up should I put it at the max rms of subs total load, 9200rms?

Right now it seems like the subs are working fairly hard but with the measurements I've done I'm only putting 30% of rated power to the subs.

Hope this makes sense.



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Weaklink
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Re: Setting up an amp.

Post by Weaklink »

Well if I remember right volts don't equal watts. It's something like voltsxcurrent/impedance=watts. So it depends on your dc voltage and your impedance load to get watts. I might be wrong on the formula though. Amp efficiency comes into play as well I think. But in an ideal world your math would work. I would hook it all up and set the gains by ear. An oscilloscope would help to make sure your not running a clipped signal.
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trickyricky
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Re: Setting up an amp.

Post by trickyricky »

If your looking for around 9000watts and your battery is steady at 14v with your amp's efficiency of 80% (if its a class D, if its AB then use 60%).

So you divide 9000 by 14 and you'll get your current of 643 amperes if the amp was 100% efficient since it isn't then we can start with 800 amperes. 800x14x0.80=8960watts . Now one way to set this accurately would be by monitoring the following: output signal (make sure it's not clipping), B+ current, B+ voltage. You'll require a sine wave in order to get accurate numbers....this is where it becomes a problem (how can you or anyone handle 9kwatts of sine wave?).

Not only is it dangerous but your putting your whole system at risk when doing this. May be someone else knows how.


I do know that you cannot measure output power simply by where the "gain" knob is set. Where did you get the 65v and .25gain number from, do you have a 1.3ohm load..is that how you came up with 3200watts? If so then your amp would need at least 160v +/- rails in order to produce 9300watts.


I've own 1200watt rms subs (cerwin strokers 1st gen) and I never had to give them more than 600watts (per sub) in order to get the output I was impressed with (not to mention I didn't have the power/electrical to give them more). My suggestion is give them 50% of RMS and see how that goes....
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Drock
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Re: Setting up an amp.

Post by Drock »

Ok. I think there might be a little confusion on my part.

So I'll try to explain better.
I am simply trying to clamp test the amp to see what it is actually producing for power in my vehicle

My amp is "the one".
I have dual 250amp alts under the hood. And 6 optima yellow top batts. Two under the hood and four in the cab under the enclosure.
Subs are 6 elite12d4's. Subs are rated 1600 rms each.

1600 x 6 = 9600 watts of power needed to push all subs.

Subs are wired to 1.33 ohms.

So if my goal is 9600 watts at 1.33 ohms. That tells me to set my gain at 112v.

But here's where I'm stuck,
I have set the gain at 112v, but when I clamped the amp I get 112v but only 32 amps.
So 3584watts.

Now to get that 112v my gain is pretty much maxed.

The difference between the first clamp test i did went from 3200 watts - 3584 watts
My volts went from 65v up to 112v but amps stayed the same at 32amps.

So basically it did not get any louder.

I must be doing something wrong here. The most I'm reading out of my amp so far is 3584 watts.
I expected to see at least 8k on this amp.
My box rise was 3.3ohm's

I am using a true rms dmm clamp meter and a 36hz tone.

I am stumped as to why I'm only seeing 3584 watts.
My measurements must be wrong somehow.


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trickyricky
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Re: Setting up an amp.

Post by trickyricky »

Sounds right according to the box rise of 3.3 ohms. Have you tried a didn't fhz such as 60hz?

Also have you measured the B+ side at the same time of the test to check out the amps efficiency?

112 x 112 / 3.3= 3800watts

If your amp is 80% efficient and your battery is 14v

3800 / .80 / 14 = 340amps B+ @14v

Are your amps pulling 340amps when doing the test? If not then how much (this will help determine approx how many watts your amp is putting out).
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Weaklink
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Re: Setting up an amp.

Post by Weaklink »

Are you using a halo type clamp meter? If so they only read amps (Ac or dc depending on the setting). They don't read volts, to do that you need a second ddm with the leads on the wires. This might be the source of confusion.
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Drock
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Re: Setting up an amp.

Post by Drock »

I used two dmm. Both can do AC or DC .

Do you mean measure the amps going into the amp?
Hard to do on this amp as it has three sets of power terminals. Or I guess the would all be the same.
Either way I should be getting a lot more power I think.

I'm going to try again tomorrow.


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ttocs
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Re: Setting up an amp.

Post by ttocs »

a volt meter used to tune your stereo is just not the right tool. Yes it can work but you can do wood carving with a flat head screw driver but you will never see a real artist use one for anything precise. Honestly if you don't have a o-scope, trust your ears and do spends some time listening/tweeking it and you will be 100x happier then all these calculations that really do not work all that well.
what else can I say I am a grumpy asshole most of the time.
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Drock
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Re: Setting up an amp.

Post by Drock »

Actually the calculations work very well.
And at the moment it's not tuning that's the goal.
The goal is knowing what power an amp does in a particular system / vehicle. The same amp in different vehicles will not necessarily do the same power. There are many factors that can effect output.
My ears will not tell me how many watts that so called 1200 watt amp is actually producing,
Nor can it tell me what my box rise is, every enclosure will be different. And these are factors/tools I need to help make my amp as efficient as it can be.
I know Scott that you have a 100x more experience than I.
But I'm more interested in the math and theory behind how things work than I an about actually just listening to music by ear.
Everything has it's place.
Oscope is on my wish list. Hopefully soon.
And the point of my original post is a problem I'm currently having with an amp I'm just not getting enough power to.


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