tuning my amp?

Hi all. Can you guys help me out to tune my amp?
My amp manual says RMS Power@14.4V, into 2Ohm = 800w so square root formula doesn't mach the car amp manual. If I calculate with the square root I need 40.00V which is three times greater than stated in the manual. Does this formula apply to every amp or is it something I don't understand? Can I apply this square formula rule to calculate other amps or follow manual instructions only? Not every amp provides these settings. Please help! :( Thanks!

Read the "How to set your gain" thread in the Hot Topics section.

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voltage on the input gain does not equal power out. they are independent of each other.

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This post was originally in " How to set your Gains"... Pretty sure he is lost...

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M.E.C.P & First-Class
Go slow and drink lots of water...Procrastinators' Unite...Tomorrow!

mantasuk wrote:

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... RMS Power@14.4V into 2Ohm = 800w ... I need 40V which is three times greater than stated in the manual.

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That is correct.

The amp has an internal SMPS that converts the input DC voltage to the voltage required for 800W into 2 Ohms.
The power formula is correct. An SMPS is required for amps over ~200W into 1 Ohm, 100W into 2 Ohms, etc.


Oddly enough this same question (with different values) was asked years ago on this forum yet nobody gave that answer. Poor guy, he never returned - though he may have read my PM that explained it to him.


One interesting question - if an amp has an SMPS, why does it have to be 14.4V for max power since the input voltage shouldn't matter - ie, 12V - 14.4V should be capable of max power output.
And if you read the specs on some high output amps, the output increases squarely with the input voltage as if the amp is a resistive load - which it can't be since it has an SMPS...

tommy... wrote:

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This post was originally in " How to set your Gains"... Pretty sure he is lost...

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OK, well my advise to the poster, if the info in that thread is too difficult, is to take the system to a local installer and pay them to do it for you. :)

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DYohn] wrote:

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tommy... wrote:

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This post was originally in " How to set your Gains"... Pretty sure he is lost...

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OK, well my advise to the poster, if the info in that thread is too difficult, is to take the system to a local installer and pay them to do it for you. :)

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That's a big 10-4...

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M.E.C.P & First-Class
Go slow and drink lots of water...Procrastinators' Unite...Tomorrow!

I can't see anything in How to set your Gains that answers the OP's question. There is mention 30V etc, but not how that relates to 14.4V.

It is a simple question with a simple answer. Soundnsecurity touched on it.

What's the big deal?
wth has this got to do with setting gains?
Why send the OP to an installer to get an answer to his question?
And why insult the OP?

oldspark wrote:

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I can't see anything in How to set your Gains that answers the OP's question. There is mention 30V etc, but not how that relates to 14.4V.

It is a simple question with a simple answer. Soundnsecurity touched on it.

What's the big deal?
wth has this got to do with setting gains?
Why send the OP to an installer to get an answer to his question?
And why insult the OP?

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The OP's question is about setting gains.

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Though it may relate to setting gains, I saw the OP's question(s) as being in relation to Power@14.4V into 2Ohm = 800w & the 40V required, namely:
Does this formula apply to every amp...?
Can I apply this square formula rule to calculate other amps...?

IMO the answer is simple. YES.

It's a case where someone has added a bit of their own analysis and found a contradiction. A case of a little bit of knowledge.... But so what? The same often occurs on the12volt, and not just by the OPs and noobs!   


As to the 12V or 14.4V versus 40V output etc versus its impact on setting gains, fine, the other thread addresses that.

But why not solve the OP's dilemma with an appropriate reply first?

I do recall in that earlier thread I referred it seemed no one could answer that. That was back in my early days on the12volt and it did somewhat trouble me at the time.   
Simply pointing out that the output was 40V or similar and NOT the 14.4V input would have saved the plethora of irrelevant replies.
(Maybe that was one week before soundnsecurity came on line LOL!)

The 40V is the measured output to achieve 800W into 2-ohms. This concerns gain setting and has nothing to do with the amplifier's power supply.

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So how do you explain to the OP how he gets 800W into 2 Ohms at 14.4V?

It sounds to me as if you are saying he just tweaks some magical gain setting that "amplifies" the 14V etc to 40V.


soundnsecurity IMO gave the correct answer with "voltage on the input gain does not equal power out. they are independent of each other" which admittedly I interpreted as "voltage of the amp (or on the input) is independent of its output voltage".

I merely added how the amp achieves the voltage required for such output. IE - that amp has an internal 40V DC bus/supply.


IMO there is nothing complicated about it. 12V high output amps have SMPS aka dc-dc converters to create a fixed higher voltage supply.
The "amplifier" section with its gains are independent of that and do their usual volume and gain stuff.

i think the OP was a bit too vague. i assumed he was talking about rca voltage, which is why i wrote "voltage on the input gain" which is what i thought the OP meant because he is talking about tuning an amp. i thought maybe he thought that he needed a certain amount of voltage at the low level RCA input to get a certain amount of power out, possibly a misplaced variable while trying to work out a formula. my answer might be sort of right but it was for the wrong reason

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I'm not aware that RCAs had 14.4V....


Like I said, I thought the OP's question was clear - a straight question about Ohm's Law etc.

But IMO no point continuing (meaning it's not my call that I answered his OP in part or otherwise).
I'll reply if mantasuk requires.

RCA's dont have 14.4v under normal conditions. they do make high voltage line drivers though.

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And how do those high voltage line drivers produce the 800W @ 2R, or how should the OP use them for to adjust his gains?


Incidentally, I suspect the OP has left the building.

oldspark wrote:

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And how do those high voltage line drivers produce the 800W @ 2R, or how should the OP use them for to adjust his gains?

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they dont... people use them with the belief that they increase the power the amp puts out because it basically makes the audio louder at a lower volume but usually wont increase the final maximum volume, unless you count the extra distortion they can create.

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You miss my point - I know that!

Paraphrased - the input voltage (whether RCA voltage or the DC supply) is irrelevant to the unit's output.   

Feel free to answer the OP's question about setting gains etc though IMO that has already been answered.

I have merely stated how a 12V device pumps 800W into a 2 Ohm load.

End of story.