Author Topic: Newbie Q - Head unit Amp then gets 'Amped' again by seperate amp???  (Read 698 times)

Offline Kola

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Hiya,

Sorry if im uneducated in this area.  So, I want to do the audio of my Mk3 golf up.  (Its currently as standard / factory apart from head unit I just installed)

So, I have my new pioneer head unit, it comes with standard amps built in.  I dunno say 4 x 25 RMS

So I know I need a separate amp to get the best sound. So I get a separate quad amp with 4 x 100 RMS.

How can I work out what speakers to get.   If I get speakers that can handle 100w RMS surely my amp is amplifying and already amplified signal.  IE head unit amplifies it to 25 watts then to the separate Amp to give that 25 watts another 100 watts what surely is gonna be way more than just 100w? 
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Offline jv

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No, because you are not sending the head unit power output AND the additional amplifier output to the same speakers.
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Offline dragonfly

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The minimum speaker wattage would be at least the maximum amp wattage i.e you wouldn't have a 25 watt speaker running off a 100 watt per channel amp because as soon as you crank up the sound you will distort the sound.

Offline brettblade

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The minimum speaker wattage would be at least the maximum amp wattage i.e you wouldn't have a 25 watt speaker running off a 100 watt per channel amp because as soon as you crank up the sound you will distort the sound.

Or blow the speaker, neither of which being a good result!

To the OP - your Pioneer HU will likely have RCA pre-outs, these are the red and white plugs on the back of the head unit and you will have the same as an input for your amp.
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Offline Kola

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Hiya fellas.  Sorrry didnt see replis. 

I dont think I have explained my point well. 

So, my hypothetical amplifier amlifies 'zero' too 250 watts RMS.   But even my piddly Pioneer head unit outputs something not Zero. IE 25 watts RMS (I think) 

So now my MP3 gets 25 watts amplification, then that 25 (not zero) gets re-amplified by 250 (from my amp).  Im not sure if that would make the end result 275 watts or what. 



My new GF gives me no problems!  Unlike ALL of the rest!!  She's only 21, black and extremely sexy. Sure she may have a slight drinking problem but nothing is perfect right?   Her name is Vicky (The VR6) Highline and I am madly in love.

Offline jv

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No 're-amplify' occurs. External amp is instead of internal amp.
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Offline Kola

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But doesnt the signal path go....

On a car with no separate amp:-
Head unit - Put a CD in > through internal amplification > Out the connections on the back to car speakers

With amp:-
Head unit - Put a CD in > through internal amplification > Out the connections on the back (IE already amplified by head unit) > into Amp for amplification (So second time as first was in head) >  Speakers
My new GF gives me no problems!  Unlike ALL of the rest!!  She's only 21, black and extremely sexy. Sure she may have a slight drinking problem but nothing is perfect right?   Her name is Vicky (The VR6) Highline and I am madly in love.

Offline Gnasher

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You are correct in your signal path idea, however...

Any external amplifier will only put out a signal at its maximum rating, no matter how big the signal is going into it, so all you'll ever get out of a 100wRMS per channel amplifier is 100wRMS per channel.

What has to happen is that the amplifier sensitivity needs to be adjusted so that the maximum input signal level means that the maximum output is at the right level. There are VERY few amps that don't have this.

If you have this set wrong, you will either be running the amplifier too gently and not getting the best out of it (IE, your 100wRMS per channel amplifier might only be putting out 50wRMS per channel) or if it's adjusted too much the other way, you will overdrive the amplifier, resulting in something known as "clipping" (the waveform will have a flat top and bottom to it) which will eventually destroy speakers, even if they are the correct power rating for the amplifier.

Very important you get this set up correctly.
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