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Old Sep 7, 2010 | 06:50 PM
  #51  
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From BCAE1

Note:
The RMS voltage of a pure sine wave is equal to the peak voltage multiplied by 0.707. The RMS voltage of a pure square wave is equal to the peak voltage. For 2 waveforms with equal amplitude (as shown above), the RMS voltage of the square wave is 1.414 times the voltage of the sine wave. If we use the example of the 100 watt amp which can produce a sine wave of 20 volts RMS, we can see that the output power at hard clipping is double the power it can produce cleanly.

Clean Signal Calculations:
P = E^2/R
P = 20^2/4 (4 ohm speaker)
P = 400/4
P = 100 watts RMS

Square Wave Signal Calculations:
P = E^2/R
P = 28.28^2/4 (the RMS voltage is 1.414 times the RMS voltage of the sine wave)
P = 800/4
P = 200 watts RMS
Old Sep 7, 2010 | 06:55 PM
  #52  
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Originally Posted by AAAAAAA
From BCAE1

Note:
The RMS voltage of a pure sine wave is equal to the peak voltage multiplied by 0.707. The RMS voltage of a pure square wave is equal to the peak voltage. For 2 waveforms with equal amplitude (as shown above), the RMS voltage of the square wave is 1.414 times the voltage of the sine wave. If we use the example of the 100 watt amp which can produce a sine wave of 20 volts RMS, we can see that the output power at hard clipping is double the power it can produce cleanly.

Clean Signal Calculations:
P = E^2/R
P = 20^2/4 (4 ohm speaker)
P = 400/4
P = 100 watts RMS

Square Wave Signal Calculations:
P = E^2/R
P = 28.28^2/4 (the RMS voltage is 1.414 times the RMS voltage of the sine wave)
P = 800/4
P = 200 watts RMS
Game, set, match. Thanks
Old Sep 8, 2010 | 10:26 PM
  #53  
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Wow, there was some terrible info at the beginning of this thread but it eventually turned around. I once started a thread on here to discuss the issue of clipping damaging speakers. I was a bit drunk and was mostly baiting a hook but it turned into an interesting thread. To me anyway, I'm a total nerd.

Goalie: Your comment on clipping and distortion ruining speakers makes no sense to me, but your arguments as to the spectral content of a square wave were great!
Old Sep 8, 2010 | 11:01 PM
  #54  
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Thanks for the insight. However I have two settings to play with- the bass eq on the HU.. Which is currently turned down to -15 (range is -18-+6) and the gain on the amp is 3/4 right now... I like that setting but I never use the bass eq above -12... So my question was regarding the current setting or would it be better to set the amp gain to 1/2 let's say and the deck to -4 or so... I'm not sure if I'm explaining it right lol Or it just doesn't matter since you mention that the gain does not control the output of the amp just the input amplitude (I assume??)?? So the jl has an input sensitivity as well (high and low volt- I assume this is for the variance in voltage output of HU), so should I treat the amp gain as a "fine" **** of the sensitivity? I thought gain was somewhat equivalent of a negative feedback portion of a simple amplifier circuit.... Which controls the actual ammount of amplification- therefore the lower (optimum) gain setting the best quality will be produced- slew rate related... But the the frequency of the signal is not high so it shouldn't (theoretically) matter - would it?

Originally Posted by veeman
The gain on an amp is not there for output...if you turn your gain down, you'll notice that you have to turn your volume control up to reach the same output level. The gain is there to match your head unit's output level to the amps input for maximum signal to noise ratio. Remember many head units have different pre amp signal level...1volt, 2 volt, 4 volt 5 volt 8 volt etc... The amp just allows you to adjust the input gain to better match the head unit. As long as your head unit has sufficient output level (at least 1-2 volts typically), you will get maximum power from your amp...you'll just have to use your entire volume control range to get there and the amp's gains will be near maximum. Let's say you have a deck with 4volt outputs, and you max the gains as in the previous example...what you'll get is max power from your amp, but at maybe 1/2 your volume control range...if you keep turning it up..you'll clip the amp. Most people fall for the high gain setting because they think that their amp is louder due to the output at a lower volume...but that's just not the case. Set your gains properly and you'll have years of good clean music and won't have to worry about damaging your equipment.

Last edited by LaZyLuke; Sep 8, 2010 at 11:08 PM.
Old Sep 8, 2010 | 11:42 PM
  #55  
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Yeah, but if you max out your decks volume, and then turn up the gains, it gets louder. Hence, it's like a damn volume control. Argue away.
Old Sep 8, 2010 | 11:46 PM
  #56  
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here i borrowed this from DUKK in previous thread about gain settings, it's one of the best and easiest I've seen and works great:

"Buy, borrow, beg, steal, or download a 1000hz tone. Turn your amp gain down, put in the CD and turn up the CD player until the tone goes "flat". Trust me, you'll hear it. Turn the deck back down to where the tone sounds normal. Turn up the amp gain until the tone again goes 'flat', back it off until it sounds normal.

Done. You have now set your amp gain to where it audibly clips at the same time the deck does. Do this process fairly quickly though as the mids can heat up a fair bit when you ramp up the power."

for further reading go to BCAE, scroll to #63 on right side:

Basic Car Audio Electronics
Old Sep 8, 2010 | 11:58 PM
  #57  
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Couldn't you:

Gain down
Deck volume up
Gain up until it's clippy
Old Sep 9, 2010 | 12:17 AM
  #58  
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yeah, but that technique is much more precise and doesn't rely on poor human hearing to decide when it's clipping...with the 1000hz signal it's pretty obvious when it's clipped...even a 16 year old can tell when it's flat (and we all know 16 year olds can't tell distortion from clean sound as they love to crank things till they blow).
Old Sep 9, 2010 | 12:25 AM
  #59  
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Originally Posted by veeman
yeah, but that technique is much more precise and doesn't rely on poor human hearing to decide when it's clipping...with the 1000hz signal it's pretty obvious when it's clipped...even a 16 year old can tell when it's flat (and we all know 16 year olds can't tell distortion from clean sound as they love to crank things till they blow).
That has to be a mental age you are talking about because I know few individuals that are in late twenties (one in his 50's) that fit mentioned above profile quite well- they often rely on their sense of smell instead...
Old Sep 9, 2010 | 06:17 AM
  #60  
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Originally Posted by kevmurray
Wow, there was some terrible info at the beginning of this thread but it eventually turned around. I once started a thread on here to discuss the issue of clipping damaging speakers. I was a bit drunk and was mostly baiting a hook but it turned into an interesting thread. To me anyway, I'm a total nerd.

Goalie: Your comment on clipping and distortion ruining speakers makes no sense to me, but your arguments as to the spectral content of a square wave were great!
I keep meaning to contact you to find out what I need to turn my laptop into a o-scope.. think all I need is a "step down" something hehe



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