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Amplifier Gains and Preouts

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<!--quoteo(post=465235:date=Jan 8 2009, 07:46 PM:name=95Honda)--><div class='quotetop'>QUOTE (95Honda @ Jan 8 2009, 07:46 PM) <a href="index.php?act=findpost&pid=465235"><{POST_SNAPBACK}></a></div><div class='quotemain'><!--quotec-->The speaker doen't cae if it is a clipped signal or unclipped, power is power and heats up the voicecoil the same. 100 watts of any signal is 100 watts. I have tested this. Thoroughly.<!--QuoteEnd--></div><!--QuoteEEnd-->

this is how i have always had it explained to me, the idea that the speaker "doesn't care" what quality of sound it is producing.

yet, i have heard many say that they can "blow" a 1000 watt speaker with only 100 watts....does this claim have anything to do with a clipped signal or are there other factors involved?

I think it's because a clipped wave is square('d), if it's square the cone stays longer at the upper and lower side of the wave.

Less movement=less cooling.

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Dont use the wattage output that is for the speakes hooked up to it (that 40 is max anyway, so pretty useless). You use the pre-out voltage, most headunits are 2 volts, 4 volts, 5 volts or 8 volts. The voltage signal of the rca outputs.

Ok. I just looked up the h/u and it is a 2V out put. So I just hook up a dmm and make it be 2V. Also what setting do you use on the dmm?

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Ok, so lets take for example the Sundown SAE-1200D. 1200W @ 1ohm and an input sensitivy ranging from .153V to 5.6V. For everything in this post lets assume no clipping of the audio signal from the source unit and say the source unit is putting out 3V from the pre-outs.

What is going to happen if you turn the gain knob "up" (as in toward the .2V) after you have matched the gains of the amp to the sensitivity of your source? I assume it will not put out more power. Will it begin to send the amplifier into clipping?

OK, I wrote this response recently to someone else asking a similar question, but it seemed to fit ehre, so I'm quing to paste what I wrote, then add a few notes to it.

yes the gain (more properly called "input sensitivity") on an amp should match the line voltage of the head unit, in short.

if the input stage (gain) on the amp is set to be too sensitive (high) then the input signal from the radio will over-drive the input stage of the amplifier, and the sine wave signal will be clipped, or cut off at the peaks and troughs of the wave, thereby sending DC voltage to the speaker, which will more quickly heat the voice coil(s), and build heat across teh coils, possibly causing damage from that heat, or from loss of linearity of coil travel within the motor structure.

If the input stage is set to be not sensitive enough, then you lose signal resolution, and you're amplifying a weak signal which means more distortion, and more noise floor (more noise per amount of actual clean signal.) ie, lower S/N ratio.

This next part is hard for me to explain without a dry erase board.

The reason the gain on an amp seems to act like a power or volume control is because you're moving the center-line of your sine wave signal up and down within the dynamic range of what the amplifier can handle as it's predefined input range limits.

It's similar to the way TV commercials are always a lot louder than the television show you're watching. The FCC passed laws against this practice decades ago, but advertisers found a way around that by boosting the recording level of the commercial so everything is compressed into the limitations of the reference range they're allowed.

If you can imagine a graph with an X and Y axis, the X axis is time, and Y is amplitude (volume, or dynamic range) We'll scale the Y axis in this example as 0 to 10, 10 being the highest volume possible for the input signal.

With a normal TV show, the center for the volume is about a 5. This allows someone who whispers to be around a 3, while a gun shot would be maybe an 8. What the TV commercial does, is cram everything into the 9-10 range.

This leaves them no dynamic variance for quiet-to-loud shifts, but it makes everything super loud based on how your TV volume is set for watching the TV programming. Tricky sneaks, huh?

I guess in short you could say setting the gain too low is like whispering so quietly that it's hard to be understood.

Setting it properly is like speaking in a clear, well enunciated voice.

setting the gain too high, is like standing next to someone's ear, and screaming at the top of your lungs.

in the first, the person can't hear you clearly over the ambient noise of the environment.

In the second, you can be heard and understood clearly and concisely.

In the third, oh, you can surely be heard, but it's painful, and clarity is out the window as you now have damaged ears, and this persistent ringing.

Now with that said, I'll answer two questions I saw when glancing at the responses, too.

Regarding the over-EQing of the source material, the OP did state that the source signal would not be clipped. You're also still limited to the line voltage limitations of the source, which in the OP's example is 3 volts. There are physical limits to the sine amplitude that the source can produce. Anything more gets clipped.

This leads me to the second thing. "What's the deal with line voltage? Why is more better?"

Simply put, the higher the line voltage, the lower the noise floor, and the more resolution your source signal will have. Think of your source signal like a JPG image, and your amplifier like PhotoShop. The more you take that JPG (the source signal) and blow it up in PhotoShop (your amplifier) the faster you see how high of a resolution the original JPG (signal) really was.

If your original signal is 500mA, when you amplify it, you only have so much signal resolution to work with. If the source signal was an 8 volt signal (Hello, Eclipse.) then you have a better signal resolution to work with when it's amplified 500 times.

I hope that helped some.

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ok so let me get this straight when I set my gains on my front stage I need to have bass and treble at zero. And as far as the equalizer i need to have the low,mid,high all at zero as well. So when I need to adjust the music I shouldnt be raising the equalizer higher than +2 otherwise ill clip the signal?

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I dont know man. I tried getting the proper voltage from the speaker wire terminals and i still cant get a reading. But whenever I put the dmm on the power and ground wire i get a voltage automatically.

Also funny thing I tried today. at first i had the eq on flat and bass and treble at zero with the gain knob turned up 1/4. Music sounded good but i like to hear my highs alot in my music. So I turned down the gain to the minimum and turned my treble all the way up and my music still plays pretty loud without distortion at around 52 and 53(Pioneer deck).

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what about phase? what is that?

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Also funny thing I tried today. at first i had the eq on flat and bass and treble at zero with the gain knob turned up 1/4. Music sounded good but i like to hear my highs alot in my music. So I turned down the gain to the minimum and turned my treble all the way up and my music still plays pretty loud without distortion at around 52 and 53(Pioneer deck).

All you did was prove you can't hear distortion. Either way you REALLY shouldn't use your eq for boost, just cut. The purpose of it is to fix anomalies and 99% of the time that means cutting them out.

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.

I tried getting the proper voltage from the speaker wire terminals and i still cant get a reading. But whenever I put the dmm on the power and ground wire i get a voltage automatically.

Wutang512 - I would guess the reason for this is the way you have the DMM set or try using a test tone for a frequency that you know is being sent to the speaker. That way you have a constant voltage to measure at the speaker terminal (output of amplifier).

The power/ground wires are a DC voltage (input, think battery) and the speaker wire terminals are AC voltage (output, think house wall outlet).

Try it again, see if that makes a difference.

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how doest he source/head unit send a clipped signal, or how do you prevent it from sending a clipped signal

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Simply put, the higher the line voltage, the lower the noise floor, and the more resolution your source signal will have. Think of your source signal like a JPG image, and your amplifier like PhotoShop. The more you take that JPG (the source signal) and blow it up in PhotoShop (your amplifier) the faster you see how high of a resolution the original JPG (signal) really was.

If your original signal is 500mA, when you amplify it, you only have so much signal resolution to work with. If the source signal was an 8 volt signal (Hello, Eclipse.) then you have a better signal resolution to work with when it's amplified 500 times.

In the case of an analog signal, the resolution is technically infinite regardless of voltage. In the case of a digital signal resolution is determined by the bit rate of the source again regardless of the voltage.

Where voltage can make a difference is in signal to noise. Even the best signal wires will have some thermal noise. This is basically caused by electrons moving naturally within the atoms of the wire. This noise voltage is not in any way related to the signal. The signal must compete with this noise though. A higher signal voltage will allow the amp gain to be kept low which minimizes the amount that the noise is amplified. That is the only benefit of higher preamp voltage.

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<!--quoteo(post=465235:date=Jan 8 2009, 07:46 PM:name=95Honda)--><div class='quotetop'>QUOTE (95Honda @ Jan 8 2009, 07:46 PM) <a href="index.php?act=findpost&pid=465235"><{POST_SNAPBACK}></a></div><div class='quotemain'><!--quotec-->The speaker doen't cae if it is a clipped signal or unclipped, power is power and heats up the voicecoil the same. 100 watts of any signal is 100 watts. I have tested this. Thoroughly.<!--QuoteEnd--></div><!--QuoteEEnd-->

this is how i have always had it explained to me, the idea that the speaker "doesn't care" what quality of sound it is producing.

yet, i have heard many say that they can "blow" a 1000 watt speaker with only 100 watts....does this claim have anything to do with a clipped signal or are there other factors involved?

I think it's because a clipped wave is square('d), if it's square the cone stays longer at the upper and lower side of the wave.

Less movement=less cooling.

The wave form output of the amp is not an accurate depiction of cone position. As long as voltage is being applied to the coil, the cone is trying to move away from center. The only reasons that it will stop is if the voltage is insufficient to overcome the centering force of the spider and surround or the driver hits an actual mechanical limit. Barring either of those happening, the cone continues to move outward during the clipped portion of the signal.

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So let me get this straight, clipped signal and unclipped signal wont do harm to speaker, its the overpowering that does? And preout voltages, they really wont change the sound that much if you have your proper settings? For example, I have a headunit with a preout thats 4volts, the only difference this one has to a headunit with a preout @ 2volts is gains are more down than the 2v? Is it worth it to spend the extra money on a headunit with preouts that's 4v compared to 2v?

I apologize if my statements sound ignorant, its the best I got lol.

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So let me get this straight, clipped signal and unclipped signal wont do harm to speaker, its the overpowering that does? And preout voltages, they really wont change the sound that much if you have your proper settings? For example, I have a headunit with a preout thats 4volts, the only difference this one has to a headunit with a preout @ 2volts is gains are more down than the 2v? Is it worth it to spend the extra money on a headunit with preouts that's 4v compared to 2v?

I apologize if my statements sound ignorant, its the best I got lol.

You answered your own question.

Q: Is it worth it to spend the extra money on a headunit with preouts that's 4v compared to 2v?

A: And preout voltages, they really wont change the sound that much if you have your proper settings?

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So let me get this straight, clipped signal and unclipped signal wont do harm to speaker, its the overpowering that does? And preout voltages, they really wont change the sound that much if you have your proper settings? For example, I have a headunit with a preout thats 4volts, the only difference this one has to a headunit with a preout @ 2volts is gains are more down than the 2v? Is it worth it to spend the extra money on a headunit with preouts that's 4v compared to 2v?

I apologize if my statements sound ignorant, its the best I got lol.

You answered your own question.

Q: Is it worth it to spend the extra money on a headunit with preouts that's 4v compared to 2v?

A: And preout voltages, they really wont change the sound that much if you have your proper settings?

oh, cool thanks! i felt like i knew what i was saying i just needed some verification lol.

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I'm trying to figure this out to. The only way to set my gain at 2volts (which is what my hu is) is to have the volume at 21/35 and the gain just a c-word hair up. Only problem is that its not loud. A bc2k on 2 sa12s is plenty. So how do I get it loud then?

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Stop trying to use the dmm method and do it by ear.

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Ok, so when I set it by ear do I still use 75‰ volume? And a 0db tone, 40-50hz. I have a 2k amp, and tho the SAs are little beasts there still 600rms. I do have a clip light but still. Trying to get loud n not blow anything up

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Clip light isn't something I'd use either.

NONE of the settings you describe make sense for where to set the gains. You have enough amp to melt your drivers so you get to pick if you turn the gain down so you can't or you use the volume knob for that. Can't pick a gain until you decide.

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Well the clip light came with the bc2k. But Ok, I'm just trying to figure out which of the 2 is betr to go with. And the correct process of setting it to the HU pre out if that's the way. I appreciate everyone's input but most people say one or the other but won't get detailed

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Well the clip light came with the bc2k. But Ok, I'm just trying to figure out which of the 2 is betr to go with. And the correct process of setting it to the HU pre out if that's the way. I appreciate everyone's input but most people say one or the other but won't get detailed

Get somebody thats done it before so you can learn.

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Well the clip light came with the bc2k. But Ok, I'm just trying to figure out which of the 2 is betr to go with. And the correct process of setting it to the HU pre out if that's the way. I appreciate everyone's input but most people say one or the other but won't get detailed

Get somebody thats done it before so you can learn.

well that's what I'm trying to do. There's 2 shops around me that don't know shit. They don't even carry 0g wire. There garbage, so I figured here would be a great option

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Well the clip light came with the bc2k. But Ok, I'm just trying to figure out which of the 2 is betr to go with. And the correct process of setting it to the HU pre out if that's the way. I appreciate everyone's input but most people say one or the other but won't get detailed

Get somebody thats done it before so you can learn.

well that's what I'm trying to do. There's 2 shops around me that don't know shit. They don't even carry 0g wire. There garbage, so I figured here would be a great option

It is but I cant teach you over the computer. There are better people who could tell you how.

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