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How to Set Your Gains


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jomin1016 
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Posted: August 11, 2011 at 10:10 PM / IP Logged Link to Post Post Reply Quote jomin1016
What about this method? setting gains with dmm
boulderguy 
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Posted: October 12, 2011 at 11:31 PM / IP Logged Link to Post Post Reply Quote boulderguy
^^ That's a great calculator, I've used it before. Nothing wrong with setting your gains that way using a DMM. Keep in mind the weak link is knowing the amp's ACTUAL power.
Quality equipment often comes with a birthsheet telling you actual test results - great, you're all set. This is maybe 1 out of 25 amps sold on the market today (guessing, it's probably much fewer).
Without that info it's easy to believe your $120 Sony/Crunch/Pyramid etc amp's claim stenciled on the front saying "2000 WATTS!"...So you set the gains to 63.2v...and your new hexagonal plastic subs with a magnet like a vault door erupt into flames...
Take-home message: Setting gains to a voltage with a DMM is great if you have RELIABLE power output specs.
DYohn 
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Posted: May 14, 2012 at 10:16 AM / IP Logged Link to Post Post Reply Quote DYohn

boulderguy wrote:
^^ That's a great calculator, I've used it before. Nothing wrong with setting your gains that way using a DMM. Keep in mind the weak link is knowing the amp's ACTUAL power.
Quality equipment often comes with a birthsheet telling you actual test results - great, you're all set. This is maybe 1 out of 25 amps sold on the market today (guessing, it's probably much fewer).
Without that info it's easy to believe your $120 Sony/Crunch/Pyramid etc amp's claim stenciled on the front saying "2000 WATTS!"...So you set the gains to 63.2v...and your new hexagonal plastic subs with a magnet like a vault door erupt into flames...
Take-home message: Setting gains to a voltage with a DMM is great if you have RELIABLE power output specs.
.

... or an oscilloscope so you can see the onset of clipping.

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troy14 
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Posted: May 30, 2012 at 9:30 AM / IP Logged Link to Post Post Reply Quote troy14
There's one issue that I have with these methods, and by no means am I implying that they are incorrect, but its the same problem I have with the SMD device that has gained so much popularity, even being overpriced.
Anyway, the issue I have is that none of these methods are comparing the input and output stages. The amplifiers job is simple, take input signal A and increase its amplitude. If A in equals A out (at a higher voltage) then the signal is clean. If there are artifacts, it's distorted. (Quite possibly the simplest definition of distortion.)
I've seen people measure with an o-scope and just turn knobs until they get a square wave, but I still maintain that you must compare the input and output signals to determine if there is clipping.
That brings us back to another post about the Audio Control Spectrum analyzer... The key benefit to this (or like products) is that it's generating it's own output (the input signal) and comparing it to the system's output. All things being equally accurate, this is the best way to get the desired result. If you want to get the most out of your amplifier, then find a nice pre-amp that will make the work of your amplifier and give it all the headroom that it could possibly have.
jason111 
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Posted: May 30, 2012 at 4:35 PM / IP Logged Link to Post Post Reply Quote jason111
I have used this method several times
http://www.youtube.com/watch?v=suX13VixU5k
DYohn 
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Posted: May 31, 2012 at 9:24 AM / IP Logged Link to Post Post Reply Quote DYohn

troy14 wrote:
Anyway, the issue I have is that none of these methods are comparing the input and output stages. The amplifiers job is simple, take input signal A and increase its amplitude. If A in equals A out (at a higher voltage) then the signal is clean. If there are artifacts, it's distorted. (Quite possibly the simplest definition of distortion.)
I've seen people measure with an o-scope and just turn knobs until they get a square wave, but I still maintain that you must compare the input and output signals to determine if there is clipping.
.

The typical "by ear" method we promote most often is intended that you first determine the max unclipped input signal then set the output to the max unclipped level.  Since we are not designing circuitry, this is close enough for normal safe operation of any car audio setup.

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androidcaraud 
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Posted: December 27, 2013 at 9:32 AM / IP Logged Link to Post Post Reply Quote androidcaraud
Thank you for sharing the useful tips. Its very valuable info.
jetfuel08 
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Posted: January 23, 2016 at 9:08 PM / IP Logged Link to Post Post Reply Quote jetfuel08
So when “clipping” is happing are is it because the sub doesn’t have ability to move that much? or that the amp can’t put out the power to make it do so?. I am asking because I have clipping on some songs. I’m not completely incompetent when It comes to this Amp stuff. I know not to have my gains all the way up. Could the box that I have be a factor in the way the Amp, and the subs perform? The box I have is a “PreFab” I have been told that Prefabs are Tuned high so is that another reason that I could be having this problem?
Cody Robinson
geepherder 
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Posted: January 24, 2016 at 8:48 AM / IP Logged Link to Post Post Reply Quote geepherder
Clipping is when the amp can't produce enough voltage, so the peaks of the AC are "clipped" off.
On an oscilloscope, this looks more like a sine wave and a square wave got together for some "sweet love making".
This will sound similar to a sub overexerting itself, but that is distortion, not clipping.
If you have access to an o-scope, you can see if it is indeed clipping or if you're overdriving your sub.
My ex once told me I have a perfect face for radio.
boulderguy 
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Posted: January 24, 2016 at 9:38 AM / IP Logged Link to Post Post Reply Quote boulderguy
geepherder wrote:
On an oscilloscope, this looks more like a sine wave and a square wave got together for some "sweet love making".
^^^ HAHahahahahah, sweet love makin', nice ;)
There are a whole mess of reasons that distortion occurs at higher levels. If you think your levels are correct (you can always double-check with the DMM-voltage method), the next place I'd look is how well the box & sub are matched.
For example, if you're using a ported enclosure, is it tuned to the right freq for the sub? If sealed, is it solid enough to produce high SPL without resonating? Lots of threads about this stuff out there.
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