radio pre out and amp gain help

[ccapital83 10+ year member]

My radio is 5v pre out and volume level goes to 60 so on my amp where should gain be set to I figured set radio volume to 30 and gain on amp to 50 percent which would be 5v

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[UnderFire 10+ year member]

Get a Digital Multimeter and do it right, there is no way to guess where it needs to be.

 

[neo_styles 10+ year member]

^^this

 

[ccapital83 10+ year member]

like this?

http://www.youtube.com/watch?v=suX13VixU5k

 

[keep_hope_alive Premium Member]

there is a sticky on the subject of amp gain setting with a DMM.

or, just set the amp input sensitivity to the 5V mark. if you are happy with the volume level, no need to change it.

if you decide you want more overall output, then you follow the gain setting tutorial and try to eeek out as much power as possible.

 

[ccapital83 10+ year member]

ok thankyou //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[calebkhill 10+ year member]

there is a sticky on the subject of amp gain setting with a DMM.
or, just set the amp input sensitivity to the 5V mark. if you are happy with the volume level, no need to change it.

if you decide you want more overall output, then you follow the gain setting tutorial and try to eeek out as much power as possible.

Isn't there a chance he couldrun into clipping

 

[keep_hope_alive Premium Member]

Isn't there a chance he couldrun into clipping

nope. that is why input sensitivity is in volts and what it's for. you tell the amp what the strongest signal it can achieve is. if he sets the input sensitivity to 5V and his headunit is rated for 5V (rated output is rarely achieved, if ever) then he cannot clip the amp due to head unit volume. using a DMM is a way to possibly achieve rated power at lower volume settings - handy if the head unit powers speakers and only goes to 50%. you could assume voltage increase is linear and use a HU volume of 50% and an input sensitivity of 2.5V.

there is always a chance you will hear clipping in the recording:

http://www.caraudio.com/forums/wiring-electrical-installation-help/566733-question-about-setting-gains-dmm-3.html#post8311320

 

[calebkhill 10+ year member]

Got ya. Hu volume isn't linear though is it, or is it.

 

[keep_hope_alive Premium Member]

Voltage is linear. Power is non-linear since P=(V^2)/R

 

[ccapital83 10+ year member]

does it make more sense to have the volume knob higher and gain lower rather than other way around generally speaking?

 

[keep_hope_alive Premium Member]

generally speaking - yes. you want gain as early as possible for the best signal-to-noise ratio. but you must also factor in the best quality source for gain. some head units are better than others. some amps are better than others. with cheap amps, you want minimal gain.

 

[maylar 10+ year member]

Voltage is linear. Power is non-linear since P=(V^2)/R

Volume controls are logarithmic. Remember analog potentiometers? You can get 2 kinds of taper - linear or "audio".

 

[calebkhill 10+ year member]

Volume controls are logarithmic. Remember analog potentiometers? You can get 2 kinds of taper - linear or "audio".

Please do explain this in a simple way //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[keep_hope_alive Premium Member]

Volume controls are logarithmic. Remember analog potentiometers? You can get 2 kinds of taper - linear or "audio".

true, but by definition, voltage has a linear relationship with impedance and current... //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif good catch, i suppose i should have read more into the question... it was late.

also, it's not possible to know exactly how your HU volume behaves without metering it because they can buy accurate or cheap audio taper potentiometers.

This shows plots of various potentiometers. We want the blue line, but some head units use cheap pots and have the red line.

my concept still holds true - assume voltage is linear when setting gains and you will always be safe... it also makes math easy.