Setting HU to Max Pre Out?

[gimling]

Ive read online a couple places that some headunits with the sub eq settings if its not turnd up to the highest lets say +15db then the pre outs wont be supplying the full rated voltage

+15 db to me just sounds like a clipping nightmare I wouldnt recommend doin that without an oscope to verify the signal isnt horribly clipped

 

[bgowdy 5,000+ posts]

Yes it is max rating its why you dont want to set wrong on the amp to keep it from clipping, here is the easiest way to set your gain, record a 60hz tone. disconnect the speakers, turn amp gain all the way down, subsonic all the way down, bass boost all the way down, LPF all the way up. turn your headunit to withing 4-5 of max. play the tone, put the multimeter to AC put it on the output of the amp where u disconnected the speakers, USE OHMS law to find out what voltage you need, IE if your Amp is rated at 1000watts rms at 1ohm use this formula, Voltage = square root of watts X's Resistance. so square root of 1000 X's 1 = 31.622 Volts. so push play on your cd player at that level within 4-5 of max turn up the gain till the meter reads 31.622 VAC.

I already know how to set my gain on the amp with meter?

 

---------- Post added at 09:02 PM ---------- Previous post was at 09:02 PM ----------

 

+15 db to me just sounds like a clipping nightmare I wouldnt recommend doin that without an oscope to verify the signal isnt horribly clipped

exactly why i didnt do it when i read it

 

[bgowdy 5,000+ posts]

Yes it is max rating its why you dont want to set wrong on the amp to keep it from clipping, here is the easiest way to set your gain, record a 60hz tone. disconnect the speakers, turn amp gain all the way down, subsonic all the way down, bass boost all the way down, LPF all the way up. turn your headunit to withing 4-5 of max. play the tone, put the multimeter to AC put it on the output of the amp where u disconnected the speakers, USE OHMS law to find out what voltage you need, IE if your Amp is rated at 1000watts rms at 1ohm use this formula, Voltage = square root of watts X's Resistance. so square root of 1000 X's 1 = 31.622 Volts. so push play on your cd player at that level within 4-5 of max turn up the gain till the meter reads 31.622 VAC.

you know his confuses me now. ive never had to calc a .5ohm stable amp. My amp is rated 3000 rms @ .5... 3000 X .5 = 1500 and square root = 38.72v

 

[gimling]

I mean really if you know how to set your gain on your amp with your meter then your pretty much set. i guess if you could turn your head unit all the way up with no clipping on the rca output and the subwoofer to +15DB without clipping all that would mean is you are going to be turning your gain on your amp down to reach the desired output voltage on the amp. kinda redundant.

 

[Jepalan]

It is a known issue with some Alpine head units that you need to turn the sub level on the head unit all the way up before setting gains, otherwise the signal out of the sub RCAs is too low. I have only heard of this with some Alpine HU's - no other brands. On all other brand, leave sub level at 0dB.

 

[Jepalan]

Read this...

http://www.caraudio.com/forums/head-units/548312-confused-set-gains-w-sub-setting-0-15-a.html#post8051340

 

[gimling]

you know his confuses me now. ive never had to calc a .5ohm stable amp. My amp is rated 3000 rms @ .5... 3000 X .5 = 1500 and square root = 38.72v
its how the amp works the power transistors or mosfets are working harderor running hotter to create that power with more of a load, if it was stable at 4 ohms with 3000 watts your looking at around 110V.

Let me rephrase that The amp will work harder but the output voltage will go down with lower load resistance on the circuit.

 

[bgowdy 5,000+ posts]

its how the amp works the power transistors or mosfets are working harder to create that power with more of a load, if it was stable at 4 ohms with 3000 watts your looking at around 110V.

mines not set with a meter right now, i did it by ear lol... I havnt had a chance to. I mean im guessing its ok, amp doesnt get excessively hot(gets alittle warm but its running .5 daily so its a givin), and subs never got smelly after playing, dust cap hasnt felt hot or nothing

 

[gimling]

yeah you dont have to use a meter im sure you can hear distortion and set it by ear, the other methods are what i use mainly too make sure i dont over push anything, if its set with meters and an oscope system should last many many years without anything blowing up =)