OTHER AMPLIFIERS …AND AUDISON AMPLIFIERS

This is the first in many AMPLIFIER related "TechTips".  It is super important to note that you should really understand that car audio amplifiers need current to make power.  So seat back and read this ….

We think it will be VERY enlightening!!!

Not All amplifiers are created "equally – like Audison (for example)
 

ENERGY ISN'T FREE!!!

One of the biggest issues with ALL car audio amplifiers, not JUST Audison,  is the fact that "energy" isn't FREE!  I know…"Don't say its so!!"

It would be nice if it was…BUT it ISN'T!!  It would especially BE NICE if all amplifiers did not draw any current. BUT…it

takes power to make power. It takes energy to make energy. 
 

SIMPLE PHYSICS

Take any Class A/B  audio power amplifiers (90% of all amplifiers available today).  If we know the power output either because of the printed literature   OR better yet …what IF we actually measured the power output of THIS particular amplifier - in the vehicle!   Simply test with a voltmeter or better yet ….an Oscilloscope!    The voltage coming out of YOUR amplifier!  

All audio in the signal path (RCA's, speaker outputs, etc) is AC volts.  AC volts Squared divided by the speaker impedance equals power.  Knowing that we then do a simple math equation – Total Power X 2 divided by the DC volts = current draw (full power) to get the current draw.

For example – a buddy of yours says his amplifier is 1,000 watts RMS (Root Means Square)… We take our trusty DVM (Digital Volt Meter) and go out to his car. Put on ANY type of music of your choice. Obviously something with a LOT of bass is preferred. Touch the leads of the volt meter to the subwoofer output terminal on his "1,000 Watt" amplifier. Read (measure) the "peak" AC volts that come out of his amplifier with the system "cranked up". Write it down.  (See belows drawing of the test procedure)

Lets say it is 34.6 volts AC. , Now run the formula. AC Volts squared divided by the speaker impedance. So 34.6 X 34.6 (that's squared for those somewhat mathematically handicapped ) And lets assume that he has 2 dual voice coil woofers (all of his woofers voice coils are 4 ohms, lets say). When these are "paralleled" then the impedance is near 1 ohm. This is DCR which is NOT the true impedance the amplifier see's (that's another tech tip)

34.6 Volts A/C X 34.6 Volts A/C into a 1 ohm load is 1197 watts. So his amp does do 1,000! Cool!!!

OK now that we have the REAL audio power we can then do the current draw math. 

       1,197 X 2 / 12 (DC volts) = 199.5 amperes        

He then tells you it is NOT a Class A/B amplifier …that it is a D class …OK…   take the current draw (which is 199.5A) and take that times 0.7 (Class D amplifiers are typically about 30% more efficient than a Class A/B)  THIS DOES NOT MEAN THEY SOUND BETTER!!!   They just do a better job of converting  energy.  NOTHING MORE!!!!

So…

       199.5 X 0.7 = 139.65 Amperes       

This is the FULL power current draw of ANY 1,000 watt Class D power amplifier.  PERIOD!!! 

(This is after testing 1,000’s of amplifiers in-car..so don’t let anyone tell you different!!)

No stock vehicle we know of has enough “energy” to sustain a 1,000 watts  of audio full power and not have “issues”.

These “issues” are:

1. Lights dimming
2. Severe clipping (distortion) which causes more issues!
3. Woofer voice coils “frying” because of the above clipping (NOT a warranty issue, by the way!)
4. Over heating because as Ohm’s Law states –“ as current rises voltage drops”
5. Premature shut down (say after 15-20 minutes) because of overheating, because of current starvation.
6. Melted fuse holders.

So what are you to do?  How do you solve this problem of not having enough current?

• Utilize the LARGEST gauge wire possible.  1/0 OT gauge preferred! Power AND ground
• Upgrade battery ground!!!
• Upgrade the battery to the LARGEST that will fit in your battery tray!!
• Upgrade the alternator (always a last resort!!) with the smallest pulley!!
• Make sure to use a headunit with at LEAST 4 volts of Pre-out (YES it makes a difference!!)

There are many things to learn about audio, and not to many of them work quite the way you think they do! Rely on logic to be your "compass". We hope that as you read all of our tech tips…and you get the sense we are here to HELP, not hinder you towards the ULTIMATE "in-car" audio experience.

REMEMBER THE FORMULAS!!!

Ac Volts measured at the amplifiers subwoofer output

(and DVM(Digital Volt Meter) set to AC volts can do this!)

To calculate current draw is a simple formula based on Ohm's law (NOT a suggestion) and it is based
on Class A/B's amplifiers having a typical effiency of 50%

Take the total power of the system X 2 and then divide by the DC volts (measured if possible at the DC inputs of the amplifier- while under load!) 

If this is a Class D power amplifer (typical of about 99% of all "sub woofer amps and monoblocks) then take whatever you got in current draw from the above formula and time that by 0.7

So a 1,000 watt amplifer will "swing" about 33 volts AC (33 X33 /1 ohm = 1089 watts RMS  

Take that times 2 = 2,178 Divide that by 12 volts and thatr is 181.5 amperes.

Since this is probably a Class D amp take that times 0.7 which equals 127.05 amperes of current draw FULL POWER.