Just a Little important Fact that many of you may not know

[jlaine 10+ year member]

Originally posted by RangerMan Awesome...which is the FET?

It's the transistor.. I call them all fet's.. stands for field effect transistor. MOSFET just signifies metal oxide field effect transistor. It's what you'll see on the power supply stages of amplifiers (MOSFET's that is), and usually the output stages too.

Do you know what component is blown, or are you playing guesswork? Be careful, because if you don't get the right component that is blown, and find one that is blown further down the chain and only replace that one, you'll blow it out again. Amp circuitry can be finicky like that. It doesn't happen all the time, but it does happen.

 

[RangerMan Premium Member]

Originally posted by jlaine It's the transistor.. I call them all fet's.. stands for field effect transistor. MOSFET just signifies metal oxide field effect transistor. It's what you'll see on the power supply stages of amplifiers (MOSFET's that is), and usually the output stages too.

 

Do you know what component is blown, or are you playing guesswork? Be careful, because if you don't get the right component that is blown, and find one that is blown further down the chain and only replace that one, you'll blow it out again. Amp circuitry can be finicky like that. It doesn't happen all the time, but it does happen.

I'm taking an educated guess...I used the V/O meter, and might borrow a transistor checker...

 

[jlaine 10+ year member]

Originally posted by RangerMan I'm taking an educated guess...I used the V/O meter, and might borrow a transistor checker...

You can't check them in the circuit RangerMan, they have to be pulled then tested-- a fet checker is a must IMO.

 

[RangerMan Premium Member]

Originally posted by jlaine You can't check them in the circuit RangerMan, they have to be pulled then tested-- a fet checker is a must IMO.

Alright, I'll do that...thanks Josh!

 

[ramos 5,000+ posts]

Originally posted by bud my 12 volt stock batt. puts out almost 15 volts so it is possiple

No it doesn't. Your alt may be putting that out but not your battery. Your battery is just a butt hair over 12v. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[ramos 5,000+ posts]

Originally posted by CarAudioAddict Very few amplifiers/speakers on the market are over/under rated.

 

If Brand X claims that their amplifier can put out 800 watts, then it can.

 

What many people don't realize is how manufacturers get these numbers.

 

Now say I own a big Car audio Manufacturing Company (I don't but this is just to help prove this fact). If I desparately need to sell my amplifier, that normally puts out say 600watts max, how would I go about it.

 

Well I could say that it puts out more wattage than it really does @ 14.4VDC, but wait, no I can't advertising regulations prohibit it (at least in Canada/USA they do).

 

So I get to thinking "what if I could make my amp put out this higher wattage? Well then I could advertise it as a higher wattage amp. Now, how do I do this?

 

I know I'll run it at a HIGHER VOLTAGE. No, that won't work, I'llburn out the amp. Wait!!! What if I FREEZE it, say, with DRY ICE?

 

The Unit would remain at a much lower temperature, so it could run longer at the higher voltage and not burn out (plus everyone knows higher voltage = higher output).

 

Using this method I get the amp running at 24V stable and discover that my 600watt amp can put out over 1000 watts. I can now advertise this amp as a 1000 watt amp, and sell it either at a higher price, or at the same price and get more sales."

 

You see I couldn't be acused of false advertising because the amplifier can put out 1000 watts. But what the people buying the amp don't know is that it only puts out the high power at high voltage levels.

 

This technique can also be used for speakers/subs. If you freeze the motor assembly (Voice coil, Magnet, & Spider), you could run the speaker at a very high wattage, much higher than at roomer temperature. This is because when you OVERPOWER a speaker the main reason it fails is the voice coil gets burnt out

 

 

Many, many companies have gotten away with this. Some of the well known, not necessarily liked, brands that do this are Pyramid, Sony Xplod, AudioVox, and pretty well anything Radio Shack carries. These amps aren't really overrated, just no-one can run them at the 24Volts without them burning up.

 

Basically go out and get a pyramid amplifier and run it exactly the same way pyramid did when they tested it. You will find that it meets their quoted specs.

 

Companies like JL, RF, PG, Alpine, Pioneer, and most other TOP NAME BRANDS will give you specs based on either 12Volts or 14.4 Volts, as this is what the equipment will be run with most of the time ( I say most because they are extremists out there that run amps at 18 volts). Thus giving you a more realistic nuber to expect for output.

Say what ? //content.invisioncic.com/y282845/emoticons/confused.gif.e820e0216602db4765798ac39d28caa9.gif I don't believe that it works quite like that. There is no set standard for amplifier manufacturers to test by. Which means most are tested differently.

Say company A has an amp that puts out 1500w at 1ohm at 14.4v.

Company B has an amp that puts out the same 1500w at 1ohm but uses 17v .

Company B wants to compete with company A. So they list their rated power as the same even though their testing method uses a higher voltage. Are they guilty of false advertising, or just embelishing a bit............. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[CarAudioAddict 10+ year member]

Thats pretty well what I said.

I just put in more detail about how they can manage to run their amp @17 volts or higher without burning up the components inside.

Technically the output of the amps are the same. But about 99.999999% of the people out there don't run their systems at high enough voltages to get the increase in power that Amp B needs.

Another brand that gets away with this is Koss.

(Was just browsing around the local F-U Shop and saw this brand. Remembering past experiences I figured I should mention it as another "embelishing brand"

 

[ramos 5,000+ posts]

Yeah but they don't freeze anything. It's just a matter of creative marketing. I don't agree with it. But that's the way business works these days. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[jlaine 10+ year member]

Originally posted by CarAudioAddict Thats pretty well what I said.

 

I just put in more detail about how they can manage to run their amp @17 volts or higher without burning up the components inside.

 

Technically the output of the amps are the same. But about 99.999999% of the people out there don't run their systems at high enough voltages to get the increase in power that Amp B needs.

 

Another brand that gets away with this is Koss.

(Was just browsing around the local F-U Shop and saw this brand. Remembering past experiences I figured I should mention it as another "embelishing brand"

Again, freezing, cryogenic stasis, dipping them in water, wishing upon a star... NONE of these is going to prevent immediate voltage overload that happens when you send an overvoltage situation to a mosfet. It'll die immediately, not over the process of a few seconds. It is not heat that will kill the amplifier, it is the failure of an internal component due to a higher than allowable voltage level.

Send 18V to a road gear amp once, see if you can even get it to power up long enough to send it a signal. If you feel like it, go ahead, plunk it in the freezer for a bit.

 

[CarAudioAddict 10+ year member]

What does overvoltage cause?

More current flow.

What does more current flow cause

HEAT!!!!!

Maybe not all companies do this, but many do.

Say you take a pyramid amp. It has 105C caps in it. That means that the cap will fail if its temp reaches 105 degrees celsius. Now which would take longer to reach this temperature an amp at room temp. or an amp at -200 degrees.

You don't need to be a scientist to figure that out. I happen to know that many mosfets used in car-audio can handle much more voltage than just the 12-14.4V that your car uses. Top name brands use fets that can handle over 100 volts. This is to prevent damage from voltage spikes that ALL alternators put out.

Alternators don't put out a constant 14.4V. The voltage fluctuates and sometimes spikes to 100's of volts. These spikes only last a few nanoseconds but they are there. If Amp A had Fets that could only handle 14.4V then as soon as you start the engine in the vehicle that amp is TOAST. The most common time for these spikes is at Start.

 

[jlaine 10+ year member]

Originally posted by CarAudioAddict What does overvoltage cause?

More current flow.

 

What does more current flow cause

 

HEAT!!!!!

 

Maybe not all companies do this, but many do.

Say you take a pyramid amp. It has 105C caps in it. That means that the cap will fail if its temp reaches 105 degrees celsius. Now which would take longer to reach this temperature an amp at room temp. or an amp at -200 degrees.

 

You don't need to be a scientist to figure that out. I happen to know that many mosfets used in car-audio can handle much more voltage than just the 12-14.4V that your car uses. Top name brands use fets that can handle over 100 volts. This is to prevent damage from voltage spikes that ALL alternators put out.

 

Alternators don't put out a constant 14.4V. The voltage fluctuates and sometimes spikes to 100's of volts. These spikes only last a few nanoseconds but they are there. If Amp A had Fets that could only handle 14.4V then as soon as you start the engine in the vehicle that amp is TOAST. The most common time for these spikes is at Start.

I see you don't know enough about amplifier design to even realize that there is a fully independant power supply in the amplifier, and that the rail voltage on the actual internal audio output fets is nothing near 14.4v... With that I don't think I need to go further than this, but I will anyway...

The fets voltage rating has no correlation to build quality... None whatsoever. It's matched to the need at hand.

//content.invisioncic.com/y282845/emoticons/banghead.gif.8606515f668c74f6de0281deb475b6fd.gif

You also realize that by placing 18V to the amplifer power supply, it's output voltage rail will increase by the common percentage of what was gained, until it destroys the fets or itself, often with little, or NO heat at all to be detected. Want a good example? Plug your home amp into 200V instead of 120. This is exactly what you are doing to the car amp when you are placing a constant 18V to it. See how long it lasts for you...

The "spikes" you are speaking of are immediately absorbed by the capacitors in the supply chain and the batteries in the vehicle, it never makes it through the vehicles power supply. The most common time for a voltage spike to take place is after a high current draw releases it's load, but only when a constant source voltage is NOT the primary source. (Read: transformer, some sort of inductive load)

Starting is NOT the area to find it, because in order for it to create a surge, it has to have a somewhat variant power source, not a DC battery. This would be fine, if you loaded down the alternator, then suddenly released load. Sure, you may spike some, but nothing worth noting. I can place an oscilloscope on a vehicle battery and start the car, and it'll not pull up anything worth noting other than the dip when the battery is discharging. Now if the alternator was supply the charge to start the car, I can see where you are coming from, but it isn't the case.

Please go back and do some research, especially in the fields of amplifier topology and vehicle electrical design, include in your reading about TVSS control and what exactly causes a surge, and what doesn't. Be sure to try and find information about spikes in a DC line when controlled by a limited voltage battery.

Another problem.

105C rated caps will not fail at 105c, that is their operational threshold.

What does this have to do with anything? You realize that the heat loss via a capacitor is next to absolutely nothing? The core temperature of the amp and the heatsink is what raises the capacitors operating temperature, not the fact that it is functioning in a circuit. If you pass a lot of current through it, it will begin to warm, but nowhere near the level of what the amp will.

Where exactly do you hear all this hogwash from? Deep freezing and overdriving amps to get a voltage reading? Who is telling you these things? I'd love to sit down with them for about a half hour and see how deep this conspiracy theory truly goes...

 

[zane 10+ year member]

Originally posted by CarAudioAddict  

Alternators don't put out a constant 14.4V. The voltage fluctuates and sometimes spikes to 100's of volts. These spikes only last a few nanoseconds but they are there. If Amp A had Fets that could only handle 14.4V then as soon as you start the engine in the vehicle that amp is TOAST. The most common time for these spikes is at Start.

Yes Voltage does fluctuate, however, not that much. The Voltage regulator prevents rapid and extreme fluxuations.

100's of volts from an alt... I dont think so.

100 volts in a car is unheard of.

BTW- you will notice voltage drops, not spikes, at startup. The starter relies on power from the battery to crank it. The alternator has not begun to cycle until the engine is started, after which the starter disengages.

The battery would be taxed with the starter load, not an excess of current.

take it easy,

-zane

 

[CarAudioAddict 10+ year member]

OK.

You proved your point about the fets.

The caps though will be at roughly the same temp as the amplifier case. And I have seen caps fail when they reach their operational temperature.

But as for there nopt being a voltage spike when you first start the vehicle, you mentioned things that proved yourself wrong.

Yes, when you first start the car you will notice a drop in the voltage, This is before your alternator starts putting out current, and the battery cannot deliver the 200+amps that a starter needs for very long.

But. Before you even release the key to stop the starter motor, the alternator is already putting out current, trying to get the battery voltage back up. When the key is release the starters load (possibly the highest load your cars electrical system will ever see, unless you are running close to 2000 amps) is dropped off the system. The alternator is still trying to get the battery's voltage up, but because the starter has been disengaged, the battery's voltage has already returned about to normal (it will be lower than before you started the car but that is minor). BAM!!!!!! huge voltage spike as the alternator balances out.

The voltage regulator in the alternator cannot instantly change the voltage on the feild current (which is what the regulator is doing by the way). When the voltage regulator "senses" a lower voltage in the system, it increases the Alts field circuit voltage to increase it's output.

Say when you start the vehicle the batteries voltage drops to say 9-volts during starting (actually drops lower on some vehicles), The voltage regulator in the alternator increases the circuit voltage to compensate, thus trying to maintain output from the alt at 14.4 Volts. Now suddenly the load is gone (starter motor has been disengaged), and the voltage regulator is still supplying the extra voltage to the field circuit.

Under normal running condition the field curcuit voltage is lower than 8-volts. When a heavy load is placed on the electrical system, the volatge drops (we've all noticed this, especially those who have a prob with dimming lights). The regulator increases the field circuit voltage to bring the charging system voltage back up to 14.4V. Keep in mid that the feild circuit voltage cannot exceed the voltage of the electrical system because the electrical system is what powers the regulator. When the voltage of the electrical system drops far enough that the field circuit has the same voltage, the regulator is siad to be running in "full-field mode".

When the load is gone the system returns to the battery voltage. Now you've got a 12volt system being charged with a 12 volt field curcuit. Note that this is 25% higher (or more) than normal.

12V + 25% = 15Volts!!!!!!!!!

Now until the regulator switches out of "full field mode" the voltage will keep increasing (Note also that amperage out of the alt will DECREASE, power in= power out + loss due to resistance/friction) On older or more worn alternators this change can take longer, and it only takes a few milliseconds to get to over 100 volts. Once the regulator is out of "full field mode" the voltage returns to normal within a few milliseconds - Notice that the whole process only takes less than 1/10th of a second, you won't notice that on ANY voltmeter (by the time the meter would read the high voltage it has already returned to normal).

Brand new Alternators can make this switch alot faster and so the volatge may never increase past 15-20 volts which is not bad most 12volt equippment won't even flinch at this.

These (this post not the main post) are facts taken right out of "Chiltons Guide to Automotive Electrical Systems"

Price at approx $150, I don't think these guys are printing myths, or false info

Most amplifiers (including the fabled pyramid units) power supplies cannot take a 18V load. In fact, hooking a 18V line up to your car is going to get you a quick trip to the dealer. How are you going to explain to them you surged the entire CPU system in your vehicle though.

The guy had just is amps running on 18volts, not the car. and it is definatly possible.

As for where I got the info on freezing. It was from a sales rep at JL audio.

 

[Corsica 5,000+ posts]

Originally posted by jlaine I can get them easily enough RangerMan, can you still read the number on the case of the FET?

Josh, If I sent u 2 burned out RF amps (provided I don't sell them) could u fix them for me? One has 2 toasted Mosfets, the other, has "water" damage. (water drop hit power input and it died). I am willing to pay, just not the local dealers fees.

J

 

[jlaine 10+ year member]

Originally posted by CarAudioAddict OK.

 

You proved your point about the fets.

Ok, so lets move on to the false information you have on capacitors..

Originally posted by CarAudioAddict The caps though will be at roughly the same temp as the amplifier case. And I have seen caps fail when they reach their operational temperature.

Then you had a bad capacitor. Even the cheapies are rated for 4000 hours of constant use @ their rated temperature.

Originally posted by CarAudioAddict But as for there nopt being a voltage spike when you first start the vehicle, you mentioned things that proved yourself wrong.

 

Yes, when you first start the car you will notice a drop in the voltage, This is before your alternator starts putting out current, and the battery cannot deliver the 200+amps that a starter needs for very long.

Actually it can, for a minute or two on a freshly charged battery. More than sufficient to start a vehicle. I fail to see any incorrect information in my posts, but I do see several holes in your theories.

Originally posted by CarAudioAddict But. Before you even release the key to stop the starter motor, the alternator is already putting out current, trying to get the battery voltage back up. When the key is release the starters load (possibly the highest load your cars electrical system will ever see, unless you are running close to 2000 amps) is dropped off the system. The alternator is still trying to get the battery's voltage up, but because the starter has been disengaged, the battery's voltage has already returned about to normal (it will be lower than before you started the car but that is minor). BAM!!!!!! huge voltage spike as the alternator balances out.

Incorrect. The vehicle alternator is not properly engaged until the vehicle is in an idle state, which means the current draw from the starter has already been disengaged. An alternator is not assisting squat at starting turnover, I could easily demonstrate this fact by turning your alternator over at the sadly slow speed the motor is turned at when the starter is engaged. You think idle current is bad...

Originally posted by CarAudioAddict The voltage regulator in the alternator cannot instantly change the voltage on the feild current (which is what the regulator is doing by the way). When the voltage regulator "senses" a lower voltage in the system, it increases the Alts field circuit voltage to increase it's output.

Somewhat right, but you are incorrect about the starter, so the point is moot.

Originally posted by CarAudioAddict Say when you start the vehicle the batteries voltage drops to say 9-volts during starting (actually drops lower on some vehicles), The voltage regulator in the alternator increases the circuit voltage to compensate, thus trying to maintain output from the alt at 14.4 Volts. Now suddenly the load is gone (starter motor has been disengaged), and the voltage regulator is still supplying the extra voltage to the field circuit.

Incorrect. The battery will remain at it's operational voltage until the cells are drained beyond their capability to produce full voltage. If you drop to 9 volts during starting, your battery is dying. Any quick probe with an oscilloscope will show that while there is some drop, nowhere near the level you are purporting. I can easily monitor a starter that makes your car starter look like a tonka toy, as I have access to a 175B Michigan Payloader, 24V system, 800A starter.

And again, you are incorrect about the alternator functioning at this point, so this discussion is invalid.

Originally posted by CarAudioAddict Under normal running condition the field curcuit voltage is lower than 8-volts. When a heavy load is placed on the electrical system, the volatge drops (we've all noticed this, especially those who have a prob with dimming lights). The regulator increases the field circuit voltage to bring the charging system voltage back up to 14.4V. Keep in mid that the feild circuit voltage cannot exceed the voltage of the electrical system because the electrical system is what powers the regulator. When the voltage of the electrical system drops far enough that the field circuit has the same voltage, the regulator is siad to be running in "full-field mode".

Has no bearing on the discussion, I'll pass on it.

Originally posted by CarAudioAddict When the load is gone the system returns to the battery voltage. Now you've got a 12volt system being charged with a 12 volt field curcuit. Note that this is 25% higher (or more) than normal.

 

12V + 25% = 15Volts!!!!!!!!!

 

Now until the regulator switches out of "full field mode" the voltage will keep increasing (Note also that amperage out of the alt will DECREASE, power in= power out + loss due to resistance/friction) On older or more worn alternators this change can take longer, and it only takes a few milliseconds to get to over 100 volts. Once the regulator is out of "full field mode" the voltage returns to normal within a few milliseconds - Notice that the whole processh only takes less than 1/10th of a second, you won't notice that on ANY voltmeter (by the time the meter would read the high voltage it has already returned to normal).

 

Brand new Alternators can make this switch alot faster and so the volatge may never increase past 15-20 volts which is not bad most 12volt equippment won't even flinch at this.

 

These (this post not the main post) are facts taken right out of "Chiltons Guide to Automotive Electrical Systems"

Price at approx $150, I don't think these guys are printing myths, or false info

 

 

 

The guy had just is amps running on 18volts, not the car. and it is definatly possible.

 

As for where I got the info on freezing. It was from a sales rep at JL audio.

Now to finish off where we were going...

Like I had said before, ANY vehicle spike from the alternator is going to be immediately absorbed by the battery and other storage devices in the supply chain. In other words, the point is moot. What does this have to do with anything on your initial post?

Sending 18V to an amplifier is going to kill it. Do not pass go, do not collect $200.

Lets stick to the subject matter at hand, I'll let Zane deal with the tidbits about the internal electrical system, my beef with you is the whole conspiracy theory about amplifier manufacturers.