BillFitzmaurice.info

technicaldave wrote:

Israel wrote: I have tried moving car stereos and power amps on pc power supplies, even they are fairly regulated, something happens that the voltage drops too much from some point maybe 22a is a peak figure. They struggle to move a 200w car stereo if i need steady power i connect a small 12v battery (power wheels, pc ups or so) between the supply and the source for voltage regulating even that it is too difficult

Perhaps if a pair of power supply capacitors were added in parallel to the PSU outputs then it might perform?

any regulating or acumulating source will help. at no charge each of my 7 PSUs show a voltage load between 11.6 and 11.8v . Once i tried with a big cap ( i think it was 16v 2200uf but im not sure) and adding the 5.5v lead of the PSU to a total of 16.5v at no charge it sounded loud with an mp3 player on the car amp inputs I dont pink it so i cant tell how much power. even that the amp decal lights will fade if i push it too loud. i was trying to make a super boombox I remember. In my old house i had a car stereo driven with a psu It looked nice on the wall and sounded good in a quiet enviroment.

ryan222h wrote:

Israel wrote:

CoronaOperator wrote: Exactly my point. You cannot in this universe get 5000w continuous out of a 1950w input. Physics doesn't work that way. The Lab Gruppens claim 10,000w out of the same 1950w input.

actually considering that it is a power amp 120v equals 3600 watts @4 ohms, 125v should be about 3900 watts. considering that it is not a big jump to the 5000 watts taking on account that it is at 1% thd. but really possible???? maybe on papers should be easier

Volts X Amps = Watts

Most electric outlets in the US are 120 volts and rated 15 or 20 amp. If you go over that the circuit breaker will blow

120 V X 20 amp circuit = 2400 watts

120 V X 15 amp circuit = 1800 watts

2400 watts is the maximum continuous power that any amp will ever put out when using a 120v wall source

Output cannot > input[/quote

hi Ryan good afternoon pal.... power amps are almost as mysterious as women, (at least for me) look at this (mimic Pixar Cars) a grumpy old speaker maker once told me a 300w amp can pull out peaks of 3000 watts peaks i know but also with 28.3v you can have either 50w, 100w, 200w, or 400w at 16,8,4 or 2 ohms respectively. ohms law can make some things possible and considering some other factors like if a 15a circuit always shut at 15a??? or it is always at 120v??? again i am 100% agreed with all paper math and figures even speaker response graphs, but i am aware that its main purpose is to compare oranges with oranges and i am hopping to get some light on that topic as i am getting older each day but i am not always getting wiser

Israel wrote:ohms law can make some things possible and considering some other factors like if a 15a circuit always shut at 15a??? or it is always at 120v???

One thing ohm's law cannot do is make power appear out of thin air.

DJPhatman wrote:

CoronaOperator wrote:

BrentEvans wrote:
3. Power claims in car-audio-land are smelly because they tend to be pulled out of the manufacturer's...

Unlike pro-audio amplifiers that claim 5000watts out of a 20amp 120volt source http://www.crownaudio.com/amp_htm/xls.htm

Read a little more and you will find that the XLS 5000 claims 5000Wrms bridge mono @ 4 Ohms. This is the same as 2500Wrms @ 2 Ohms stereo. And, it requires 1950 watts at either voltage.

This would be a case of perpetual motion. You can't create more power out than what's supplied to the power amp from the AC wall socket. 20A @ 120 volts is 2400 watts RMS maximum output, theoretically with an amplifier having 100% efficiency, but unfortunately such an amp doesn't exist.

At 12 volts, You would need a bank of car batteries to provide 300 watts of power for any length of time, or a battery with a 25 amp continuous charger connected to it, in which case, it would have been easier just to use an appropriate AC powered amplifier instead.

Carver made an amp, a PT2400 that would deliver 2400 watts out, but it had two separate power supplies, and two line cords that had to be fed from 2 different 15A 120V circuits.

Once you do the math, you realize how much BS there is in promotional advertising.

byacey wrote: This would be a case of perpetual motion. You can't create more power out than what's supplied to the power amp from the AC wall socket. 20A @ 120 volts is 2400 watts RMS maximum output, theoretically with an amplifier having 100% efficiency, but unfortunately such an amp doesn't exist.

At 12 volts, You would need a bank of car batteries to provide 300 watts of power for any length of time, or a battery with a 25 amp continuous charger connected to it, in which case, it would have been easier just to use an appropriate AC powered amplifier instead.

Carver made an amp, a PT2400 that would deliver 2400 watts out, but it had two separate power supplies, and two line cords that had to be fed from 2 different 15A 120V circuits.

Once you do the math, you realize how much BS there is in promotional advertising.

It's not very difficult for an amp to produce short bursts of power in that calculates to an amount in excess of the available power. Power into an amp is continuous, power out of an amp is non-continuous (in standard music program). Music program isn't sine waves... the power capacitity that isn't used in music program can be buffered and used to achieve higher voltage out, but only for a period of what the amp's storage capacity can provide.

Some, but certainly not all ratings are BS, but you have to understand what they actually mean. An amp claiming 3000 watts continuous sine out of a 20A circuit is BS, but an amp claiming 3000 watts music program might not be... as long as the amp can provide burst power for a given interval at that voltage, the spec isn't BS.

Music power and peak power are loose specifications that can vary from amp to amp, depending on the filter capacitor reserve capacity. At any rate, short transient bursts of power don't mean a whole lot as it doesn't contribute much to the overall duty cycle of the output.

This is why I commented on another thread that RMS measurements is the only accurate measurement for comparing amps; you can't jack around with the numbers game when it comes to RMS volts or watts RMS. This is probably why many manufacturers instead publish music power, program power or peak output power, as these can all through interpretation to appear bigger and better than what the amp really is.

Just looking at the AC input fuse rating tells much about what the amp is capable of. An amp with a 10A line fuse certainly isn't going to provide 2000W RMS, probably more likely around 1000W at the most.

A similar deception is the shop vac folks that advertise the machine as having a 5HP motor that draws only 8 amps @120V.