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Class D Switching Power Amplifiers and Power D/A conversion

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Old 1st November 2002, 12:35 PM   #21
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Quote:
Originally posted by peranders


Every(?) class D amp is bridged already. The output stage is a H-bridge and can not be bridged with an another amp.
not so:
http://www.memphiscaraudio.com/publi...%20Diagram.pdf

shows running both amps to one load. The bridging module is to invert the phase to one amp. the lanzar has a phase button on each amp so you oly need 2 amps and some wire for 2400x1@ 2ohm.
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Old 1st November 2002, 06:12 PM   #22
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That module has to do a bit more than invert the phase, It essentially turns one amp on for only the +half of the wave, and the otherfor only the -half. This set up does not double the voltage, essentially it doubles the power supply (available current). This bridging set up is real different from a class b bridge, where both amps work at the same time. While this bridging adaptor is neat, i doubt it would sound good as it adds a region of cross over distortion. In these amps if the power supply more closely matched the output stage then bridging it would be useless as no extra power could be supplied.
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Old 4th November 2002, 06:20 AM   #23
griff is offline griff  Australia
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Ok thanks for the replies guys.

I will buy 2 JBL 1200.1's or maybe DEI2400's. These will give me more then enough wattage for the system.

One thing you should note about car audio is that there can never be enough decibels. Recently at the World champs in Nashville, 177dB's was reached and above. The idea is to keep it clean whilst at such levels, in order to maintain SQ.

Thanks again
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Old 4th November 2002, 09:33 AM   #24
skaara is offline skaara  Slovenia
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But how do they reach that spl?? Maybe because car is small room and spl is higher?
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Old 4th November 2002, 10:55 AM   #25
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It's called transfer function which gains upto around 12dB/octave when the sound drops below the wavelength of the vehicle.
So if the gain of the vehicle starts around 150hz at 37.5hz you have just gained 24dB....
Also using multiple drivers gains more db's again and on it goes especially if you are using ported or bandpass enclosures.

In the past i ran 2 10 inch subs with a low effiency of around 89dB/w/m from an 80 watt amp and got 129dB without using a ported enclosure or a bandpass enclosure...
Hope this helps you some...
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Old 4th November 2002, 08:53 PM   #26
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I once attended the dB Drag Racing World Finals in Nashville, TN in November of 1998. Then the world record was set at 173+ dB. For those of you who are not familiar with this competition it consists of a competitor attempting to achieve the highest SPL possible within a 30 second interval. The sensitive microphone is place at the exact same positon for each vehicle according to rules. The placement is amount of inches from the passenger side pillar, y inches above the dash, and z inches from the front windshield (which is no longer glass but replaced with several inches of plexiglass which is reinforced with steel beams.) There are usually between 12 and 100 subwoofers in the vehicle (depending on the power class) and power amplifiers adding up to over 100,000 Watts in some occasions. This usually requires many many additional chain driven alternators and banks of gel cell batteries. The cometitors play short bursts of single tone frequencies attempting to achieve the highest SPL by hitting the resonant frequency of the car. Also, in order to conserve internal energy, each team (12 members) pushes on the outsides of the car in order to prevent the acoustical energy from transfering to the reinforced body of the car.
Keep in mind this is an exhibition and is show. Usually the teams of competitor's are sponsored by a major manufacturer or a local dealer. It is a popular exhibition that travels around the country and is neat to see. Wear earplugs...
But for me I prefer to use stero equipment for what is was made for....and to experience what the music was intended to be.

www.dbdrag.com
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Old 4th November 2002, 09:37 PM   #27
jwb is offline jwb  United States
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I always get a laugh out of the dB drag race. My friend had the idea to put a tornado or air raid siren in his car and enter that. I don't think he ever did it, though.
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Old 4th November 2002, 10:01 PM   #28
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I always get a kick out of my old "train horn in the trunk" idea. I think it would be great fun. Especially at night nowhere near any tracks. I still have no idea how big a train horn is and im not sure i want to know... keep the old idea aroung for a few more chuckles.
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Old 1st July 2004, 12:26 PM   #29
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recently I went around all the car audio shops in town to find a good big amp and speakers I tested a lot of them the 1500w 15"brahma 2ohm went up in smoke at 28vrms around 350w rms that was the only pricie speaker they would let me play with but the 1500w 15" sony went up at 26vrms the 1100w 12" 25vrms as for the amps the only ones they would let me test was the 2200w sony =27.6v rms 2 ohm and some pro audio fan cooled thing was ment to be 2600w was 26.4 v rms 1ohm
So as i found a car audio w rms is not worth the paper it is writin on.On top of the most car charging systems can only do 750w on a good day and the car has to run off some of that so you are not going to get any more than that with the cars power supply.so if you want good power try what i did rewind a 24v 90A geni to +/-/center tap 65v ac 40A so you have good power to start with and put a real amp on that. it is a lot cheaper and nothin around here even comes close to the sound my truck makes.
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Old 1st July 2004, 01:10 PM   #30
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Car audio is mostly about wank factor. Brands like Sony, Pioneer, Boss etc. thrive on Max ratings and cheap products. Personly I hate the mainstream car audio products and most of thier owners. The amount of people that believe thier sony coaxial speakers jammed into thier door's whilst running off a .8% THD amp @ 30wrms (300w max....) sounds good is amazing. Several of my friends make thier own box and simply cut any old hole (!) for a port (They don't listen to my advice though i did make him download WinISD).
Apart from that, I quite like car audio
My first DIY'd amp was two P3a's running a small SMPS (+-35v) and sounded quite well without the engine on. An inductor would have fixed the noise issue but it was only a prototype.
My current project may be of interest to you however. In theory it should be able to create well over 1kW (off +- 95v rails using a half bridge). The design is Ssamors (Sorry if I got that wrong) using a MAX4295 which driver a buffered IR2110 in order to switch a total of 10 output mosfets. I have something like 2500 amps worth of mosfets for the project.
I couldn't really care if I don't hit 500w rms, it's just for fun
I'll let you know in a few weeks if its possible
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