The H bridge concept & Building an amplifier

[amit1101]

hello navin and all bhp brothers

i m making my own car amp.
i have completed few parts of my design, is there any one who can help me with any useful suggestion or knowledge or idea.
my amp is currently working as non bridge +/- 28 volts and pumps +/-25 volt peak to peak in a 4 ohm speaker to blow out 70rms.
do i need to make my design more powerfull
will 70rms into 2 do 4 coax
140rms bridge for sub, will this much power be enough or i should put more power.

thanks a lot

[navin]

Originally Posted by amit1101

hello navin and all bhp brothers
i m making my own car amp. will 70rms into 2 do 4 coax
140rms bridge for sub

coax speakers tend to be more sensitive than components becuase their crossover is so simple the insertion loss (due to a more complex crossover) is not there.

1. in a car 40W rms/ch is more than enough for most front and rear speakers
2. for a sub you need to swing more volts and depending on the sub's T/S specs you may need even 500W

I built a car amp about 20 years ago that puts out about 35W rms x 4 at < 0.1% distortion, a bit more than 40W at clipping.

when testing your car amp i'd suggest using the following test load - 1mh 12SWG inductor in series with a 4 ohm/25W resistor. If you cant find a 4ohm/25W resistor use 2 x 10W/10ohms in parallel, 3 or 4 10W resistors if you want to stress test the amp.

[amit1101]

Originally Posted by navin

coax speakers tend to be more sensitive than components becuase their crossover is so simple the insertion loss (due to a more complex crossover) is not there.

1. in a car 40W rms/ch is more than enough for most front and rear speakers
2. for a sub you need to swing more volts and depending on the sub's T/S specs you may need even 500W

I built a car amp about 20 years ago that puts out about 35W rms x 4 at < 0.1% distortion, a bit more than 40W at clipping.

when testing your car amp i'd suggest using the following test load - 1mh 12SWG inductor in series with a 4 ohm/25W resistor. If you cant find a 4ohm/25W resistor use 2 x 10W/10ohms in parallel, 3 or 4 10W resistors if you want to stress test the amp.

thanks a lot navin
1) I saw most pioneer coax rated as 60-70rms, should i drive them upto 40rms only as you are saying.
2) when you said 500 watt for subs, was that rms.
3) Wat kind of power supply did you use for your amp.
4) please advice me on distortion etc. i have uploaded my amps output waveform at this link http://geocities.com/melvinisback/
CAN YOU PLEASE ADVICE IF THE DISTORTION IS OK OR IT SHOULD BE FURTHER REDUCED. is it close to .1%THD (i donno how to measure distortion)
if my link does not work please try after some time, it take some time to load onto geocities server.

thank you

[amit1101]

http://www.geocities.com/melvinisback/subhtml/amp
this is the link and its working fine now
plese advice on distortion

[navin]

I have not built a 500W rms amp. To measure distortion you need a distortion meter. dont consider thermal watt ratings. most speakers overload due to physical constraints lot before 50W rms. 50W rms at 1kHz is a lot different from 50W rms at 50Hz.

[amit1101]

Originally Posted by navin

I have not built a 500W rms amp. To measure distortion you need a distortion meter. dont consider thermal watt ratings. most speakers overload due to physical constraints lot before 50W rms. 50W rms at 1kHz is a lot different from 50W rms at 50Hz.

i am just a student and cant arrange any distortion meter
please visit my link i have posted my waveforms there @ 1khz and 10khz
can you just look at the waveform and give a rough idea if my amp will sound good or i need to make its responce better.
http://www.geocities.com/melvinisback/subhtml/amp

[amit1101]

see my derivation was not wrong
http://www.jbl.com/car/products/prod...at=AMP&ser=GTI
A6000GTI
specifications
2600 Watts RMS x 2 channels at 4 ohms
and ≤ 1%THD+N

8110 Watts RMS x 1 channel at 4 ohms,
14.4V supply and ≤ 1%THD+N

see here the power has become 4 times instead of 2 times when u make a bridge,
BUT NAVIN is also right the full capacity is LIMITED BY CURRENT in MOST OF THE CASES so the power is not generally 4 times but close to 2 times instead

2600 Watts RMS x 2 channels at 4 ohms
and ≤ 1%THD+N

8110 Watts RMS x 1 channel at 4 ohms,
14.4V supply and ≤ 1%THD+N

7400 Watts RMS x 1 channel at 1 ohm,******** limited due to current as navin said
14.4V supply and ≤ 1%THD+N

[navin]

Originally Posted by amit1101

i am just a student and cant arrange any distortion meter
please visit my link i have posted my waveforms there @ 1khz and 10khz
can you just look at the waveform and give a rough idea if my amp will sound good or i need to make its responce better.
http://www.geocities.com/melvinisback/subhtml/amp

the waveform is clipping. now in a car the amp might be i a tougher enviroment. drop the amp a bit 5A is more than enough. better to have stability than power.

[amit1101]

Originally Posted by navin

the waveform is clipping. now in a car the amp might be i a tougher enviroment. drop the amp a bit 5A is more than enough. better to have stability than power.

thanks navin i will, i will put more Iq that might reduce clipping at hign freq.
my currnet is 6A max and 6/1.414 rms = 4.3A rms
i will reduce it to 5 instead of 6
lets see