Thinking about a gainclone for the car.

[punchpeanut]

I was wondering if the standard or inverted design would be better. From what I understand, the inverted can have some problems with long interconnect runs. Would a buffer be a good idea?

What gain should I shoot for it I have 4V of input?

Thanks.

 

[peranders]

Your main problem is to get supply voltage high enough.

 

[jackinnj]

wait 'til cars go 48 Volts -- coming in a few years.

actually, there are quite a few folks lurking here who have built the SG3524 switch mode power supply to power the LM3875. I have a different switcher chip mounted with an LM3875 in an old PC-ATX supply chasis.

 

[Hybrid fourdoor]

what abut a bridged gainclone, that way they can make up for the low voltage, plus the speakers would be running at 4 ohm's in most cases, so that could be helpfull with some LM3886's.

Just my 2 cents

 

[punchpeanut]

Sweet, that may work out the best of all. That way I wouldn't even need a smps ps, just a standard type.

 

[ronc]

The only problem with a GC and late mdl car is the alternator controls is based on pulse width modulation.If you hook a scope to a late mdl car battery while its running(approx 1998 or>) there is a constantly changing square wave response (looks like a spastic square wave) as the alternator cuts in and out every .005 to.050 seconds (depends on the system load). I dont know what this may do to the signal response and have never really looked into it.I built a GC for a friend that went into his car but it had 2-12v isolated batteries and the speakers were a kinda MLTL using RS-1354a drivers. he was very pleased.
ron
(BTW i am NOT into car systems)

 

[jackinnj]

The only problem with a GC and late mdl car is the alternator controls is based on pulse width modulation.If you hook a scope to a late mdl car battery while its running(approx 1998 or>) there is a constantly changing square wave response (looks like a spastic square wave) as the alternator cuts in and out every .005 to.050 seconds (depends on the system load). I dont know what this may do to the signal response and have never really looked into it.I built a GC for a friend that went into his car but it had 2-12v isolated batteries and the speakers were a kinda MLTL using RS-1354a drivers. he was very pleased.
ron
(BTW i am NOT into car systems)

The first time I ran an inverted LM3875 on a plain vanilla switching supply the distortion increased about 10 fold. I performed the same test on some Linear Tech opamps and the result was exactly the same -- so there is an obvious need for care.

 

[JoeBob]

Ron, you seemed to have done almost what I want to do.

I wanted to use 4 12V batteries to power a gainclone for a friends car, power different speakers, TB W4-657S, but it's very simmilar to what you have done.

What I was wondering about was charging the batteries, you wouldn't want to charge them while the car was off (don't drain the cars battery) so they would have to be charged while running. Did you ever run into problems of the batteries being dead and having to turn the amp off for the to charge while driving?

I mean it's not like at home where you can charge them overnight...