GC lacking power

[Chris8sirhC]

my younger brother just finished putting together his GC and he has it hooked up to this speaker but it doesnt even have enough power (with no volume selector even attatched) to get that speaker to a normal quiet listening level? what could be wrong?

[analog_sa]

Most probably not enough input signal.

[mhelin]

Those JBL's seem quite efficient. Maybe the chip is not cooled properly, it's got internal protection which will start working if temp goes too high. Either that or input level is not high enough. Or the gain of the amp.

[Chris8sirhC]

we've tried his ipod and a cd player, it could be the thermal power issue, its just bolted to a thin sheet of metal right now. Would the thermal protection kick on instantly when you first start up the amp?

[richie00boy]

No. The protection sounds NASTY and it will be obvious that it's kicking in. And it will take at least a few secs for the thermal protection to kick in as well.

I reckon the gain is wrong. Check the resistors that determine the gain.

There is the alternative small possibility that the input impedance is too low hence attenuating the input signal too much, a wrong value resistor again.

[djQUAN]

There is the alternative small possibility that the input impedance is too low hence attenuating the input signal too much, a wrong value resistor again.

possible but not likely, if driven from the ipod's headphone out, the output has enough driving ability.

I'm guessing, the wrong value for the gain setting resistors. double check those to be sure. BTW, what values did you use for those?

[jackinnj]

Originally posted by Chris8sirhC
my younger brother just finished putting together his GC and he has it hooked up to this speaker but it doesnt even have enough power (with no volume selector even attatched) to get that speaker to a normal quiet listening level? what could be wrong?

what's the voltage on the +/- rails? Plug into this spreadsheet the device you are using (3875?) and rail voltage and you can see how much power to expect out of the device:
http://www.national.com/appinfo/audi...gn_Guide13.xls

[janneman]

On the input side there probably is a serie resistor and a resistor to gnd. Mix these two up and you got what you describe.
You got a schematic you can post?

Jan Didden

[ashok]

Hi Chris8sirhC,
A thin sheet might not be good enough for the heat sink. I have a fairly chunky heat sink with fins that is not enough.
Look at my post :

http://www.diyaudio.com/forums/showt...079#post479079

Like others said the gain may also be wrong .
But better fix the heat sink first.
Cheers,
Ashok.

[janneman]

The heatsink issue is the easiest to check. Does it get warm, hot or burning hot?

Jan Didden