STK4050V and it's use in Definitive Tech PF15TL subwoofer

[at1receptor]

Sorry but this schematic is totally different from the one being discussed. This is the DF PF15TL & not the PF15TL+. I don't believe there's a way to drop the amplifier response to 10 Hz. This class D amp was made to deliver only up to 15 Hz which I believe is fairly low.

But wait, some other person might have a better idea.

[Stuart Easson]

of the schematic you posted...

hpf2 looks like it controls the low end of the freq response. The schematic gives explicit instructions on how to disable it. Not sure if the same technique can be applied to the other band pass filter.

As to the capabilities of the woofer and power amp at the frequencies you need, someone else will need to chime in.

HTH

Stuart

[jyhfeei]

The amp I have is the PF-15TL (actually 1500TL) so this is the correct schematic.

I don't want to get rid of the filtering circuit as I still want to filter DC. I just want to lower the corner frequency to about half of what it is such that the amp is still putting out power at 15Hz or so.

So.....should I double the values of the input caps to these hp opamp filters or change the values the input resistors. I'm looking for a more qualified person to confirm what is the best path to acheive this.

I'll also have to modify the band pass circuit as it is also filtering the low frequencies before the amplificaion.

Thanks for any help you'all can provide. It's appreciated.

[curtisholson]

Sorry for the dumb question, but I had the same problem as the creator of this thread. My friend has a PF15TL that quit working. (Power light comes on but would not pass sound) I did some checking and found that R89 (19.1k 1/2w) was bad. I replaced it with a 20k 1/2w resistor and it works. The only problem now, is that the woofer "pops" when the AC is unplugged. I'm not sure if this is normal or if it's because of the higher value resistor. So my question is, will ordering 19.1k resistor and replacing it fix the problem, or should I just leave the 20k in and call it good? Will this create other problems in the future?

[Stuart Easson]

I doubt the exact value is critical, but if the sub is working again, it is probably worth finding a 19.1k resistor, but in a power rating at least twice as high as the original, so perhaps 1 or 2W or you risk the same thing happening again. Parts express have a reasonable range of resistors if you don't feel like dealing with mouser or digikey.

I doubt the pop is critical, at least if it is not too loud. Can you see the cone, does it move a lot? My Velodyne used to do the same when powered off, after a couple of seconds the light would go out and the cone would do an inwards 'plop'.

HTH

Stuart