Line out for subwoofer in tube amps

[Gilbert]

Hi all,

I want to add a line out for a subwoofer on a tube amp. Figured I pull it right off the volume control but I'm not sure about loading of the grid that would more or less be in parallel with the line out.

Here's some assumptions:

1.) subwoofer input impedance, guessing around 100k

2.) I use mainly a 100k pot for volume control feeding the input grid of the first stage. But volume usually never exceeds half way up so typical resistance to ground that the grid sees is 50k or less, probably averages around 25k at normal volumes.


So it appears that the input resistance of a subwoofer might not load the input too bad???

You could add series resistance to the line out to further reduce loading too, right? Obviously that would reduce signal level to the subwoofer, but you just turn the subwoofer up to compensate.

Anyone ever do this? Things to watch out for? Any schematics on how this is typically done?

Thanks for the input,
Gilbert

 

[Eli Duttman]

Gilbert,

Consider a completely different tack. Drive the sub via speaker level I/Ps. Don't "daisy chain". Simply connect the sub in parallel with your main speakers. The advantage of the arrangement described is that the sub picks up some of the sonic signature of the main amp. Therefore, blending is better.

BTW, no mods. need be made to the main unit.