I have a setup where an amplifier with 2 channels drives four 8 ohms 80 watts speakers on each channel. The amplifier has a single volume knob which controls volume of both channels at once. What I would like to do is add a volume control for both channels separately between amplifier and speaker. This as I understand is not the right way because the potentiometer required will have to handle 80 watts of power, and thats why a volume knob is used at the input of amplifier instead of output. Unfortunately i have to use the setup i described. I have looked into T-pad and L-pad attenuaters/resistor divider.
I would like to know whether I can get some good ones in Europe? I am presently living in Austria, and I really cannot find anyone who deals with it in Europe. Also does anyone have experience/suggestions with controlling volumes of 2 channels separately?
Best Answer
There are a couple of ways of doing what you want.
The most obvious method is to use a commercially-available "L-Pad". I've seen these available with power ratings up to about 100 Watts. The higher-power versions can be expensive.
Note that the internal wire-wound resistor elements have an appropriate audio taper. The larger versions have resistance elements that change wire size as the resistance gets lower and the power being handled gets higher.
Another method is to use a tapped transformer. These are available for both 70V and 25V distributed loudspeaker systems.
What is not commonly known about these transformers is that although they are intended for use in a constant-voltage loudspeaker distribution system, they can be used directly between a low-impedance amplifier and a low-impedance speaker. It is simply a matter of choosing the right transformer.
Look for a tapped transformer that will work with both 70V and 25V systems with a power rating of at least 100W. Depending upon how low you want the frequency response to go, they can be relatively inexpensive. The least expensive versions of these only go down to about 200Hz and are intended for ceiling speakers. The better ones go much lower and are used in large venues such as sporting facilities (with much better speakers).