Turning down the volume controls of the amp ALSO changes the input sensitivity on most amplifiers. Basically, that means that the input of the amp may more easily "clip". If you clip the input of a power amplifier, it is capable of producing 5 times it's rated maximum output!!! That is not so good for speakers eh?
In the end, you might just NEED to turn down the input of the amp to create a better taper on the volume control knob of the circuit before the amp. I use a Hafler P3000, and instead of input controls that go from full on the full off (full attenuation), it offers up to -14 of attenation. You cannot fully turn down the amp.
Recently, at the studio, we replaced the P4000 with a P3000 (we closed down one of the editing rooms, so we had both amps available). With the P4000, the volume controls had to be set to around 7 or it was just too loud. The P4000 has a full "to infinity" input control. Anyway, when we put the P3000 in, we of course had to leave the volumes at full to achieve the same volume coming out of the monitors because of the output wattage differences between the two amps (bascially, the P4000 NEEDED to be set at 7 to match the same output level of the P3000 at full volume...) So, on the Control Room Output on the mixer, our normal listening volume setting was around 3 or 4.
I didn't like this. The taper of most rotary pot's starts getting extremely sensitive as you get to the lower regions of it. So, the difference between "3" and "4" was pretty drastic. I wanted a smoother taper, so I turned the input of the P3000 to -14. This allowed us to turn the C/R Output knob up to 5 to achieve a similar volume that 3 provided with the P3000 at full volume. But now, I get a much more smooth taper when turning the C/R Out up and down. The difference between "5" and "6" is not the same with the P3000 at -14 as the difference between "3" and "4" was with the P3000 at full volume.
Okay, so basically I just traded some input sensitivity on the input of the amp to allow for me to use a wider taper on the C/R Out (I could have said just that, but I KNOW that that would have confused some people...I find too many people don't follow good gain structure practices....)
The reason I don't like doing something like this is because you are then relying on the input knobs accuracy on the amp. These pot's are not always showing you the best accuracy, but usually, full off produces no volume, and full on produces max volume on the amp. It is the "inbetween" that usually concerns me.
Now, an amp that was maybe half the power of the P3000 at 4 ohms would have meant that I could run the amp at full volume and still have the C/R Out set to around 5 to enjoy a better taper on the C/R Out pot. BUT, I believe in running amps that are at least 150% the rated power of the speakers. Doing so FORCES you to keep gains before the amp set lower
So, I could have traded more rated power for not having to use reduction in the input sensitivity of the amp, but would have possibly traded "security" in my knowledge that the higher wattage amp would force me to reduce volume before the amp.
Blah blah blah....The point I am making here is that gain structure is simple AND complex.
Do what works, but do so logically.
In your case I would:
Try running the amp at full volume first. This is the only way you can be assured that the input sensitivity knobs are not creating unbalanced outputs for left to right channels. Just because there is a silkscreen printing on the front of the amp that says "7" on both channels doesn't mean that both pot's are taper EXACTLY the same. 7 on one side might truely translate into 7.5 on the other! On cheaper amps, I have found this to happen a lot unfortunately. Running both volumes at full will at least assure that both sides of the amp have EXACT input sensitivity, or at least that the knob is not part of the difference that still may be present. You are also forcing yourself to reduce gain's in the circuit before the amp, which is desirable considering that clipping the input of an amp will produce output peaks up to 5 times it's rated max power.
Next, check to see that you can in fact get a good range of volume with the Control Room Output you are using to feed the amp. If you can get a good range, then keep the amps at full. If you have to turn the C/R Out down pretty low just to get the loudest volume you would want to work at, and when you turn it down even lower you notice that the balance from left to right starts to change (one channels goes lower than the other...this is something that CAN happen on stereo signals that are controlled by the same volume knob when that knob is at it's lower part of the knobs taper) then you need to create a way to keep that C/R Out at a higher setting to avoid this problem. About the only way to do this is to turn down the input's on the amp.
If that is the case, then run a mono sine wave through your monitors and sit in the ideal listening position and make the adjustments that way. Don't ASSUME that 6 or 7 on both volumes on the amp is the same. That may not be true. Use your EARS to tell you .
I have had first hand experience with Samson amps. I have found that I usually needed to adjust one side differently than the other to get proper balance. Maybe a faulty input pot on one side of the amp? Who knows. My Hafler usually doesn't suffer from this, but Hafler is consider fairly high end stuff, so I could expect it to provide better accuracy between what actually happens and what the tactile surface says.
Anyway, hope this helps a bit.
Ed
