Who knows volume and gain controls? (1 Viewer)

[James Slade]

After reading the forum for months and building two subs of my own I still don't totally understand volume controls for subs. Seems to me that a lot of others are in the same boat based on all of the conflicting information. Can we clear all of this up? I think we should divide it into two cases

1) Subs with Plate amps

Exactly how to set things up is gray area to me. Cranking the plate amp just doesn't work. I could never get down to a useful level. If I set the trim on the receiver two low the sub never turns on.

2) subs with Pro amps

Most people say crank the amp and control the level with the trim level on your receiver.

What is the right way to set-up a sub in each case and why?

What exactly is the difference between volume and gain controls, and how do the work when used together (receiver + plate or pro amp)?

 

[Pete Mazz]

First off....the difference between a volume control and a gain control. A volume control can boost the signal coming in to the amp(usually found on plate amps). A gain control can only attenuate(cut) the signal coming in to the amp.

#1) Plate amps:

Best way to set the level using a plate amp is to set the processors sub level at ~25%(level at -5 if range of control is +10 to -10). Then set the plate amps volume control to level match the sub to the system. If the plate amps auto turn on doesn't kick it on, then raise the sub level of the processor some and compensate by lowering the volume on the sub.

#2) Pro amps:

Set the gain control of the amp all the way up(unity gain), and adjust the processors sub level control to level match the the sub to the system. If the level can not be reduced enough to level match, then use the gain control to attenuate the signal to the amp.

The reason to try to keep the processors sub level low is to not introduce distortion of the sub level signal. Some processors were measured and found to distort the subs signal when set too high.

Pete

 

[Jim A. Banville]

If you're using a powered subwoofer, you should set the receiver's sub out volume at "0" (when given a range like -10 to +10). You should then use the sub's own volume control to adjust it to match your main speakers' volume.

 

[James Slade]

Can my plate amp clip when the gain control is only at 1/4?

If yes how? and how likely is it? I guess it seems possible to me but probably wouldn't happen.

 

[jeff lam]

Can my plate amp clip when the gain control is only at 1/4?

If yes how? and how likely is it? I guess it seems possible to me but probably wouldn't happen.

Sure can! You can clip any amp with enough input voltage. Even if the amp is only set at 10%. For example, say you have a plate amp with 300mv input sensitivity, if you load the thing with 5-10v you will surely get full power from the amp at any level, even if the gain is up only 10%. when you exceed the full power of the amp, that's when it clips. Most likely you will not clip the amp with a normal receiver and the sub amp set at half way or less (plate amp).

My suggestion would be to use 25% gain on the receivers sub output level and use the sub level (plate amp) to set your calibration level (like what Pete said), but only if you listen at very loud levels (15-10dB below reference or higher). At these levels you shouldn't have a problem with the sub not turning on.

Use Jim's method if you listen at levels lower than that (to help turn on the sub). I currently use the 1/2 way on the processor sub output because I don't listen nearly that loud. Although if I wanted to listen at reference I would get distortion at 1/2 level. I have tried this and can hear distortion at the loudest bass sceens like TS2 or TPM THX intro (although it could be my BFD).