Portable Amplifier Volume control with decreasing battery voltage

JonRosko

Member
2009-10-17 3:26 pm
I'm thinking about creating a lithium battery powered portable amplifier using one of the cheapo class-D amplifier boards from parts express. The only thing that trips me up is the decreasing battery voltage affecting the volume output of the amplifier over time.

Off the top of my head I can think of 2 strategies for dealing with the issue:

1. Use a DC-DC converter to supply a constant voltage to the amplifier regardless of battery voltage.

2. Implement some sort of micro controller active variable gain or digital volume controller to increase the gain/volume as the batteries drain.

I'm not sure how commercial portable systems overcome this, but I was wondering if anyone here has some thoughts or knows what might already be the standard solution for what seems to be a fairly ubiquitous engineering challenge.
 
You are not analyzing theproblem the proper way.
I'm thinking about creating a lithium battery powered portable amplifier using one of the cheapo class-D amplifier boards from parts express. The only thing that trips me up is the decreasing battery voltage affecting the volume output of the amplifier over time.
No, it will affect *maximum possible* volume output, at clipping.
A terrible way to use an amplifier so don´t, whether with full or discharged batteries.ou must always use the amplifier at *less* than maximum power.

Off the top of my head I can think of 2 strategies for dealing with the issue:

1. Use a DC-DC converter to supply a constant voltage to the amplifier regardless of battery voltage.
No need to, because amp must be sized so as not to clip under normal use.

2. Implement some sort of micro controller active variable gain or digital volume controller to increase the gain/volume as the batteries drain.

Gain does not decrease on lower supply voltage, and increasing gain will send amp into clipping, as Rayma said.
I'm not sure how commercial portable systems overcome this,
They don´t because it´s not a realistic situation.
but I was wondering if anyone here has some thoughts or knows what might already be the standard solution for what seems to be a fairly ubiquitous engineering challenge.
Specify a proper power amplifier, with a proper sized battery so it stands the duration of the event.

If battery noticeably dies during it, then get a larger capacity one.