Q on loudspeaker amplification

weinstro · 22nd July 2007, 06:05 AM

It's funny how one thought leads to another, and then another, and then....

I really like the concept of a digital crossover, such as the DCX2496. The universal nit with this device is a) it has pro voltage output levels and b) it doesn't have a ready means of controlling volume.

I'm in the process of working through how to control volume. My leaning at the moment is towards some sort of digital pot, controlled by a Basic Stamp, placed between the DCX and the power amps. Some of these IC's have gain stages built in. Then it occurred to me, how much voltage do I need to feed to the power amps, anyway?

All the amps I have are supposed to generate rated output at 1.5 V input, give or take. The output of the DAC's in the DCX max out at +/- 2.5 Vdc. It has 10dB of gain before this signal is presented to the output jacks.

I'd prefer to avoid the situation common on home audio, where the volume is effectively at max with the volume knob at 1/3rd of a turn.

I can appreciate that it might be desireable to overdrive the input slightly. But, if the player is putting out 0dBfs and the volume knob is at max, how much output voltage is really needed?

Thanks and regards,

Rob

MadMutt · 23rd July 2007, 01:08 AM

Well my take would be that if you have more signal than you need to drive the amp, then (if you can) turn the amps inputs down.
This will reduce the amount of noise getting into the amp to start with.

22nd July 2007, 06:05 AM	#1
weinstro diyAudio Member Join Date: May 2003 Location: California	Q on loudspeaker amplification It's funny how one thought leads to another, and then another, and then.... I really like the concept of a digital crossover, such as the DCX2496. The universal nit with this device is a) it has pro voltage output levels and b) it doesn't have a ready means of controlling volume. I'm in the process of working through how to control volume. My leaning at the moment is towards some sort of digital pot, controlled by a Basic Stamp, placed between the DCX and the power amps. Some of these IC's have gain stages built in. Then it occurred to me, how much voltage do I need to feed to the power amps, anyway? All the amps I have are supposed to generate rated output at 1.5 V input, give or take. The output of the DAC's in the DCX max out at +/- 2.5 Vdc. It has 10dB of gain before this signal is presented to the output jacks. I'd prefer to avoid the situation common on home audio, where the volume is effectively at max with the volume knob at 1/3rd of a turn. I can appreciate that it might be desireable to overdrive the input slightly. But, if the player is putting out 0dBfs and the volume knob is at max, how much output voltage is really needed? Thanks and regards, Rob

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23rd July 2007, 01:08 AM	#2
MadMutt diyAudio Member Join Date: Nov 2006	Well my take would be that if you have more signal than you need to drive the amp, then (if you can) turn the amps inputs down. This will reduce the amount of noise getting into the amp to start with.

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