Here's the scenario:
Typical Audigy output is 2 Vrms.
An amplifier has an input sensitivity adjustment from 200mV to 4V.

I'm not exactly sure exactly how to convert Vrms to V, so I go by this assumption:
1) Many users say the output of the soundcard is a relatively low ~1V.
2) Amplifier RMS calculations are based on a sinusoidal input, but the conversion factor isn't 0.707 because that is near the clipping ceiling. So the multiplication factor of 0.636 is used instead.

I just multiplied 2 and 0.636 to get roughly 1.24V output of the soundcard. Ok, close enough eh?

I want to set the input sensitivity to match the sound card output since I plan to drive the amp directly from these outputs. Preamp/Processors are expensive, and a DIY project to amplifiy the soundcard signal will introduce even more noise to the system.

Suggestions? Yea, I've asked about soundcard->amplifier... but now I want to make sure the Input Sensitivity is set as accurate as possible.

[Wah? The Alpine V12 amps have NO gain controls!?]

 

I think you've got it backwards.

2 Volts RMS (root-mean-squared) is already 0.707 times the peak-to-peak measurement giving you the "working" voltage of 2V. Your amplifier sensitivity isn't rated as RMS or peak-to-peak but will accept a rather large range of voltages from 200 millivolts (0.200 Volts) to 4 volt (4000 millivolts) which I would guess is RMS. You use 0.636 to obtain the average voltage ... IIRC from my classes 30 years ago! Your 2 volts RMS is really 2.8 volts peak-to-peak.

The most accurate way to set your voltages to avoid clipping is with a test tone and o'scope. I have a test CD burned with maximum volume tones which I can play back though the head-end or external CD-player. You connect up an o'scope and watch for the peaks to start clipping off. First you check your head end to make sure the whole volume control is good and then you check the output of your amplifiers. You adjust the gain of the amps up to just the clipping point. You can also over drive your woofers bouncing them to the mechanical limits in a poorly designed system. For that you'll need a microphone listening to the speaker's motion.

 

OOps... yea, you're right. It was a redundant calculation. I was definitely wondering about the input sensitivity, and wanted to correlate it with the soundcard output.

BTW, the amp I'm looking at has input sensitivity adjustment, but no gain control. So if it has some fixed gain, is this just as good?

I looked at a different model that had gain control, but no input sensitivity. :-/

I don't want to put anything between the two components since my outputs are already good coming out of the Burr Brown op amps I dropped in place of the cheapies.