Volume Control

kirk78h · 03-11-2008, 09:48 PM

I know this sounds like a simple issue, but I'm having a hard time controlling the volume in my system. With the master window volume control set at 5%, it is too loud. If I move it down to 4%, it cuts out the volume completely. I have tried adjusting the master volume, wave volume, line-in volume (for Sirius) -- all with very little success. I'm using a USB sound card (Turtle Beach Audio Advantage), that has a dial control for volume. Adjusting that helps some, but seems to just shift the point between silence and too loud to a different point (say, 34% and 35%). When I bring the computer inside, and hook it up to regular computer speakers, it works and sounds great -- I have a full range of volume adjustment. Also, I can connect an mp3 player to the amp in my car, and adjust it through it's full range. Unfortunately, my PC and my car amp / speakers just don't play nice together. I get the feeling that there is a big step integrating the two that I skipped. If someone could help me work through my ignorance, I would be very appreciative!
My other components:
Kicker KX650.4 amp
Elemental Design components in the front
Elemental Design 12" Sub

Thanks,
Kirk

scott_fx · 03-11-2008, 10:01 PM

have you played with the gains on the amp?

kirk78h · 03-12-2008, 09:09 AM

Quote: Originally Posted by scott_fx

have you played with the gains on the amp?

I could have sworn I zeroed them out; but I double-checked this morning, and they were both too high (about 5/10 for the front; about 7/10 for the sub). I turned both way down, and that gave me the range I was looking for. (I also kicked myself in the rear for not checking this...)
I have always used the old rule to set gains as this - set the volume at 75% and increase gain until distortion starts; then back it off a little. If I do this, where should I set the volume control on the USB sound card? This is kind of a "middle man" I've never dealt with before.

Thanks Scott!

hithere · 03-12-2008, 09:30 AM

I'd set gains like this:

1. Acquire a 1-kHz sine wave test tone file recorded digitally at -5dB (for crossed over/component setups, you might choose to find a tone in the middle of the frequencies that each speaker will be playing, and repeat these steps as necessary).
2. Turn all amp gains to a very low level (counterclockwise nearly all the way, towards a higher voltage input if marked).
3. Turn all "software" volumes on the PC to 100%
4. Turn soundcard external volume to zero.
5. Play your test tone through whatever audio software you plan to use, again, with all soft volumes at 100%.
6. Turn the external volume on the sound card up until either: a. you hear clipping from the soundcard (change in pitch of the tone) or b. you reach 100% output on the sound card's volume. If you hear the pitch change, back off very slightly until you don't.
7. You have now found the "-5dB clip point" for your system sources as presented to your amps at the RCA input. Set your amp gains up to match this "maximum clean" input signal, using your preferred gain setting procedures (either outlined in your amp's documentation, or found at other trusted sources).

The reason to use a test tone at -5dB rather than a higher level tone at 0dB, is to maximize the available power to the system. While this is technically pushing your system too far with regard to a given test tone, no one I know listens to test tones....music spends the vast majority of its time well away from a 0dB reference point (0dB is the "loudest" digital signal you can represent on a CD), so you are safe with the system set up with reference to a -5dB sine wave as the "maximum". Doing the steps above ensures that you are sending the maximum "clean" signal to your amps, and that the amp gains are set up with reference to that signal, provide maximum clean output at the speaker. Purists may choose to set gains with reference to a 0dB signal, but such a practice can needlessly hamstring a system's available power, all for the gain of some tiny fraction of a percent THD typically well below the losses in SNR it represents by way of limiting the output of various sources in the signal chain. In the unlikely event that your sound card provides some monster voltage signal out that forces you to bottom out your amplifier gains to match it, you can set things up with reference to a 0dB signal for steps 1-6, then for a -5dB at step 7, and not worry about losing fidelity to noise in the system...or, in the case that your sound card doesn't clip, even with a 0dB tone at maximum volume, you can just back off the sound card's external volume a bit. Most sound cards, however, have rather weak voltages so this isn't a concern.

kirk78h · 03-12-2008, 10:08 AM

Quote: Originally Posted by hithere

I'd set gains like this:

<snip>

WOW! Thank you VERY much for the quick and detailed reply!

Kirk

hithere · 03-12-2008, 02:52 PM

Quote: Originally Posted by kirk78h

WOW! Thank you VERY much for the quick and detailed reply!

Kirk

If you want the quick and dirty version, you can do the above with a loud piece of music instead of the test tone. Look up recordings associated with the "loudness war" in google, or just use something you typically listen to at high volume levels that fits that description....typically, the more recent the recording, the better.