Techies - matching line output levels ???

slushieken · 09-10-2004, 10:57 AM

I have gotten to the point that to save a few $$$ I am going headless, and to save a bit more, use a plain ol' EQ with a seperate line drive amp, rather than a combined device like the three.1.

So I know that the Audigy NX I use puts out a 0-2v signal, and the amps I use want a 4v signal.

Since I am using a static line drive amp, I won't be able to adjust the gain on the fly after the car is closed up. So I guess I need to make sure that the levels are matched using a more stable method than my ears? I started doing some research, and I think I am on the right track, but not so sure...

Can I do this with this process:
use a test sound (http://www.rme-audio.com/english/download/audtest.htm)
Play that through the soundcard
Adjust PC volume to just before the distortion point.
put in line driver
measure voltage with AC voltmeter after line driver, and adjust line driver gain until I see as close to 4v as I can get, without going over, and without distortion.

some ??'s:
Amp says it takes up to 4v, how close to this should my final line drive strength be?

Should these measurements be done as dBu (unloaded) or dBv (loaded), and does (un)loaded mean ouput wires connected/not connected to the next device?

Is there any way to do this better? like with a dB meter? I have no idea how those work or what they actually measure (from my reasearch it looks like it is just a factoring iof voltage). Maybe I can borrow one if so.

I won't feel bad if someone tells me to insert hand in rear and pull down firmly on head, cause I am just piecing together what I found so far, and I could be way off...

chut · 09-10-2004, 11:14 AM

Actually I think you are expressing a valid concern and since I am going to be installing two cheap line drivers on my system this weekend, I am understandibly curious also. Can we not just turn them up until they sound loud and clear to our ears?

slushieken · 09-10-2004, 03:31 PM

All I know for sure, is that if you use one of the line drive amps like the three.1, you can just adjust it on the fly (got a gain knob on the front). So ears would work fine for that.

Another thing I thought of - I know from research to go from audio source to the line amp with the shortest wire possible, then take the amplified signal to the EQ. Will the EQ cause a signal drop?

I would think so, since it is dividing the signal up to front/rear and sub out. Plus *any* device on the line should cause at least some drop.

I was thinking that if my initial thoughts above are right, it would make sense to also recheck athe voltage after the EQ. Probably best to check this all the way at the end of the line out cable where it goes into the amps in fact, to compensate for voltage loss through the wires too.

chut · 09-10-2004, 03:57 PM

Sounds good.
I don't have an EQ inline anymore so I'm not really worried about signal loss. The lines to input from pc to amp are 3' long that's the shortest I could make it without making the cables myself. PC is located right next to the amp.