I've tried connecting my iPod to my car's aux in via the iPod's headphone jack so far, haven't bought a line out adapter yet, and I have to turn the volume all the way up on the iPod to get a signal that rivals my head unit's CD player and radio. I'd like to have the signal this loud so I won't have to turn up and turn down the volume on my head unit everytime I switch between iPod and my head unit.

However, I'd also would like to use the line out signal (via an adapter like the SIK IMP) to get cleaner sound, but I'm afraid the line out signal will be very weak compared to my head unit's cd player/radio. Can anyone with a line out adapter give me a general idea of how the line out signal strength compares to the headphone out when at max volume?

If the line out volume is too low, I'd consider using the belkin Auto Kit since it has a small amplifier built in, but my concern there is that the amplifer on the Belkin will degrade the signal. Can anyone give me a gereral idea just how bad (or how "not bad") the Belkin Auto Kit distorts the line out signal? Thanks.

Let me answer this in a different way. Standard line level voltage is 1V. I've heard third hand that the iPod is only 0.5V. However, if you were to take a poll amongst us that utilize the iPod's line out to head unit's aux line level in, you'd probably get 90%+ say that it works fine/great.

Check your head unit to see what it accepts for line in.

One way to test it out is to put your iPod in the OEM dock (assuming you have one) and plug the 3.5mm to the line-out jack on the dock. Mine works very well and it sounds a little better than the Belkin Auto Kit.

Quote: Originally posted by coppermine
One way to test it out is to put your iPod in the OEM dock (assuming you have one) and plug the 3.5mm to the line-out jack on the dock. Mine works very well and it sounds a little better than the Belkin Auto Kit.

That's the thing, I don't have any line out adapter and I'm trying to decide which one to buy.... the belkin with the mini-amplifier on it, or any other one with a straight line-out passthrough. I wish I could get my hands on one to borrow and test it myself.

Anyway, sounds like the straight line-out is definitely better and the voltage from it, though a bit weaker, will be high enough so that I won't have to turn the volume knob on my car headunit WAY UP to get a normal volume. But if I get better sound quality with the straight line-out, I guess I can live with remembering to turn down the volume knob on my headunit before switching back to CD or Radio if need be.

OK, I just plugged in my earphones to the dock and the sound is strong. I go for unamplified.

I just got my iPod line-out adapter (SiK IMP) and man, the line out is pretty strong. It's almost as loud as the headphone jack at full volume. I suspect this is more than 0.5V. Anyway, I'm very happy with it, my last MP3 player's line-out was SO WEAK. I had to turn up the volume in my car to at least 1/2 to get a reasonable volume, now I can turn it only to 1/4, which is what I usually do for CDs and the radio.

pdp - part of the reason is impedance matching. The line out is meant to drive the high impedance of the aux input. The headphone out is meant to drive the low impedance of the headphones.