Is the iPod USB out a true line out?

[gdg]

Is there a reason that some people choose to mod their iPod so that the earphone jack provides a line out rather than use something like a Turbodock to access the USB port line out? I've heard that the iPod USB output is not a true line out. Is that true?
Gerry

 

[ComfyCan]

Quote:

Originally Posted by gdg Is there a reason that some people choose to mod their iPod so that the earphone jack provides a line out rather than use something like a Turbodock to access the USB port line out? I've heard that the iPod USB output is not a true line out. Is that true? Gerry

I'm not sure I understand your post; I'm pretty sure that all Ipod docks/adapters with a USB connection have a USB port for the sole purpose of permitting you to power/charge the I-Pod via USB, not as a means of conveying an analogue signal to another device. I have the Pocket Dock w/ USB, and that is certainly what it does. You get a line out by plugging a 1/8 miniplug interconnect into the jack on the dock, or by using the built-in line w/miniplug hardwired on some such devices.

All such devices are designed to bypass the headphone out circuitry, which also means bypassing the headphone jack itself.

The exception is a mod like the Rewine mod which can be done on 4th Gen Ipods, which transforms the existing headphone out on the player to a true lineout.

I can't speak to the sound quality difference between a redwine modded Ipod vs. an Ipod with a lineout via an adapter. However, I've never read a post by anyone who paid for a redwine mod who wasn't extremely happy with it. Hope this helps.

 

[aragorn18]

I think there's a bit of confusion. When gdg says "USB out" I believe he means the line out in the dock connector.

 

[Chef Medeski]

Quote:

Originally Posted by gdg Is there a reason that some people choose to mod their iPod so that the earphone jack provides a line out rather than use something like a Turbodock to access the USB port line out? I've heard that the iPod USB output is not a true line out. Is that true? Gerry

All a line-out is a level signal that would be created by bypassing the built in headphone amp of the iPod, to take the signal straight from the DAC, making it a lot cleaner.

Yet, when people convert their iPod headphone outs to Line-out (its called a Red Wine iMod) they aren't just bypassing the headphone amp, Vinnie (the one who does the mods) actually installs superior signal wires and different caps. This all causes it to sound superior to a line-out. So, its not the line-out that changes but the internals of the iPod. If you were to merely convert the top of the iPod to a regular line-out without changing any of the things Vinnie does, the difference would be negligible. Yet, since he does all that, its worth $200.

They do all this:
Even if you use the very best iPod cable with your stock iPod, you are still not avoiding the serious degradation
of sound that results from the cumulative effects of the following "offenders" in the signal path:

-- The low quality stock SMT coupling caps after the Wolfson WM8975 DAC (used in all 4th gen. iPods)
-- Opamp output stage following the Wolfson DAC
-- The minuscule circuit board traces that travel from the top of the mother board down to the
dock connector jack
-- SMD resistors and inductors directly in the signal path
-- The dock connector jack at the bottom of the iPod
-- The signal path inside the iPod dock, which contains: the dock connector plug, a very cheap
ribbon cable, more minuscule pcb traces, SMD resistors, and finally the line out jack.

The goal of the Red Wine iMod is to significantly minimize the analog signal path that follows the
output of the internal Wolfson dac chip. We take the analog output (line out) off of the dac chip and
send it directly to the internal 1/8" headphone jack (converting it into a dedicated line-out jack) via
high-end Black Gate Non-Polarized NX-Hi-Q coupling capacitors.

Check it out at: Red Wine Audio iMod

 

[gdg]

Thanx for the detailed explanation Chef.
Gerry

 

[Chef Medeski]

Quote:

Originally Posted by gdg Thanx for the detailed explanation Chef. Gerry

No problem.