The GF needs a new head unit after a break in where they stole her Alpine 7894 (????) face plate.
Looking at these Pioneer HUs. DEH-P680MP & DEH-P6800MP

http://www.pioneerelectronics.com/pna/v3/pg/product/details/0,,2076_310069882_291094587,00.html

http://www.pioneerelectronics.com/pna/v3/pg/product/details/0,,2076_310069880_291078777,00.html

The online tech sheets show the Premier (860) unit comes with a 2yr warranty vs a 1 yr with the 8600.
Also the Premier unit has 3 instead of 2 "loudness" settings.
Other than that the only difference I can see is:
Preout Voltage & Impedance Hi-Volt (4V), 100 Ohm
Preout Voltage & Impedance 2.2V, 1k Ohm

How will these effect "real world" performance?
Particularly the impedance?

The Hammer

 

You might or might not notice the diff between a 2 and 4v preout voltage. I consider more = better. I'd advise you to get a Premier just because of 4v preout and longer warranty. I did when I first got my system. It wasn't much of a difference, is it now?

Real life example: I had alpine 9853 deck with 2v preout and then switched to 9835 with 4v preout, didn't hear too much of a difference, readjusted the gains of course.

 

You aren't really supposed to "hear" a difference (I'm assuming your hinting to quality) but a larger voltage will give you more volume...

 

What "volume" you refer to?

 

Well its a stronger signal, so you can turn amplifier gains down, so I guess the correct term would be higher "gains"...

 

heres my opinion for what its worth

higher voltage out of a deck allows for a lower gain setting on the amplifier for the same power output... your amplifier voltage gain has now decreased allowing the amplifier to work a little more efficiently also allowing for a higher signal to noise ratio..meaning less hiss and humm if any...
the lower impedance basically means it is capable of driving a higher current on the output rca line ...sort of like a low impedance amplifiers output can drive more current to a speaker... well it could be used to drive more than one amplifier input without sacrificing a voltage drop of the RCA line output and cause clipping

hopefully thats understandable

 

Thank you,


The Hammer

 

Very good explanation.

 

X2 .... i never acually sat down and thought about it

 

Higher preamp output voltage and lower impedance really only reduces the amount of noise picked up by the rca cabling, and as such higher voltage is better. Going from 2 to 4 volts is 3db more and thus results in a 3 db better signal to noise. Reducing the impedance will reduce the noise voltage generated by the noise current a tiny bit more. But PA inputs are 10Kohm or higher and thus going from 1Kohm to 100ohm preamp output impedance does not help much. To get better performance both the preamp out and the PA in have to be low impedance and balanced. An example is pro audio gear that is 600 ohm balanced. This give the best noise immunity.

There is no improvement in efficency in the power amp since it is the preamp stages that add the gain in the power amp.
If you assume no noise picked up by the RCA cabling then you are really only comparing the quality of the preamp in the HU vs the preamp in the PA.