HU Pre-out Voltage - Does it matter?

 

Silver Member
Username: James_g

TN

Post Number: 376
Registered: Jul-05
Both of my amps have an input sensitivity adjustable from 170mV-5V. Will it make any difference if my HU has 2V pre-outs as opposed to 4V pre-outs?

This is the HU I'm considering:

http://www.sonicelectronix.com/item_3304.html

Any recommendations on other HUs?
 

Silver Member
Username: James_g

TN

Post Number: 379
Registered: Jul-05
How about this HU?

http://www.sonicelectronix.com/item_3488.html

If the list price they claim is a legit retail price, then this looks like a whale of a deal. How about the 1.7V pre-outs?
 

Bronze Member
Username: Maddrakkett

Post Number: 23
Registered: Sep-05
I originally bought a Pioneer DEH-P7700MP with 2.2V outs feeding Memphis PR amps which have input gain of .5V - 5V.

Circumstances lead to me exchanging the Pioneer for the better Premier version DEH-P770MP which has 4V outs.

The difference in pre-out voltage is noticeable; the signal is significantly cleaner, meaning MUCH LESS hiss/noise and LOTS MORE headroom and dynamic range.

I like this unit, plus it has direct access to complete control of the subwoofer!

Check it out:

http://www.sonicelectronix.com/item_3532.html
 

Gold Member
Username: Illuminator

USA

Post Number: 2198
Registered: Apr-05
Wow, all of the headunits in this thread are nice.

It is really a matter of preference, but everyone seems happy with Pioneer...not sure if they have really tried anything else, but it is a great brand nonetheless.



 

Silver Member
Username: James_g

TN

Post Number: 380
Registered: Jul-05
How about the 2V outs compared to the 4V outs? Should I be sure to get a HU with 4V outs?

I was leaning toward Alpine or Clarion, but I'm open to any and all recommendations on HUs. I'll spend as much as $400 online, but I'd rather keep it less than that.

By the way, I can use double-din HUs in my vehicle, so they are also an option.



 

Gold Member
Username: Illuminator

USA

Post Number: 2202
Registered: Apr-05
They're becoming so common, it shouldn't be too hard to find one with 4v preouts. I would recommend it, yes.

Double-dins are pricey, a single din will do the job much better...
 

Silver Member
Username: Tjmutlow

Post Number: 141
Registered: Sep-05
I wnet from a high end unit to the AVIC-D1 and the sound quality sucks, going to add audicontrol three.1 to increase voltage to signal volatage to amps to help get sound quality bACK
 

Bronze Member
Username: Maddrakkett

Post Number: 24
Registered: Sep-05
RE: James G:

Quote: "How about the 2V outs compared to the 4V outs? Should I be sure to get a HU with 4V outs?"

After having both 2.2 and 4.0 volt units of the same model, I highly recommend going 4 volts!

You will get better dynamics, headroom and much less hiss from the signal. This means you can turn it up as loud as a 2 volt HU, but with cleaner and better sound quality that you can easily notice. :-)
 

Silver Member
Username: James_g

TN

Post Number: 382
Registered: Jul-05
Thanks, folks.

I purchased an Alpine CDA-9855 with three 4V outs earlier tonight. All I have left is my HO alt. and 4" mids. Finding the proper 4" speakers has been tough though.
 

New member
Username: Spradio

Post Number: 7
Registered: Nov-05
The reason for higher head unit output voltage is to combat noise. The vehicle environment is an electrically noisy one.

Your amplifier is receives a low voltage from the head unit and increases it to a higher voltage (and current). This voltage is music. The problem is, electrical noise may be present and that too will be amplified resulting in alternator whine, ignition noise, etc. If you turn the amplifier gains down, the electrical noise is amplified less, but so is the music. The higher voltage head units put out more so you can still get satisfactory volume with the power amp gains reduced thus the system sound to noise ratio is improved!

If you do not have random electrical noise coming out of your speakers, then higher voltage head units will not make any difference for your particular installation.

The test for this is to turn the radio all the way down and listen to the speakers with the engine running. If you hear objectionable noises, then turn your amp gains down. If you then can not get enough volume out of your system, consider a head unit with higher output voltage so you can keep the amp gains low enough to stop the noise.

Noise is more common in older vehicles and can also result from poor installation practices. One thing to avoid is running the RCA's in the same channel the vehicle trunk feed harness is in. This allows noise coupling just because of the close proximity and long parallel run. The passenger side of the vehicle is usually better because it has fewer or no wires. The power amplifier ground wire should be the heaviest gage wire in the system. It should be connected as far forward as possible. The most common mistake I have seen is grounding the amp to a trunk latch bolt. Bad RCA's are a major source of noise, and they are the most failure prone wires in any installation!
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