Got my Alpine CDA-9855 today. When I took it out of the box I noticed that there's this small metal box attached to it with a relatively thick cable. The box is labeled "DC/DC Convertor". There are no plugs or ports on this metal box, it just seems to be hanging there by the cable for no apparent reason. It doesn't seem to be able to be unplugged, either.

Just curious what this little metal box does. And wondering where I can put it when I install the head unit...

 

A DC/DC converter takes DC of one voltage, converts it to AC, then back to DC of a (usually) different voltage. I have no idea what use this could possibly be on the outside of a head unit. You generally see filters on the power wires, those large round things, but I can't say I've ever seen a DC/DC converter.

 

http://www.powerdesigners.com/InfoWeb/desi.../converter.shtm

its a noise filter, I have the same unit, and I looked up the info.

 

as i recall -- these DC to DC converters first started showing up when Alpine released the 'V-drive' head units which sported more wattage than your average HU. i've always figured they were stepping up the DC voltage to increase the amp's output.

either way, you want this thing located away from any of your RCA wiring if at all possible. i tucked mine by the knee panel on the console. my new HU didn't have one. (9833)


i could be wrong -- check this hit on the Alpine Euro site: http://www.alpine-europe.com/content/engli...Volt-PreOut.htm

or i could be right -- another hit on the Alpine Euro site:
http://www.alpine-europe.com/content/cms/i...2a09104fecd5b48

*shrug*

 

It's a good way to go, but I'm surprised they put this in due to the increased cost... they must have really needed the heavy isolation, 'cause there are cheaper ways to do it.

 

"An exclusive Alpine DC-DC converter doubles PreOut voltage from two to four volts. This boost in voltage ensures that the music signal will not distort at high volume levels."

Sounds like marketing-speak to me. First, DC-DC is pretty useless on an AC signal, which is what audio is. Second, ANY amplification process adds distortion, so unless some completely different low-distortion pre-amp is used, increasing the gain (voltage) increases the distortion. And if that's the case, it's the better pre-amp that's responsible for the lower distortion, not the higher output.

The actual purpose of 4v outputs is to allow you to reduce the gain at the power amp, which in turn reduces noise that may be picked up in the cabling. But unless you listen to the stereo in the garage with the engine off and the volume turned all the way DOWN, you'll never notice the difference.

"Alpine gives you massive power from a head unit with the V-Drive amp. Using a hybrid design (DCDC like a regular amp plus BTL), it boosts voltage to 17.2 volts for conversion into a powerful 60W x 4 output."

This one is closer to the truth, and basically means it's operating like an external amp in bridged mode. I bet they used an out-board converter because A) there's no room in the HU, and B) to keep the heat out. I've built similar DC-DC converters to power an 18-volt laptop directly from the cigarette lighter socket. Even thought they're reasonably efficient switch-mode converters they get pretty hot.

But I'd be surprised if you can really get 60W per channel out of it.

.

 

those are my thoughts as well Bob. and iirc, the specs for that HU are rating it for 22 Wrms x 4, which imo 22 Wrms is a stretch to call 60 Watts peak.



btw, did you want me to check on that ZR7+shifters for you?

 

Notice how they never give you the current at the "said" wattage peak?