question for stereo guru, regarding head unit
 

Hi guys,

I wonder how much sound quality I lose by switching from an Alpine head unit (CDM 7829) to this Boss head unit. The reason I want this head unit is the SD card to store MP3 while not spending much $.

Currently I have an Alpine (7829) head unit and an Alpine CD changer. The Alpine head unit has 4 channel RCA connected to a 4 channel amp for 4 speakers. From this amp, it bridge to another amp for the subwoofer, which power two 15" at the rear seats.

I believe I have to convert the speakers output from this Boss unit to RCA then plug directly into the amp.

My guess is that sound quality doesn't change much, because sound quality base more on speakers quality, when I have all the amps handle the power output. Am I correct?

Here is the Boss unit:
http://www.amazon.com/dp/B004S50WPG/?tag=mh0b-20&hvadid=7000638433&ref=pd_sl_2z7b5q414t_e

The unit does have one set of RCA outputs, which should give you good sound, i would assume those are for the front channels and if you use rear speakers, those would be fed from the built in amp?

Do you have a crossover, or does the amp have a built in crossover to feed the subs the low frequencies?

I don't see any separate crossover anywhere. I do see the 4 channel amp bridge out to the second amp for sub . The Alpine have 4 RCA jacks, they all go to the 4 channel amp.

Doesn't any amp has adjustable crossover to adjust the frequency? The sub's amp is hard for me to get to to check on it.

rnin,

Some amps will have an adjustable crossover, but it's not the norm. Judging that your subs are using a separate amp, I think that there is a good chance it has a crossover built in or they are getting fed a full signal and it isn't causing problems.

The new deck only has one set of RCA outputs, so you'll either need to "Y" off of them to feed all your channels or use the outputs for the front speakers and the built in amp for the rear speakers and the RCAs for the front and subs. If you go the "Y" route, the fader on the head unit won't work, but you could turn the gains down on the rear channels of the amp to adjust. Personally, I don't care for rear speakers and just use fronts and a sub in my Targa.

Plus, 50Wx4, probably REQUIRING 2 ohm speakers, means the BOSS lacks a DC-DC MOSFET voltage upconverter putting in the low grade audio class.

If you value audio this highly... BASS BLING, you should be driving a Lexus LS430 series, NOT a 911.....

If you are going to upgrade your stereo,you should put in a nice system with blue tooth an amp and a good set of speakers and maybe a subwoofer.
It will not take away from the 911 experience ,all you have to do if you want to hear the awsome sound of your 911 is turn the stereo off and then if you take a highway drive or feel like listening you can enjoy a good clean stereo sound.best of both world.

BOSS head unit @ $25 indicates Op isn't interested in high fidelity, just car shaking BASS...

UPGRADE..??

No, DOWNGRADE...!!!

rwest,
Here I found some pics of the 4 channel amp, Alpine MRC F250

input, it has options for RCA and low level speaker wires.
http://img3.auto24.ee/auto24/product...1/14723011.jpg

And here is the pic of the output to another amp, RCA on the right, with all kind of adjustments.
http://img1.auto24.ee/auto24/product...5/14723025.jpg

I think I am ok with the connecting options. The thing I need to know now is if sound quality will degrade much by swapping only the head unit.

For such a long time, I don't listen to music in the car much anymore, except when I feel sleepy on the long trip (this is why I don't even remember what I have in my car). Man, I don't even drive this car that much. When it comes, I need some loud and reasonable sound to keep me awake.
The reason which lead me to this thought is because I see this price, with the SD CARD.
- one, I can just pop the SD card in and it has all the MP3 in there
- I can get rid of the CD charger
But I don't want to ruin much the current sound quality I have. Will I?

Thanks.

Simple answer/solution...

Hook the BOSS' 2 RCA outputs to the amp's input, bridge the f/r together, play something that has a large DB range. Now connect the BOSS' front speaker outputs using RCA adapters, bridging the same way. You might have to attenuate the BOSS' high (speaker drive) output level so as to not overdrive the alpine inputs.

Listen closely to the 2 configurations.

Unless you have a tin ear the loss in dynamic range, flat-topping of the high notes, using the speaker outputs will be VERY noticeable.

"keeping awake...."

Not advisable, but...

Coke for sugar content, and.... CHOCOLATE.

Make sure you get a decent warranty with your new stereo. I've had experience with Boss and although the equipment functioned as designed, I did have to return a couple of their amps due to premature failures. I've installed car audio for 25 years and suggest holding off until you're able to get a better quality unit.

do you have an iPhone/android phone as a music/mp3 source? If so, it's now surprisingly easy to add bluetooth functionality to an existing stereo (even your existing alpine), especially if you're willing to sacrifice the cd changer. You'd basically get an adaptor that plugs into your alpine that allows it to accept a line level signal and then buy a bluetooth audio adaptor that interfaces with your phone and sends the audio out via line level rca jacks . . .

Sorry, my apologies....

Just looked up your Alpine amp and so you must be well used to hearing signal flat-topping at high signal levels.

What you are saying is that regardless of brand and all, talking about the different between low level RCA and speaker wires level alone, there is noticeable different?

Will the result the same if the amp has both option of input, RCA and speaker wire? Will the result is still the same ?

Thanks.

The Boss unit is on sales now and is cheap enough that I am not too worry about return, knowing their warranty policy is not so good. What I consider is the labor, don't want to swap it in, then have to swap it out again for nothing.

Strange is that long time ago, if I remember right, Boss is the higher end product (home audio). What makes them so cheap now.

Well, years ago when I was younger and loved to play with car audio, I did changed head unit which experience low level RCA output and speaker wires output to amp. but I can't remember how diff in sound quality. Again, I have not touch these stuff for such a long time.

Oh Ron, Just get better, put the top down and drive her, It's a nice high 70's out right now. :D

rnin,

Generally, your low level or RCA outputs have a lot lower level of distortion, so when you take the speaker level outputs that have gone through the built in amp with a high level of distortion, about 10%, you end up amplifying that distortion to boot, so use the RCA outputs to your amps for the best sound.

I think you could pretty easily run power to the Boss unit and plug the RCAs into your amp and speaker set up to see how it sounds. The Alpine unit will be of higher quality, but given the noise floor and the music quality of a SD card, I doubt you'll easily notice a difference.

I can't tell from the picture, but it sure appears like the one amp has a crossover built in.

Best,
Rutager

An amp with 25W speaker output wire INPUT?

Suspect such an animal doesn't exist....

From strictly an engineering viewpoint there would be little reason.

Pre-amp outputs are voltage level, Maximum of ~3V typical. Speaker output are current level to drive the speaker's low impedance voice coil. Without a DC-DC voltage converter 12V, battery voltage, 24V (+/- 12V) for output "H" bridge circuit.

Speaker output levels will likely be highly distorted driving a high resistance amp input rather than a voice coil.

Ok, going for a short drive, sitting in the garage anyway.

rwest, wwest, and all,
Sound like wirth a try. Worst case is a day of labor.

Thanks all.

This an another amp I had comes with low level input (RCA) and high level input (speaker wires). On high level input, I don't know enough if the amp takes it as it is and amplify it, or take it in, then reduce it, then amp it up or if it's only a myth.

Sounds like you're making the best decision for you. I respect that. Boss is entry level equipment in the car audio world. That's why you can find it for such good prices. Please keep us posted on how your system turns out.

Do you mean speaker type "wires" to connect pre-amp signal to an amp or speaker output signal wires to connect to the amp?

I don't think the latter would be a wise move.

wwest,
no, west. What you are saying is taking the speaker wires and connect them to RCA jacks then plug them into the amp. I know this will work, but might not be good. What I meant was there are RCA inputs on the amp (low level input), and there are also wire connecter inputs on the amp. (high level input), to connect speaker wires to it. What I was saying is that I am not sure how this option (connect speaker wires directly to the high input of the amp) works internally.

I have owned a car audio shop in NY for 30yrs. SoundFX. The boss line of equiupment in plane english is total JUNK. Save some extra money and you can buy a good head unit for 125.00 or so. Stay with a pioneer, alpine, or kenwood.
Hi level inputs were designed for amplifying a stock headunit with no RCA outputs. You can get decent results. The RCAs are the way to go. A standard headunit will put out about 2v. Were your better headunits put out 4v. The Boss is probably putting out about .5v and horrible quality signal also.
https://www.facebook.com/pages/Sound-Fx/132546535630

Thanks JBrrown,
With this comment, I won't want to waste my time. I guess same comment goes for those "XO, DP, ..."? They all looked the same so I assume they are the same manufacture.

For the name brand, have you seen one with an SD card?

Thanks.

rnin,

Check out this Blaupunkt at Crutchfield:

Blaupunkt Adelaide 130 Digital media receiver at Crutchfield.com

They have others as well from many brands that are media only, no CD.

Based on jbrown's post and this Blau option for $50 more, I would skip the Boss.

Based on the very reasonable cost of head units, maybe sniff around and go all out and spend $125.

If cost is very important, search your sofa for quarters and get the $75 unit.

Thanks guys. Frys has a JVC, no SD card but there is a USB. I might go there tonight to see if I can listen to it.
Thanks again.

this may work for you too -- it's an alpine M-bus (which your existing alpine head unit appears to use) adaptor that replaces the cd changer with a sd card and usb reader that lets the alpine play mp3s . . . Yatour M bus USB Car Adapter CD player mp3 interface cd changer CDM 9825RB, CDM 9823R TDM 9501R/RM Fit Alpine-in Audio from Automobiles & Motorcycles on Aliexpress.com | Alibaba Group

Stick with the SD card functionality. Sounds like you will use it.

Bob kontak,
yes, cost is important on this, because I don't value the car music as much as when I'm younger anymore.

Rodek,
I went to a local store to look at the boss and other off brands. Oh mine, just the look can turn you off. Sales guys laughed when they hear I am thinking of taking those to replace my Alpine. So I finally got a JVC with USB and all preamp outputs to keep the configuration the same as it is.

guys,
Honestly, I like the look of the older type head unit better. Most of the new head unit look bulky and flashy. Also, the older type is more user friendly. On all the modern head units, it is hard to get to any feature because there are so many features now and there are much less interface. It took me a lot of tries to get to where the balance and fader are.

Thanks everyone for advices.