Why do my MP3s sound horrible when connected to a receiver

[unclet]

When playing a MP3 while the normal Harman/Kardon computer speakers are connected, then the sound is pretty clear and nice.  When I have the audio jack from the computer split into red/white RCA jacks and then connect the RCA jacks to a nice Kenwood receiver (VR-407), then how come the sound is not nice at all?  It seems like there is a bunch of hiss, clicks, other general noise and also seems like the sound is muffled as well.  This obviously makes listening to the MP3 through a receiver not the best.

I thought I read about someone who purchased a (MP3 --> receiver) converter box which allowed MP3 files to interface with a receiver properly (whatever this means).   Anyway, is this something I will need to fix the problem?  Is a stereo receiver not equipped to handle MP3 sound from a computer properly? 

Hopefully someone has some ideas for me ..... otherwise I have no idea what to do here.

(EDIT)
Here is the site which I was referring to which indicates they used a "Creative Labs Soundblaster MP3+ external USB sound card" ... which is ... "specifically designed to decode MP3s for home stereo purposes".

from BYOAC member --> scylla2

    http://drobins.wave.prohosting.com/jukebox.html

The description is located under the "Audio Components:" section.    Any ideas if this would solve my problems?  Or does this small box simply let you tweak the highs/lows/treble/bass settings stuff?

[JimmyU]

That's weird.  What's your sampling rate (kb/s) on your MP3's?

[unclet]

I don't know the sample rates since I got them from many different people.   Although I bet most of them are 128kbs.   Of course, these are not fantastic CD-quality MP3 files, but they sound absolutely fine (to me) through my computer speakers.  I just want them to sound the same through the receiver as they do through the computer speakers.

Does the Kenwood Receiver (VR-407) I am using expect more power or something? 

What does an amp do?  I never thought I would need anything more than speakers, but I have no idea what is going wrong.

[polaris]

i think its just a case of the mp3 being poor quality, a good system is enhancing the fact that the initial sound is crap, making it a louder crap sound.

[Paul Olson]

It would have to be poor quality MP3s, or a bad connection or cable to the receiver. I always had trouble trying to hook my laptop up to my receiver, it just always sounded bad. I try to keep the MP3 bitrate at 192 or above because I can hear the difference with lower bitrates playing through good speakers.

Paul

[unclet]

OK, I figured something out ..... I originally had the RCA jacks plugged into the "Phono" jacks of the receiver.  Once I moved them to the "Tape" jacks, everything sounded excellent .... loud and excellent .....

I need to make sure there are no other things which need to be done, but at least I am getting normal sound now and I feel a bit more relived now .... 

[BobA]

Good fxing unclet.  You were quick.

Now the reason for the problem is that the Phono input is expecting a very low level signal (2.5mv) from a phono cartridge.  Because of the low signal the phono inputs of a stereo apply amplification and equilization to the signal to get rid of record noise and provide preamp for the amp.   This is what gives a less then ideal sound when you plug in the signal from an mp3 player or a computer audio output.   The line inputs or tape inputs should be used depending on what is available on your stereo amp.

Hope this info helps others using their home stereos.

[Disturbed013]

Depending on PC soundcard, some have line-level outputs as well as the standard pre-amped speaker/headphone output.  If you want your sound as clean as possible use the line-out on the PC and a line-in connection on the receiver (many have Aux. for this purpose).  This ensures that the PC soundcard doesn't tinker with the signal and all the amplification is done at the receiver where you want it.  MP3 encode quality does make a difference which can get more noticeable as you boost it through with cleaner signals and better amplifiers, but I'm no audiophile either.

[unclet]

Thanks for everyone's input  ..... and thanks Bob for explaining why the Phono connection was no good.    Anyway, I am happy with the sound now and am on to finalizing my cabinet design and acquiring a few extra parts.