I always find this to be a double edge sword. I understand that someone would want to keep a "stock appearance" if they are trying to maintain the original condition of the vehicle. But for any reason other than that,....Who wants an analog radio based on 80's tech, and a cassette deck? Having to use the factory head unit for ANYTHING is a compromise. You cannot adapt the cassette deck to allow you to play your Iphone through w/o it sounding like ass,..you cannot use an FM modulator for the same purpose, w/o it sounding like ass,... seriously.
Here's the same thing I posted over on crotchedy town where the prune juice gang over at FEP prefers their factory stuff to something like what's posted above because the sound is "good enough", or that they'd rather listen to their "Flows".
*** papers rustling as he steps up to the lectern...
As an audio guy, it always pains me when I read stuff like this on a forum. Using ANY adapter is just one more erosion of what people accept as decent sound quality.
Music sources have always been measured by two references: Frequency response, and Signal to noise.
Frequency response is typically seen as a measurement of the sources ability to reproduce the distance between the lowest low frequency, to the highest high frequency, measured in hertz (Hz)
The normal human ear can hear a range between 20hz to 20,000 hz (most commonly referred to 20 kilohertz, or 20 khz)
A super low thud from a bass guitar, kick drum, or bass machine can easily reproduce a 20 hz note, and is more often "felt" by us, rather than heard.
Conversely, a 20khz note is a super bright ting of a cymbal, or the noise your ear hears as a ping when a tuning fork is struck.
Every musical instrument, including a human voice falls between those two ranges.
Signal to Noise is the sources ability to convey that signal w/o adding anything else (in the form of distortion) to that signal conveyance. Think of that as a percentage.
So, as an example: If you sat in front of band making a recording in a studio environment free from any other noise clutter, that would be 100% authentic. The S/N would be 100db. You'd be able to hear everything, from the lowest low to the highest high.
A CD copy of that session would be at the 90%, or 90db S/N. The frequency response would be between 10-22khz (beyond human hearing)
A Cassette copy of that session would be at the 70db S/N. W/ a 30hz-18khz FR. (when played back on a high quality, home cassette deck)
A FM broadcast of that session would also be around 70db, w/ even less FR more like 30hz-15khz.
Now, when you add in the old factory radio which was notoriously bad in the mid 80's, you can also subtract about 10% from anything rated above.
Lastly,...add in the degradation of a cheap adapter, and you get a flaming pile of crap.
A cheap dollar store cassette adapter will probably show actual S/N in the 60-65db range, w/ a FR somewhere in the 50hz-15khz range
A FM modulator placed in line of the antenna will be even worse, 55-60db, w/ a lousy FR at 50hz to 13.5-15khz.
If your radio has an aux input on the back (which some factory head units have) use it. The S/N, and FR will be best that way, as it is a direct audio connection. I cannot tell what that input source is rated at though, but it will be as close to CD quality as you'll get. The pic of that female aux jack wired into the front trim is just a quick way to connect your listening device w/o having a cable laying around that is hooked to the back of the factory aux input.
http://www.crutchfield.com/S-1mCjqJzp78X/learn/learningcenter/car/oem/connections_sound_quality.html
Newer stand alone head units have HD radio,..and granted, it's only FM,..but now local stations sound better than Sirius, and are typically broadcasting multiple "streams" of music on each of their dedicated frequencies. In other words,...if you like a classic rock channel, and have one in your market,..they are usually playing two-three different songs at the same time on two-three different sub channels under that frequency.
Compressed music files, and the service that hosts them, i.e. Itunes are just that....compressed. When music is compressed for the sake of fitting more songs into a given space, the end result is that both ends of the frequency response are clipped off.
The direct end result being that when comparing a compressed version of that song, to a CD version,..the compressed version lacks the punch the realism, and clarity that the CD versions has.
Why is that OK?
Why is that good enough?
There is stuff out there,...and if all you're trying to do is put the factory face on, and hide a bluetooth interface so that you can stream music via bluetooth, it's only a google away. But depending on how it's tied into the existing audio system...(in other words,..if it uses the factory amplification and speakers to be heard,)..it offers little more than convenience.
In order to truly get a foot up over the factory junk,..it all has to be replaced. The factory speakers (if not completely shot) sounded like ass the day that car rolled off the assembly line.
The single most significant thing you can do to improve sound quality in one of these cars is to junk the factory speakers.
The 3.5" speaker in the dash, and the 6 x 8's in the rear quarter trim were one way speakers w/ "whizzer cones". i.e they have a little paper cone lookin dealy that was an attempt to "confine" the high frequencies and separate them from the rest of the blah-blah-blah sound quality of most one way speakers.
Throw that junk away,...aftermarket speakers intended to replace the factory crap are all over the market and are a vast improvement over the stock crap. (and nobody will be the wiser that you changed a thing)
After that,..if you just gotta have your factory facade,..then there are several companies selling a invisible interface that replaces the factory HU as the amp and serves as an interface to tie your phone into so that Pandora/Spotify/Rhapsody, and a whole buttload of other streaming services can play through to your system from your phone.
Then you can split the power wire so your little green clock on the radio stays hot, and still have something better sounding than that dumped, no cat,
Flowmaster 40 drone to listen to.
Done.