Home stereo to PC hookup

[dale51]

Hello,
Want to hook up my PC to my home stereo system. Found two different cable hookups online: one from dak.com that consists of the 3.5mm PC plug, 2 transformers and RCA cords to complete the connection to the stereo. The other is simply a special 3.5mm plug with an outlet on the back for the PC speakers with the RCA plugs on the other end(FXsound.com). Is it really that important to use transformers in the hookup to prevent hum? Or would I be OK with the simple cable setup from FXsound.com?

 

[soundguruman]

No, the hum usually comes from the cable TV system, we use a cable TV isolation transformer, it goes on the coax.
The audio can usually hook up without transformers, and the transformers will kill your Bass Frequencies.

 

[dale51]

just got the wires to make the hookup and when I tried them I get a constant hum or buzzing sound. It occurs an all functions of the stereo. I get the music signal from the PC, but also the annoying hum. Any suggestions?

"Soundguruman" had suggested using a cable TV isolation transformer......but Im not sure what this is or where to get one. The only coax that I have connected to the stereo is for a FM antenna on the roof. But my TV is right next to the stereo in the same cabinet.

 

[anwaypasible]

when you start to connect everything, you will likely get a hum.
and that hum is usually when you have the cable or satellite receiver connected to the audio equipment.

i can hookup my receiver to the speakers.. the PC to the receiver.. the television to the graphics card.. and the cable box to the soundcard.
no problems.
but when i screw the cable onto the back of the cable box, i get interference on the televisions picture.. indicating a ground problem.

audio hum can come from a few places.
1. there is too many unfiltered connections to the soundcard or receiver
2. the reciever's amplifier might have a high noise floor and the hum you hear is the amplifier.

it might be a direct injection from a specific connection.. and it might be because the amount of connections are simply too high.

start with only the speakers connected to the amplifier and listen for hum.
then connect each thing one by one to see when the hum starts.
once you plug something in and hear a hum.. unplug some of the other things and see if the hum goes away.
if it doesnt, it means whatever you plugged in last is causing the hum.
if the hum does go away.. it means the amplifier cannot handle all of the connections and some isolation needs to take place.
you would then have to go through your list of connections to determine which one is the easiest to add an isolator.

isolation transformers are all about the frequencies you need and the frequencies you dont need.
it might be easier to find an isolation transformer for a specific range of frequencies, which should help your decision as to which connection to add an isolator.

 

[dale51]

found the source of the hum! Soundguruman was correct when he said that it is most likely coax cable causing the trouble. Actually it was a coax cable that I have running to a roof mounted FM antenna. When I disconnected that, the hum instantly went away. . Experimenting with sound and function now. Everything comes through the stereo very clearly from my PC but I did notice a considerable loss in the volume level compared to using the stereo tuner. Maybe this is due to the 50 ft length of wire that I had to use to make the connection between the PC and stereo in different rooms? Is there any way to boost this or is it just the way this hookup performs normally? Anyway..........thanks evreyone for your knowledge and experience

 

[anwaypasible]

a line driver from the car audio market will boost the voltage in the 50ft cord.

start with the low setting and work your way up.
you dont want to overdrive the stereo inputs.

 

[dale51]

anwaypasible.............can you give me some more specific info on line drivers? What type to buy, where to buy, how to hook up? I Googled them and noticed that they need a 12v power supply, how can this be done for a home stereo system?

 

[anwaypasible]

anwaypasible.............can you give me some more specific info on line drivers? What type to buy, where to buy, how to hook up? I Googled them and noticed that they need a 12v power supply, how can this be done for a home stereo system?

i dont know the amperage requirements of the various line drivers.. but i would imagine a 12 volt power supply or 'pack' would work.
there are lots of 12 volt power supplies.
kinda hard to find in a retail store.
they make some, but they are really expensive.. so expensive that it would seem they are punishing the person for losing the original power pack.
ebay has tons of 'em.
i'm sure other online stores have 'em too.

a line driver is an amplifier that boosts the preamp signals.
typical soundcard output is 2 volts.
line drivers can raise that voltage for longer runs of cable.
video distrbution systems often have an amplifier because the signal gets cut again and again, lowering the signal.
back when televisions were analog, a loss of signal power would really show an affect on the screen.

without a line driver, the signal might be too low at the end of the cord.. meaning you have to turn the volume of the receiver/amplifier up higher to get normal output.
how much higher, i dont know.
the cables can really play a role on the determining factor, as to how much extra you have to raise the volume knob.

have a look at the input and output resistances of the amplifiers for car and home audio.
they might be totally different and incompatible.
using headphones connected directly to the satellite radio.. most headphones are 32ohms, but can go high to 600ohms
i would think most preamp outputs and inputs are the same for both audio markets.
if the input resistance of the line driver is too high, the satellite player will struggle to provide output.
if the input resistance is too low, the little amplifier inside the satellite player will collapse.
thats why the 'experts' would recommend input/output resistance matching for optimal performance.

my receiver has analog inputs that are for 250mV and 50 kilohms
the input of one line driver is 20k ohms
perhaps that means the line driver is easier to power.. unless kilohms is different than __k ohms
the output of the line driver is 45 ohms..!
and i dont know a whole lot about what that means.
i'd assume the signal goes straight to the heart of the amplification, which could allow different degrees of damage if the positive and negative where touched.

http/www.sonicelectronix.com/item_28924_AudioControl-OVERDRIVE-OVERDRIVE-PLUS-Gray.html

check out the specifications though..!

Frequency Response: 10-100,000 Hz
Signal-to-Noise Ratio: >110 dB
THD (Total Harmonic Distortion): 0.005%
Light indicates 2-, 5-, or 7.5 volt output
Maximum Output Level: 9.5 volts RMS, 13 volts peak

what happens is, the long run of cable has resistance.. the more cable, the more resistance.
the signal at the other end is very dim.. which is why the loss in volume takes place.
usually the stereo tuner has less audio than everything else.

50ft is a really long run of wire.. and i dont think they make premium cords for that much distance.
premium cords are supposed to have more signal at the opposite end of the cable, compared to 'average' cables.
probably not as much boost as that line driver will give though :lol: