How to hook up home stereo amp to computer?

If the amp uses standard RCA-type phono sockets all you need is a standard PC-type minijack-to-phono cable available at computer store,

Here is a link that shows you how to connect PC to turntable/amp

There are several options depending on what your sound card has for options. If you have RCA jacks on your sound card then it is obvious. One easy method is to have a 1/8" stereo jack on one end of a cable and two RCA jacks on the other. Plug it into your PC and straight to your pre-amp/amp. These types of cables are available on the Web. For true computer audiophile reproduction you will need a DAC.

Try the $5 1/8" stereo to RCA adapter first with the Adcom Pre-amp. See what you think. I dont know if the pre-amp has a headphone out.
That amp wont help you in this situation, so just box it up and send it to me.  

Sorry guys. I didn't look at the outputs on my Adcom amps or Adcom pre-amp before I posted. Looks like it won't work. My intent was to some how use one of my Adcom GFA-555 amps (I have 2 of them) to power the headphones using the headphone-out jack on my Adcom pre-amp. I dug the Adcoms out of the closet and now see that there is no way to send the high output from the amps back into the pre-amp and through the headphone jack.

goobaah - Since I can't use my GFA-555's, I'll ship them both to you. Just provide me with your address...along with a $1000 money order to cover shipping. I'll pack 'em up real nice!  

FYI - I got the Sennheiser 650's in the mail today. They sound 'good' plugged into the X-Fi Titanium soundcard in my PC, but definitely under-powered. Looks like I have to pry my wallet open and buy a headphone amp.

Any recommendations on a headphone amp from someone who currently has a pair of HD650's?

Also, why do I need a DAC?

Here are the specs of my PC -

Mobo - ASUS Rampage II Extreme
CPU - Intel i7 965 Extreme
RAM - 6 GB Corsair Dominator PC3-1600MHz
GPU's - (2) EVGA GTX 285's
HD's - (4) 640GB Western Digital Caviar Black's
Audio - Sound Blaster X-Fi Titanium
OS - Win 7 - 64 Bit
PSU - Corsair HX1000
Monitor 1 - Dell 30" 3007WFP
Monitors 2 & 3 - Dual Samsung P2370 23" displays

Your Sound Blaster is your DAC. If I remember correctly, the SB has RCA jacks. If so, then just plug it straight into your pre-amp/amp. You will want to set the SB up for music mode instead of gamer mode. The SB is not a bad unit. I had one for awhile and was pleased with the sound it produced. I am using some Beyerdynamic DT 770 Pro's. I also had it feeding into a pair of studio monitors and the sound was fine. You may get a better sound if you want to spend some money, but the sound of the SB will be good enough for most people.

Do you want to build your own headphone amp? If so here is a sweet kit. It looks like a pretty easy build. I am going to be getting one this summer. But, having the SB you already have a headphone amp of sorts. The SB has the 1/4" input it's face plate.

If you want to go the audiophile way, then you would replace the SB with a DAC, headphone amp, etc. Going this way will cost some big bucks in the end. If you decide on getting a DAC, then these folks get some of the highest ratings.

I need those amps like a need a hole in the head. I have a good kenwood amp collecting dust since I'm too lazy to connect it. The denon 987? or whatever is good enough for the time being. Though, you could use all that dough to get one of those tube DAC, amp thingies out there. Check parts express for some headphone amps and read the reviews. You could probably find something good enough over there. After all, its just two channel computer stuff. You can get the dac, some super awesome tubalicious headphone amp, etc, but you are still going to likely be listening to mp3's and compressed stuff. Unless you have another plan. This stuff is such a slippery slope and its hard to tell what is voodoo and what is worth it. Have fun.