I want to connect Optimus CD-8100 5 disc cd player to powered speakers, what preamp should I use? Can I use a simple phono preamp?

connections 3 or 4 on preamp. Turntable requires pre amp out from preamp to amp.

Sorry no. Unless the old phono preamp built into that, Which is a new thing just started in the last few years with new turntables. Old ones need a phono preamp with RIAA curves built in and GAIN as the cartridges are very low output.

PLAY the record on a turntable that either HAS a PHONO preamp or through a PHONO preamp.

cd player(tape out)-------equalizer in------equalizer out-----amp line in.
tuner out-----to another line in in amp.

The answer isn't with the CD player, it's with the amp.
Does the amp have selectable inputs, or does it just have one input for each channel?

If it's a simple power amp, then you'll have to unplug the CD player and connect your iPod to the amp inputs. I'm guessing that the CD player connects to the amp with RCA (phono) connectors like these ones.
If that's the case, you can get a cable (like this one at Radio Shack, but any office supply store will have one too) to connect your iPod to the amp.

If both speakers work okay on other inputs .Then cable from pre-amp to amp and main amp are okay. If phone RCA jacks go directly to electronics board .Then its possible solder on phono jacks need to be resoldered or other connections in that section.If unit needs repair you can also purchase a phono preamp from radioshack hook up your and use it on other good inputs such as CD etc..Please note PHONO inputs are only for turntables .If a non turntable input such as CD,TAPE,TV Etc is used on PHONE .Then you will overdrive this input .

Appreciate the additional information.

To recap what you need is a receiver that can accommodate:
4 - Pioneer S-DF1-K (15-100W, 8 ohms)
1 - Pioneer PD-F407 25 Disc CD Player
1 - Pioneer CT-300 dual tape deck
1 - Kenwood KD-491F turntable

Possible choices are (keeping in mind that the power output should be less if not equal to 100 watts and a turntable/phono input):
i. Onkyo TX-8522 Stereo Receiver;
ii. Yamaha RX-397 100 Watt Natural Sound AM/FM Stereo Receiver;
iii. Sony STR DE695 AV receiver;
iv. Teac AG-790 200 Watt Stereo Receiver;
v. Denon AVR 888 - AV receiver - 7.1 channel.

Some of the above also includes feature(s) to hook up to your video system. Some may even require a fifth speaker (subwoofer).

Incidentally, you can also choose another brand/model even without a turntable/phono input. As initially posted, a turntable/phone to line level pre-amplifier is only required. Here are some examples:
a. XP200 Turntable Preamp - Nano Series;
b. Pyle® Pro PP999 Phono Preamplifier;
c. Pro-Ject Phono Box Turntable Preamplifier;
d. Radial J33 RIAA Turntable Preamp Direct Box

Good luck with your project.

You won't get any sound unless you connect your CD player to an appropriate input on your amplifier (any but phono or tape/md) and connect your speakers to this amp.

Shout if you need more help.

There are many answers to your questions but Ill have a go with the basics...
Audio connections should be matched.... its called Frequency impedance,.... to get a signal along wires or cables (or Fibre) the Impedance of the cables and wires must be matched to the device they are connected to transfer the signal along the cables without distortion...

Manufacturers provide many sockets on the input side of amplifiers and preamplifiers to allow the consumer to connect various devices of different impedance.

They label these inputs like CD, or Tuner, or PHONO etc etc,

That means if you have a CD player it must be plugged into the CD input socket then the impedance will be correct and the sound will transfer along the CD cables correctly, without distortion..same with the Phono input etc...
You will find on the sound output to the speakers terminals are also labelled 4-6ohm, or 8-10ohm, these are the impedance expected for the coil ratings of the speakers them selves and its important to get the correct speakers to the correct out put terminals...

In your case all you have to do is follow these simple rules and all will be well....you say you have a squeeze box well there probably isnt a port labelled squeeze box so you need to experiment and try out each input port for the squeeze box to see what input gives you the correct sound output...Watch the Phono inputs as these are very sensative to input sound levels and must be treated very carefully as they have a double stage of sound amplification and as such you need to have the volume right down when connecting up the Phono inputs then increase the volume carefully after the cable connections are completed.

If you follow these rules then all will be well,,,,there is no difference if the Pre amp or Power amp is valve or transistor or FET or has IC outputs to the speaker the same impedance rules apply..just treat it as a box with input and output terminals and all the impedance will be taken care of for you...if you read the lables...

You need to connect you signal source to the Preamp inputs the out put from the Preamp connects to the power amp input then the power amp output goes to the speakers. this is a basic configuration for sound systems, there are other variations but are outside this discussion.

Cheers From YUBEUT

You will need a phono preamp. Ipods, radios and cd players all give out a LINE level signal..which means you can plug headphones or speakers, adjust volume and be set. A turntable needs a phono preamp. Usually a dj mixer or stereo receiver with a phono input is all that is needed. A simple phono pre amp is like $20 from radio shack.

keep me posted.