Hook up Plasma TV to Audio system

I just bought a Panasonic Plasma smart TV and need to connect to my audio system. The TV has an Optical out and my Pre amp which is a TAD 150 only has RCA connects. WHat low cost connection would benefit my system. I am running through TAD Hibachi monos and Vandy 3aSigs.
If the TV doesn't have analog audio outputs, you will need to run the optical through a DAC. Otherwise you would need to run analog audio from your video sources directly to the 150, bypassing the TV.
Also, probably, the DAC will have to support DolbyDigital, not just PCM.
I was anticipating the same as you when I got my new Plasma as I thought the speakers wouldn't be good enough for casual listening. For HT (blu ray) I simply run the OPPO directly to my integrated.

If all you have is a Toslink audio out, you can try this:

Hope this helps.

All the best,
You also have to consider what kind of audio you want to send out of the TV to your receiver/DAC. 5.1 surround coming over the air through a digital antenna is almost always piped out of the TV's optical input, but audio coming thru HDMI (high def or not) is almost *never* piped out of the TV's digital output. I don't know about audio signals coming from cable boxes or DVRs, I don't own any of these. It has to do with the internal boards inside the TV, this defines which audio input, and what kind of audio, gets output thru Toslink.
Eagleman6722, I intended to buy Panasonic Plasma and connect it to my DAC in 2 channel (PCM only) system but found out that it does not have DOLBY/PCM optical output format selection in the menu. It outputs automatically PCM with NTSC and DOLBY with ATSC.
Looking at the TAD 150 on line it appears to be two channel only. You can buy a Radio SHack DAC (1500093) for 39.95 and it will give you the option of Toslink or Coax to stereo RCA output. I use it for my wireless headphones in my office and it does just fine. It isn't "audiophile" quality but neither is a signal coming from a TV. If you don't like it you get 30 days to take it back.
It's too bad that the TV manufactures are finding ways to cut sales prices but eliminating input and output selections.
Are you using a cable box? Some have RCA outputs on the back.
The TV is connected to a DVR via HDMI cable...
I had the exact same issue nearly a year ago when i purchased my tv. Only the cheapest models offered analog outputs. None of the tvs with optical outs offered a dolby/pcm conversion option. To make maters worse digital broadcast is now all in Dolby 2 or 5.1.

To solve the problem I picked up a used ht processor for 65$. It works great for processing the tv optical signal, but it won't win any prizes for high fidelity. still it is certainly better then the processor that are built in to the cheap tvs and is better then rat-shack crap. The unit is a technics sh-ac500d.

I have it set to down mix 5.1 to 2 channel stereo.

I wasn't able to find any other solutions, and I must say i am quite satisfied except that the device looks really ugly in my rack and takes far too much valuable space for what it does. I hope this helps.
To the OP: Do you use any other sources to watch TV (e.g., Blu-ray) other than the cable box/DVR?

Nick_sr's solution is the most complete. Any surround processor that supports Dolby Digital surround and has a Toslink input will solve your problem. And if you add other video sources such as Blu-ray, you can use the Blu-ray's Toslink output and connect it to the surround processor as well. And as Nick_sr said, configure the surround processor to downmix everything to 2-channel, feed your TAD the analog 2-channel output and you're good to go.

Even though the DVR has an HDMI output, it almost certainly also has an analog stereo output. You can run the HDMI cable to your TV for best picture and the analog stereo output to your TAD for best sound quality. In this case turn your TV's audio off. And if you have or plan to add Blu-ray, every Blu-ray player I've ever seen also has an analog stereo output. In these cases (DVR and Blu-ray) the stereo downmix has already been done before it goes to the stereo analog outputs.
To Johnny's point about the blu-ray player, I only decode the tv signal through the processor, everything else passes through my Cambridge bd751 universal (blu-ray) player. It has a dedicated analog stereo output. I use it for blu-rays, CDs, dvda, and high-res music flies as well as to stream youtube and networked media files.