I've not entered this part of the forum before, so bear with me. I'm planning to spend a bit of money this weekend on a digi amp. I'm having a demo of two models, an Onkyo 595 and a Yamaha A5.
Apparently the Onkyo has something called Pro Logic 11. What does this actually do and is it worth it. I have a Yamaha at the moment, should i be swayed by the Onkyo, not exactly a name i've heard of.

You're probably meaning Pro logic II (i.e. 2 not 11) this offers a better sound which can be broadcast using conventional means (i.e. not requiring an optical output to amp) the sound is better than dolby prologic but not better than dolby digital 5.1 obviously. Worth going for but i don't know if any broadcasters are using the new version 2 technology.

Onkyo is an established name, you can trust them, they're very good!!

I have moved recently from Yamaha DSPa-595 to the A5. It is an improvement - I have DD5.1 and dts now.....so I could not hesitate in recommending the A5.

As for the other model, I think you're going about it the right way - listen and see.....

Here is a link which tells you a bit about Prologic II

http://www.dolby.com/company/is.ot.0...ew.05.html#s5c

From what I understand I think Prologic II mimics Dolby Digital 5.1 but over traditional analogue ways and only when recorded in Prologic II to start off with. It would, however, offer an improvement in sound with media recorded in Dolby Prologic I. As Nikhil says I don't think anything has been recorded in it for general purchase at the moment.

I am more interested in advances in Dolby Digital and DTS. I currently have an amp capable of playing 5.1 and DTS. However if I had the cash I would buy an amp capable of playing the next advances in these, eg Dolby Digital EX and higher levels of DTS. The Dolby site explains all its different formats.

Dolby Pro-Logic II was invented by Jim Fosgate and then licenced by Dolby Labs. It creates a surround sound affect from any audio signal, giving it a Dolby Digital 5.1 style sound . Although it's obviously not as good as DD 5.1 ( it cannot create 5 discrete channels) it is an improvement on Dolby Pro-Logic.