Whenever I play a movie which has DTS encoding and connect to a receiver that can decode DTS 96/24 the volume output is more and the sound fidelity is crystal clear.
However when I connect to a Plain DTS Decoder the volume output is low (lower than Dolby Digital) and the sound lacks the fidelity. May I know what could be the reason behind this variation in sound levels and fidelity ?

What plain DTS decoder are you using (a pre-pro?), and what is between it and the speakers?

I assume the comparison to DD that you mentioned is using the same decoder and (pre-amp/)amp/speaker arrangement (just trying to make sure there aren't any other variables that may be the cause of the difference).

-Max

I have a Yamaha 5.1 HTIB and the AMP has DTS Surround, Dolby Digital and Dolby Prologic II decoding. When I connected by DVD Player to another HTIB that has DTS 96/24 decoding I found the sound to be more clear, crisp and loud. I have nothing running between my AMP and Speakers except the speaker cables. Can the lowness in Volume be due to the frequency range rating of the speaker ?

Okay, so you are using "receivers" in both cases. (A receiver is a single device that contains a surround-sound decoder, radio tuner, pre-amp, and amplifier.)

Here's some information on DTS, including the 96/24 variant, that you may find informative:
http://en.wikipedia.org/wiki/Digital_Theater_System

The difference in volume level is easily resolved by simply turning the volume knob. I wouldn't worry about the difference in volume level relative to Dolby Digital too much, since it could just be a difference in how each system handles the different formats.

But you may still find that the receiver capable of DTS 96/24 sounds better due to the higher resolution of the format (versus standard DTS). Or not, depending on a variety of factors including the rest of the system, the room, the source material and the listener.

-Max