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Pro Logic Reciever DD, DTS, PLII questions.

 

New member
Username: Optimus_prime

Post Number: 1
Registered: Feb-05
I have an Optimus STAV-3680 Pro Logic Reciever.
http://support.radioshack.com/support_audio/doc62/62594.pdf

I know that Pro Logic II can decode/translate DD5.1 and DTS signals and play them through the appropriate speakers in your setup but I had no idea the old Pro Logic could do the same.

My reciever appears to be playing Pro Logic, Pro Logic II, Dobly Digital 5.1, and DTS even though there are no optical tos-link hookups for the unit. I get full 5.1 sound from my Xbox and from my PS2.

Exactly why is this happening. I had considered upgrading to a reciever that could do DTS and DD5.1 but now I think I'll just keep what I have.

I'm just curious as to what exactly is going on. Maybe I am not understanding how Pro Logic works.

btw, the reciever does have the old 5-D Theater sound options and I assume that has something to do with it.
 

New member
Username: Shokhead

Lakewood, CA USA

Post Number: 9
Registered: Jan-05
You cant decode DTS without a player that has DTS and a reciever the decodes DTS.
 

New member
Username: Optimus_prime

Post Number: 2
Registered: Feb-05
That is exactly what I thought.

Perhaps my PS2 is doing the decoding and seding the decoded signals to the Pro Logic Receiver then?

I have a DVD Calibration disk and when testing out my DTS sound setup it has a warning saying that unless you have a DTS decoder you will not hear any sound.

However, I hear the entire DTS 5.1 sound field.
 

Bronze Member
Username: Usa2k4

Post Number: 71
Registered: Dec-04
In order to get true 5.1 surround from Dolby Digital and DTS sources, your receiver must have a digital input and the DD/DTS signal must be transmitted through it.

Dolby Prologic II does not decode Dolby Digital and DTS signals. It can't and your receiver can't either. What they do is only simulating 5.1 sound from a stereo or non-5.1 source such as FM radio, cassette tapes... Most DVD discs also contain a 2.0 sound track besides DD and/or DTS so that your system can play them as well even if it doesn't have the correct decoders. By connecting the RCA left & right output from the DVD player to the RCA input on the receiver, you only feed the analog 2.0 signal to the receiver and then the receiver just simulates the surround sound from that stereo signal. Most of the time, 5.1 simulated surround sounds very good especially for movies but it is not really the sound that the director intended for you to hear.
 

New member
Username: Optimus_prime

Post Number: 3
Registered: Feb-05
Kevin J.

I found out the reciever does not play the Subwoober chanel but it DOES play:

Left Front
Right Front
Left Rear + Right Rear (together not seperated)
Center

I do NOT get this when using a stereo signal.
When playing DTS or DD5.1 or PLII signals I get the channels described above.

*I verified and tested this with a DVD Calibration disk.*

The reciever is capable of driving bass signals to the subwoofer preamp from the center chanel though.

In other words, when sending the reciever a stereo signal through the RCA left and right inputs I only get a stereo sound but when sending it a 5.1 audio source through the RCA left and right inputs I am getting the sound described above.

Something else must be at work here. Possibly the PS2 is decoding the 5.1 signals from the calibration DVD and sending them as Pro Logic signals through the two wires. I noticed if I play an Encoded PLII video game I get the surround sound but when playing a non encoded PLII game I only get stereo.

Also, if my Xbox is setup for stereo I only get stereo but if I set it up as 5.1 I get 5.1 or the approximation I described earlier.

 

Bronze Member
Username: Usa2k4

Post Number: 72
Registered: Dec-04
You can't send a 5.1 signal through the RCA left and right input. The signal going through the RCA left and right input is actually an analog stereo 2.0 signal. You can only get true DD/DTS 5.1 surround if:

1) Your receiver has built-in DD/DTS decoders and it has digital coaxial/optical input to accept the raw digital signal from the DVD player. Or

2) Your receiver has direct 5.1 input (the 6 RCA 5.1 input jacks) to accept the 5.1 signals decoded by the DVD player decoders.

Most of the analog 2.0 signals from 5.1 movie DVDs are encoded with Dolby Prologic, which is compatible with plain old stereo systems so that if your system has Dolby Pro/Pro II decoder, it would give you Dolby Pro surround. Dolby Prologic only gives you mono surround with limited bandwidth (about 70-7,000Hz or so) whereas, Dolby Digital/DTS 5.1 would give you stereo surround with full bandwidth (20-20,000Hz). Dolby Prologic II and the likes (such as 5-D Theater in this case) may also give you stereo surround with full bandwidth but that's only simulated surround derived from the analog 2.0 signal.
 

DDBlues
Unregistered guest
As Kevin has pointed out, you can't get a true Dolby Digital or DTS 5.1 surround sound without the source and receiver producing and decoding the same respectively.

I believe what Joe is experiencing is the greatness of Prologic decoding from a stereo source.

I have been enjoying this ever since my first HTiB back in 2002. It was as Panasonic brand which had Prologic decoding as well as Dolby Digital and DTS.

I had my game systems hooked up to my home theater via stereo rca jacks and when I played a game with the prologic feature on , it would seem like surround sound for most of the games. For instance, if there was any important action going on directly behind me while playing a video game, both of the surround speakers would come on to "simulate" a surround sound experience. A very cool way to enhance your enjoyment and get you into the game.

I recently got a new HTiB with PrologicII EX or expanded. Now when I play a PrologicII video game with PrologicII Expanded selected on the receiver, I get simulated 5.1 effects from a stereo source! For example, when I play Medal of Honor I can hear the enemy talking directly behind and slightly to the left or right. Now I know exactly where my enemy is and can quickly turn around to shoot him!! Very cool!! If I spin my direction around in a video game, I can hear single audio sounds do a 360* in my room while I'm playing the game!!

I know that even PrologicII EX is still not true 5.1 surround, but it makes for an awsome video game experince as a lot of video games are PrologicII encoded.

I don't think there are many video games encoded in true Dolby Digital 5.1



 

DDBlues
Unregistered guest
If you want to experience movies in true surround sound, I urge you to get a receiver that has Dolby Digital decoding and at least one digital input with two or more analog (rca) inputs. You will not regret it.
 

Silver Member
Username: Shantao

Post Number: 108
Registered: Apr-04
JoeBlow;
most DVD's and Games come encoded with prologic or prologic II on their soundtrack. They feed the prologic/II signal through the red/white rca stereo jacks. Your prologic receiver decodes this and it simulates surround. The effect is pretty good. On my PS2 and Gamecube, the prologicII surround really adds to the realism of the game, although it is not as good as DolbyDigital or DTS.

DDBlues, you said:
"I don't think there are many video games encoded in true Dolby Digital 5.1 "

That is true of PS2 and Gamecube, there are almost no games in PS2 that are DD (there are a few DTS). On the other hand, almost all xbox games are DD5.1, many of which are incredible sound wise.
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