Marantz SR770 Surround Channels Mixed Up



I decided to add surround sound capabilities to the SR770 which does not have a digital input but requires 6 channel direct inputs. I therefore purchased a 5.1 SPDIF Decoder for HD AC3 DTS Digital Audio and connected the outputs on this to the inputs on the SR770. Note - I am not using a subwoofer so no connection for this.

Outputs on the decoder are connected to the correct inputs on the SR770 and the speakers are connected correctly.

However, using different sources (Laptop, STB, BD Player) the sound isn't correct - channels are mixed up.

Using some 5.1 test files downloaded from Fraunhofer (and others) confirmed my suspicions. e.g. Playing one of the test files (ac3) resulted in what should come from Front Left came from Front Left, Front Right and Surround Left. No sound from other speakers. Other test files resulted in variations of this jumble.

I am making a rash assumption that the decoder box is OK as I can't think of any way of proving/disproving this.

I believe the problem is in the SR770 setup (or the way I am using it) but I don't have a manual, nor can I find one. I do have the remote.

I have the source set as 6CH Direct and there appear to be some Surround Modes (ProLogic, 3 Logic, Movie, Matrix, Hall, Stereo) but I can't work out how to access these.

Any help in sorting this out will be greatly appreciated.


When testing and you don't get the results that you expect - go back to the test source and verify down the chain ........

Testing source (the files mentioned previously) being sent from my Toshiba Satellite laptop (Win 8.1). This laptop doesn't have a separate digital audio output so I am using an HDMI 2ch/5.1ch audio extractor.

To verify source is working correctly the output from the audio extractor is connected to another AVR that I know outputs surround sound the way it should.

Sound control in Windows shows default device as Toshiba TV (that's correct) with a 5.1 speaker configuration. Test the speakers - sound from the front left and right only.

Play the test files - sound from the front left and right only. (What the .....)

Play a couple of DVDs in the laptop - sound great, all 5 channels.

Maybe that audio extractor is causing problems in some circumstances? I will keep checking.
For the six channel direct input the receiver does not process for surround sound so none of the modes will work as you found.
It sounds like the decoder box is screwed up. If you get 3 channels when you should get only one the Marantz can't do that since it is not processing the signal just passing then through the master volume control to the amplifiers.
You can check this by connecting only one channel of the decoder box and make sure that you only get one output on the Marantz.


All sorted now -

Played the test file (ac3) through Foobar2000 (what I was using before) - stereo only
Played the test file (ac3) through MPC-HC - stereo only
Played the test file (ac3) through VLC - all channels
Played the test file (ac3) through WMP - all channels

Using VLC channels were still mixed up -

Swapped input cables around (trial and error), - audio now coming from the correct speakers but still not sounding right.

Managed to work out how to change 'modes' on the SR770 and using 'trial and error' again now have the sound I was looking for (and expecting).

Thanks to all for their advice.